Evidence of CD4+ T cell-mediated immune pressure on the Hepatitis C virus genome

Hepatitis C virus (HCV)-specific T cell responses are critical for immune control of infection. Viral adaptation to these responses, via mutations within regions of the virus targeted by CD8+ T cells, is associated with viral persistence. However, identifying viral adaptation to HCV-specific CD4+ T cell responses has been difficult although key to understanding anti-HCV immunity. In this context, HCV sequence and host genotype from a single source HCV genotype 1B cohort (n = 63) were analyzed to identify viral changes associated with specific human leucocyte antigen (HLA) class II alleles, as these variable host molecules determine the set of viral peptides presented to CD4+ T cells. Eight sites across the HCV genome were associated with HLA class II alleles implicated in infection outcome in this cohort (p ≤ 0.01; Fisher’s exact test). We extended this analysis to chronic HCV infection (n = 351) for the common genotypes 1A and 3A. Variation at 38 sites across the HCV genome were associated with specific HLA class II alleles with no overlap between genotypes, suggestive of genotype-specific T cell targets, which has important implications for vaccine design. Here we show evidence of HCV adaptation to HLA class II-restricted CD4+ T cell pressure across the HCV genome in chronic HCV infection without a priori knowledge of CD4+ T cell epitopes

Accuracy of Doppler-Echocardiographic Mean Pulmonary Artery Pressure for Diagnosis of Pulmonary Hypertension

Background: The validity of Doppler echocardiographic (DE) measurement of systolic pulmonary artery pressure (sPAP) has been questioned. Recent studies suggest that mean pulmonary artery pressure (mPAP) might reflect more accurately the invasive pressures. Methodology/Principal Findings: 241 patients were prospectively studied to evaluate the diagnostic accuracy of mPAP for the diagnosis of PH. Right heart catheterization (RHC) and DE were performed in 164 patients mainly for preoperative evaluation of heart valve dysfunction. The correlation between DE and RHC was better when mPAP (r = 0.93) and not sPAP (r = 0.81) was assessed. Bland-Altman analysis revealed a smaller variation of mPAP than sPAP. The following ROC analysis identified that a mPAP$25.5 mmHg is useful for the diagnosis of PH. This value was validated in an independent cohort of patients (n = 50) with the suspicion of chronic-thromboembolic pulmonary hypertension. The calculated diagnostic accuracy was 98%, based on excellent sensitivity of 98 % and specificity of 100%. The corresponding positive and negative predictive values were 100%, respectively 88%. Conclusion: mPAP has been found to be highly accurate for the initial diagnosis of PH. A cut-off value of 25.5 mmHg might be helpful to avoid unnecessary RHC and select patients in whom RHC might be beneficial

Immune monitoring-guided vs fixed duration of antiviral prophylaxis against cytomegalovirus in solid-organ transplant recipients. A Multicenter, Randomized Clinical Trial.

BACKGROUND The use of assays detecting cytomegalovirus (CMV)-specific T-cell-mediated immunity may individualize the duration of antiviral prophylaxis in transplant recipients. METHODS In this open-label randomized trial, adult kidney and liver transplant recipients from six centers in Switzerland were enrolled if they were CMV-seronegative with seropositive donors or CMV-seropositive receiving anti-thymocyte globulins. Patients were randomized to a duration of antiviral prophylaxis based on immune-monitoring (intervention) or a fixed duration (control). Patients in the control group were planned to receive 180 days (CMV-seronegative) or 90 days (CMV-seropositive) of valganciclovir. Patients were assessed monthly with a CMV-specific interferon gamma release assay (T-Track® CMV); prophylaxis in the intervention group was stopped if the assay was positive. The primary outcomes were the proportion of patients with clinically significant CMV infection and reduction in days of prophylaxis. Between-group differences were adjusted for CMV serostatus. RESULTS Overall, 193 patients were randomized (92 in the immune-monitoring and 101 in the control group) of which 185 had evaluation of the primary endpoint (87 and 98 patients, respectively). Clinically significant CMV infection occurred in 26/87 (adjusted percentage, 30.9%) in the immune-monitoring group and in 32/98 (adjusted percentage, 31.1%) in the control group (adjusted risk difference -0.1, 95%CI -13.0%, 12.7%; p = 0.064). The duration of antiviral prophylaxis was shorter in the immune-monitoring group (adjusted difference -26.0 days, 95%-CI -41.1 to -10.8 days, p < 0.001). CONCLUSIONS Immune monitoring resulted in a significant reduction of antiviral prophylaxis, but we were unable to establish noninferiority of this approach on the co-primary endpoint of CMV infection

Tracking Virus-Specific CD4+ T Cells during and after Acute Hepatitis C Virus Infection

CD4+ T cell help is critical in maintaining antiviral immune responses and such help has been shown to be sustained in acute resolving hepatitis C. In contrast, in evolving chronic hepatitis C CD4+ T cell helper responses appear to be absent or short-lived, using functional assays. Here we used a novel HLA-DR1 tetramer containing a highly targeted CD4+ T cell epitope from the hepatitis C virus non-structural protein 4 to track number and phenotype of hepatitis C virus specific CD4+ T cells in a cohort of seven HLA-DR1 positive patients with acute hepatitis C in comparison to patients with chronic or resolved hepatitis C. We observed peptide-specific T cells in all seven patients with acute hepatitis C regardless of outcome at frequencies up to 0.65% of CD4+ T cells. Among patients who transiently controlled virus replication we observed loss of function, and/or physical deletion of tetramer+ CD4+ T cells before viral recrudescence. In some patients with chronic hepatitis C very low numbers of tetramer+ cells were detectable in peripheral blood, compared to robust responses detected in spontaneous resolvers. Importantly we did not observe escape mutations in this key CD4+ T cell epitope in patients with evolving chronic hepatitis C. During acute hepatitis C a CD4+ T cell response against this epitope is readily induced in most, if not all, HLA-DR1+ patients. This antiviral T cell population becomes functionally impaired or is deleted early in the course of disease in those where viremia persists

Hepatitis C virus-specific cellular immune responses in individuals with no evidence of infection

The detection of hepatitis C virus (HCV)-specific T cell responses in HCV-uninfected, presumably unexposed, subjects could be due to an underestimation of the frequency of spontaneously resolving infections, as most acute HCV infections are clinically silent. To address this hypothesis, HCV-specific cellular immune responses were characterized, in individuals negative for an HCV PCR assay and humoral response, with (n = 32) or without (n = 33) risk of exposure to HCV. Uninfected volunteers (n = 20) with a chronically HCV-infected partner were included as positive controls for potential exposure to HCV and HCV infection, respectively. HCV-specific T cell responses in freshly isolated peripheral blood mononuclear cells were studied ex vivo by ELISPOT and CFSE-based proliferation assays using panels of HCV Core and NS3-derived peptides. A pool of unrelated peptides was used as a negative control, and a peptide mix of human cytomegalovirus, Epstein-Bar virus and Influenza virus as a positive control. Overall, 20% of presumably HCV-uninfected subject tested had detectable T-cell responses to the virus, a rate much higher than previous estimates of HCV prevalence in developed countries. This result would be consistent with unapparent primary HCV infections that either cleared spontaneously or remained undetected by conventional serological assays

Enumeration of Functional T-Cell Subsets by Fluorescence-Immunospot Defines Signatures of Pathogen Burden in Tuberculosis

IFN-γ and IL-2 cytokine-profiles define three functional T-cell subsets which may correlate with pathogen load in chronic intracellular infections. We therefore investigated the feasibility of the immunospot platform to rapidly enumerate T-cell subsets by single-cell IFN-γ/IL-2 cytokine-profiling and establish whether immunospot-based T-cell signatures distinguish different clinical stages of human tuberculosis infection.We used fluorophore-labelled anti-IFN-γ and anti-IL-2 antibodies with digital overlay of spatially-mapped colour-filtered images to enumerate dual and single cytokine-secreting M. tuberculosis antigen-specific T-cells in tuberculosis patients and in latent tuberculosis infection (LTBI). We validated results against established measures of cytokine-secreting T-cells.Fluorescence-immunospot correlated closely with single-cytokine enzyme-linked-immunospot for IFN-γ-secreting T-cells and IL-2-secreting T-cells and flow-cytometry-based detection of dual IFN-γ/IL-2-secreting T-cells. The untreated tuberculosis signature was dominated by IFN-γ-only-secreting T-cells which shifted consistently in longitudinally-followed patients during treatment to a signature dominated by dual IFN-γ/IL-2-secreting T-cells in treated patients. The LTBI signature differed from active tuberculosis, with higher proportions of IL-2-only and IFN-γ/IL-2-secreting T-cells and lower proportions of IFN-γ-only-secreting T-cells.Fluorescence-immunospot is a quantitative, accurate measure of functional T-cell subsets; identification of cytokine-signatures of pathogen burden, distinct clinical stages of M. tuberculosis infection and long-term immune containment suggests application for treatment monitoring and vaccine evaluation

Analysis of FOXP3+ Regulatory T Cells That Display Apparent Viral Antigen Specificity during Chronic Hepatitis C Virus Infection

We reported previously that a proportion of natural CD25+ cells isolated from the PBMC of HCV patients can further upregulate CD25 expression in response to HCV peptide stimulation in vitro, and proposed that virus-specific regulatory T cells (Treg) were primed and expanded during the disease. Here we describe epigenetic analysis of the FOXP3 locus in HCV-responsive natural CD25+ cells and show that these cells are not activated conventional T cells expressing FOXP3, but hard-wired Treg with a stable FOXP3 phenotype and function. Of ∼46,000 genes analyzed in genome wide transcription profiling, about 1% were differentially expressed between HCV-responsive Treg, HCV-non-responsive natural CD25+ cells and conventional T cells. Expression profiles, including cell death, activation, proliferation and transcriptional regulation, suggest a survival advantage of HCV-responsive Treg over the other cell populations. Since no Treg-specific activation marker is known, we tested 97 NS3-derived peptides for their ability to elicit CD25 response (assuming it is a surrogate marker), accompanied by high resolution HLA typing of the patients. Some reactive peptides overlapped with previously described effector T cell epitopes. Our data offers new insights into HCV immune evasion and tolerance, and highlights the non-self specific nature of Treg during infection