small tools for big problems: microchips for global health...

Monday, 24 November 2008

Small Tools for Big Problems: Microchips for Small Tools for Big Problems: Microchips for Global Health AIDS Diagnostics

Xuanhong Chengua o g C e gMaterials Science and Engineering

Bioengineering

Overview of Presentation

1 Global Health Challenges

2 HIV/AIDS Statistics and Biology

3 HIV/AIDS Diagnostics

4 Mi hi T h l f HIV/AIDS Di i 4 Microchip Technology for HIV/AIDS Diagnostics

Leading causes of death, Global

1 Ischemic heart disease 12.7

2 Cerebrovascular disease 9 9

Rank % of total

2 Cerebrovascular disease 9.9

3 Acute lower respiratory infections 7.1

4 HIV/AIDS 4.8

5 Chronic obstructive pulmonary disease 4.8

6 Perinatal conditions 4.2

7 Diarrheal diseases 4 07 Diarrheal diseases 4.0

8 Tuberculosis 3.0

11 Malaria 1.9

Source: WHO , The World Health Report 2000

Leading causes of death, Africa

1 HIV/AIDS 20.6

2 Acute lower respiratory infections 10.3

Rank % of total

2 Acute lower respiratory infections 10.3

3 Malaria 9.1

4 Diarrheal diseases 7.3

5 Perinatal conditions 5.9

6 Measles 4.9

7 Tuberculosis 3 47 Tuberculosis 3.4

8 Cerebrovascular disease 3.2

9 Ischemic heart disease 3.0

10 Maternal conditions 2.4

Source: WHO , The World Health Report 2000

Cell Bacteria(TB, Typhoid)

Virus(HIV, hepatitis, SARS, influenza)

.

HIV emerging from a cellHIV emerging from a cell

Cell

HIV

Global diversity of different HIV-1 strains

Source: Los Alamos Database http://hiv-web.lanl.gov/

39 million adults living with HIV/AIDS, 2006

Source: WHO

Growth of the AIDS Epidemic

40

45

People With HIV/AIDS, Cumulative Regional TotalsMillions

25

30

35

40

15

20

25

0

5

10

1986 1988 1990 1992 1994 1995 1998 2000 2002 20041986 1988 1990 1992 1994 1995 1998 2000 2002 2004

Sub-Saharan Africa Asia Latin AmericaEurope & N. America* Eastern Europe & Central Asia North Africa & Middle EastCaribbean

*Western and Central Europe & North America.Source: UNAIDS/WHO, 2004.

People With HIV/AIDS, by Region

Eastern Europe and Central Asia

Western and Central Europe

Latin America4%

Caribbean1%

4%

Oceania

North America3%

p2%

S th d S th

Oceania<1%

East Asia3%

Sub-Saharan Africa64%N h Af i d

South and South-East Asia

18%

64%North Africa and Middle East

1%

Source: UNAIDS, AIDS Epidemic Update 2004.

Changes in Life Expectancy, 1950 - 2000

65

55

60

Botswana

Uganda

45

50South Africa

Uga da

Zambia

40

45Zimbabwe

351950 1960 1970 1980 1990 2000

Source: United Nations Population Division, 1998

AIDS’ Toll on Population Structure, Botswana

Population Structure in 2020 (Projected)Thousands

Age80+

Males Females

80+75706560555550454035303025201510

150 100 50 0 50 100 150

With AIDS Without AIDS

50

With AIDS Without AIDS

Source: U.S. Census Bureau demographic estimates and projections, 2004.

P t f A i lt l L b F L t t HIV/AIDS 1985 2020

AIDS’ Effect on African Agriculture

26Namibia

Percent of Agricultural Labor Force Lost to HIV/AIDS, 1985-2020 (Projected)

23

23

Botswana

Zimbabwe

20

20

Mozambique

South Africa

17

14

Kenya

Malawi

14

13

Uganda

Tanzania

Source: Food and Agriculture Organization (FAO), “AIDS—A Threat to Rural Africa: Fact Sheet” (www.fao.org/focus/e/aids/aids6-e.htm).

HIV destroys immune defenses against TB

TuberculosisTuberculosis

HIVHIV

HIV Pathophysiology Life CycleHIV Pathophysiology - Life Cycle

HIVHIV

CD4

CD4 cell

HIVHIV

HIV Pathophysiology Life CycleHIV Pathophysiology - Life Cycle

CD4 Binding

Co-receptor

d g

CD4

p(CCR5 or CXCR4)

HIVHIV

HIV Pathophysiology Life CycleHIV Pathophysiology - Life Cycle

Fusion

HIVHIV

HIV Pathophysiology Life CycleHIV Pathophysiology - Life Cycle

Virion entryVirion entry

HIVHIV

HIV Pathophysiology Life CycleHIV Pathophysiology - Life Cycle

HIVHIV

HIV Pathophysiology Life CycleHIV Pathophysiology - Life Cycle

Reverse transcription

HIV DNA

HIVHIV

HIV Pathophysiology Life CycleHIV Pathophysiology - Life Cycle

Translocation to nucleus

HIVHIV

HIV Pathophysiology Life CycleHIV Pathophysiology - Life Cycle

Integrationg

HIVHIV

HIV Pathophysiology Life CycleHIV Pathophysiology - Life Cycle

Transcription / Translationof HIV mRNA / polyprotein/ p yp

HIVHIV

HIV Pathophysiology Life CycleHIV Pathophysiology - Life Cycle

Protease processingand viral assembly

HIV infection

HIV attacks CD4 cells, the generals of the immune system’s army

HIV inserts itself into our genes

HIV creates many different strainsHIV creates many different strains

CD4 cell

HIV infection

Viral loadViral load

CD4

time Years Weeks

Relationship Between CD4 count and Viral Load

Slow: <5,000, Fast: 50,000+

WHO Stage 2 and 3:Symptomatic HIV infectionC 4 200 00

WHO Stage 1:Asymptomatic HIV infectionCD4 >500

1000CD4 200 - 500Mild infectionsWeight loss, fatigueTB Thrush

WHO Stage 4AIDSCD4 200

TB, Thrush

CD4Count

CD4 < 200TB, infectionsDeath ~18 months

200

642

Time(years)

642

WHO Stage 1 - Asymptomatic HIV Disease

• Minimal symptoms

• Daily battle between virus and immune system; 10,000,000 new virus copies each dayday

• CD4 count drops gradually• CD4 count drops gradually

WHO Stage 2 - Symptomatic HIV Disease

• Early signs of chronic HIV infection:– Weight loss (3-5 kg)– Skin rashes– Respiratory infections

Herpes zoster (“shingles”)– Herpes zoster (“shingles”)

– CD4 count =350-500

• Normal activity, able to work / attend school

Opportunistic Infections - Côte d’Ivoire, Thailand

Prevalence• Tuberculosis 29-37%• Cryptococcosis 19-38%• Wasting syndrome 8-28%• Wasting syndrome 8-28%• Pneumocystis pneumonia 5-20%• Bacterial pneumonia 4%• Esophageal candidiasis 3-6%• Toxoplasmosis 2-3%

Cryptosporidiosis 1 2%• Cryptosporidiosis 1-2%

Sources: Chariyalertsak, 2001; Tansuphasawadikul, 1999; Lorsina, 2004

Goals of HIV Treatment

• Improve quality of life

• Prevent opportunistic infections

• Prevent progression to AIDS

• Prevent death

d h l k l h d f h• Reduce the likelihood of transmission to others (“Secondary prevention”)

HIV Treatment - Antiretrovirals

Fusion/EntryInhibitors (1) Maturation

Inhibitors (~2008)

ProteaseInhibitors(8)

Inhibitors ( 2008)

(8)

ReverseTranscriptaseInhibitors(11) Integration

Inhibitors (~2008)

HIV Treatment - Antiretrovirals

25

30

20 No therapyMonotherapy

15Dual therapy

5

10

Triple therapy

0

5

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

HIV Treatment - Timing of HIV Treatment

• Therapy is delayed until patients develop WHO Stage 3 or Stage 4 disease

Delaying therapy until Stage 3 or 4 if done carefully does not – Delaying therapy until Stage 3 or 4, if done carefully, does not decrease the likelihood of successful treatment

– Treatment is lifelong and expensive, do not want to start g p ,unnecessarily early

– Delayed therapy minimizes opportunity for side effects

– Delayed therapy minimizes opportunity for drug resistance

CD4 and Mortality - Zimbabwe

1.00

y

CD4 > 200

0.75

0.50Prob

abili

ty

CD4 50-2000.50

0.25

Surv

ival

P

0

0 1 2 3 4

S

CD4 < 50

0 1 2 3 4Time from enrolment to death (years)

Impact of Treatment

Before

AfterAfter

Impact of Treatment

After 9 months

Impact of Treatment

After 9 months

Impact of Treatment

“I was a walking skeleton before I began therapy. I was afraid to gog g py gout of my house and no one would buy things from my shop. Butnow I am fine again… My wife has returned to me and now mychildren are not ashamed to be seen with me. I can work again.”

Impact of Treatment

Impact of Treatment

Begin ART

CD4

Viral load(HIV RNA level)

time Years Weeks

Impact of Treatment - Society

Effective ARVs available

30

35

40Unintentionalinjury

Cancer

20

25

Deaths per 100,000 Population

Heart disease

Suicide

5

10

15

pHIV infection

Homicide

0

5

1982 1984 1986 1988 1990 1992 1994 1996 1998

Chronic liver

disease

Stroke

Diabetes

Source: Centers for Disease Control, 200

YearDiabetes

Current Status of Treatment - December 2004

Source: WHO

Current Status of Treatment - June 2005

Source: WHO

Number of Individuals Receiving ART

Source: WHO

Community-based Care

Care takes place pin the community. Reinforced in the

lclinic.

Basic Water SupplyClinical Indicators

900900101088

‘Viral load’‘Viral load’

CD4 cell countCD4 cell count

800800

700700

10107 7

101066

HIV RNAHIV RNAlevellevel

(cells/(cells/μμL blood)L blood)600600

500500101055

101044

(copies/(copies/mL plasma)mL plasma)

400400

300300

1010

101033

200200

100100

101022

101011

Years Years

WeeksWeeks 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8

00101000

Basic Water SupplyState of the Art Technologies

BD FACSCalibur

CD4-countCD4 countstart treatment < 200 cells/ul

RT PCR

Viral load countViral load countmeasure resistance to treatment

Basic Water SupplyLab Diagnostics in Resource Poor Settings

What is Needed

• Low cost

• Easy to use

• Rapid and Robust

• Portable

S d f• Sensitive and specific

Basic Water SupplyMicrochip Technology for Medicine

Basic Water SupplyMicrochips for Bioseparation

–O –O–Si–(CH2)3–S––O

O O

N N–O

O

–O –O–Si–(CH2)3–S––O

O O

N N–O

O

–O –O–Si–(CH2)3–S––O

O O

N N–O

O

silane linker avidin anti-CD4

Basic Water SupplyMicroelectrodes for Biosensing

3x10-14

K+ Cl-

Na+K+K+

Cl-

Cl-lysis3x10-14

K+ Cl-

Na+K+K+

Cl-

Cl-lysis3 0mole ions

Low

NaK K+Cl-

High

3 0mole ions

Low

NaK K+Cl-

Highoconductance

gconductance

oconductance

gconductance

(ohm

-1)

0.0015

0.0020

due

to C

ell L

ysis

(

0.0005

0.0010

ucta

nce

Cha

nge

d

-0.0005

0.0000

MSE Lunch and Learn, Oct 16, 2008Captured Cells on Chip by Optical Microscopy

0 2000 4000 6000 8000 10000 12000

Con

du

-0.0015

-0.0010

Basic Water SupplyClinical Validation of the Microchip

S iti itTest Positive

N = 49R2 = 0.86

N = 49R2 = 0.86

Sensitivity =

Specificity =

Total PositiveTest NegativeTotal Negativey = x

y = 1.1x

y = x

y = 1.1x

Total Negative

SpecificitySensitivityCD4 Counts(cells/μL)y

0.970.90< 350

1.00.86< 200

(ce s/μ )

0.940.97< 500

Basic Water SupplyCommercial Development