Monocyte Based Correlates of Immune Activation and Viremia in HIV-Infected Long-Term Non-Progressors

Abstract

Background: Disease progression monitoring through CD4 counts alone can be inadequate in HIV infection as ongoing immune activation may result in Serious non-AIDS events (SNAEs). SNAEs involve monocyte activation driven chronic inflammation with significant sequelae observed even during HAART. Here, we attempted to delineate functional monocyte based signatures across stages of HIV disease progression.Methods: Participants spanning four cohorts were recruited—pre-ART (PA; <7 years of infection; n = 20), long-term non-progressors (LTNP; >7 years of infection, CD4 > 350 cells/μL, n = 20), individuals on therapy (ART; n = 18) and seronegative controls (SN; n = 15). Immunophenotyping of monocyte subsets and evaluation of expression of HIV-binding receptors—CD4 and CCR5, marker of immune activation- HLA-DR and M2 phenotype—mannose receptor (CD206) was followed by association of monocyte-specific parameters with conventional markers of disease progression such as absolute CD4 count, CD4/CD8 ratio, viral load, and T cell activation.Results: A significant expansion of intermediate monocytes (CD14++CD16+) with a concomitant decline in classical subset (CD14++CD16–) was observed in all infected cohorts compared to seronegative controls. In addition, an expansion of the non-classical subset (CD14+CD16++) was observed in long-term non-progressors. Dysregulation in monocyte subsets associated with CD4 count and CD4/CD8 ratio in PAs but not in LTNPs. We report for the first time that expression of CD206 is most prominent on intermediate monocytes which also have the highest expression of CD4, CCR5, and HLA-DR. Despite preserved CD4 counts, LTNPs had similar immune activation profiles to PAs, as evidenced by elevated HLA-DR expression across monocyte subsets. HLA-DR expression, similar to that in SNs, observed in the ART group indicated partial immune restoration within the monocyte compartment. Increased CD206 expression on monocytes together with frequency of activated CD4+ T lymphocytes (HLA-DR+CD38+) showed significant and positive association with viral load in LTNPs, but not PAs.Conclusion: Our results describe for the first time the presence of monocyte dysregulation involving increased activation in LTNPs, who, in spite of preserved CD4 counts, may remain susceptible to prolonged effects of systemic inflammation and highlight CD206, as a unique non-T correlate of viremia, in viremic non-progression.

Vaginal Epithelium Transiently Harbours HIV-1 Facilitating Transmission

“…Interestingly, CD206, a marker of alternate activation (M2 phenotype) observed on blood monocytes as reported earlier by our group ( Prabhu et al., 2019 ) was observed to be highly expressed both on primary vaginal epithelial cells and epithelial cell lines (Vk2/E6E7 and TZM-bL) ( Figure 1B and Supplementary Figure 4 ). These results highlighted the suitability of using the VK2/E6E7 cell line to study CD4-independent interaction of HIV with the vaginal epithelium.…”

“…Vaginal epithelial cells were gated based on scatter and examined for their expression of HIV-binding receptors CD4, CCR5 and CD206 compared to unstained controls ( Supplementary Figure 3 ). T-lymphocytes and monocytes were identified based on forward and side scatter properties and expression of CD3 and CD14/CD16 respectively as described previously ( Prabhu et al., 2019 ). Figure 1A depicts representative histograms of HIV-specific receptor expression across these cell types.…”

“…Vk2/E6E7 and TZM-bl cell lines, seeded in T-25 flasks, were detached with 0.25% Trypsin-EDTA (TE), washed with DMEM/F12 containing 10% FBS, before re-suspending in stain buffer. Whole blood subset/cell line staining was carried out as described previously ( Prabhu et al., 2019 ) with fluorochrome-conjugated antibodies including anti-CD4 (clone: RPA-T4), anti-CCR5 (clone: 2D7), anti-CXCR4 (clone: 12G5) and anti-CD206 (clone: 15-2) (BD Biosciences or Biolegend (US)). Stained cells were acquired on BD Accuri C6 flow cytometer and data was analysed on FlowJo 10.6 (BD Biosciences, USA).…”

IL-15 and sMAdCAM: Novel roles in COVID-19 pathogenesis

“…Our study also evaluated the non-lymphocyte compartment in terms of monocytes and their profiles in mild and hypoxemic COVID-19 disease. This compartment has been known to modulate inflammatory responses to a variety of viral infections (21, 22). Interestingly, as opposed to the T cell compartment and when compared with healthy seronegative individuals, a pan-disease signature was delineated within monocytes comprising of elevated frequencies of intermediate monocytes.…”

Ageing with HIV: Challenges and biomarkers

“… 14 HIV infection leads to elevated immune activation markers such as CD38 and HLA-DR molecules on T-cells, 15 and the release of soluble inflammatory factors such as IFN, IL-6, TNF, sCD14, sCD163. 16 Other cell types, such as B-cells, monocytes and natural killers (NK) also show signs of activation and dysfunction, 17 , 18 In this regard, a recent study showed a high-inflammatory profile in B-cells of HIV-infected individuals compared to non-HIV. 19 Likewise, an excessive accumulation of senescent cells in other tissues may also be a source of pro-inflammatory cytokine secretion in HIV positive individuals.…”