HCV viraemia associates with NK cell activation and dysfunction in antiretroviral therapy-treated HIV/HCV-co-infected subjects.

The impact of hepatitis C virus (HCV) RNA levels on immune status in chronically HCV mono-infected when compared to HIV/HCV co-infected on antiretroviral therapy (ART) remains poorly understood. A total of 78 African American subjects HCV viraemic/naïve to HCV treatment (33 HCV genotype 1 mono-infected, 45 ART-treated HIV/HCV genotype 1 co-infected) were studied. Clinical and liver enzyme measurements were performed. Whole blood was analysed for immune subset changes by flow cytometry. Peripheral blood mononuclear cells (PBMC) were used for same-day constitutive and in vitro Interferon (IFN)-α-induced signal transducer and activator of transcription (STAT) phosphorylation, K562 target cell lysis and K562 target cell recognition-mediated IFN-γ production. Statistical analysis was performed using R (2.5.1) or JMP Pro 11. While both groups did not differ in the level of liver enzymes, HIV/HCV had higher T-cell activation/exhaustion, and constitutive STAT-1 phosphorylation compared to HCV. In contrast, CD4+ FoxP3+ CD25+ frequency, IFN-αR expression on NK cells, as well as constitutive and IFN-α-induced direct cytotoxicity were lower in HIV/HCV. Linear regression models further supported these results. Finally, increase in HCV viral load and CD4+ T-cell count had an opposite effect between the two groups on NK cell activity and T-cell activation, respectively. HCV viral load in ART-treated HIV/HCV co-infection was associated with greater immune activation/exhaustion and NK dysfunction than HCV viral load alone in HCV mono-infection. The more pronounced immune modulation noted in ART-treated HIV-co-infected/untreated HCV viraemic subjects may impact HCV disease progression and/or response to immunotherapy.

Limited magnitude and breadth in the HLA-A2-restricted CD8 T-Cell response to Nef in children with vertically acquired HIV-1 infection.

CD8 T cells are believed to play a key role in the immune control of human immunodeficiency virus-1 (HIV-1) infection in children as well as in adults. We have used an enhanced EliSpot (AmpliSpot) assay to quantitate CD8 T-cell responses directed to five human leucocyte antigen (HLA)-A2-presented HIV-1 epitopes derived from the key viral antigen Nef. Responses were assayed in one group of 21 children with vertically acquired HIV infection and one group of 19 adult subjects with chronic infection. The paediatric group displayed significantly weaker and more narrowly focused CD8 T-cell responses as compared with the adult subjects. Two epitopes stood out as the most frequently and strongly recognized, suggesting that they should be considered immunodominant in the CD8 T-cell response to HIV-1 Nef. Interestingly, the most frequently and strongly recognized epitope in both adults and children was previously identified in HLA-A2-transgenic mice, demonstrating the usefulness of such mice in finding natural viral epitopes. These findings indicate significant weakness in strength and breadth of the CD8 T-cell response to the target protein Nef in infected children and prompt renewed efforts into the immunology of vertically acquired HIV-1 infection.

HIV-1 Vpr regulates expression of beta chemokines in human primary lymphocytes and macrophages.

The HIV-1 vpr gene encodes a 14-kDa virion-packaged protein that has been implicated in viral pathogenesis. Vpr exhibits profound effects on human primary cells influencing proliferation, differentiation, apoptosis, and cytokine production, in part through NF-kappaB-mediated transcription. NF-kappaB, a potent transcription factor, activates many proinflammatory cytokines/chemokines upon infection. Here, we analyzed the effect of extracellular Vpr as well as the virion-associated Vpr on beta chemokines (MIP-1alpha, MIP-1beta, and RANTES) production in human macrophages and primary lymphocytes (PBLs). Macrophages and PBLs exposed to HIV-1 vpr+ viruses or to recombinant Vpr protein produced significantly less beta chemokines compared with cells infected with HIV-1 vpr-viruses or irrelevant control protein (Gag)-exposed cells. These results suggest that a Vpr-mediated increase in virus replication could be in part through down-regulation of chemokine production.

Enhancement of human immunodeficiency virus type 1-specific CD4 and CD8 T cell responses in chronically infected persons after temporary treatment interruption.

Immunologic and virologic outcomes of treatment interruption were compared for 5 chronically human immunodeficiency virus (HIV)-infected persons who have maintained antiretroviral therapy-mediated virus suppression, as compared with 5 untreated controls. After a median interruption of 55 days of therapy accompanied by rebound of virus, reinitiated therapy in 4 of 5 subjects resulted in suppression of 98.86% of plasma virus load by 21-33 days and no significant decrease in CD4 T cell percentage from baseline. Increased T helper responses against HIV-1 p24 antigen (P=. 014) and interferon-gamma-secreting CD8 T cell responses against HIV-1 Env (P=.004) were present during interruption of therapy and after reinitiation of treatment. The remaining subject whose treatment was interrupted did not resume treatment and continued to have a low virus load (<1080 HIV-1 RNA copies/mL) and persistent antiviral cell-mediated responses. In summary, cellular immunity against autologous HIV-1 has the potential to be acutely augmented in association with temporary treatment interruption in chronically infected persons.

Inhibition of IL-12 production in human monocyte-derived macrophages by TNF.

IL-12 is a pivotal cytokine that links the innate and adaptive immune responses. TNF-alpha also plays a key role in orchestrating inflammation and immunity. The reciprocal influence of these two inflammatory mediators on each other may have significant impact on the cytokine balance that shapes the type and extent of immune responses. To investigate the relationship between TNF-alpha and IL-12 production, we analyzed the effects of exposure of human monocyte-derived macrophages to TNF-alpha on LPS- or Staphylococcus aureus-induced IL-12 production in the presence or absence of IFN-gamma. TNF-alpha is a potent inhibitor of IL-12 p40 and p70 secretion from human macrophages induced by LPS or S. aureus. IL-10 is not responsible for the TNF-alpha-mediated inhibition of IL-12. TNF-alpha selectively inhibits IL-12 p40 steady-state mRNA, but not those of IL-12 p35, IL-1alpha, IL-1beta, or IL-6. Nuclear run-on analysis identified this specific inhibitory effect at the transcriptional level for IL-12 p40 without down-regulation of the IL-12 p35 gene. The major transcriptional factors identified to be involved in the regulation of IL-12 p40 gene expression by LPS and IFN-gamma, i.e., c-Rel, NF-kappaB p50 and p65, IFN regulatory factor-1, and ets-2, were not affected by TNF-alpha when examined by nuclear translocation and DNA binding. These data demonstrate a selective negative regulation on IL-12 by TNF-alpha, identifying a direct negative feedback mechanism for inflammation-induced suppression of IL-12 gene expression.