Toll-Like Receptor abundance in colonic epithelium is selectively altered in HIV disease and partially normalizes with effective Antiretroviral Therapy

Background

Since the intestinal mucosa and microbiome are disrupted in HIV disease, we studied the abundance of innate immune sensors, Toll-Like Receptors (TLR), in the epithelia of patients with Viremia, prior to antiretroviral therapy (ART) initiation, Immune Success (IS- >500 CD4 T cells/ul after 2 years of ART; suppressed viremia), and Immune Failure (IF- <350 CD4 T cells/ul after 2 years of ART; suppressed viremia). Viremia and IF show increased systemic immune activation; therefore, modulation of intestinal TLR abundance may offer a mechanism behind persistent inflammation in HIV.

Method

Immunofluorescence for TLR3, TLR4, and TLR9 on sections cut from paraffin embedded colonic biopsies of uninfected, viremic, IS, and IF was imaged with a DeltaVision microscope and quantified with Metamorph software.

Results

Viremic patients have significantly higher viral TLR9 and TLR3, and significantly lower bacterial TLR4, on the surface epithelium when compared to levels seen on uninfected control. Viremic patients have significantly higher TLR9, similar TLR3, and significantly lower TLR4 expression, in the crypts when compared to uninfected control. TLR9 abundance remains elevated in IF, while normalization occurs in IS. TLR3 abundance on surface epithelium and crypt is even more elevated in IF and IS, suggesting an effect of ART. TLR4 abundance on surface epithelium normalizes in IF and IS; in the crypt, in IS TLR4 decreases further.

Conclusion

Epithelial TLR abundance is selectively altered in HIV disease; effective ART partially normalizes some TLRs, and enhances TLR3. Mucosal TLR desensitization or hyper-vigilance, possibly caused by disrupted cytokine levels in the HIV+ colon, may contribute to systemic inflammation.

Altered Monocyte Phenotype in HIV-1 Infection Tends to Normalize with Integrase-Inhibitor-Based Antiretroviral Therapy

Background

Monocytes are increasingly implicated in the inflammatory consequences of HIV-1 disease, yet their phenotype following antiretroviral therapy (ART) initiation is incompletely defined. Here, we define more completely monocyte phenotype both prior to ART initiation and during 48 weeks of ART.

Methods

Cryopreserved peripheral blood mononuclear cells (PBMCs) were obtained at baseline (prior to ART initiation) and at weeks 12, 24, and 48 of treatment from 29 patients participating in ACTG clinical trial A5248, an open label study of raltegravir/emtricitibine/tenofovir administration. For comparison, cryopreserved PBMCs were obtained from 15 HIV-1 uninfected donors, each of whom had at least two cardiovascular risk factors. Thawed samples were stained for monocyte subset markers (CD14 and CD16), HLA-DR, CCR2, CX3CR1, CD86, CD83, CD40, CD38, CD36, CD13, and CD163 and examined using flow cytometry.

Results

In untreated HIV-1 infection there were perturbations in monocyte subset phenotypes, chiefly a higher frequency and density (mean fluorescence intensity–MFI) of HLA-DR (%-p = 0.004, MFI-p = .0005) and CD86 (%-p = 0.012, MFI-p = 0.005) expression and lower frequency of CCR2 (p = 0.0002) expression on all monocytes, lower CCR2 density on inflammatory monocytes (p = 0.045) when compared to the expression and density of these markers in controls’ monocytes. We also report lower expression of CX3CR1 (p = 0.014) on patrolling monocytes at baseline, compared to levels seen in controls. After ART, these perturbations tended to improve, with decreasing expression and density of HLA-DR and CD86, increasing CCR2 density on inflammatory monocytes, and increasing expression and density of CX3CR1 on patrolling monocytes.

Conclusions

In HIV-1 infected patients, ART appears to attenuate the high levels of activation (HLA-DR, CD86) and to increase expression of the chemokine receptors CCR2 and CX3CR1 on monocyte populations. Circulating monocyte phenotypes are altered in untreated infection and tend to normalize with ART; the role of these cells in the inflammatory environment of HIV-1 infection warrants further study.