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TLR8 regulation of LILRA3 in monocytes is abrogated in human immunodeficiency virus infection and correlates to CD4 counts and virus loads.

ABSTRACT: LILRA3 is an immunostimulatory molecule which can conditionally induce the proliferation of cytotoxic cells. LILRA3 has a deletion genotype which is associated with multiple immune disorders. In this study, we wanted to analyze the regulation of LILRA3 and its significance in the context of HIV infection.We analyzed a panel of TLR agonists and found that ssRNA40, a TLR8 agonist, is a potent inducer of LILRA3 in healthy individuals. However, this regulation is much diminished in HIV. Comparison of TLR8 to TLR4 induction of LILRA3 indicated that LPS induces less LILRA3 than ssRNA40 among healthy controls, but not HIV patients. Levels of LILRA3 induction correlated to virus load and CD4 counts in untreated patients. Recombinant LILRA3 can induce a host of proinflammatory genes which include IL-6 and IL-1?, as well as alter the expression of MHC and costimulatory molecules in monocytes and B-cells.Our experiments point towards a beneficial role for LILRA3 in virus infections, especially in ssRNA viruses, like HIV, that engage TLR8. However, the potentially beneficial role of LILRA3 is abrogated during a HIV infection. We believe that more work has to be done to study the role of LILRA3 in infectious diseases and that there is a potential for exploring the use of LILRA3 in the treatment of virus infections.

SUBMITTER: Low HZ

PROVIDER: S-EPMC4788896 | biostudies-literature | 2016 Mar

REPOSITORIES: biostudies-literature

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Project description:BackgroundHuman endosomal Toll-like receptors TLR7 and TLR8 recognize self and non-self RNA ligands, and are important mediators of innate immunity and autoimmune pathogenesis. TLR7 and TLR8 are, respectively, encoded by adjacent X-linked genes. We previously established that TLR7 evades X chromosome inactivation (XCI) in female immune cells. Whether TLR8 also evades XCI, however, has not yet been explored.MethodIn the current study, we used RNA fluorescence in situ hybridization (RNA FISH) to directly visualize, on a single-cell basis, primary transcripts of TLR7 and TLR8 relative to X chromosome territories in CD14+ monocytes and CD4+ T lymphocytes from women, Klinefelter syndrome (KS) men, and euploid men. To assign X chromosome territories in cells lacking robust expression of a XIST compartment, we designed probes specific for X-linked genes that do not escape XCI and therefore robustly label the active X chromosome. We also assessed whether XCI escape of TLR8 was associated with sexual dimorphism in TLR8 protein expression by western blot and flow cytometry.ResultsUsing RNA FISH, we show that TLR8, like TLR7, evades XCI in immune cells, and that cells harboring simultaneously TLR7 and TLR8 transcript foci are more frequent in women and KS men than in euploid men, resulting in a sevenfold difference in frequency. This transcriptional bias was again observable when comparing the single X of XY males with the active X of cells from females or KS males. Interestingly, TLR8 protein expression was significantly higher in female mononuclear blood cells, including all monocyte subsets, than in male cells.ConclusionsTLR8, mirroring TLR7, escapes XCI in human monocytes and CD4+ T cells. Co-dependent transcription from the active X chromosome and escape from XCI could both contribute to higher TLR8 protein abundance in female cells, which may have implications for the response to viruses and bacteria, and the risk of developing inflammatory and autoimmune diseases.

Project description:In individuals with HIV-1 infection, depletion of CD4+ T cells is often accompanied by a malfunction of CD8+ T cells that are persistently activated and/or exhausted. While the dynamics and correlates of CD4 counts have been well documented, the same does not apply to CD8 counts. Here, we examined the CD8 counts in a cohort of 497 Africans with primary HIV-1 infection evaluated in monthly to quarterly follow-up visits for up to 3 years in the absence of antiretroviral therapy. Statistical models revealed that (i) CD8 counts were relatively steady in the 3- to 36-month period of infection and similar between men and women; (ii) neither geography nor heterogeneity in the HIV-1 set-point viral load could account for the roughly 10-fold range of CD8 counts in the cohort (P > 0.25 in all tests); and (iii) factors independently associated with relatively high CD8 counts included demographics (age ? 40 years, adjusted P = 0.010) and several human leukocyte antigen class I (HLA-I) alleles, including HLA-A*03:01 (P = 0.013), B*15:10 (P = 0.007), and B*58:02 (P < 0.001). Multiple sensitivity analyses provided supporting evidence for these novel relationships. Overall, these findings suggest that factors associated with the CD8 count have little overlap with those previously reported for other HIV-1-related outcome measures, including viral load, CD4 count, and CD4/CD8 ratio.ImportanceLongitudinal data from 497 HIV-1 seroconverters allowed us to systematically evaluate the dynamics and correlates of CD8+ T-cell counts during untreated primary HIV-1 infection in eastern and southern Africans. Our findings suggest that individuals with certain HLA-I alleles, including A*03 (exclusively A*03:01), persistently maintain relatively high CD8 counts following HIV-1 infection, a finding which may offer an intriguing explanation for the recently reported, negative association of A*03 with HIV-1-specific, broadly neutralizing antibody responses. In future studies, attention to HLA-I genotyping data may benefit in-depth understanding of both cellular and humoral immunity, as well as the intrinsic balances of these types of immunity, especially in settings where there is emerging evidence of antagonism between the two arms of adaptive immunity.

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TLR8 regulation of LILRA3 in monocytes is abrogated in human immunodeficiency virus infection and correlates to CD4 counts and virus loads.

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