Comparison of the vaginal environment in rhesus and cynomolgus macaques pre- and post-lactobacillus colonization

Microbiome Studies in Non-human Primates

Purpose of Review

Observations of differing bacterial, intestinal microbiomes in people living with HIV have propelled interest in contributions of the microbiome to HIV disease. Non-human primate (NHP) models of HIV infection provide a controlled setting for assessing contributions of the microbiome by standardizing environmental confounders. We provide an overview of the findings of microbiome contributions to aspects of HIV disease derived from these animal models.

Recent Findings

Observations of differing bacterial, intestinal microbiomes are inconsistently observed in the NHP model following SIV infection. Differences in lentiviral susceptibility and vaccine efficacy have been attributed to variations in the intestinal microbiome; however, by-and-large, these differences have not been experimentally assessed.

Summary

Although compelling associations exist, clearly defined contributions of the microbiome to HIV and SIV disease are lacking. The empirical use of comprehensive multi-omics assessments and longitudinal and interventional study designs in NHP models is necessary to define this contribution more clearly.

Oral-fecal mycobiome in wild and captive cynomolgus macaques (Macaca fascicularis)

Cynomolgus macaque (Macaca fascicularis) is currently a common animal model for biomedical research. The National Primate Research Center of Thailand, Chulalongkorn University (NPRCT-CU) translocated wild-borne macaques to reared colony for research purposes. At present, no studies focus on fungal microbiome (Mycobiome) of this macaque. The functional roles of mycobiome and fungal pathogens have not been elucidated. Thus, this study aimed to investigate and compare oral and fecal mycobiome between wild and captive macaques by using high-throughput sequencing on internal transcribed spacer 2 (ITS2) rDNA. The results showed that the mycobiome of wild macaque has greater alpha diversity. The fecal mycobiome has more limited alpha diversity than those in oral cavity. The community is mainly dominated by saprophytic yeast in Kasachstania genus which is related to aiding metabolic function in gut. The oral microbiome of most captive macaques presented the Cutaneotrichosporon suggesting the fungal transmission through skin-oral contact within the colony. The potential pathogens that would cause harmful transmission in reared colonies were not found in either group of macaques but the pathogen prevention and animal care is still important to be concerned. In conclusion, the results of gut mycobiome analysis in Thai cynomolgus macaques provide us with the basic information of oral and fecal fungi and for monitoring macaque's health status for animal care of research use.

Anti-HIV-1 Activity of Lactic Acid in Human Cervicovaginal Fluid

Women of reproductive age with a Lactobacillus-dominated vaginal microbiota have a reduced risk of acquiring and transmitting HIV and a vaginal pH of ~4 due to the presence of ~1% (wt/vol) lactic acid. While lactic acid has potent HIV virucidal activity in vitro, whether lactic acid present in the vaginal lumen inactivates HIV has not been investigated. Here we evaluated the anti-HIV-1 activity of native, minimally diluted cervicovaginal fluid obtained from women of reproductive age (n = 20) with vaginal microbiota dominated by Lactobacillus spp. Inhibition of HIVBa-L was significantly associated with the protonated form of lactic acid in cervicovaginal fluid. The HIVBa-L inhibitory activity observed in the <3-kDa acidic filtrate was similar to that of the corresponding untreated native cervicovaginal fluid as well as that of clarified neat cervicovaginal fluid subjected to protease digestion. These ex vivo studies indicate that protonated lactic acid is a major anti-HIV-1 metabolite present in acidic cervicovaginal fluid, suggesting a potential role in reducing HIV transmission by inactivating virus introduced or shed into the cervicovaginal lumen.IMPORTANCE The Lactobacillus-dominated vaginal microbiota is associated with a reduced risk of acquiring and transmitting HIV and other sexually transmitted infections (STIs). Lactic acid is a major organic acid metabolite produced by lactobacilli that acidifies the vagina and has been reported to have inhibitory activity in vitro against bacterial, protozoan, and viral STIs, including HIV infections. However, the anti-HIV properties of lactic acid in native vaginal lumen fluids of women colonized with Lactobacillus spp. have not yet been established. Our study, using native cervicovaginal fluid from women, found that potent and irreversible anti-HIV-1 activity is significantly associated with the concentration of the protonated (acidic, uncharged) form of lactic acid. This work advances our understanding of the mechanisms by which vaginal microbiota modulate HIV susceptibility and could lead to novel strategies to prevent women from acquiring HIV or transmitting the virus during vaginal intercourse and vaginal birth.

Protection Efficacy of C5A Against Vaginal and Rectal HIV Challenges in Humanized Mice

Introduction:

In the absence of a vaccine, there is an urgent need for the identification of effective agents that prevent HIV transmission in uninfected individuals. Non-vaccine Biomedical Prevention (nBP) methods, such as topical or systemic pre-exposure prophylaxis (PrEP), are promising strategies to slow down the spread of AIDS.

Methods:

In this study, we investigated the microbicidal efficacy of the viral membrane-disrupting amphipathic SWLRDIWDWICEVLSDFK peptide called C5A. We chose the bone marrow/liver/thymus (BLT) humanized mouse model as vaginal and rectal HIV transmission models.

Results:

We found that the topical administration of C5A offers complete protection against vaginal and rectal HIV challenges in humanized mice. After demonstrating that C5A blocks genital HIV transmission in humanized mice, we examined the molecular requirements for its microbicidal property. We found that the removal of four amino acids on either end of C5A does not diminish its microbicidal efficacy. However, the removal of four amino acids at both the ends, abolishes its capacity to prevent vaginal or rectal HIV transmission, suggesting that the length of the peptide is a critical parameter for the microbicidal activity of C5A. Moreover, we demonstrated that the amphipathicity of the helical peptide as well as its hydrophobic surface represents key factors for the microbicidal activity of C5A in humanized mice.

Conclusion:

With its noncellular cytotoxic activity, its property of neutralizing both HSV and HIV, and its unique mechanism of action that disrupts the stability of the viral membrane, C5A represents an attractive multipurpose microbicidal candidate to be combined with other anti-HIV agents including antiretrovirals.