It relies on amplification and sequencing of the marker genes (such as the 16S ribosomal RNA (rRNA) gene) and has greatly increased appreciation for the complexity, in even seemingly simple microbial consortia, CP-673451 including the genital microbiota. Researchers have begun to assert that the human microbiome should be considered in vaccine research [36]. Data are mounting that the gut microbiota plays a role in modulating immune response both locally and systemically [37], [38] and [39]. Among

participants in clinical trials testing the efficacy of oral vaccines against polio, rotavirus and cholera, there were disparities in host immune response outcomes based on geography (developing vs. developed countries) [36]. It is hypothesized that the gut microbiota may have contributed to the AZD8055 datasheet diverse vaccine efficacy. Ferreira et al. [36] reviewed several studies of probiotic strains which were used for a short time frame, on the order of 1–5 weeks, and concluded that probiotics boosted antibody responses to oral vaccines against rotavirus [40] and [41], Salmonella [42], poliovirus [43] and Vibrio cholera

[44], [45] and [46]. Among infants who were parenterally administered vaccines against diphtheria, tetanus, Haemophilus influenzae type B, and hepatitis B, probiotics proved beneficial in improving immune responses [47], [48] and [49]. While these findings are exciting, the mechanism of interaction between the gut microbiota and host responses remains largely unknown. An even more unfamiliar territory is the role of the penile or vaginal microbiota in the context of STI vaccinations. Vaginal bacterial communities are thought to play an important role in preventing colonization by pathogenic organisms, including those responsible

for sexually transmitted infections (STIs), vulvovaginal because candidiasis, and urinary tract infections [50] and [51]. Fundamental differences exist in the microbial diversity of vaginal communities present among reproductive-age women [52] and [53]. Molecular studies based on the 16S rRNA gene have identified over 265 microbial species in the vagina [52] and [54]. Composition and relative abundance of these species varies dramatically between women and rapid fluctuations between Lactobacillus-dominated and non-dominated states are common [52] and [54]. Lactobacillus spp. play a critical role in maintaining a healthy vagina. It is postulated that lactobacilli restrict the growth of non-indigenous organisms by acidifying the milieu and producing bacteriocins and lactic acid [55]. There are five consistent groupings, referred to by Ravel et al. as community state types (CSTs), into which the vaginal microbiota can be categorized (Fig. 2) [52].