HIV infection does not alter interferon α/β receptor 2 expression on mucosal immune cells

Comparative analysis of human gut- and blood-derived mononuclear cells: contrasts in function and phenotype

Introduction

Alterations in the gut immune system have been implicated in various diseases.The challenge of obtaining gut tissues from healthy individuals, commonly performed via surgical explants, has limited the number of studies describing the phenotype and function of gut-derived immune cells in health.

Methods

Here, by means of recto-sigmoid colon biopsies obtained during routine care (colon cancer screening in healthy adults), the phenotype and function of immune cells present in the gut were described and compared to those found in blood.

Results

The proportion of CD4+, CD8+, MAIT, γδ+ T, and NK cells phenotype, expression of integrins, and ability to produce cytokine in response to stimulation with PMA and ionomycin. T cells in the gut were found to predominantly have a memory phenotype as compared to T cells in blood where a naïve phenotype predominates. Recto-sigmoid mononuclear cells also had higher PD-1 and Ki67 expression. Furthermore, integrin expression and cytokine production varied by cell type and location in blood vs. gut.

Discussion

These findings demonstrate the differences in functionality of these cells when compared to their blood counterparts and validate previous studies on phenotype within gut-derived immune cells in humans (where cells have been obtained through surgical means). This study suggests that recto-sigmoid biopsies collected during colonoscopy can be a reliable yet more accessible sampling method for follow up of alterations of gut derived immune cells in clinical settings.

Qualitative Differences Between the IFNα subtypes and IFNβ Influence Chronic Mucosal HIV-1 Pathogenesis

The Type I Interferons (IFN-Is) are innate antiviral cytokines that include 12 different IFNα subtypes and IFNβ that signal through the IFN-I receptor (IFNAR), inducing hundreds of IFN-stimulated genes (ISGs) that comprise the 'interferome'. Quantitative differences in IFNAR binding correlate with antiviral activity, but whether IFN-Is exhibit qualitative differences remains controversial. Moreover, the IFN-I response is protective during acute HIV-1 infection, but likely pathogenic during the chronic stages. To gain a deeper understanding of the IFN-I response, we compared the interferomes of IFNα subtypes dominantly-expressed in HIV-1-exposed plasmacytoid dendritic cells (1, 2, 5, 8 and 14) and IFNβ in the earliest cellular targets of HIV-1 infection. Primary gut CD4 T cells from 3 donors were treated for 18 hours ex vivo with individual IFN-Is normalized for IFNAR signaling strength. Of 1,969 IFN-regulated genes, 246 'core ISGs' were induced by all IFN-Is tested. However, many IFN-regulated genes were not shared between the IFNα subtypes despite similar induction of canonical antiviral ISGs such as ISG15, RSAD2 and MX1, formally demonstrating qualitative differences between the IFNα subtypes. Notably, IFNβ induced a broader interferome than the individual IFNα subtypes. Since IFNβ, and not IFNα, is upregulated during chronic HIV-1 infection in the gut, we compared core ISGs and IFNβ-specific ISGs from colon pinch biopsies of HIV-1-uninfected (n = 13) versus age- and gender-matched, antiretroviral-therapy naïve persons with HIV-1 (PWH; n = 19). Core ISGs linked to inflammation, T cell activation and immune exhaustion were elevated in PWH, positively correlated with plasma lipopolysaccharide (LPS) levels and gut IFNβ levels, and negatively correlated with gut CD4 T cell frequencies. In sharp contrast, IFNβ-specific ISGs linked to protein translation and anti-inflammatory responses were significantly downregulated in PWH, negatively correlated with gut IFNβ and LPS, and positively correlated with plasma IL6 and gut CD4 T cell frequencies. Our findings reveal qualitative differences in interferome induction by diverse IFN-Is and suggest potential mechanisms for how IFNβ may drive HIV-1 pathogenesis in the gut.

High abundance of genus Prevotella is associated with dysregulation of IFN-I and T cell response in HIV-1-infected patients

OBJECTIVE

HIV-1-associated dysbiosis is most commonly characterized by overall decreased diversity, with abundance of the genus Prevotella, recently related to inflammatory responses.

DESIGN

A pilot study including 10 antiretroviral therapy-treated HIV-1-infected men and 50 uninfected controls was performed to identify the main gut dysbiosis determinants (e.g. Prevotella enrichment), that may affect mucosal antiviral defenses and T cell immunity in HIV-1-infected individuals.

METHODS

16rRNA gene sequencing was applied to the HIV-1-infected individuals' fecal microbiota and compared with controls. Measurements of CD4 and CD8 T cell activation [CD38, human leukocyte antigen (HLA)-DR, CD38 HLA-DR] and frequencies of Th17, obtained from lamina propria lymphocytes isolated from five different intestinal sites, were performed by flow cytometry. IFNβ, IFNAR1 and MxA gene expression level was evaluated by real-time PCR in lamina propria lymphocytes. Nonparametric t tests were used for statistical analysis.

RESULTS

HIV-1-infected men had a significant fecal microbial communities' imbalance, including different levels of genera Faecalibacterium, Prevotella, Alistipes and Bacteroides, compared with controls. Notably, Prevotella abundance positively correlated with frequencies of CD4 T cells expressing CD38 or HLA-DR and coexpressing CD38 and HLA-DR (P < 0.05 for all these measures). The same trend was observed for the activated CD8 T cells. Moreover, Prevotella levels were inversely correlated with IFN-I genes (P < 0.05 for IFNβ, IFNAR1 and MxA genes) and the frequencies of Th17 cells (P < 0.05). By contrast, no statistically significant correlations were observed for the remaining bacterial genera.

CONCLUSION

Our findings suggest that Prevotella enrichment might affect gut mucosal IFN-I pathways and T cell response in HIV-1-infected patients, thus contributing to immune dysfunction.