Early treatment with reverse transcriptase inhibitors significantly suppresses peak plasma IFNα in vivo during acute simian immunodeficiency virus infection

GALT CD4+PD-1hi T follicular helper (Tfh) cells repopulate after anti-retroviral therapy

Human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) infections are characterized by dramatic alterations in the mucosal CD4 T cell compartment. Though viremia is effectively suppressed, and peripheral CD4 T cell numbers recover to near healthy levels after highly active anti-retroviral therapy (HAART), some of the dysfunctional consequences of HIV infection continue to persist during therapy. We hypothesized that CD4 T follicular helper (Tfh) cell deficiencies may play a role in this process. Using the macaque model we show that SIV infection was associated with a significant loss of Tfh cells in the GALT that drain the mesentery lining the gastrointestinal tract (GIT). Loss of Tfh cells significantly correlated with the depletion of the overall memory CD4 T cell compartment; most Tfh cells in the GALT expressed a CD95+CD28+ memory phenotype suggesting that infection of the memory compartment likely drives the loss of GALT Tfh cells during infection. Continuous anti-retroviral therapy (cART) was accompanied by a significant repopulation of Tfh cells in the GALT to levels similar to those of uninfected animals. Repopulating Tfh cells displayed significantly higher capacity to produce IL-21 as compared to SIV infected animals suggesting that cART fully restores Tfh cells that are functionally capable of supporting GC reactions in the GALT.

Gut Microbiome Homeostasis and the CD4 T- Follicular Helper Cell IgA Axis in Human Immunodeficiency Virus Infection

Human Immunodeficiency Virus (HIV) and Simian Immunodeficiency Virus (SIV) are associated with severe perturbations in the gut mucosal environment characterized by massive viral replication and depletion of CD4 T cells leading to dysbiosis, breakdown of the epithelial barrier, microbial translocation, immune activation and disease progression. Multiple mechanisms play a role in maintaining homeostasis in the gut mucosa and protecting the integrity of the epithelial barrier. Among these are the secretory IgA (sIgA) that are produced daily in vast quantities throughout the mucosa and play a pivotal role in preventing commensal microbes from breaching the epithelial barrier. These microbe specific, high affinity IgA are produced by IgA+ plasma cells that are present within the Peyer’s Patches, mesenteric lymph nodes and the isolated lymphoid follicles that are prevalent in the lamina propria of the gastrointestinal tract (GIT). Differentiation, maturation and class switching to IgA producing plasma cells requires help from T follicular helper (Tfh) cells that are present within these lymphoid tissues. HIV replication and CD4 T cell depletion is accompanied by severe dysregulation of Tfh cell responses that compromises the generation of mucosal IgA that in turn alters barrier integrity leading to commensal bacteria readily breaching the epithelial barrier and causing mucosal pathology. Here we review the effect of HIV infection on Tfh cells and mucosal IgA responses in the GIT and the consequences these have for gut dysbiosis and mucosal immunopathogenesis.

Microbial Dysbiosis During Simian Immunodeficiency Virus Infection is Partially Reverted with Combination Anti-retroviral Therapy

Human immunodeficiency virus (HIV) infection is characterized by a massive loss of CD4 T cells in the gastrointestinal tract (GIT) that is accompanied by changes in the gut microbiome and microbial translocation that contribute to inflammation and chronic immune activation. Though highly active antiretroviral therapy (HAART) has led to better long-term outcomes in HIV infected patients, it has not been as effective at reverting pathogenesis in the GIT. Using the simian immunodeficiency virus (SIV) infection model, we show that combination antiretroviral therapy (c-ART) partially reverted microbial dysbiosis observed during SIV infection. Though the relative abundance of bacteria, their richness or diversity did not significantly differ between infected and treated animals, microbial dysbiosis was evident via multiple beta diversity metrics: Jaccard similarity coefficient, Bray-Curtis similarity coefficient, and Yue & Clayton theta similarity coefficient. Principal coordinates analysis (PCoA) clustered SIV-infected untreated animals away from healthy and treated animals that were clustered closely, indicating that c-ART partially reversed the gut dysbiosis associated with SIV infection. Metastats analysis identified specific operational taxonomic units (OTUs) falling within the Streptococcus, Prevotella, Acinetobacter, Treponema, and Lactobacillus genera that were differentially represented across the three groups. Our results suggest that complete viral suppression with c-ART could potentially revert microbial dysbiosis observed during SIV and HIV infections.

Gender differences in innate responses and gene expression profiles in memory CD4 T cells are apparent very early during acute simian immunodeficiency virus infection

Gender differences in Human immunodeficiency virus (HIV) disease progression and comorbidities have been extensively reported. Using the simian immunodeficiency virus (SIV) infected rhesus macaque model, we show that these differences are apparent very early during the course of infection. Though there were no major changes in the proportions of CD4 T cells or its subsets, central memory CD4 T cells from female macaques were found to differentially regulate a significantly larger number of genes at day 4 post-infection (PI) as compared to males. Pathway analysis revealed divergence of both canonical and biological pathways that persisted at day 10 PI. Changes in gene expression profiles were accompanied by a significant increase in plasma levels of pro-inflammatory mediators such as MCP-1/CCL2, I-TAC/CXCL11, and MIF. Though plasma levels of IFNα did not differ between male and female macaques, the expression levels of IFNα subtype-14, 16, IFNβ, and IFNω were significantly upregulated in the lymph nodes of female macaques at day 10 PI as compared to male macaques. Our results suggest that the pathogenic sequelae seen during chronic infection may be shaped by gender differences in immune responses induced very early during the course of HIV infection.

Chronic simian immunodeficiency virus infection is associated with contrasting phenotypes of dysfunctional Bcl6+ germinal center B cells or Bcl6- Bcl2+ non-germinal center B cells

Human immunodeficiency virus (HIV) infection is characterized by dysfunctional B cell responses. Here we show that chronic simian immunodeficiency virus (SIV) infection is characterized by an expansion of either lymph node germinal center (GC) B cells that co-express Bcl6, Ki-67 and IL-21R and correlate with expanded T follicular helper (Tfh) cells or B cells that lack Bcl6, Ki-67 and IL-21R but express high levels of anti-apoptotic Bcl2 that negatively correlate with Tfh cells. The lack of Tfh cells likely contributes to persistence of dysfunctional non-proliferating B cells during chronic infection. These findings have implications for protective immunity in HIV-infected individuals who harbour low frequencies of Tfh cells.

A compartmentalized type I interferon response in the gut during chronic HIV-1 infection is associated with immunopathogenesis

OBJECTIVE(S)

Type I interferon (IFN-I) responses confer both protective and pathogenic effects in persistent virus infections. IFN-I diversity, stage of infection and tissue compartment may account for this dichotomy. The gut is a major site of early HIV-1 replication and microbial translocation, but the nature of the IFN-I response in this compartment remains unclear.

DESIGN

Samples were obtained from two IRB-approved cross-sectional studies. The first study included individuals with chronic, untreated HIV-1 infection (n = 24) and age/sex-balanced uninfected controls (n = 14). The second study included antiretroviral-treated, HIV-1-infected individuals (n = 15) and uninfected controls (n = 15).

METHODS

The expression of 12 IFNα subtypes, IFNβ and antiviral IFN-stimulated genes (ISGs) were quantified in peripheral blood mononuclear cells (PBMCs) and colon biopsies using real-time PCR and next-generation sequencing. In untreated HIV-1-infected individuals, associations between IFN-I responses and gut HIV-1 RNA levels as well as previously established measures of colonic and systemic immunological indices were determined.

RESULTS

IFNα1, IFNα2, IFNα4, IFNα5 and IFNα8 were upregulated in PBMCs during untreated chronic HIV-1 infection, but IFNβ was undetectable. By contrast, IFNβ was upregulated and all IFNα subtypes were downregulated in gut tissue. Gut ISG levels positively correlated with gut HIV-1 RNA and immune activation, microbial translocation and inflammation markers. Gut IFN-I responses were not significantly different between HIV-1-infected individuals on antiretroviral treatment and uninfected controls.

CONCLUSION

The IFN-I response is compartmentalized during chronic untreated HIV-1 infection, with IFNβ being more predominant in the gut. Gut IFN-I responses are associated with immunopathogenesis, and viral replication is likely a major driver of this response.

Interferon-α Subtypes As an Adjunct Therapeutic Approach for Human Immunodeficiency Virus Functional Cure

Human immunodeficiency virus (HIV) establishes life-long latency in infected individuals. Although highly active antiretroviral therapy (HAART) has had a significant impact on the course of HIV infection leading to a better long-term outcome, the pool of latent reservoir remains substantial even under HAART. Numerous approaches have been under development with the goal of eradicating the latent HIV reservoir though with limited success. Approaches that combine immune-mediated control of HIV to activate both the innate and the adaptive immune system under suppressive therapy along with “shock and kill” drugs may lead to a better control of the reactivated virus. Interferon-α (IFN-α) is an innate cytokine that has been shown to activate intracellular defenses capable of restricting and controlling HIV. IFN-α, however, harbors numerous functional subtypes that have been reported to display different binding affinities and potency. Recent studies have suggested that certain subtypes such as IFN-α8 and IFN-α14 have potent anti-HIV activity with little or no immune activation, whereas other subtypes such as IFN-α4, IFN-α5, and IFN-α14 activate NK cells. Could these subtypes be used in combination with other strategies to reduce the latent viral reservoir? Here, we review the role of IFN-α subtypes in HIV infection and discuss the possibility that certain subtypes could be potential adjuncts to a “shock and kill” or therapeutic vaccination strategy leading to better control of the latent reservoir and subsequent functional cure.