Key Concepts in the Early Immunology of HIV-1 Infection

Altered Gut Microbiota in HIV Infection: Future Perspective of Fecal Microbiota Transplantation Therapy

HIV infection progressively destroys CD4+ mononuclear cells, leading to profound cellular immune deficiency that manifests as life-threatening opportunistic infections and malignancies (i.e., AIDS). Gut microbiota plays key roles in the modulation of host metabolism and gene expression, maintenance of epithelial integrity, and mediation of inflammatory and immunity. Hence, the normal intestinal microbiota plays a major role in the maintenance of health and disease prevention. In fact, a large number of studies have shown that the alteration of the gut microbiota contributes to the pathogenesis of several diseases, such as inflammatory bowel diseases, irritable bowel syndrome, metabolic diseases, anorexia nervosa, autoimmune diseases, multiple sclerosis, cancer, neuropsychiatric disorders, and cardiovascular diseases. Recently, accumulating evidence has shed light on the association of dysbiosis of gut microbiota with HIV infection. Hence, the modification of gut microbiota may be a potential therapeutic tool. Fecal microbiota transplantation may improve the conditions of patients with HIV infection by manipulating the human intestinal bacteria. However, the relevant research is very limited, and a large amount of scientific research work needs to be done in the near future.

Extracellular Matrix Proteins Mediate HIV-1 gp120 Interactions with α4β7

Gut-homing α₄β₇^high CD4⁺ T lymphocytes have been shown to be preferentially targeted by human immunodeficiency virus type 1 (HIV-1) and are implicated in HIV-1 pathogenesis. Previous studies demonstrated that HIV-1 envelope protein gp120 binds and signals through α₄β₇ and that this likely contributes to the infection of α₄β₇^high T cells and promotes cell-to-cell virus transmission. Structures within the second variable loop (V2) of gp120, including the tripeptide motif LDV/I, are thought to mediate gp120-α₄β₇ binding. However, lack of α₄β₇ binding has been reported in gp120 proteins containing LDV/I, and the precise determinants of gp120-α₄β₇ binding are not fully defined. In this work, we report the novel finding that fibronectins mediate indirect gp120-α₄β₇ interactions. We show that Chinese hamster ovary (CHO) cells used to express recombinant gp120 produced fibronectins and other extracellular matrix proteins that copurified with gp120. CHO cell fibronectins were able to mediate the binding of a diverse panel of gp120 proteins to α₄β₇ in an in vitro cell binding assay. The V2 loop was not required for fibronectin-mediated binding of gp120 to α₄β₇, nor did V2-specific antibodies block this interaction. Removal of fibronectin through anion-exchange chromatography abrogated V2-independent gp120-α₄β₇ binding. Additionally, we showed a recombinant human fibronectin fragment mediated gp120-α₄β₇ interactions similarly to CHO cell fibronectin. These findings provide an explanation for the apparently contradictory observations regarding the gp120-α₄β₇ interaction and offer new insights into the potential role of fibronectin and other extracellular matrix proteins in HIV-1 biology.IMPORTANCE Immune tissues within the gut are severely damaged by HIV-1, and this plays an important role in the development of AIDS. Integrin α₄β₇ plays a major role in the trafficking of lymphocytes, including CD4⁺ T cells, into gut lymphoid tissues. Previous reports indicate that some HIV-1 gp120 envelope proteins bind to and signal through α₄β₇, which may help explain the preferential infection of gut CD4⁺ T cells. In this study, we demonstrate that extracellular matrix proteins can mediate interactions between gp120 and α₄β₇ This suggests that the extracellular matrix may be an important mediator of HIV-1 interaction with α₄β₇-expressing cells. These findings provide new insight into the nature of HIV-1-α₄β₇ interactions and how these interactions may represent targets for therapeutic intervention.

The comparison of Th1, Th2, Th9, Th17 and Th22 cytokine profiles in acute and chronic HIV-1 infection

The aim of this study was to compare cytokine expression on both gene and protein levels in acute and chronic phase of HIV type 1 (HIV-1) infection. Thirty four patients were enrolled for cytokine expression analysis on protein level in acute and chronic stage of HIV-1 infection. Using PCR array technology, expression of 84 cytokine genes was measured in 3 patients in acute and 3 patients in chronic stage of HIV-1 infection. Bead-based cytometry was used to quantify levels of Th1/Th2/Th9/Th17/Th22 cytokines. The results showed statistically significant increase of 13 cytokine gene expression (cd40lg, csf2, ifna5, il12b, il1b, il20, lta, osm, spp1, tgfa, tnfsf 11, 14 and 8) and downregulation of the il12a expression in chronic HIV type 1 infection. Concentrations of IL-10, IL-4 and TNF-α were increased in the acute HIV type 1 infection when compared to control group. During chronic HIV type 1 infection there was an increase of IL-10, TNF-α, IL-2, IL-6, IL-13 and IL-22 levels when compared to control group. Comparison of cytokine expression between two stages of infection showed a significant decrease in IL-9 concentration. This study showed changes in cytokine profiles on both gene and protein levels in different stages of HIV-infection.

Drug delivery strategies and systems for HIV/AIDS pre-exposure prophylaxis and treatment

The year 2016 will mark an important milestone - the 35th anniversary of the first reported cases of HIV/AIDS. Antiretroviral Therapy (ART) including Highly Active Antiretroviral Therapy (HAART) drug regimens is widely considered to be one of the greatest achievements in therapeutic drug research having transformed HIV infection into a chronically managed disease. Unfortunately, the lack of widespread preventive measures and the inability to eradicate HIV from infected cells highlight the significant challenges remaining today. Moving forward there are at least three high priority goals for anti-HIV drug delivery (DD) research: (1) to prevent new HIV infections from occurring, (2) to facilitate a functional cure, i.e., when HIV is present but the body controls it without drugs and (3) to eradicate established infection. Pre-exposure Prophylaxis (PrEP) represents a significant step forward in preventing the establishment of chronic HIV infection. However, the ultimate success of PrEP will depend on achieving sustained antiretroviral (ARV) tissue concentrations and will require strict patient adherence to the regimen. While first generation long acting/extended release (LA/ER) DD Systems (DDS) currently in development show considerable promise, significant DD treatment and prevention challenges persist. First, there is a critical need to improve cell specificity through targeting in order to selectively achieve efficacious drug concentrations in HIV reservoir sites to control/eradicate HIV as well as mitigate systemic side effects. In addition, approaches for reducing cellular efflux and metabolism of ARV drugs to prolong effective concentrations in target cells need to be developed. Finally, given the current understanding of HIV pathogenesis, next generation anti-HIV DDS need to address selective DD to the gut mucosa and lymph nodes. The current review focuses on the DDS technologies, critical challenges, opportunities, strategies, and approaches by which novel delivery systems will help iterate towards prevention, functional cure and eventually the eradication of HIV infection.

Gut Microbiota in HIV Infection: Implication for Disease Progression and Management

Survival rates among HIV patients have significantly improved since the introduction of antiretroviral therapy (ART) in HIV management. However, persistent disease progression and clinical complications in virally suppressed individuals point to additional contributing factors other than HIV replication; microbial translocation is one such factor. The role of underlying commensal microbes and microbial products that traverse the intestinal lumen into systemic circulation in the absence of overt bacteraemia is under current investigation. This review focuses on current knowledge of the complex microbial communities and microbial markers involved in the disruption of mucosal immune T-cells in the promotion of inflammatory processes in HIV infections. Unanswered questions and aims for future studies are addressed. We provide perspective for discussing potential future therapeutic strategies focused on modulating the gut microbiota to abate HIV disease progression.