Gut Microbiota Linked to Sexual Preference and HIV Infection

Abstract

The precise effects of HIV-1 on the gut microbiome are unclear. Initial cross-sectional studies provided contradictory associations between microbial richness and HIV serostatus and suggested shifts from Bacteroides to Prevotella predominance following HIV-1 infection, which have not been found in animal models or in studies matched for HIV-1 transmission groups. In two independent cohorts of HIV-1-infected subjects and HIV-1-negative controls in Barcelona (n = 156) and Stockholm (n = 84), men who have sex with men (MSM) predominantly belonged to the Prevotella-rich enterotype whereas most non-MSM subjects were enriched in Bacteroides, independently of HIV-1 status, and with only a limited contribution of diet effects. Moreover, MSM had a significantly richer and more diverse fecal microbiota than non-MSM individuals. After stratifying for sexual orientation, there was no solid evidence of an HIV-specific dysbiosis. However, HIV-1 infection remained consistently associated with reduced bacterial richness, the lowest bacterial richness being observed in subjects with a virological-immune discordant response to antiretroviral therapy. Our findings indicate that HIV gut microbiome studies must control for HIV risk factors and suggest interventions on gut bacterial richness as possible novel avenues to improve HIV-1-associated immune dysfunction.

Keywords: 16S rDNA; Bacteroides; HIV-1; Microbiome; Microbiota; Prevotella.

Fig. 1

Both HIV transmission group and HIV-1 infection are linked to the human fecal microbiome richness and diversity. a) The highest richness and diversity in human fecal microbiota were observed in men who have sex with men (MSM). There were no differences between heterosexual subjects (HTS) and people who acquired HIV-1 infection through intravenous drug use (PWID). Kruskal–Wallis p-values in a were adjusted for multiple comparisons using the Benjamini–Hochberg method. b) HIV-1 infection was associated with significant reductions in fecal human microbiome richness after stratifying for sexual preference. Comparisons were made with the Wilcoxon rank sum test with continuity correction. All alpha diversity findings were consistent in Barcelona (test cohort, month 0) (BCN0) and Stockhom (STK). Identical results were found in BCN at month 1 (Supplementary Fig. 2) and when using an independent sequence analysis pipeline (Supplementary Fig. 14). Note: “Simpson” refers to 1-Simpson index. The remaining ecological index names are self-explanatory. *p < 0.1, **p < 0.05, ***p < 0.001.

Fig. 2

Alpha diversity by HIV-1 phenotype. HIV-1-infected subjects with an immune discordant phenotype (i.e. those who do not recover CD4 + counts > 300 cells/mm³ despite at least 2 years of effective antiretroviral therapy) had the lowest microbiome richness of all HIV-1 phenotypes. Individuals with an immune concordant phenotype (i.e., those achieving CD4 + count reconstitution > 500 cells/mm³ on antiretroviral therapy) also had lower microbiome richness than HIV-1-negative individuals, but not as low as immune discordant subjects. “Simpson” refers to 1-Simpson index. The remaining ecological index names are self-explanatory. Comparisons were done using a Kruskal–Wallis test including post-hoc pairwise analyses. Benjamini–Hochberg-adjusted p-values are shown at the top of each index; for post-hoc pairwise comparisons: *p < 0.1, **p < 0.05, ***p < 0.001.

Fig. 3

Spearman correlation by genus abundance. Only significant values (Holm's-corrected p < 0.05) are shown. The plot confirms previous observations, i.e.: a) strong positive correlations between Bacteroides, Parabacteroides, Barnesiella, Alistipes and Odoribacter, b) strong positive correlations between Prevotella, Alloprevotella, Mitsuokella and Intestinimonas, among others, and c, strong inverse correlations between the groups including Prevotella and Bacteroides.

Fig. 4

The bacterial genus composition of the human fecal microbiome is mainly linked to HIV transmission group. a) The bacterial genus composition of the fecal microbiota in the Barcelona test dataset (BCN0) was largely determined by HIV transmission group, with MSM being enriched in the Prevotella cluster and non-MSM in the Bacteroides cluster. Genera with mean abundance of at least 2% across all samples are represented in colors; those with < 2% abundance are grouped into the category “Others”. Each column represents one individual. A similar plot for the Stockholm cohort is shown in Supplementary Fig. 12. b) Non-metric multidimensional scaling (NMDS) ordination plots of Bray–Curtis distances showing that microbiomes in the BCN0, BCN1 and STK datasets mainly cluster by HIV transmission group (MSM vs. non-MSM) rather than by HIV serostatus. Ellipses include 95% of samples. Similar plots using other distances are shown in Supplementary Figs. 8 to 10. c) Partitioning around medoids (PAM) analysis of the BCN0 dataset showing this population structure in this dataset is better explained by 2 rather than more clusters, with reasonable Silhouette support. This information was used to define the Bacteroides and Prevotella clusters in our study. d) Abundance box plots showing that MSM were enriched in Prevotella and non-MSM (HTS or PWID) were enriched in Bacteroides. Comparisons between MSM and the non-MSM categories were always highly significant (p < 0.001) after adjusting for multiple comparisons using the Benjamini–Hochberg method. Plots of all genera showing significant differences between MSM and non-MSM categories are shown in the Supplementary Figs. 13 to 15.

Fig. 5

Global microbiota classifier by sexual preference group and HIV-1 status. A and C) Relative abundances of 28 gut microbial genera collectively associated with MSM and HIV-1 infection, respectively, are displayed as heatmap of log-abundance z-scores with the direction of association indicated to the left. To avoid confounding by sexual preference, the HIV-1 classifier only includes MSM subjects. The mean contribution of each marker species to the classification is shown to the left (bars correspond to log-odds ratio in logistic regression). Below each heatmap the classification score of the microbial signature from cross-validation is shown as gray scale. HIV-1 status and HIV-1 risk group are color-coded below the first heatmap (see color key). B and D) Cross-validation accuracy of the microbiota classifier is depicted as receiver–operator-characteristic (ROC) curve summarizing mean test predictions made in ten times resampled tenfold cross-validation with the area under the curve (AUC) indicated inside each plot. As shown, there was a strong association between the global microbiome genus composition and sexual orientation, whereas the association with HIV-1 infection was much weaker and of uncertain significance.

Fig. 6

Limited effect of diet on the composition of the microbiome. a) Subjects belonging to the Prevotella cluster and men who had sex with men (MSM) had significantly higher total energy intake. Therefore, all subsequent nutritional analyses were normalized for this factor. b) Main associations between bacterial genera, normalized amounts of nutrients (left) and food portions (right), according to a Dirichlet multinomial regression model. Positive and negative associations are shown in red and blue, respectively. Line thickness is proportional to the strength of the association. c) Of all links identified by the Dirichlet approach, the only significant differences between groups after adjusting for multiple comparisons (Benjamini–Hochberg FDR < 0.1) were increased consumption of meat in the cluster Bacteroides and increased intake of dietary water in MSM. d) Spearman correlations between normalized amounts of nutrients and Bray–Curtis distance to the furthest subject in the opposite cluster. Negative correlations imply increased amounts of nutrient with shorter distance to each cluster. Therefore, values in red and blue represent increased and decreased amounts of nutrients within each cluster, respectively. Although, in general, the direction of the correlations was concordant with previous publications, note the small effect sizes (R² below the color key). None of the comparisons were statistically significant after correction for multiple comparisons (Benjamini–Hochberg FDR < 0.1); Permanova p = 0.20 for overall differences between clusters. e, f) Mean and 95% confidence intervals for the differences between clusters in consumption of nutrients (e) and portions of food (f). Comparisons were significant if the 95 confidence interval did not cross 0 (dashed red line).