Background: Hydrogen peroxide-producing (H₂0₂⁺) Lactobacillus is a key regulator of the vaginal ecosystem and may decrease HIV-1 replication through direct effects as well as by suppression of pathogenic bacteria. We evaluated the effects of H₂0₂⁺ Lactobacillus on cervicovaginal lavage (CVL) HIV-1 RNA concentrations over time, with the hypothesis that acquisition of H₂0₂⁺ Lactobacillus would result in a decrease in CVL HIV RNA.

Methods:  For this prospective, observational cohort study, 57 HIV-1-infected women from Seattle, Washington (n = 38) and Rochester, N ew York (n = 19) contributed 390 visits (median 6, range 1 to 15). Data collection was completed on November 30, 2007. Study visits occurred every 3 to 4 months and included collection of plasma (lower limit of quantitation (LLQ) 30 copies/mL) and CVL (LLQ 1500 copies/mL) samples for HIV RNA quantitation by an independently validated real-time polymerase chain reaction (PCR) assay, and vaginal cultures to identify H₂0₂⁺ Lactobacillus. Longitudinal analyses used linear regression with generalized estimating equations to examine the change in log-transformed CVL HIV RNA between 2 consecutive visits for the same subject, as a function of change in H₂0₂⁺ Lactobacillus colonization, with adjustment for plasma HIV RNA log₁₀ copies/mL and ART.

Results:  Of 57 participants, 31 (54%) were on ART and 22 (39%) had undetectable plasma HIV RNA <30 copies/mL at study entry. The 390 study visits yielded 270 visit pairs with complete data for this longitudinal analysis. HIV RNA was detectable in CVL at 47 (17%) of visits, and was highly associated with plasma HIV RNA (P< .001) but not ART (p <0.78). H₂0₂⁺ Lactobacillus colonization appeared to be dynamic: 121 (47%) of visit pairs had stable colonization between visits, 39 (15%) acquired and 36 (14%) lost H₂0₂⁺ Lactobacillus, and 62 (24%) showed no evidence of H₂0₂⁺ Lactobacillus at either visit. Acquisition of H₂0₂⁺ Lactobacillus resulted in a 0.7 log₁₀ decrease in CVL HIV RNA (p = 0.015), while loss of H₂0₂⁺ Lactobacillus resulted in a 0.5 log₁₀ increase in CVL HIV RNA (p = 0.029) compared to stable colonization after adjustment for change in plasma HIV RNA and ART status.

Conclusions:  These prospective, longitudinal data demonstrate that acquisition of H₂0₂⁺ Lactobacillus is associated with a significant reduction in vaginal HIV load, while loss of H₂0₂⁺ Lactobacillus results in an increase in vaginal HIV load. These findings may have relevance for secondary prevention strategies.