Subversion of early innate antiviral responsesduring antibody-dependent enhancement of

Dengue virusinfection induces severe disease in

immunocompetent mice

Julia T. de Castro

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THEM

UNIVERSIDADE FEDERAL DE MINAS GERAISIMMUNOFARMACOLOGY GROUP

Where is… I STUDY AND WORK!

Summary

• Introduction to Dengue• Antibody-Dependent Enhancement (ADE)• Methods• Results• Conclusion

Paper discussion

Dengue Fever• Tropical and subtropical disease• Transmitted by the bite of the female mosquito

Aedes aegypti • Female mosquitoes generally lay their eggs above

the water inside containers as tires, buckets, birdbaths, water storage jars, and flower pots.

dengue.org.br nature.com

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Dengue Map

Absent Improbable Probable Present

Dengue virus• DENV is a RNA virus• Four well-known serotypes (DENV1, DENV2,

DENV3 and DENV4)• A fifth type was discovered in 2013

Immune Response

• Infection of Langerhans cells• Innate immunity• Secretion of IFN• Infected cells go to lymph nodes• Adaptive immunity• Abs, complement, Cytotoxic T lymphocytes

Dengue fever

Severe Dengue

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How severe disease is developed?

Few hypotheses

Antibody-Dependent Enhancement (ADE)

Antibody-Dependent Enhancement (ADE)

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• Antibodies from the first infection are cross-reactive with other DENV serotypes

• But Abs are subneutralizing• FcγR recognizes Abs and internalizes immunocomplex • Evidences suggest that the mechanism is associated with both

increase in the number of infected cells, a phenomenon called “Extrinsic ADE,” and a subversion of the intracellular innate immune host responses through suppression of a the type I IFN and proinflammatory cytokines production—an event denominated as “Intrinsic ADE”

Let’s go to the paper…Methods

• ELISA• PCR• Immunohistochemistry• Plaque Assay• Plaque reduction neutralization test in Vero

Cells (PRNT)

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Results

Fig. 1

B cells are necessary for host resistance to primary Dengue infection

*B-cell-deficient mice (μMT−/−)

Conclusions

• B cells are protective to primary infection

Fig. 2

Preexisting immunity can exacerbate disease?

*Mice injected with anti-DENV3 serum and infected with DENV-2

Conclusions

• B cells are protective to primary infection• B-cell activation and antibody production can

exert a dual role

Fig. 3

To test whether the levels of Ab would directly impact on severe disease

*Commercial anti-DENV clone 4G2 (15 μg and 400 μg) at day −1, day +1 and day +3

Conclusions

• B cells are protective to primary infection• B-cell activation and antibody production can

exert a dual role• Presence of non-neutralizing or

subneutralizing levels of Ab can worsen disease (ADE)

Fig. 4

ADE-mediated severe disease resembles primary disease with high inoculum

*4G2 treated mice, sub lethal inoculum (100 PFU) and lethal (1000 PFU)

Fig. 5

Parameters of disease in day 7 (peak)

Conclusions

• B cells are protective to primary infection• B-cell activation and antibody production can

exert a dual role• Presence of non-neutralizing or subneutralizing

levels of Ab can worsen disease (ADE)• subneutralizing levels of anti-DENV antibodies

enhance viral replication to similar extents found in mice primarily infected with a higher DENV inoculum

Fig. 6

Involvement of FcγRs

*Mice treated with an FcγR-blocking Ab in the presence or not of 4G2

Conclusions

• B cells are protective to primary infection• B-cell activation and antibody production can exert a

dual role• Presence of non-neutralizing or subneutralizing

levels of Ab can worsen disease (ADE)• subneutralizing levels of anti-DENV antibodies

enhance viral replication to similar extents found in mice primarily infected with a higher DENV inoculum

• FcγRs play an essential role in disease

Fig. 7

Intrinsic ADE

Mice A129 -/- have more severe disease (supplementary figures)

Conclusions

• B cells are protective to primary infection• B-cell activation and antibody production can exert a dual

role• Presence of non-neutralizing or subneutralizing levels of Ab

can worsen disease (ADE)• subneutralizing levels of anti-DENV antibodies enhance

viral replication to similar extents found in mice primarily infected with a higher DENV inoculum

• FcγRs play an essential role in disease• Type I IFN play an essential role during primary and

secondary infections

Fig. 8

Passive intravenous immunoglobulin therapy (IVIG) containing subneutralizing titers of Ab

Conclusions

• B cells are protective to primary infection• B-cell activation and antibody production can exert a dual

role• Presence of non-neutralizing or subneutralizing levels of Ab

can worsen disease (ADE)• subneutralizing levels of anti-DENV antibodies enhance

viral replication to similar extents found in mice primarily infected with a higher DENV inoculum

• FcγRs play an essential role in disease• Type I IFN play an essential role during primary and

secondary infections

Conclusions

• Vaccines• Treatments