OBJECTIVE Gut microbial translocation (MT) is a major driving force behind chronic immune activation during HIV-1 infection. HIV-1-related intestinal dysbiosis, including increases in mucosa-associated pathobionts, may influence MT and contribute to mucosal and systemic inflammation. Thus, it is critical to understand the mechanisms by which gut microbes and their metabolic products, such as butyrate, influence immune cell function during HIV-1 infection. DESIGN A cross-sectional study was performed to compare the relative abundance of butyrate-producing bacterial species (BPB) in colonic biopsies and stool of untreated, chronic HIV-1 infected (n=18) and uninfected (n=14) study participants. The effect of exogenously added butyrate on gut T cell activation and HIV-1 infection was evaluated using an ex vivo human intestinal cell culture model. METHODS Species were identified in 16S ribosomal RNA sequence datasets. Ex vivo isolated lamina propria (LP) mononuclear cells were infected with CCR5-tropic HIV-1Bal, cultured with enteric Gram-negative bacteria and a range of butyrate doses, and LP T cell activation and HIV-1 infection levels measured. RESULTS Relative abundance (RA) of total BPB and specifically of Roseburia intestinalis, were lower in colonic mucosa of HIV-1 infected versus uninfected subjects. In HIV-1 infected study participants, R. intestinalis RA inversely correlated with systemic indicators of MT, immune activation and vascular inflammation. Exogenous butyrate suppressed enteric Gram-negative bacteria-driven LP T cell activation and HIV-1 infection levels in vitro. CONCLUSIONS Reductions in mucosal butyrate from diminished colonic BPB may exacerbate pathobiont driven gut T cell activation and HIV replication, thereby contributing to HIV-associated mucosal pathogenesis.

Background: Early HIV-1 infection is characterized by high levels of HIV-1 replication and substantial CD4 T cell depletion in the intestinal mucosa, intestinal epithelial barrier breakdown, and microbial translocation. HIV-1-induced disruption of intestinal homeostasis has also been associated with changes in the intestinal microbiome that are linked to mucosal and systemic immune activation. In this study, we investigated the impact of representative bacterial species that were altered in the colonic mucosa of viremic HIV-1 infected individuals (HIV-altered mucosal bacteria; HAMB) on intestinal CD4 T cell function, infection by HIV-1, and survival in vitro. Lamina propria (LP) mononuclear cells were infected with CCR5-tropic HIV-1 BaL or mock infected, exposed to high (3 gram-negative) or low (2 gram-positive) abundance HAMB or control gram-negative Escherichia coli and levels of productive HIV-1 infection and CD4 T cell depletion assessed. HAMB-associated changes in LP CD4 T cell activation, proliferation and HIV-1 co-receptor expression were also evaluated. Results:The majority of HAMB increased HIV-1 infection and depletion of LP CD4 T cells, but gram-negative HAMB enhanced CD4 T cell infection to a greater degree than gram-positive HAMB. Most gram-negative HAMB enhanced T cell infection to levels similar to that induced by gram-negative E. coli despite lower induction of T cell activation and proliferation by HAMB. Both gram-negative HAMB and E. coli significantly increased expression of HIV-1 co-receptor CCR5 on LP CD4 T cells. Lipopolysaccharide, a gram-negative bacteria cell wall component, up-regulated CCR5 expression on LP CD4 T cells whereas gram-positive cell wall lipoteichoic acid did not. Upregulation of CCR5 by gramnegative HAMB was largely abrogated in CD4 T cell-enriched cultures suggesting an indirect mode of stimulation. Conclusions:Gram-negative commensal bacteria that are altered in abundance in the colonic mucosa of HIV-1 infected individuals have the capacity to enhance CCR5-tropic HIV-1 productive infection and depletion of LP CD4 T cells in vitro. Enhanced infection appears to be primarily mediated indirectly through increased expression of CCR5 on LP CD4 T cells without concomitant large scale T cell activation. This represents a novel mechanism potentially linking intestinal dysbiosis to HIV-1 mucosal pathogenesis.

The majority of Canadian children are not physically active enough for healthy development. School playgrounds are a primary location to promote physical activity and motor skill practice. The benefits of children’s play in nature have also been highlighted, but few studies have evaluated children’s access and exposure to nature for play on school grounds. This study examined children’s access to nature on school grounds and the opportunities afforded by those natural elements for motor skill practice. Results: Extensive naturescapes (multiple nature elements in one setting) were not common, and natural elements were limited, ranging from 1.97 to 5.71 elements/school. The most common element was a forested area (26.5% of all natural elements identified). In comparison to built structures, the number of natural elements was low. Some elements differed between school districts and appeared to be related to local geography and terrain (hilly, rocky terrain, tidal flats, etc.). Our assessment showed that naturescape elements afforded opportunities for the development of some key fundamental motor skills (FMS), specifically, locomotor and stability skills, but opportunities to develop manipulative skills were limited. To maximize potential FMS development, physical literacy, and psycho-social benefits, additional elements or more comprehensive multi-element naturescapes and facilitation (social or environmental) are recommended.