HIV-infected infants are at an increased risk of progressing rapidly to AIDS in the first weeks of life. Here, we evaluated immunological and virological parameters in 25 SIV-infected infant rhesus macaques to understand the factors influencing a rapid disease outcome. Infant macaques were infected with SIVmac251 and monitored for 10 to 17 weeks post-infection. SIV-infected infants were divided into either typical (TypP) or rapid (RP) progressor groups based on levels of plasma anti-SIV antibody and viral load, with RP infants having low SIV-specific antibodies and high viral loads. Following SIV infection, 11 out of 25 infant macaques exhibited an RP phenotype. Interestingly, TypP had lower levels of total CD4 T cells, similar reductions in CD4/CD8 ratios and elevated activation of CD8 T cells, as measured by the levels of HLA-DR, compared to RP. Differences between the two groups were identified in other immune cell populations, including a failure to expand activated memory (CD21-CD27+) B cells in peripheral blood in RP infant macaques, as well as reduced levels of germinal center (GC) B cells and T follicular helper (Tfh) cells in spleens (4- and 10-weeks post-SIV). Reduced B cell proliferation in splenic germinal GCs was associated with increased SIV+ cell density and follicular type 1 interferon (IFN)-induced immune activation. Further analyses determined that at 2-weeks post SIV infection TypP infants exhibited elevated levels of the GC-inducing chemokine CXCL13 in plasma, as well as significantly lower levels of viral envelope diversity compared to RP infants. Our findings provide evidence that early viral and immunologic events following SIV infection contributes to impairment of B cells, Tfh cells and germinal center formation, ultimately impeding the development of SIV-specific antibody responses in rapidly progressing infant macaques.

Liver disease is a significant contributor to morbidity and mortality in HIV-infected individuals, even during successful viral suppression with combination antiretroviral therapy (cART). Similar to HIV infection, SIV infection of rhesus macaques is associated with gut microbiome dysbiosis and microbial translocation that can be detected systemically in the blood. As microbes leaving the intestines must first pass through the liver via the portal vein, we evaluated the livers of both SIV-infected (SIV+) and SIV-infected cART treated (SIV+cART) rhesus macaques for evidence of microbial changes compared to uninfected macaques. Dysbiosis was observed in both the SIV+ and SIV+cART macaques, encompassing changes in the relative abundance of several genera, including a reduction in the levels of Lactobacillus and Staphylococcus. Most strikingly, we found an increase in the relative abundance and absolute quantity of bacteria within the Mycobacterium genus in both SIV+ and SIV+cART macaques. Multi-gene sequencing identified a species of atypical mycobacteria similar to the opportunistic pathogen M. smegmatis. Phosphatidyl inositol lipoarabinomannan (PILAM) (a glycolipid cell wall component found in atypical mycobacteria) stimulation in primary human hepatocytes resulted in an upregulation of inflammatory transcriptional responses, including an increase in the chemokines associated with neutrophil recruitment (CXCL1, CXCL5, and CXCL6). These studies provide key insights into SIV associated changes in hepatic microbial composition and indicate a link between microbial components and immune cell recruitment in SIV+ and SIV+cART treated macaques.

Background: Liver disease remains a significant contributor to morbidity and mortality in HIV-infected individuals, even during successful treatment with combination antiretroviral therapy (cART). In non-human primates, SIV infection is associated with gut microbiome dysbiosis as well as bacterial translocation into the colonic lamina propria and liver via the portal vein. Here the liver microbiome was evaluated in rhesus macaques to discern the influence of SIV infection alone (SIV+) and during cART administration (SIV+cART) on liver bacterial dysbiosis and neutrophil infiltration.Results: Dysbiosis in liver bacterial composition was observed, encompassing changes in a number of genera, during SIV infection in the absence and presence of cART. The most striking finding was an increase in the level of Mycobacterium, which while barely detectable in the uninfected macaques, was the most abundant genus observed in the livers of a majority SIV+ and SIV+cART macaques. Multi-gene sequencing analyses identified a species of environmental mycobacteria similar to the opportunistic pathogen M. smegmatis. The effect of M. smegmatis on host gene expression in primary hepatocytes was evaluated in vitro utilizing PILAM, a glycolipid cell wall component found in atypical Mycobacteria. PILAM induced an upregulation of inflammatory responses, including an increase in the chemokines associated with neutrophil chemotaxis (CXCL1, CXCL5, and CXCL6). Assessment of the macaque livers by microscopy determined that neutrophil levels were reduced in SIV+cART macaques, suggesting that the SIV infection and/or cART treatment influence the liver-associated neutrophil response. Conclusions: A number of liver bacteria genera were altered following SIV infection even in the context of cART, possibly as a consequence of reduced neutrophil recruitment. Mycobacteria became a major component of the SIV infected macaque liver microbiome, raising the possibility that bacteria of this genus might contribute to liver disease in HIV infected patients.

HIV-infected infants are at an increased risk of progressing rapidly to AIDS in the first weeks of life. Here, we evaluated immunological and virological parameters in 25 SIV-infected infant rhesus macaques to understand the factors influencing a rapid disease outcome. Infant macaques were infected with SIVmac251 and monitored for 10 to 17 weeks post-infection. SIV-infected infants were divided into either typical (TypP) or rapid (RP) progressor groups based on levels of plasma anti-SIV antibody levels and SIV plasma viral load (with RP infants having low SIV-specific antibodies and high viral loads). Following SIV infection, 11 out of 25 infant macaques exhibited an RP phenotype, with 5 of these succumbing to AIDS-related infections. Interestingly, the TypP and RP infants were similar in their CD4 depletion and activation of CD8 T cells as measured by the levels of HLA-DR on the cell surface. However, differences between the two groups were identified in other immune cell populations, including a failure to expand activated memory (CD21-CD27+) B cells in peripheral blood in RP infant macaques, as well as reduced levels of germinal center (GC) B cells and T follicular helper (Tfh) cells in spleens (4- and 10-weeks post-SIV). Reduced B cell proliferation in splenic germinal GCs was associated with increased SIV+ cell density and follicular type 1 interferon (IFN)-induced immune activation. Further analyses determined that at 2-weeks post SIV infection TypP infants exhibited elevated levels of the GC-inducing chemokine CXCL13 in plasma, as well as significantly lower levels of viral envelope diversity compared to RP infants. Our findings provide evidence that early viral and immunologic events following SIV infection contributes to impairment of B cells, Tfh cells and germinal center formation, ultimately impeding the development of SIV-specific antibody responses in rapidly progressing infant macaques.

Non-alcoholic fatty liver disease (NAFLD) contributes to morbidity and mortality in HIV-infected individuals. To evaluate liver immune changes during SIV infection of macaques, we obtained liver biopsies laparoscopically at 2, 6, and 16 weeks post-infection as well as at necropsy (32 weeks). SIV infection was associated with liver dysfunction that included elevated liver enzymes during acute infection, higher liver weight at necropsy, and histologic changes within the liver lobule (functional unit of the liver) including sinusoidal dilatation near central veins and portal expansion. The type-1 interferon (IFN-1) response (MX1 expression) increased over time post-SIV infection, initially being observed in macrophages (week 2) with a switch to a mixed hepatocyte/monocyte/macrophage response by 16–32 weeks. Over the course of SIV infection, macrophage frequencies also increased – both infiltrating (CD68+CD163+CD206-) and resident (CD68+CD163+CD206+) tissue macrophages – and these macrophages were found more near central veins over time. In contrast, CD68+CD163-CD206− trafficking myeloid cells/monocytes were detected predominantly in the periportal zone of the lobule and associated with elevated MX1 expression in that zone. Our findings identify pathologic changes within the livers of SIV infected macaques as early as 2 weeks post-infection, IFN-1 responses that are initially observed in liver macrophages, and an accumulation of macrophages associated with signs of inflammation by week 32. These studies offer quantitative and spatial insights to inform macrophage-targeted therapeutic approaches that may improve liver function during HIV infection. Supported by grants from NIH (R01AI134630)