Altered Immunity and Microbial Dysbiosis in Aged Individuals With Long-Term Controlled HIV Infection

Abstract

The introduction of highly active antiretroviral therapy (HAART) resulted in a significant increase in life expectancy for HIV patients. Indeed, in 2015, 45% of the HIV+ individuals in the United States were ≥55 years of age. Despite improvements in diagnosis and treatment of HIV infection, geriatric HIV+ patients suffer from higher incidence of comorbidities compared to age-matched HIV- individuals. Both chronic inflammation and dysbiosis of the gut microbiome are believed to be major contributors to this phenomenon, however carefully controlled studies investigating the impact of long-term (>10 years) controlled HIV (LTC-HIV) infection are lacking. To address this question, we profiled circulating immune cells, immune mediators, and the gut microbiome from elderly (≥55 years old) LTC-HIV+ and HIV- gay men living in the Palm Springs area. LTC-HIV+ individuals had lower frequency of circulating monocytes and CD4+ T-cells, and increased frequency CD8+ T-cells. Moreover, levels of systemic INFγ and several growth factors were increased while levels of IL-2 and several chemokines were reduced. Upon stimulation, immune cells from LTC-HIV+ individuals produced higher levels of pro-inflammatory cytokines. Last but not least, the gut microbiome of LTC-HIV+ individuals was enriched in bacterial taxa typically found in the oral cavity suggestive of loss of compartmentalization, while levels of beneficial butyrate producing taxa were reduced. Additionally, prevalence of Prevotella negatively correlated with CD4+ T-cells numbers in LTC-HIV+ individuals. These results indicate that despite long-term adherence and undetectable viral loads, LTC-HIV infection results in significant shifts in immune cell frequencies and gut microbial communities.

Keywords: HAART; HIV; aging; dysbiosis; inflammation.

Figure 1

LTC-HIV results in alterations in T but not B cell subsets. (A) Numbers of circulating CD3+ T cells (B) CD20+ B cells (C) CD3+CD4+ helper T cells, and (D) CD3+CD8+ cytotoxic T cells. (E,F) Relative frequencies of CD4+ (E) and CD8+ (F) T cell subsets (E). Each point represents a study subject. Horizontal bars and whiskers indicate the mean ± SEM. Significance was determined using an unpaired t-test. ^*p < 0.05, ^**p < 0.01, ^****p < 0.0001.

Figure 2

A reduction in circulating monocytes and increase in NK cell activation seen with LTC-HIV infection. (A) Number of total circulating dendritic cells (DC) (B) myeloid DCs, and (C) plasmacytoid (DC). (D) Number of total circulating CD14+ monocytes and (E) relative abundance of CD16- Classical monocytes, and (F) CD16+ non-classical monocytes. (G) Number of total circulating CD56+ natural killer (NK) cells and (H) relative frequency of CD57+ NK cells and (I) granzymeB+CD16+ cytotoxic NK cells. Horizontal bar and whisker indicate the mean ± SEM. Significance was determined using an unpaired t-test. ^*p < 0.05, ^**p < 0.01.

Figure 3

Change in circulating and production of immune mediators following stimulation. (A) Serum level of immune mediators measured using a multiplexed ELISA assay. Horizontal bar and whiskers indicate the mean ± SEM. Significance was determined using an unpaired t-test. ^*p < 0.05, ^**p < 0.01, ^***p < 0.001 (B) Principal component analysis of immune mediators released by PBMC's from HIV- and LTC-HIV+ individuals in the absence and presence of PMA/ionomycin. (C) Heat map of differentially abundant immune mediators produced by PBMCs upon stimulation (all immune mediators statistically significant via 1-way ANOVA, Significant Tukeys post-hoc comparison of stimulated samples vs. corresponding baseline samples) #p < 0.05, ##p < 0.01, ###p < 0.001, ####p < 0.0001. Unpaired T-tests of absolute change followed by Welch's correction [Stimulation—baseline] in immune mediator production ^*p < 0.05, ^**p < 0.01, ^***p < 0.001.

Figure 4

LTC-HIV infection alters PBMC transcriptional response to PMA/Ionomycin. (A) Principal component analysis of unstimulated and PMA/ionomycin stimulated PBMCs from HIV- and LTC-HIV and Venn diagram of stimulation DEGs showing unique and common protein coding genes. (B) Network visualization using Cytoscape of functional enrichment output of DEGs detected in PBMC from LTC-HIV+ and HIV- subjects following PMA stimulation obtained using Metascape. The size of node represents the number of DEGs associated with each gene ontology (GO) term and the pie chart filling represents relative proportion of each group's DEGs that enriched to that GO term. Heat maps of select DEGs for Common (C), HIV- (D), and LTC-HIV+ (E).

Figure 5

Taxonomic differences in the gut microbiome of LTC-HIV (A) Stack bar plot illustrating the abundance of bacterial orders and phyla in HIV- and LTC-HIV+ individuals. (B) Differentially abundant bacterial taxa between LTC-HIV+/HIV- determined using LEfSE (Log₁₀ LDA score >2) at the Phyla, Order and Genus level. (C) Differentially abundant genera between LTC-HIV+ High CD4+ and LTC-HIV+ Low CD4+ individuals (Log₁₀ LDA score > 2). (D) Spearman rank correlation between CD4+ T cell abundance and relative abundance of Prevotella in LTC-HIV+ individuals. (E) Spearman rank correlation between CD4+ T cell abundance and relative abundance of Prevotella in HIV- individuals.