Background

Several observations support the hypothesis that vector-driven selection plays an important role in shaping dengue virus (DENV) genetic diversity. Clustering of DENV genetic diversity at a particular location may reflect underlying genetic structure of vector populations, which combined with specific vector genotype x virus genotype (G x G) interactions may promote adaptation of viral lineages to local mosquito vector genotypes. Although spatial structure of vector polymorphism at neutral genetic loci is well-documented, existence of G x G interactions between mosquito and virus genotypes has not been formally demonstrated in natural populations. Here we measure G x G interactions in a system representative of a natural situation in Thailand by challenging three isofemale families from field-derived Aedes aegypti with three contemporaneous low-passage isolates of DENV-1.

Results

Among indices of vector competence examined, the proportion of mosquitoes with a midgut infection, viral RNA concentration in the body, and quantity of virus disseminated to the head/legs (but not the proportion of infected mosquitoes with a disseminated infection) strongly depended on the specific combinations of isofemale families and viral isolates, demonstrating significant G x G interactions.

Conclusion

Evidence for genetic specificity of interactions in our simple experimental design indicates that vector competence of Ae. aegypti for DENV is likely governed to a large extent by G x G interactions in genetically diverse, natural populations. This result challenges the general relevance of conclusions from laboratory systems that consist of a single combination of mosquito and DENV genotypes. Combined with earlier evidence for fine-scale genetic structure of natural Ae. aegypti populations, our finding indicates that the necessary conditions for local DENV adaptation to mosquito vectors are met.

Objective

Microbial translocation and innate immune action characterize HIV infection. Continued gut mucosal dysfunction during treatment and its relationship to CD4 T-cell recovery has not been well described.

Design

A cross-sectional study was performed of antiretroviral therapy (ART)-suppressed (immunologic responders with CD4 > 500 cells/μl and immunologic nonresponders with CD4 < 350 cells/μl), untreated HIV-infected, and seronegative participants consenting to gut biopsies and a blood draw.

Methods

Neutrophil infiltration as a surrogate response to epithelial breach, colorectal epithelial proliferation as a measure of repair, and mucosal apoptosis by immunohistochemistry were determined in gut biopsies. Plasma markers of monocyte activation (sCD14), immune activation (interleukin-6), and indoleamine 2,3-dioxygenase-1 activity (plasma kynurenine/tryptophanratio) were concurrently measured.

Results

Each HIV-infected group had greater neutrophil infiltration than controls. Similarly, untreated HIV-infected participants and ART-suppressed immunologic responders had increased epithelial proliferation compared with controls, but immunologic nonresponders had no appreciable increase in epithelial proliferation despite elevated neutrophil infiltration. The CD4 T-cell count was positively correlated with epithelial proliferation and was modestly negatively correlated with neutrophil infiltration in ART-suppressed patients. Epithelial proliferation was inversely correlated with mucosal apoptosis, and apoptosis was linked to plasma sCD14 and modestly to kynurenine/tryptophan ratio.

Conclusions

Neutrophil infiltration and mucosal apoptosis remain abnormally high despite ART. Epithelial proliferation increases in HIV, but may be impaired in immunologic nonresponders. Whether mucosal apoptosis is a cause or consequence of epithelial proliferative defects is unclear, but appears to be associated with systemic inflammation. The impact of ART and interventions targeting the gut epithelial barrier in treated HIV infection warrant further investigation.

Type I IFNs (TI-IFNs) drive immune effector functions during acute viral infections and regulate cell cycling and systemic metabolism. That said, chronic TI-IFN signaling in the context of HIV infection treated with antiretroviral therapy (ART) also facilitates viral persistence, in part by promoting immunosuppressive responses and CD8+ T cell exhaustion. To determine whether inhibition of IFN-α might provide benefit in the setting of chronic, ART-treated SIV infection of rhesus macaques, we administered an anti-IFN-α antibody followed by an analytical treatment interruption (ATI). IFN-α blockade was well-tolerated and associated with lower expression of TI-IFN-inducible genes (including those that are antiviral) and reduced tissue viral DNA (vDNA). The reduction in vDNA was further accompanied by higher innate proinflammatory plasma cytokines, expression of monocyte activation genes, IL-12-induced effector CD8+ T cell genes, increased heme/metabolic activity, and lower plasma TGF-β levels. Upon ATI, SIV-infected, ART-suppressed nonhuman primates treated with anti-IFN-α displayed lower levels of weight loss and improved erythroid function relative to untreated controls. Overall, these data demonstrated that IFN-α blockade during ART-treated SIV infection was safe and associated with the induction of immune/erythroid pathways that reduced viral persistence during ART while mitigating the weight loss and anemia that typically ensue after ART interruption.

Objective

Persistent systemic inflammation is associated with the inability of some HIV-infected patients to normalize circulating CD4 T-cell levels after years of suppressive antiretroviral therapy. In this study, we sought to understand whether such systemic inflammation is also associated with detectable signs of inflammation in biopsies from the rectosigmoid colon.

Design

Immunologic and virological parameters were studied in the peripheral blood and in rectosigmoid colon biopsies from individuals with viral suppression for at least 2 years and with peripheral CD4 T-cell levels of <350 cells per cubic millimeter (immunologic nonresponders, n = 18) or >500 cells per cubic millimeter (immunologic responders, n = 16).

Methods

Peripheral blood and rectosigmoid colon biopsies were analyzed by flow cytometry, enzyme-linked immunosorbent assay, and quantitative polymerase chain reaction.

Results

Nonresponders had elevated T-cell activation and inflammatory cytokines in the circulation, but inflammatory gene expression in colon biopsies was not different as compared with responders, and there was little relationship between blood and colon markers of inflammation. Blood inflammatory markers were positively associated with soluble CD14 levels indicative of monocyte activation.

Conclusions

These findings demonstrate that, in the context of treated HIV disease, it is easier to detect parameters of inflammation (including blood monocyte activation) in the peripheral blood than in isolated rectosigmoid colon biopsies. Accordingly, interventions to block such inflammation in this population might be most conveniently and accurately assessed in blood.

Progressive HIV infection is characterized by dysregulation of the intestinal immune barrier, translocation of immunostimulatory microbial products, and chronic systemic inflammation that is thought to drive progression of disease to AIDS. Elements of this pathologic process persist despite viral suppression during highly active antiretroviral therapy (HAART), and drivers of these phenomena remain poorly understood. Disrupted intestinal immunity can precipitate dysbiosis that induces chronic inflammation in the mucosa and periphery of mice. However, putative microbial drivers of HIV-associated immunopathology versus recovery have not been identified in humans. Using high-resolution bacterial community profiling, we identified a dysbiotic mucosal-adherent community enriched in Proteobacteria and depleted of Bacteroidia members that was associated with markers of mucosal immune disruption, T cell activation, and chronic inflammation in HIV-infected subjects. Furthermore, this dysbiosis was evident among HIV-infected subjects undergoing HAART, and the extent of dysbiosis correlated with activity of the kynurenine pathway of tryptophan catabolism and plasma concentrations of the inflammatory cytokine interleukin-6 (IL-6), two established markers of disease progression. Gut-resident bacteria with capacity to catabolize tryptophan through the kynurenine pathway were found to be enriched in HIV-infected subjects, strongly correlated with kynurenine levels in HIV-infected subjects, and capable of kynurenine production in vitro. These observations demonstrate a link between mucosal-adherent colonic bacteria and immunopathogenesis during progressive HIV infection that is apparent even in the setting of viral suppression during HAART. This link suggests that gut-resident microbial populations may influence intestinal homeostasis during HIV disease.