H2O2-Producing Lactobacilli Associated With Lower Levels of Vaginal Interleukin-1β, Independent of Bacterial Vaginosis

There has been an association between the presence of hydrogen peroxide (H₂O₂)-producing lactobacilli in the vagina and decreased rates of preterm birth & HIV acquisition. The present study hypothesized that this might be due to the immunomodulatory effects of these species.

The study quantified Concentrations of interleukin (IL)-1β, IL-6, IL-8, secretory leukocyte protease inhibitor, and human β-defensin two from vaginal swabs from 4 groups of women: women with and without bacterial vaginosis (BV) by Nugent score, who were further stratified by detection of H2O2-producing lactobacilli by semiquantitative culture. Further, it employed Ten quantitative polymerase chain reaction assays to characterize the presence and quantity of select Lactobacillus and BV-associated species in each group. The study compared levels of immune markers and bacteria between the four groups using analysis of variance, Kruskal-Wallis, Mann-Whitney U, or χ tests.

The study observed:

The 110 swabs analyzed from the women from 4 groups showed-

         o 26 had a normal Nugent score (BV-), and no H₂O₂-producing lactobacilli (H2O2-)

          o 47 were BV-, H2O2+ 

          o 27 BV+, H2O2-

          o 10 BV+, H2O2+. 

• The groups demonstrated similarity in terms of age, marital status, and reproductive history, but not ethnicity: the BV-, H2O2- group contained more white participants. 
• Women with and without BV showed lower IL-1β in the H2O2+ groups.
• Human β-defensin 2 was lowest in BV+ H2O2- women and highest in BV-, H2O2-. 
• Secretory leukocyte protease inhibitors were lower in women with BV, and it did not differ by the existence of H2O2-producing lactobacilli. 
• Higher quantities of Lactobacillus crispatus showed an association with lower quantities of IL-1β. 
• Detection and quantity of BV-associated species by quantitative polymerase chain reaction showed a significant difference between women with and without BV but not between women with and without H2O2-producing lactobacilli within those groups.

This study shows that the presence of H2O2-producing lactobacilli lowers the levels of some vaginal proinflammatory cytokines, even in women with BV.

Source: Sex Transm Dis. 2015 Jul;42(7):358-63. doi: 10.1097/OLQ.0000000000000298. PMID: 26222747; PMCID: PMC4520248.