Gut microbiota from high-risk men who have sex with men drive immune activation in gnotobiotic mice and in vitro HIV infection

Men who have sex with men (MSM) have differences in immune activation and gut microbiome composition compared with men who have sex with women (MSW), even in the absence of HIV infection. Gut microbiome differences associated with HIV itself when controlling for MSM, as assessed by 16S rRNA sequencing, are relatively subtle. Understanding whether gut microbiome composition impacts immune activation in HIV-negative and HIV-positive MSM has important implications since immune activation has been associated with HIV acquisition risk and disease progression. To investigate the effects of MSM and HIV-associated gut microbiota on immune activation, we transplanted feces from HIV-negative MSW, HIV-negative MSM, and HIV-positive untreated MSM to gnotobiotic mice. Following transplant, 16S rRNA gene sequencing determined that the microbiomes of MSM and MSW maintained distinct compositions in mice and that specific microbial differences between MSM and MSW were replicated. Immunologically, HIV-negative MSM donors had higher frequencies of blood CD38+ HLADR+ and CD103+ T cells and their fecal recipients had higher frequencies of gut CD69+ and CD103+ T cells, compared with HIV-negative MSW donors and recipients, respectively. Significant microbiome differences were not detected between HIV-negative and HIV-positive MSM in this small donor cohort, and immune differences between their recipients were trending but not statistically significant. A larger donor cohort may therefore be needed to detect immune-modulating microbes associated with HIV. To investigate whether our findings in mice could have implications for HIV replication, we infected primary human lamina propria cells stimulated with isolated fecal microbiota, and found that microbiota from MSM stimulated higher frequencies of HIV-infected cells than microbiota from MSW. Finally, we identified several microbes that correlated with immune readouts in both fecal recipients and donors, and with in vitro HIV infection, which suggests a role for gut microbiota in immune activation and potentially HIV acquisition in MSM.

男男性行为者（Men who have sex with men, MSM）与与女性发生性行为的男性（Men who have sex with women, MSW）相比，即使未感染HIV，二者的免疫激活状态与肠道微生物组组成亦存在差异。即便在控制MSM群体混杂效应后，与HIV感染本身相关的肠道微生物组差异，经16S rRNA测序评估后相对细微。明确肠道微生物组组成是否会影响HIV阴性与HIV阳性MSM的免疫激活，具有重要意义——因免疫激活与HIV感染风险及疾病进展密切相关。为探究MSM相关及HIV相关肠道微生物群对免疫激活的影响，本研究将HIV阴性MSW、HIV阴性MSM以及未经治疗的HIV阳性MSM的粪便移植至悉生小鼠体内。移植后通过16S rRNA基因测序证实，MSM与MSW的微生物组在小鼠体内仍维持各自独特的组成，且二者间的特异性微生物差异得以重现。免疫学层面，与HIV阴性MSW供体及其受体小鼠相比，HIV阴性MSM供体的血液中CD38+ HLADR+与CD103+ T细胞频率更高，其粪便受体小鼠的肠道内CD69+与CD103+ T细胞频率亦显著升高。在本研究的小型供体队列中，未检测到HIV阴性与HIV阳性MSM间存在显著微生物组差异，二者受体小鼠的免疫差异虽呈趋势性，但未达到统计学显著性。因此，若要检测与HIV相关的免疫调节微生物，或需更大规模的供体队列。为探究本研究在小鼠中的发现是否对HIV复制具有参考价值，我们用分离得到的粪便微生物群刺激原代人黏膜固有层细胞并进行感染，结果发现MSM来源的微生物群诱导的HIV感染细胞频率高于MSW来源的微生物群。最后，本研究鉴定出数种同时与粪便受体小鼠及供体的免疫检测指标相关、且与体外HIV感染相关的微生物，这提示肠道微生物群在MSM的免疫激活及潜在HIV感染风险中发挥着一定作用。