Effect of antiretroviral therapy on gut microbiota, immune activation, and inflammatory markers in newly diagnosed HIV patients.

INTRODUCTION: People living with HIV (PLWH) exhibit gut dysbiosis and chronic immune activation. The early dynamics of the gut-immune axis during the transition from diagnosis to viral suppression remain incompletely understood.

METHODS: We characterized fecal microbiota (16S rRNA), bacterial translocation (16S rDNA) and gut barrier integrity (serum intestinal fatty acid-binding protein, I-FABP, level) in newly diagnosed PLWH at baseline (t0) and after six months of suppressive ART (t6), compared to uninfected controls. Systemic inflammation (serum concentrations of interleukins 6 and 10, soluble CD163), and peripheral blood T-cell activation were also analyzed.

RESULTS: Alpha diversity was similar across groups (p>0.05); beta diversity differed significantly between PLWH at t0 and controls (p=0.002). Linear Discriminant Analysis Effect Size (LEfSe) analysis identified an enrichment of short chain fatty acids (SCFA)-producing genera (Alloprevotella, Mitsuokella, Succinivibrio, Megasphaera) in PLWH at t0. PLWH at t0 showed elevated bacterial translocation [16S rDNA, 4281 (4018-4485) vs 2162 (2023-2286) copies/mL, p<0.001], gut barrier damage [I-FABP, 950 (800-1168) vs 767 (574-902) ng/mL, p=0.012], inflammation [IL-6, 4.8 (3.1-8.8) vs 0.8 (0.3-1.3) pg/mL, p<0.001; sCD163, 1173 (872-1417) vs 561 (425-662) ng/mL, p<0.001], and T-cell activation [CD4+CD38+HLA-DR+ (percentage of CD4+ T lymphocytes), 9.7 (2.8-18.5) vs 1.3 (0.3-2.2), p=0.007; CD8+CD38+HLA-DR+ (percentage of CD8+T lymphocytes), 19.0 (12.0-31.1) vs 1.7 (0.6-5.7), p=0.005], compared with controls. Treated PLWH (t6) showed similar alpha and beta diversities of fecal microbiota compared to untreated PLWH (p>0.05 in each case). LEfSe analysis identified an enrichment of Campylobacter and Atopobium at t6. ART mitigates systemic inflammation [t6 vs t0, IL-6, 3.3 (1.7-4.0) vs 4.8 (3.1-8.8) pg/mL, p=0.022; sCD163, 795 (549-915) vs 1173 (872-1417) ng/mL, p<0.001], and T-cell activation [t6 vs t0, CD4+CD38+HLA-DR+ (percentage of CD4+ T lymphocytes), 2.7 (1.7-6.3) vs 9.7 (2.8-18.5), p=0.047; CD8+CD38+HLA-DR+ (percentage of CD8+T lymphocytes), 6.5 (3.7-15.5) vs 19.0 (12.0-31.1), p=0.086].

CONCLUSIONS: Untreated PLWH show a dysbiotic signature, characterized by enrichment of SCFA-producers. Compared to controls, the fecal microbiota of PLWH after 6 months of ART (t6) continued to show differences characterized by a predominance of Alloprevotella and Succinivibrio, among others, and continued elevations in intestinal injury, bacterial translocation, and inflammatory/immune activation markers, underscoring the incomplete normalization of gut-immune homeostasis.