immune reconstitution under anti retro viral therapy - the new challenge in hiv-1 infection

8/3/2019 Immune Reconstitution Under Anti Retro Viral Therapy - The New Challenge in HIV-1 Infection

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Immune reconstitution under antiretroviral therapy:

the new challenge in HIV-1 infection

Pierre Corbeau1,2,3

and Jacques Reynes3,4,5

1Unit Fonctionnelle d'Immunologie, CHU de Nmes, 2Institut de Gntique Humaine, CNRS

UPR1142, Montpellier,3Universit Montpellier I, 4Dpartement des Maladies Infectieuses et

Tropicales, CHU de Montpellier,5UMI 233, Montpellier, France

Running head: Immunologic response to antiretroviral therapy

Blood First Edition Paper, prepublished online March 14, 2011; DOI 10.1182/blood-2010-12-322453


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Abstract

Although highly active antiretroviral therapy has enabled constant progress in reducing HIV-1

replication, in some patients who are aviremic during treatment, the problem of

insufficient immune restoration remains, and this exposes them to the risk of immune

deficiency-associated pathologies. Various mechanisms may combine and account for this

impaired immunologic response to treatment. A first possible mechanism is immune

activation, which may be due to residual HIV production, microbial translocation, co-

infections, immunosenescence or lymphopenia per se. A second mechanism is ongoing HIV

replication. Finally, deficient thymus output, gender and genetic polymorphism influencing

apoptosis may impair immune reconstitution. In this review we will discuss the tools at our

disposal to identify the various mechanisms at work in a given patient and the specific

therapeutic strategies we could propose based on this etiologic diagnosis.


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Introduction

Highly active antiretroviral therapy (HAART) is increasingly efficient at reducing HIV-1

load. Currently, even with salvage therapy, up to 90% of treated HIV-1-infected adults are

aviremic , i.e. have viral RNA plasma levels under the level of detection of commercially

available tests1. Consequently, most of these patients reconstitute their immunity under

treatment. Yet, in some patients CD4+ T cell recovery is abnormally low in spite of their full

virologic response to HAART. An impaired immunologic response is linked to increased risk

of disease progression and death2-6

, but we currently have no efficient therapeutic strategy in

these situations. It is therefore becoming more and more important to understand the

pathophysiological mechanisms responsible for this lack of immune reconstitution, to design

assays capable of diagnosing these mechanisms, and to propose therapies adaptated to each

situation.

Immunologic responses to HAART : both quality and quantity matter

Peripheral CD4+ T cell increase under treatment is a 3-phase process, whatever the regimen is

(figure 1). During the 1 to 6 first months of HAART, the average rate of reconstitution is of

20 to 30 cells/l monthly 7-10. Bosch et al. have estimated this first phase to last for exactly 10

weeks11

. Most of this initial reconstitution seems to be the consequence of a redistribution of

memory CD4+ T cells12

from the lymphoid tissues towards the blood compartment. The

decrease in immune activation induced by the inhibition of viral replication results in a

downregulation of adhesion molecules at the surface of CD4+ T cells, including vascular cell


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lasts until the end of the second year of therapy, and the third phase, of about 2 to 5 cells/l

monthly extends beyond this second year for at least 7 years10,12,14-16

. Various mechanisms

account for the rise in mostly naive CD4+ T cells12,17

during these two phases : first, de novo

production of T lymphocytes by the thymus ; second, the homeostatic proliferation of the

residual CD4+ T cells, and third, the extension of CD4+ T cell half life, a mechanism

responsible for sustaining the number of naive CD4+ T cells in older individuals in whom

thymic production is impaired18

. From a qualitative point of view, these three mechanisms of

reconstitution are not equivalent. A healthy individual harbours a pannel of T-cells able to

recognize a large set of antigens, his T-cell repertoire. HIV-induced CD4+ T cell loss results

in the shrinkage of this repertoire. If CD4+ T cell recovery under therapy is based on the

production of new CD4+ T cells, this repertoire may be at least partially restored. In contrast,

if the increase in CD4 count mainly stems from CD4+ T cell proliferation and survival, the T-

cell repertoire will remain truncated, eventhough the total number of CD4+ T cells is

normalized (figure 2).

What is an impaired CD4+ T cell restoration on HAART ? Unfortunately there is no

consensus on the definition. Some authors have called non immunologic responders patients

whose CD4+ T cell count remained below a threshold (e.g., 350 to 500 cells/l) after a

variable period of time of treatment (e.g., 4 to 7 years). For instance, Kelley et al. showed that

24% of individuals with a CD4+ T cell count


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Because of the so far lack of consensus on this definition, and because of the variability of the

patients populations studied, the estimation of the frequency of virologic responder-only

varied from 6 to 24%3-5,12,14,19-23

.

Of note, not only CD4+ T cell number and quality are impaired in HIV infection, but many

functions of many immune cells may be impaired, and not fully recovered under HAART. For

instance plasmacytoid dendritic cell and natural killer cell activities have been reported to

remain incompletly reconstituted after one year of effective antiretroviral therapy24

. Thus, by

routinely monitoring only CD4+ T cell count, we not only overlook CD4+ T cell functionality

but also the functionality of the other immune cells. The observation that in vivo immune

response to immunization may remain impaired in treated patients with over 450 CD4+ T

cells/l25

emphasizes this notion that CD4 count is an imperfect surrogate marker of immune

restoration. The failure of IL-2 therapy to protect from disease progression in spite of a robust

effect on CD4 counts26

is in keeping with this idea. This means that we will need to define

better indicators, for instance subpopulations of CD4+ T cells, expression of specific CD4+ T

cell surface antigens, in vitro functional assays or in vivo tests to monitor immune

reconstitution.

The many determinants of impaired immune reconstitution in virologic-

responders

The reason why the drastic reduction in viral load does not always result in the normalization

of the CD4+ T cell count may be multifactorial. It is of major importance to understand these

various factors at work if we want to establish an etiologic diagnosis and propose an


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and/or genetically determined increase in the programmed cell death of lymphocytes (figure

3).

Thymic output

The level of de novo T cell production is a determining factor for CD4+ T cell recovery.

Many studies have shown that poor CD4+ T cell regeneration is linked to a low proportion of

naive cells among CD4+ T lymphocytes27-31

. Smith et al. have reported a link between the

importance of the naive CD4+ T cell gain during the first 4 weeks of therapy and the

abundance of thymic tissue32

. Freshly matured T cells, also called recent thymus emigrants

(RTE), are characterized by the fact that they harbour a scar that is a consequence of the

rearrangement of the genes coding for the T cell receptor (TCR). This scar is an extra-

chromosomic circular DNA that is a by-product of the rearrangement, called TCR excision

circle (TREC). TREC have been therefore used as a surrogate marker of thymus output,

although cell division may dilute their content. Some27,33

, but not all31

groups have reported

low levels of TRECs in T lymphocytes in subjects with low CD4+ T cell response. This might

be the consequence of an impaired bone marrow30

and/or thymic34

production. It could also

account for the frequent observation that older individuals, in whom thymic activity has

declined35

, are at higher risk of persistently reduced CD4+ T cell count during HAART than

younger ones 5,36,37.

Another factor that may hinder thymocyte production is HIV-1 infection per se, as it impairs

haematopietic stem cell metabolism38

and thymic function39

. As some of this impairment


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In final support of the importance of thymus output, polymorphisms in genes coding for the

cytokines interleukin (IL)-2, IL-15 and the receptor for IL-15, involved in the maturation and

development of T-cells, have been associated with non immunologic response to HAART40

.

Persistent viral replication

In aviremic patients under HAART some cells may still produce virions, so that ultra-

sensitive techniques can detect HIV RNA in the blood41,42

and in tissues43

. The question thus

arises as to whether these residual virions stem from reservoir cells that continuously release

non-infecting particles (residual production) or from recently infected cells that produce

infectious particles that permanently infect new cells (ongoing replication). Whereas most

authors agree that residual production persists in some patients, the possibility of ongoing

replication is controversial. Various observations argue for the existence of ongoing

replication. First, some authors41,43,44

, but not all45

have observed the diversification of HIV

sequences in aviremic patients, a phenomenon consecutive to mutations occurring during

reverse transcription and therefore necessitating viral life cycles. Second, extra-chromosomic

HIV DNA, including circular DNA containing 2 LTR, a putative marker of recent infection,

has been evidenced in virologic responders46

. Third, Petitjean et al. have shown that under in

vitro activation, the production of virions by peripheral blood CD4+ T cells from virologic

responders may be prevented by an integrase inhibitor. These results indicate that some of

these cells had pre-integrated forms of viral genome i.e. had been recently infected47

.


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HIV-1 viremia in virologic responders argue against the hypothesis of ongoing replication49-

51. Finally, the finding that monocytes from subjects aviremic under HAART may harbour

HIV proviral DNA52

is an additional argument for ongoing replication since these cells

transit very rapidly in the blood.

Thus, if ongoing replication occurs in some aviremic patients, in lymphoid organs for

instance, the cytopathogenicity of the virus may still be at work, particularly if it uses CXCR4

as a coreceptor31

, and this could hamper the reconstitution of the CD4+ T cell count.

Moreover, Doitsh et al. have recently shown that HIV replicative cycle does not need to be

complete to induce CD4+ T cell death53

.

Immune activation

Many authors have linked immune activation to impaired rise in peripheral blood CD4+ T

cell count under treatment28-30,54-56

. This link may have at least two causes. On one hand, as

above-discussed, activated CD4+ T cells may be trapped in secondary lymphoid organs. And

on the other hand, most CD4+ T cells die by apoptosis once they have been stimulated.

Various phenomena, listed below, may be responsible for immune activation in the course of

HIV-1 disease (figure 3).

Residual viral production

Persistent production of viral particles by reservoir cells in aviremic treated patients even

in absence of ongoing replication may induce an immune activation. This is due to the anti-

HIV immune response and to the fact that various HIV components are able to stimulate the

57


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activation. In line with this, HAART intensification has been reported to decrease immune

activation in some patients60

.

Age

Older persons have a higher background of immune activation than younger ones61

. This

might contribute, in addition to their reduced thymic output, to the link between age and

suboptimal CD4+ T cell progression. From a general point of view, immunosenescence might

be a cause and a consequence of immune activation, leading to a vicious circle.

High level of CCR5-induced activation

As the main HIV-1 coreceptor, C-C chemokine receptor type 5 (CCR5) is now recognized as

a co-activation molecule at the surface of CD4+ T cells62

, it could be involved in immune

activation and thereby in the rise in CD4 count. This could explain why the administration of

a CCR5 antagonist resulted in a decrease in T cell activation63,64

. Accordingly, a high

efficiency of CCR5-induced activation, as a consequence of genetic polymorphism65

or of a

high CD4+ T cell-surface CCR5 density (personal data) may favour the persistence of

immune activation under HAART. In support of this notion, Ahujas group has established a

correlation between CD4+ T cell recovery and the genetic polymorphism of the gene

encoding CCR5, and the number of copies of the gene encoding one of the natural ligand of

this coreceptor, C-C chemokine ligand 3-like 1 (CCL3L1)65

. In this study, the authors

observed that this polymorphism was predictive of the intensity of CD4 count increase in

virologic responders. This raises the interesting hypothesis that CCR5, in addition to its

virologic roles as an HIV-1 coreceptor, might play a role in immune reconstitution. This


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polymorphisms in genes encoding the cytokines IL-6, tumour necrosis factor (TNF), and

interferon (IFN)40 have been involved in HAART-induced CD4+ T cell count gain 75.

Other genetic factors

Genes involved in apoptosis

Apoptosis is a form of cell death responsible for CD4+ T cell loss during HIV infection. The

intensity of spontaneous27

, Fas-27

and HIV-induced54

ex vivo apoptosis of CD4+ T cells has

been inversely correlated with CD4+ T cell progression after HAART. Therefore, it is not

surprising that polymorphisms in genes involved in apoptosis such as TRAIL40

, Bim40

, Fas

76, and FasL

76have been linked to the rise in CD4+ T cell count through therapy.

Gender

Men have been reported to be at higher risk of non CD4+ T cell response under HAART than

women28,37

. The reasons for that are unclear. One explanation might be that thymic output is

higher in females than in males35

. Another one could be an anti-apoptotic effect of female sex

steroids on CD4+ T cells as observed for instance on neutrophils77

. Moreover, the level of

expression of CCR5 at the surface of CD4+ T cells, linked to CD4+ T cell recovery66

as

above-mentioned, is lower in women than in men78

.

Other genes

Genetic polymorphisms in the genes coding for the CXCR4-binding chemokine CXCL12 or

SDF-179

, for the chemokine receptor CX3CR179

, and in genes located in the major

histocompatibility complex75,80

have also been linked to treatment-induced CD4+ T cell


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Some antiretroviral agents such as AZT may be toxic for haematopoietic progenitor cells81

,

and could thereby hamper CD4+ T cell count reconstitution. Likewise, the combination of

tenofovir with high doses of ddI has been involved in poor recovery of CD4+ T cells

eventually induced by a deleterious effect of ddI on T cell maturation and differenciation82

.

On the contrary, a better immunologic response has initially been reported with protease

inhibitor83

. Yet, other studies have shown that CD4+ T cell gain was independent of the

antiretroviral regimen28,84

. Recently, the integrase inhibitor raltegravir has been shown to

induce a greater increase in CD4 count in treatment-naive patients at week 48 but not at week

96 as compared with efavirenz85

. The same result was reported at week 48 for the CCR5

antagonist maraviroc, that persisted at week 9686

.

CD4+ T cell nadir

Low nadir CD4+ T cell count36,54,87

and low pre-therapeutic CD4 count37,88

have been

identified as predictive factors of persistently reduced CD4+ T cell count. Obviously, if the

definition of immune response is exclusively based on the CD4 count reached, rather than on

the CD4 slope, the baseline CD4 count will definitely influence the level of immune response.

Moreover low nadir CD4+ T cell count and low pre-therapeutic CD4 count may cause

emergence of X4 strains89

, intense microbial translocation55

, development of co-infections

and immunosenescence, all factors hindering CD4+ T cell regeneration as discussed above.

HIV RNA plasma level

CD4+ T cell response has been reported to be low when the pre-therapeutic viremia is low28

.

The reasons for this correlation remain to be unveiled.


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marker of recent infection, is also not a routine assay47

. Other strategies need to be tested,

such as, for instance, the detection of HIV DNA in peripheral blood monocytes52

.

Immune activation

The marker of immune activation that is the best predictor of disease progression might be the

percentage of CD8+ T cells that overexpress CD3892

. But we also need to discriminate

between the different causes of immune activation. Residual production of virions may be

detected by quantitating the viremia with ultrasensitive techniques41

. Alternatively, the

quantification of unspliced HIV RNA in PBMC might be used to track persistent synthesis of

viral particles93

. Active co-infection may be diagnosed by assays that are specific for the

various infectious agents participating in the residual immune activation. High level of CCR5

activation could be detected by genotyping the CCR5 gene and by determining the CCL3L1

gene copy number65

or by measuring CD4+ T cell surface CCR5 density66

. Finally,

microbial translocation has been initially measured by quantifying lipopolysaccharides (LPS)

plasma level 94, but the quantification of bacterial ribosomal 16S RNA DNA (16S rDNA)

plasma level is more sensitive, more specific and more comprehensive74

.

Therapeutic possibilities

According to the etiology, various therapies may be considered (table 1).

Insufficient thymic activity


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HAART-treated subjects96

. The limitations might be that lymphopenic patients already

produce high amounts of IL-7, and a potential drawback is that by inducing CXCR4

expression, IL-7 might favour the emergence of X4 strains97

. IL-15 has also been considered

to boost immune recovery98

.

Another option might be to inhibit the production of sex steroids. As estrogens, progesterone

and testosterone induce thymic atrophy, probably mainly through their effect on thymic

stroma, castration has been tested with success in order to boost thymic activity in animals99

.

Accordingly, in humans the administration of luteinizing hormone-releasing hormone

(LHRH) agonist has resulted in transient enhancement of thymic function100

, particularly

after hematopoietic stem cell transplantation101

. Obviously, although chemical castration is

temporary, the gain in thymic output will have to be balanced with the side effects.

An alternative way to sustain thymic activity is to induce thymic epithelial cell proliferation

by using the keratinocyte growth factor (KGF). In mice, KGF administration reverses age-

induced thymic and T cell dysfunction102

. The effect of KGF after hematopoietic stem cell

transplantation is currently being tested.

Finally, growth hormone (GH) is supposed to enhance hematopoiesis and immune function

both directly and via insulin-like growth factor 1103

. GH treatment has been shown to

improve thymic function in HIV-1-infected subjects104

. Yet, here again the risk of adverse

events, as carpal tunnel syndrome, hyperglycemia or cancer progression will have to be

carefully considered.


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payed to ensuring that the chosen therapeutic agents reach inhibiting concentrations in the

organs where this replication persits.

Immune activation

Two strategies may be adopted : on one hand, a symptomatic therapy aiming at reducing the

global level of polyclonal immune activation, and on the other hand, etiologic therapies

targetting the mechanisms responsible for this activation.

Symptomatic therapy

In the past, various attempts to downregulate the polyclonal immune activation observed in

HIV-1-infected patients have been made. These attempts included the use of hydroxyurea,

thalidomide, mycophenolate, corticosteroids, IL-10, anti-TNF agents, cyclosporin A,

FK506, and rapamycin105

. Most of these attempts have been disappointing. If CCR5 is

actually involved, as a co-activation molecule, into this immune activation, CCR5 antagonists

could exert some inhibitory effect on it. Of note, HAART intensification with the CCR5

antagonist maraviroc has resulted in a decrease in the proportion of activated peripheral blood

CD4+64

and CD8+63

T cells, and in an increase in CD4+ T cell slopes that trended to achieve

significance63

in non-immunologic responders. Thus, agents targeting CCR5 could have an

immunological effect sparing CD4+ T cells in addition to their antiviral effects.

Residual viral production

In this case, the way to stop HIV-induced immune activation will be to get rid of the reservoir

cells that continue to release virions eventhough these virions do not cause de novo infection.


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chromatin, intravenous immunoglobulin injection and microRNA manipulation have been

proposed100-108

.

Co-infections

If active co-infections reinforce the global immune activation, the infectious agents

responsible for these co-infections might be targeted. Thus, therapeutic clearance of HCV

RNA in HIV/HCV co-infected adults has been shown by some authors to decrease immune

activation67

and to improve immune reconstitution under HAART68

. In the same way, 8

weeks of treatment with valganciclovir of CMV-seropositive HIV-infected patients with

CD4+ T cell counts


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Conclusion

Various mechanisms may be responsible in a given patient for an impaired immune recovery

under HAART in spite of a control of viral replication. In order to correctly address this issue

we need to design convenient tools to identify which ones of these mechanisms are at work in

each non immunologic responder. Based on this personnalized etiologic diagnosis we then

will be able to propose specific therapeutic strategies. Beyond the challenge of restoring

immunity to prevent AIDS-associated events, the measurement of immune hyperactivation,

the identification of the causes of this hyperactivation, and the fight against it will also

decrease the risk of non AIDS-linked pathologies.


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Authorship

Conflicts of interest : PC has received honoraria for lectures or advisory boards from Bristol-

Myers Squibb, GlaxoSmithKline, Merck Sharp & Dohme-Chibret, Pfizer and ViiV Healthcare,

and a research grant from Pfizer. J.R. has received honoraria for lectures or advisory boards

and/or research support from Abbott, BMS, Boehringer Ingelheim, Gilead, GSK, Merck,

Pfizer, Roche, Schering-Plough, Tibotec.

P.C. wrote the manuscript; J.R. reviewed and edited it.

Correspondence: Pierre Corbeau, Laboratoire d'Immunologie, Hpital Saint Eloi, 80 avenue A.

Fliche, 34295, Montpellier cedex 5, tel : +33 467 33 71 35, fax: +33 467 33 71 29, e-mail address:

[email protected]


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References

1. Yazdanpanah Y, Fagard C, Descamps D, et al. High rate of virological suppression

with raltegravir plus etravirine and darunavir/ritonavir among treatment-experienced patients

infected with multidrug-resistant HIV: results of the ANRS 139 TRIO Trial. Clin Infect Dis.

2009;49(9):1441-1449.

2. Lewden C, Chne G, Morlat P, et al. HIV-infected adults with a CD4 count grater than

500 cells/mm3 on long-term combination antiretroviral therapy reach same mortality rates as

the general population.J Acquir Immune Defic Syndr. 2007;46(1):72-77.

3. Nicastri E, Chiesi A, Angeletti C, et al. Clinical outcome after 4 years follow-up of

HIV-seropositive subjects with incomplete virologic or immunologic response to HAART. J

Med Virol. 2005;76(2):153-160.

4. Tan R, Westfall AO, Willig JH, et al. Clinical outcome of HIV-infected antiretroviral-

naive patients with discordant immunologic and virologic responses to highly active

antiretroviral therapy.J Acquir Immune Defic Syndr. 2008;47(5):553-558.

5. Gutierrez F, Padilla S, Masia M, et al. Patients' characteristics and clinical

implications of suboptimal CD4 T-cell gains after 1 year of successful antiretroviral therapy.

Curr HIV Res. 2008;6(2):100-107.

6. Life expectancy of individuals on combination antiretroviral therapy in high-income

countries: a collaborative analysis of 14 cohort studies.Lancet. 2008;372(9635):293-299.

7. Guihot A, Tubiana R, Breton G, et al. Immune and virological benefits of 10 years of

permanent viral control with antiretroviral therapy.AIDS. 2010;24(4):614-617.


21/37

9. Ledergerber B, Lundgren JD, Walker AS, et al. Predictors of trend in CD4-positive T-

cell count and mortality among HIV-1-infected individuals with virological failure to all three

antiretroviral-drug classes.Lancet. 2004(9428);364:51-62.

10. Le Moing V, Thiebaut R, Chene G, et al. Predictors of long-term increase in CD4(+)

cell counts in human immunodeficiency virus-infected patients receiving a protease inhibitor-

containing antiretroviral regimen.J Infect Dis. 2002;185(4):471-480.

11. Bosch RJ, Wang R, Vaida F, Lederman MM, Albrecht MA, Team ftACTGS. Changes

in the slope of the CD4 cell count increase after initiation of potent antiretroviral treatment. J

Acquir Immune Defic Syndr. 2006;43(4):433-435.

12. Autran B, Carcelaint G, Li TS, et al. Restoration of the immune system with anti-

retroviral therapy.Immunol Lett. 1999;66(1-3):207-211.

13. Bucy RP, Hockett RD, Derdeyn CA, et al. Initial increase in blood CD4(+)

lymphocytes after antiretroviral therapy reflects redistribution from lymphoid tissues. J Clin

Invest. 1999;103(10):1391-1398.

14. Kaufmann GR, Perrin L, Pantaleo G, et al. CD4 T-lymphocyte recovery in individuals

with advanced HIV-1 infection receiving potent antiretroviral therapy for 4 years: the Swiss

HIV Cohort Study.Arch Intern Med. 2003;163(18):2187-2195.

15. Hunt PW, Brenchley J, Sinclair E, et al. Relationship between T cell activation and

CD4+ T cell count in HIV-seropositive individuals with undetectable plasma HIV RNA

levels in the absence of therapy. J Infect Dis. 2008;197(1):126-133.

16. Lok JJ, Bosch RJ, Benson CA, et al. Long-term increase in CD4+ T-cell counts during


22/37

18. Tsukamoto H, Clise-Dwyer K, Huston GE, et al. Age-associated increase on lifespan

of nave CD4 T cells contributes to T-cell homeostasis but facilitates development of

functional defects. Proc Natl Acad SCci USA. 2009;106(43):18333-18338.

19. Kelley CF, Kitchen CM, Hunt PW, et al. Incomplete peripheral CD4+ cell count

restoration in HIV-infected patients receiving long-term antiretroviral treatment. Clin Infect

Dis. 2009;48(6):7878-7794.

20. Grabar S, Le Moing V, Goujard C, et al. Clinical outcome of patients with HIV-1

infection according to immunologic and virologic response after 6 months of highly active

antiretroviral therapy.Ann Intern Med. 2000;133(6):401-441.

21. Moore DM, Hogg RS, Yip B, et al. Discordant immunologic and virologic responses

to highly active antiretroviral therapy are associated with increased mortality and poor

adherence to therapy.J Acquir Immune Defic Syndr. 2005;40(3):288-293.

22. Piketty C, Castiel P, Belec L, et al. Discrepant responses to triple combination

antiretroviral therapy in advanced HIV disease.AIDS. 1998;12(7):745-750.

23. Marimoutou C, Chene G, Mercie P, et al. Prognostic factors of combined viral load

and CD4+ cell count responses under triple antiretroviral therapy, Aquitaine cohort, 1996-

1998.J Acquir Immune Defic Syndr. 2001;27(2):161-167.

24. Chehimi J, Azzoni L, Farabaugh M, et al. Baseline viral load and immune activation

determine the extent of reconstitution of innate immune effectors in HIV-1-infected subjects

undergoing antiretroviral treatment.J Immunol. 2007;179(4):2642-2650.

25. Lange CG, Lederman MM, Medvik K, et al. Nadir CD4+ T-cell count and numbers of


23/37

27. Benveniste O, Flahault A, Rollot F, et al. Mechanisms involved in the low-level

regeneration of CD4+ cells in HIV-1-infected patients receiving highly active antiretroviral

therapy who have prolonged undetectable plasma viral loads. J Infect Dis.

2005;191(10):1670-1679.

28. Gandhi RT, Spritzler J, Chan E, et al. Effect of baseline- and treatment-related factors

on immunologic recovery after initiation of antiretroviral therapy in HIV-1-positive subjects:

results from ACTG 384.J Acquir Immune Defic Syndr. 2006;42(4):426-434.

29. Marziali M, De Santis W, Carello R, et al. T-cell homeostasis alteration in HIV-1

infected subjects with low CD4 T-cell count despite undetectable virus load during HAART.

AIDS. 2006;20(16):2033-2041.

30. Isgro A, Leti W, De Santis W, et al. Altered clonogenic capability and stromal cell

function characterize bone marrow of HIV-infected subjects with low CD4+ T cell counts

despite viral suppression during HAART. Clin Infect Dis. 2008;46(12):1902-1910.

31. Delobel P, Nugeyre M-T, Cazabat M, et al. Nave T-cell depletion related to infection

by X4 Human Immunodeficiency Virus type 1 in poor immunological responders to highly

active antiretroviral therapy. J Virol. 2006;80(20):10229-10236.

32. Smith KY, Valdez H, Landay A, et al. Thymic size and lymphocyte restoration in

patients with human immunodeficiency virus infection after 48 weeks of zidovudine,

lamivudine, and ritonavir therapy.J Infect Dis. 2000;181(1):141-147.

33. Torti C, Cologni G, Uccelli MC, et al. Immune correlates of virological response in

HIV-positive patients after highly active antiretroviral therapy (HAART). Viral Immunol.


24/37

35. Pido-Lopez J, Imami N, Aspinall R. Both age and gender affect thymic output: more

recent thymic migrants in females than males as they age. Clin Exp Immunol.

2001;125(3):409-413.

36. Kaufmann GR, Furrer H, Ledergerber B, et al. Characteristics, determinants, and

clinical relevance of CD4 T cell recovery to


25/37

44. Gnthard HF, Frost SD, Leigh-Brown AJ, et al. Evolution of envelope sequences of

Human Immunodeficiency Virus type 1 in cellular reservoirs in the setting of potent antiviral

therapy.J Virol. 1999;73(11):9404-9412.

45. Bailey JR, Sedaghat AR, Kieffer T, et al. Residual Human Immunodeficiency Virus

type 1 viremia in some patients on retroviral therapy is dominated by small number of

invariant clones rarely found in circulating CD4+ T cells. J Virol. 2006;80(13):6441-6457.

46. Sharkey ME, Teo I, Greenough T, et al. Persistence of episomal HIV-1 infection

intermediates in patients on highly active anti-retroviral therapy.Nat Med. 2000;6(1):76-81.

47. Petitjean G, Al Tabaa Y, Tuaillon E, et al. Unintegrated HIV-1 provides an inducible

and functional reservoir in untreted and highly active antiretroviral therapy-treated patients.

Retrovirology. 2007;4:60.

48. Buzon MJ, Massanella M, Llibre JM, et al. HIV-1 replication and immune dynamics

are affected by raltegravir intensification of HAART-suppressed subjects. Nat Med.

2010;16(4):460-465.

49. Dinoso JB, Kim SY, Wiegand AM, et al. Treatment intensification does not reduce

residual HIV-1 viremia in patients on highly active antiretroviral therapy. Proc Natl Acad Sci

U S A. 2009;106(23):9403-9408.

50. Gandhi RT, Zheng L, Bosch RJ, et al. The effect of raltegravir intensification on low-

level residual viremia in HIV-infected patients on antiretroviral therapy: a randomized

controlled trial. PLoS Med. 2010;7(8):e1000321.

51. McMahon D, Jones J, Wiegand A, et al. Short-course raltegravir intensification does


26/37

52. Mavigner M, Delobel P, Cazabat M, et al. HIV-1 residual viremia correlates with

persistent T-cell activation in poor immunological responders to combination antiretroviral

therapy. PloS ONE. 2009;4(10):e7658.

53. Doitsh G, Cavrois M, Lassen KG, et al. Abortive HIV infection mediates CD4 T cell

depletion and inflammation in human lymphoid tissue. Cell. 2010;143(5):789-801.

54. Piconi S, Trabattoni D, Gori A, et al. Immune activation, apoptosis, and Treg activity

are associated with persistently reduced CD4+ T-cell counts during antiretroviral therapy.

AIDS. 2010;24(13):1991-2000.

55. Marchetti G, Bellistri GM, Borghi E, et al. Microbial translocation is associated with

sustained failure in CD4+ T-cell reconstitution in HIV-infected patients on long-term highly

active antiretroviral therapy.AIDS. 2008;22(15):2035-2038.

56. Ostrowski SR, Katzenstein TL, Thim PT, Pedersen BK, Gerstoft J, Ullum H. Low-

level viremia and proviral DNA impede immune reconstitution in HIV-1-infected patients

receiving highly active antiretroviral therapy.J Infect Dis. 2005;191(3):348-357.

57. Beignon AS, McKenna K, Skoberne M, et al. Endocytosis of HIV-1 activates

plasmacytoid dendritic cells via Toll-like receptor-viral RNA interactions. J Clin Invest.

2005;115(11):3265-3275.

58. Lee C, Liu QH, Tomkowicz B, Yi Y, Freedman BD, Collman RG. Macrophage

activation through CCR5- and CXCR4-mediated gp120-elicited signaling pathways.J Leukoc

Biol. 2003;74(5):676-682.

59. Wang JK, Kiyokawa E, Verdin E, Trono D. The Nef protein of HIV-1 associates with


27/37

61. Desai A, Grolleau-Julius A, Yung R. Leukocyte function in the aging immune system.

J Leukoc Biol. 2010;87(6):1001-1009.

62. Camargo JF, Quinones MP, Mummidi S, et al. CCR5 expression levels influence

NFAT translocation, IL-2 production, and subsequent signaling events during T lymphocyte

activation.J Immunol. 2009;182(1):171-182.

63. Wilkin T, Lalama C, Tenorio AR, et al. Maraviroc intensification for suboptimal

CD4+ cell response despite sustained virologic suppression: ATCG 5256. 17th Conference on

Retroviruses and Opportunistic Infections. 2010;Abstract 285.

64. Gutirrez C, Diaz L, Hernandez-Novoa B, et al. Effect of the intensification with a

CCR5 antagonist on the decay of the HIV-1 latent reservoir and residual viremia. 17th

Conference on Retroviruses and Opportunistic Infections. 2010;Abstract 284.

65. Ahuja SK, Kulkarni H, Catano G, et al. CCL3L1-CCR5 genotype influences durability

of immune recovery during antiretroviral therapy of HIV-1-infected individuals. Nat Med.

2008;14(4):413-420.

66. Vincent T, Portals P, Baillat V, et al. The immunological response to highly active

antiretroviral therapy is linked to CD4+ T-cell surface CCR5.J Acquir Immune Defic Syndr.

2006;43(3):377-378.

67. Gonzalez VD, Falconer K, Blom KG, et al. High levels of chronic immune activation

in the T-cell compartments of patients coinfected with hepatitis C virus and human

immunodeficiency virus type 1 and on highly active antiretroviral therapy are reverted by

alpha interferon and ribavirin treatment.J Virol. 2009;83(21):11407-11411.


28/37

69. Santin M, Mestre M, Shaw E, et al. Impact of hepatitis C virus coinfection on immune

restoration during successful antiretroviral therapy in chronic human immunodeficiency virus

type 1 disease.Eur J Clin Microbiol Infect Dis. 2008;27(1):65-73.

70. Seminari E, Tinelli C, Ravasi G, et al. Hepatitis C infection on immune recovery in

HIV-positive patients on successful HAART: the role of genotype 3. Curr HIV Res.

2010;8(3):186-193.

71. Villacres MC, Lacey SF, La Rosa C, et al. Human Immunodeficiency Virus-infected

patients receiving highly active antiretroviral therapy maintain activated CD8+ T cell subsets

as a strong adaptative immune response to cytomegalovirus. J Infect Dis. 2001;184(3):256-

267.

72. Lazaro E, Coureau G, Guedj J, et al. Change in T-lymphocyte count after initiation of

highly active antiretroviral therapy in HIV-infected patients with history of Mycobacterium

avium complex infection.Antivir Ther. 2006;11(3):343-350.

73. Brenchley JM, Schacker TW, Ruff LE, et al. CD4+ T cell depletion during all stages

of HIV disease occurs predominantly in the gastrointestinal tract. J Exp Med.

2004;200(6):749-759.

74. Jiang W, Lederman MM, Hunt P, et al. Plasma levels of bacterial DNA correlate with

immune activation and the magnitude of immune restoration in persons with antiretroviral-

treated HIV infection. J Infect Dis. 2009;199(8):1177-1185.

75. Fernandez S, Rosenow AA, James IR, et al. Recovery of CD4+ T cells in HIV patients

with a stable virologic response to antiretroviral therapy is associated with polymorphism of


29/37

76. Nasi M, Pinti M, Bugarini R, et al. Genetic polymorphisms of Fas (CD95) and Fas

ligand (CD178) influence the rise in CD4+ T cell count after antiretroviral therapy in drug-

naive HIV-positive patients.Immunogenetics. 2005;57(9):628-635.

77. Molloy EJ, O'Neill AJ, Grantham JJ, et al. Sex-specific alterations in neutrophil

apoptosis: the role of estradiol and progesterone.Blood. 2003;102(7):2653-2659.

78. Portales P, Clot J, Corbeau P. Sex difference in HIV-1 viral load due to sex difference

in CCR5 expression.Ann Intern Med. 2001;134(1):81-82.

79. Puissant B, Roubinet F, Massip P, et al. Analysis of CCR5, CCR2, CX3CR1, and

SDF1 polymorphisms in HIV-positive treated patients: impact on response to HAART and on

peripheral T lymphocyte counts.AIDS Res Hum Retroviruses. 2006;22(2):153-162.

80. Rauch A, Nolan D, Furrer H, et al. HLA-Bw4 homozygosity is associated with an

impaired CD4 T cell recovery after initiation of antiretroviral therapy. Clin Infect Dis.

2008;46(12):1921-1925.

81. Du DL, Volpe DA, Grieshaber CK, Murphy MJ Jr. In vitro toxicity of 3'-azido-3'-

deoxythymidine, carbovir and 2',3'-didehydro-2',3'-dideoxythymidine to human and murine

haematopoietic progenitor cells.Br J Haematol. 1992;80(4):437-445.

82. Karrer U, Ledergerber B, Furrer H, et al. Dose-dependent influence of didanosine on

immune recovery in HIV-infected patients treated with tenofovir. AIDS. 2005;19(17):1987-

1994.

83. MacArthur RD, Novak RM, Peng G, et al. A comparison of three highly active

antiretroviral treatment strategies consisting of non-nucleoside reverse transcriptase


30/37

84. Waters L, Stebbing J, Jones R, et al. A comparison of the CD4 response to

antiretroviral regimens in patients commencing therapy with low CD4 counts. J Antimicrob

Chemother. 2004;54(2):503-507.

85. Lennox JL, DeJesus E, Berger DS, et al. Raltegravir versus efavirenz regimens in

treatment-naive HIV-1-infected patients: 96-week efficacy, durability, subgroup, safety, and

metabolic analyses.J Acquir Immune Defic Syndr. 2010;55(1):39-48.

86. Sierra-Madero J, Di Perri G, Wood R, et al. Efficacy and safety of maraviroc versus

efavirenz, both in combination with zidovudine/lamivudine: 96-week results from the MERIT

studyHIV Clin Trials. 2010;11(3):125-132.

87. Moore RD, Keruly JC. CD4+ cell count 6 years after commencement of highly active

antiretroviral therapy in persons with sustained virologic suppression. Clin Infect Dis.

2007;44(3):441-446.

88. Falster K, Petoumenos K, Chuah J, et al. Poor baseline immune function predicts an

incomplete immune response to combination antiretroviral treatment despite sustained viral

suppression.J Acquir Immune Defic Syndr. 2009;50(3):307-313.

89. Hunt PW, Harrigan PR, Huang W, et al. Prevalence of CXCR4 tropism among

antiretroviral-treated HIV-1-infected patients with detectable viremia. J Infect Dis.

2006;194(7):926-930.

90. Kimmig S, Przybylski GK, Schmidt CA, et al. Two subsets of naive T helper cells

with distinct T cell receptor excision circle content in human adult peripheral blood. J Exp

Med. 2002;195(6):789-794.


31/37

92. Bofill M, Mocroft A, Lipman M, et al. Increased numbers of primed activated CD8+

CD38+ CD45RO+ T cells predict the decline of CD4+ T cells in HIV-1-infected patients.

AIDS. 1996;10(8):827-834.

93. Pasternak AO, Jurriaans S, Bakker M, Prins JM, Berkhout B, Lukashov VV. Cellular

levels of HIV unspliced RNA from patients on combination antiretroviral therapy with

undetectable plasma viremia predict the therapy outcome. PloS ONE. 2009;4(12):e8490.

94. Brenchley JM, Price DA, Schaker TW, et al. Microbial translocation is a cause of

systemic immune activation in chronic HIV infection.Nat Med. 2006;12(12):1365-1371.

95. Jiang Q, Li WQ, Aiello FB, et al. Cell biology of IL-7, a key lymphotrophin. Cytokine

Growth Factor Rev. 2005;16(4-5):513-533.

96. Lvy Y, Lacabaratz C, Weiss L, et al. Enhanced T cell recovery in HIV-1-infected

adults through IL-7 treatment.J Clin Invest. 2009;119(4):997-1007.

97. Llano A, Barretina J, Gutirrez A, et al. Interleukin-7 in plasma correlates with CD4

T-cell depletion and may be associated with emergence of syncytium-inducing variants in

human immunodeficiency virus type 1-positive individuals. J Virol. 2001;75(21):10319-

10325.

98. Leone A, Picker LJ, Sodora DL. IL-2, IL-7 and IL-15 as immuno-modulators during

SIV/HIV vaccination and treatment. Curr HIV Res. 2009;7(1):83-90.

99. Windmill KF, Lee VW. Effects of castration on the lymphocytes of the thymus, spleen

and lymph nodes. Tissue Cell. 1998;30(1):104-111.

100. Sutherland JS, Goldberg GL, Hammett MV, et al. Activation of thymic regeneration in


32/37

102. Min D, Panoskaltsis-Mortari A, Kuro OM, Hollander GA, Blazar BR, Weinberg KI.

Sustained thymopoiesis and improvement in functional immunity by exogenous KGF

administration in murine models of ageing.Blood. 2007;109(6):2529-2537.

103. Welniak LA, Sun R, Murphy WJ. The role of growth hormone in T-cell development

and reconstitution.J Leukoc Biol. 2002;71(3):381-387.

104. Napolitano LA, Schmidt D, Gotway MB, et al. Growth hormone enhances thymic

function in HIV-1-infected adults.J Clin Invest. 2008;118(3):1085-1098.

105. Argyropoulos C, Mouzaki A. Immunosuppressive drugs in HIV disease. Curr Top

Med Chem. 2006;6(16):1769-1789.

106. Archin NM, Margolis DM. Attacking latent HIV provirus: from mechanism to

therapeutic strategies. Curr Opin HIV AIDS. 2006;1(2):134-140.

107. Lindkvist A, Edn A, Norstrm MM, et al. Reduction of the HIV-1 reservoir in resting

CD4+ T-lymphocytes by high dosage intravenous immunoglobulin treatment: a proof-of-

concept study.AIDS Res Ther. 2009;6:15.

108. Zhang H. Reversal of HIV-1 latency with anti-microRNA inhibitors. Int J Biochem

Cell Biol. 2009;41(3):451-454.

109. Hunt P, Martin J, Sinclair E, et al. Valganciclovir reduces CD8+ T cell activation

among HIV-infected patients with suboptimal CD4+ T cell recovery during ART. 17th

Conference on Retroviruses and Opportunistic Infections. 2010;Abstract 380.

110. Kwon H-K, Lee C-G, So J-S, et al. Generation of regulatory dendritic cells and

CD4+Foxp3+ T cells by probiotics administration suppresses immune disorders. Proc Natl


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Etiology Marker Treatment

Insufficient thymus activity

Naive T / memory T

Sj/TREC% CD31+ T cells

IL-7, IL-15

GH, KGFLHRH agonist

Immune

activation

Residual HIV

Production

Plasma viral load

Intracellular HIV RNA

Immunomodulator ?

CCR5 antagonist ?

Reservoir eradication

Bacterial

translocation

LPS plasma level16S rDNA plasma level

HAART intensificationProbiotics

Co-infection Specific diagnosis Specific treatment

CCR5

genetics

Genotyping CCR5 antagonist

Ongoing HIV replication

2-LTR

HIV sequence diversification

Intramonocytic HIV DNAPreintegrated HIV DNA

HAART intensification


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Legends to figures

Figure 1 : Average CD4+ T cell recovery under HAART. The increase in CD4+ T cell count

and the mechanisms responsible for this increase are represented at various time points.

Figure 2 : T cell repertoire reduction under HIV-1 infection, and reconstitution under

HAART. The quality of the reconstitution is represented depending on the various

mechanisms accounting for the increase in CD4+ T cell count.

Figure 3 : Causes of impaired CD4+ T cell recovery under HAART.


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1-6 months 2 years 4 years

+20-30/month

+5-10/month

+2-5/month

+300-350

cells+200-250

cells

TimeCD4+

T

cell

count

Lymph

nodes Blood

Blood

Thymus

Cell division Lifespan increase

Figure 1

Thymus


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Thymus

W Y

W Y

W Y

W Y

HIVinfection

Figure 2


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Ongoing HIV

replication

Gender

Co-infection

Bim, Fas,

FasL, TRAIL

Bacterialtranslocation

Immune

activation

Bone marrow/thymus

output

HIV pathogenesis

Residual HIV

production

Genetics

CCR5

CCL3L1

IL-15, IL-15R

IL2

X4

TNFIL-6

Lymphopenia

Figure 3

Senescence

HAART

immune reconstitution under anti retro viral therapy - the new challenge in hiv-1 infection

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