Bacterial vaginosis increases the risk of female-to-male HIV-1 transmission: a prospective cohort analysis among African couples

Craig R. Cohen, Jairam R. Lingappa, Jared M. Baeten, Musa O. Ngayo, Carol A. Spiegel, Ting Hong, Deborah Donnell, Connie Celum, Saidi Kapiga, Sinead Delany, Elizabeth A. Bukusi, for the Partners in Prevention HSV/HIV Transmission Study Team

Department of Obstetrics, Gynecology & Reproductive

Sciences

School of Medicine

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• 33 million HIV-infected persons

– 60% in sub-Saharan Africa• Women account for the majority of cases

• Antiretroviral therapy associated with 96% reduction in HIV transmission

– Only 37% qualifying for ART receive ART (UNAIDS, 2010)

• New strategies to reduce HIV transmission required

Background

Department of Obstetrics, Gynecology & Reproductive

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Background• Bacterial vaginosis (BV)

– Common disorder 30% - 55% in sub-Saharan Africa

– Polymicrobial• Decrease in lactobacilli

– Associated with 60% increase Male-to-Female HIV transmission (Atashili, 2008)

– Associated with increase genital tract HIV RNA (Coleman, 2007)

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Normal Flora

Intermediate Flora

Bacterial Vaginosis

Department of Obstetrics, Gynecology & Reproductive

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Hypothesis

• HIV-1-infected women with BV have an increased risk of female-to-male HIV transmission than women with normal vaginal flora

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♀ HIV+/ve ♂

Department of Obstetrics, Gynecology & Reproductive

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Methods

• 2,236 south and East African HIV-serodiscordant couples

– HIV+/ve woman• CD4 ≥ 250 cells/mm3, HSV-2 +/ve, no ART

(enrollment)

• Vaginal Gram stain enrollment, & every 3-months

• Plasma VL: enrollment, 3, 6, 12 months, study exit

• Genital VL: 6 month visit

– HIV-/ve man• HIV testing every 3-months

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Department of Obstetrics, Gynecology & Reproductive

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School of Medicine

Laboratory Methods

• Gram stain per Nugent’s criteria

– Normal vaginal flora: 0 – 4

– Intermediate vaginal flora: 5 – 6

– Bacterial vaginosis: 7 – 10

• HIV testing:

– HIV genotyping (env & gag) to confirm transmission linkage (Campbell, 2011)

• HIV RNA testing– Lower limit detection = 240 copies per mL/swab

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Department of Obstetrics, Gynecology & Reproductive

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Analysis Methods

• Primary outcome– Genitally-linked HIV transmission

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-6 Months -3 Months Time 0

HIV-1-seroconversion

Vaginal flora

Sensitivity Analysis

Primary Analysis

Department of Obstetrics, Gynecology & Reproductive

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Enrollment characteristics

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HIV infected female

HIV uninfected male

Age, years, mean, IQR 30 (25-35) 35 (30-42)

Education, years, median, IQR

8 (6-10) 9 (7-12)

Male circumcised N/A 1228 (54.9%)

East vs. southern Africa 1452 (64.9%)

Married 1647 (73.7%)

Years lived together, median, IQR

5 (2-9)

Unprotected sex with partner past month

682 (30.5%)

Plasma HIV, log10

copies/mL, median, IQR3.95 (3.24-4.53) N/A

CD4 count, cells/mm3 median, IQR

481 (354-663) N/A

Department of Obstetrics, Gynecology & Reproductive

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School of Medicine

Vaginal flora at enrollment and follow-up

Norm

al flo

ra

Inte

rmed

iate

flora

Bacte

rial v

agino

sis0%

5%

10%

15%

20%

25%

30%

35%

40%

45% • 14,791 female visits

– 10,472 (70.8%) with vaginal Gram stain data

– Vaginal flora across quarterly visits (Median)• BV: 34.9%

• Intermediate flora: 22.8%

• Normal flora: 42.8%

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Department of Obstetrics, Gynecology & Reproductive

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Incidence of HIV-1 transmission to men, by the vaginal flora category of women

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HIV cases HIV incidence/100 person-years

All seroconversions 57 1.72

Seroconversions with missing BV status

7 -

Seroconversions with BV status 50 1.71

Normal vaginal flora 9 0.76

Abnormal vaginal flora 41 2.35

Intermediate vaginal flora 10 1.48

BV 31 2.91

Department of Obstetrics, Gynecology & Reproductive

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School of Medicine

Risk of female-to-male HIV-1 transmission among men whose female partners had BV vs. normal vaginal flora

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Model HR Adjusted HR*

Primary analysis

Pre-visit BV 3.62 (1.74-7.52) 3.06 (1.35-6.95)

Sensitivity Analyses

Current visit BV 5.30 (2.21-12.74) 3.97 (1.67-9.43)

More severe BV status 7.19 (2.59-19.94) 6.98 (2.12-23.0)

*Fixed covariates: age, geographic region, partner HSV-2 status, circumcision, randomization assignment and STD; Time-dependent covariates: pregnancy, hormonal contraception, plasma HIV-1 RNA, unprotected sex act with study partner, CD4 count, outside partners, number of sex act with study partner, and genital ulcer disease.

Department of Obstetrics, Gynecology & Reproductive

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Log10 HIV RNA concentration in plasma and female genital secretions compared by vaginal flora category Vaginal Flora Log10 HIV

Mean ± SD

P-Value vs. normal

vaginal flora

P-Value* vs. normal

vaginal flora

Genital HIV RNA

Normal vaginal flora 3.04 ± 0.99 N/A N/A

Intermediate vaginal flora 3.25 ± 1.01 0.0035 0.058

BV 3.23 ± 0.99 0.0023 0.095

Plasma HIV RNA

Normal vaginal flora 3.81 ± 1.00 N/A N/A

Intermediate vaginal flora 3.96 ± 1.07 0.037 N/A

BV 3.99 ± 1.07 0.0056 N/A

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*After controlling for plasma HIV RNA

Department of Obstetrics, Gynecology & Reproductive

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Hypotheses to explain 3-fold increase risk of ♀ to ♂ HIV transmission

1. BV increases female genital concentration of HIV RNA– Modest increase (0.2 log10) in genital HIV RNA

concentration

2. BV increases proportion of “infectious” HIV– Lactobacilli are virucidal against HIV (Klebanoff, 1999

3. BV indirectly increases HIV susceptibility in male partner– Female & male genital microbiota are shared (Bukusi,

2011; Gray, 2009)– Bacteria may activate Langerhans cells and CD4+ T-cells

(Donoval, 2006)

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Department of Obstetrics, Gynecology & Reproductive

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School of Medicine

Suggested Future Directions

• Exploit human microbiome to promote normal vaginal flora

– Frequent presumptive treatment (McClelland, 2008)

– Probiotic lactobacilli (Hemmerling, 2011)

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*Association of abnormal vaginal flora with male-to-female HIV-1 transmission among HIV-1 serodiscordant couples in sub-Saharan Africa. M.O. Ngayo, TUPE188

Department of Obstetrics, Gynecology & Reproductive

Sciences

School of Medicine

Acknowledgements• University of

Washington– Partners in

Prevention HSV/HIV Coordination Center

– Central Laboratories

• Study sites and Principal Investigators

• Study participants

• Bill & Melinda Gates Foundation

• Kenya Medical Research Institute – Center for

Microbiology Laboratory

– Director, KEMRI

• DF/Net Research

• University of Witwatersrand– Contract Laboratory

Services

• National Institutes of Health

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