Transcriptomic response and immunological responses to chimpanzee adenovirus- and MVA viral-vectored vaccines for RSV in healthy adults.

Cohorts of healthy younger adults (18-50yrs) and healthy older adults (60-75yrs) were immunized intramuscularly or intranasally with an adenovirus-vectored RSV vaccine (PanAd3-RSV) as a prime dose and boosted with PanAd3-RSV or a poxvirus-vectored vaccine (MVA-RSV) encoding the same insert. Whole blood gene expression was measured at baseline, 3- and 7-days post vaccination. Intramuscular prime vaccination with PanAd3-RSV induced differential expression of 643 genes (DEGs, FDR < 0.05). Intranasal prime vaccination with PanAd3-RSV did not induce any differentially expressed genes (DEGs) in blood samples at 3 days post vaccination. Intranasally primed participants showed greater numbers of DEGS on boosting than intramuscularly primed participants. The most highly enriched biological processes related to DEGs after both prime and boost vaccination were type-1 interferon related pathways, lymphocytic and humoral immune responses.

Coronavirus disease 2019 subphenotypes and differential treatment response to convalescent plasma in critically ill adults: secondary analyses of a randomized clinical trial.

PURPOSE: Benefit from convalescent plasma therapy for coronavirus disease 2019 (COVID-19) has been inconsistent in randomized clinical trials (RCTs) involving critically ill patients. As COVID-19 patients are immunologically heterogeneous, we hypothesized that immunologically similar COVID-19 subphenotypes may differ in their treatment responses to convalescent plasma and explain inconsistent findings between RCTs . METHODS: We tested this hypothesis in a substudy involving 1239 patients, by measuring 26 biomarkers (cytokines, chemokines, endothelial biomarkers) within the randomized, embedded, multifactorial, adaptive platform trial for community-acquired pneumonia (REMAP-CAP) that assigned 2097 critically ill COVID-19 patients to either high-titer convalescent plasma or usual care. Primary outcome was organ support free days at 21 days (OSFD-21) . RESULTS: Unsupervised analyses identified three subphenotypes/endotypes. In contrast to the more homogeneous subphenotype-2 (N = 128 patients, 10.3%; with elevated type i and type ii effector immune responses) and subphenotype-3 (N = 241, 19.5%; with exaggerated inflammation), the subphenotype-1 had variable biomarker patterns (N = 870 patients, 70.2%). Subphenotypes-2, and -3 had worse outcomes, and subphenotype-1 had better outcomes with convalescent plasma therapy compared with usual care (median (IQR). OSFD-21 in convalescent plasma vs usual care was 0 (- 1, 21) vs 10 (- 1, to 21) in subphenotype-2; 1.5 (- 1, 21) vs 12 (- 1, to 21) in suphenotype-3, and 0 (- 1, 21) vs 0 (- 1, to 21) in subphenotype-1 (test for between-subphenotype differences in treatment effects p = 0.008). CONCLUSIONS: We reported three COVID-19 subphenotypes, among critically ill adults, with differential treatment effects to ABO-compatible convalescent plasma therapy. Differences in subphenotype prevalence between RCT populations probably explain inconsistent results with COVID-19 immunotherapies.

Expression of type I interferon-associated genes at antiretroviral therapy interruption predicts HIV virological rebound.

Although certain individuals with HIV infection can stop antiretroviral therapy (ART) without viral load rebound, the mechanisms under-pinning 'post-treatment control' remain unclear. Using RNA-Seq we explored CD4 T cell gene expression to identify evidence of a mechanism that might underpin virological rebound and lead to discovery of associated biomarkers. Fourteen female participants who received 12 months of ART starting from primary HIV infection were sampled at the time of stopping therapy. Two analysis methods (Differential Gene Expression with Gene Set Enrichment Analysis, and Weighted Gene Co-expression Network Analysis) were employed to interrogate CD4+ T cell gene expression data and study pathways enriched in post-treatment controllers versus early rebounders. Using independent analysis tools, expression of genes associated with type I interferon responses were associated with a delayed time to viral rebound following treatment interruption (TI). Expression of four genes identified by Cox-Lasso (ISG15, XAF1, TRIM25 and USP18) was converted to a Risk Score, which associated with rebound (p < 0.01). These data link transcriptomic signatures associated with innate immunity with control following stopping ART. The results from this small sample need to be confirmed in larger trials, but could help define strategies for new therapies and identify new biomarkers for remission.

Identification of neutralising pembrolizumab anti-drug antibodies in patients with melanoma.

Development of anti-drug antibodies (ADAs) can interfere with therapeutic monoclonal antibodies and may lead to drug neutralisation and clinical disease progression. Measurement of circulating drug levels and development of ADAs in the setting of anti-programmed cell death-1 agent pembrolizumab has not been well-studied. Enzyme-linked immunosorbent assays were used to measure pembrolizumab drug level and ADAs in 41 patients with melanoma at baseline, Time-point 1 (3 weeks) and Time-point 2 (21 weeks). Assay results were related to patient demographics and clinical outcome data at 6 months. The median pembrolizumab drug level at 3 weeks was 237 ng/µL and did not correlate with age, sex or body surface area.17/41 patients had an ADA detected at any timepoint, with the highest prevalence at Timepoint 1 (median concentration = 17 ng/µL). The presence of an ADA did not correlate with clinical progression at 6 months. 3/41 (7%) of patients displayed a falling pembrolizumab drug level and rising ADA titre between Timepoint 1 and 2 suggestive of a neutralising ADA. Pembrolizumab drug levels and ADAs can be readily measured. The rates of total and treatment-emergent ADAs may be higher in "real-word" settings than those previously reported. Larger studies are needed to determine effect of neutralising ADAs on long-term clinical outcome.

Mucosal-associated invariant T (MAIT) cells are activated in the gastrointestinal tissue of patients with combination ipilimumab and nivolumab therapy-related colitis in a pathology distinct from ulcerative colitis.

The aim of this study was to investigate the pathogenesis of combination ipilimumab and nivolumab-associated colitis (IN-COL) by measuring gut-derived and peripheral blood mononuclear cell (GMNC; PBMC) profiles. We studied GMNC and PBMC from patients with IN-COL, IN-treated with no adverse-events (IN-NAE), ulcerative colitis (UC) and healthy volunteers using flow cytometry. In the gastrointestinal-derived cells we found high levels of activated CD8+ T cells and mucosal-associated invariant T (MAIT) cells in IN-COL, changes that were not evident in IN-NAE or UC. UC, but not IN-C, was associated with a high proportion of regulatory T cells (Treg ). We sought to determine if local tissue responses could be measured in peripheral blood. Peripherally, checkpoint inhibition instigated a rise in activated memory CD4+ and CD8+ T cells, regardless of colitis. Low circulating MAIT cells at baseline was associated with IN-COL patients compared with IN-NAE in one of two cohorts. UC, but not IN-COL, was associated with high levels of circulating plasmablasts. In summary, the alterations in T cell subsets measured in IN-COL-affected tissue, characterized by high levels of activated CD8+ T cells and MAIT cells and a low proportion of Treg , reflected a pathology distinct from UC. These tissue changes differed from the periphery, where T cell activation was a widespread on-treatment effect, and circulating MAIT cell count was low but not reliably predictive of colitis.

Local heroes or villains: tissue-resident memory T cells in human health and disease.

Tissue-resident memory T (TRM) cells are increasingly associated with the outcomes of health and disease. TRM cells can mediate local immune protection against infections and cancer, which has led to interest in TRM cells as targets for vaccination and immunotherapies. However, these cells have also been implicated in mediating detrimental pro-inflammatory responses in autoimmune skin diseases such as psoriasis, alopecia areata, and vitiligo. Here, we summarize the biology of TRM cells established in animal models and in translational human studies. We review the beneficial effects of TRM cells in mediating protective responses against infection and cancer and the adverse role of TRM cells in driving pathology in autoimmunity. A further understanding of the breadth and mechanisms of TRM cell activity is essential for the safe design of strategies that manipulate TRM cells, such that protective responses can be enhanced without unwanted tissue damage, and pathogenic TRM cells can be eliminated without losing local immunity.

Humoral and cellular immunity to RSV in infants, children and adults.

BACKGROUND: Respiratory syncytial virus (RSV) causes respiratory disease throughout life. Here we report differences in naturally acquired immunity with age and presumed exposure. METHODS: A longitudinal, non-interventional, observational study was performed in healthy adults (20 paediatric healthcare workers and 10 non-healthcare workers), children (10 aged 3-6 years) and infants (5 aged 2-4 months and 20 aged 6-12 months). Blood samples were analysed for RSV-neutralising antibody titre, F/Ga/Gb-specific antibody titres, F-specific IgG/IgA memory B-cell frequencies and T-cell production of IFNγ, IL-4, IL-13 and IL-17. RESULTS: Serum G-specific antibody titres were significantly lower in infants and children than adults. However, serum titres of F-specific and RSV-neutralising antibody and IFNγ-producing T-cell frequencies were low or absent in the infants, but comparable between children and adults. Interestingly, F-specific memory IgA B-cells could not be detected in paediatric samples and in samples from non-healthcare workers, but recordable IgA memory B-cells were found in 9/18 paediatric healthcare workers and 2/8 non-healthcare workers at the end of the RSV season. These responses waned 4-6 months later. By contrast, F-specific IgG memory B-cells were detectable in samples from all adults without significant variation across time points. T-cells producing IL-4, IL-13 and IL-17 responses were not detectable in peripheral blood from a subset of volunteers. CONCLUSIONS: Repeated RSV exposure in early life generates immune responses that are inversely related to frequency of severe disease. Induction of F-specific antibody and cellular immune responses through infant vaccination might help to accelerate the development of protective immune responses at an early age. Clinicaltrials.gov reference NCT01563692 and NCT01640652.

High MDR-1 expression by MAIT cells confers resistance to cytotoxic but not immunosuppressive MDR-1 substrates.

High expression of the ATP-binding cassette-multi-drug efflux protein 1 (MDR1) is a striking feature of mucosal-associated invariant T (MAIT) cells, a prominent human innate-like T cell subset. We demonstrate significantly higher MDR1 expression by CD8 + CD161 ++ Vα7.2 + MAIT cells than the phenotypically and functionally related CD8 + CD161 ++ Vα7.2-subset and show MDR1 expression to be similarly high throughout MAIT CD4 + , CD8 + , double-negative (DN) and double-positive (DP) cell subsets. We demonstrate the MAIT cell-predominant CD8+ CD161++ subset to uniquely and efficiently efflux the cytotoxic anthracycline daunorubicin, retain function on daunorubicin exposure and demonstrate MDR1-dependent protection from daunorubicin-induced apoptosis. By contrast, CD8+ CD161++ Vα7.2+ MAIT cells were not protected from the anti-proliferative and cytotoxic effects of the immunosuppressive MDR1 substrates tacrolimus and mycophenoic acid, although function following MAIT cell-specific T cell receptor (TCR)-dependent and -independent stimulation was preserved on in-vitro exposure to these agents. Overall, our data further define MDR1 expression by CD161++ T and MAIT cells and demonstrate the potential for high MDR1 expression by MAIT cells to confer resistance to cytotoxic MDR1 substrates in vivo . As our understanding of the importance of MAIT cells in human immunity and immunopathology grows, this is an important observation for clinical contexts such as the treatment of malignancy, autoimmunity and post-transplant immunosuppression.

The impact of immunoglobulin in acute HIV infection on the HIV reservoir: a randomized controlled trial.

OBJECTIVES: Antiretroviral therapy (ART) during acute HIV infection (AHI) restricts the HIV reservoir, but additional interventions are necessary to induce a cure. Intravenous immunoglobulin (IVIG) is not HIV-specific but is safe and temporarily reduces the HIV reservoir in chronic HIV infection. We present a randomized controlled trial to investigate whether IVIG plus ART in AHI reduces the HIV reservoir and immune activation compared with ART alone. METHODS: Ten men with AHI (Fiebig II-IV) initiated ART (tenofovir, entricitabine, ritonavir boosted darunavir and raltegravir) at HIV-1 diagnosis and were randomized to ART alone or ART plus 5 days of IVIG, once virally suppressed (week 19). Blood samples were evaluated for viral reservoir, immune activation, immune exhaustion and microbial translocation. Flexible sigmoidoscopy was performed at weeks 19, 24 and 48, and gut proviral DNA and cell numbers determined. RESULTS: IVIG was well tolerated and no viral blips (> 50 HIV-1 RNA copies/mL) occurred during IVIG therapy. From baseline to week 48, total HIV DNA in peripheral blood mononuclear cells (PBMCs) (cases: -3.7 log10 copies/106 CD4 cells; controls: -3.87 log10 copies/106 CD4 cells) declined with no differences observed between the groups (P = 0.49). Declines were observed in both groups from week 19 to week 48 in total HIV DNA in PBMCs (P = 0.38), serum low copy RNA (P = 0.57) and gut total HIV DNA (P = 0.55), but again there were no significant differences between arms. Biomarkers of immune activation, immune exhaustion and microbial translocation and the CD4:CD8 ratio were similar between arms for all comparisons. CONCLUSIONS: Although safe, IVIG in AHI did not impact total HIV DNA, immune function or microbial translocation in peripheral blood or gut tissue.

First Complete Genome Sequences of Zika Virus Isolated from Febrile Patient Sera in Ecuador.

Here, we present the complete genome sequences of two Zika virus (ZIKV) strains, EcEs062_16 and EcEs089_16, isolated from the sera of febrile patients in Esmeraldas City, in the northern coastal province of Esmeraldas, Ecuador, in April 2016. These are the first complete ZIKV genomes to be reported from Ecuador.

Elevated Serum IgG4 Levels in Diagnosis, Treatment Response, Organ Involvement, and Relapse in a Prospective IgG4-Related Disease UK Cohort.

OBJECTIVES: Elevated serum immunoglobulin G4 (IgG4) levels have been associated with autoimmune pancreatitis and IgG4-related disease (IgG4-RD) for over a decade. However, an elevated serum IgG4 is not specific for the disease. There have been inconsistent reports of its use in diagnosis, as a marker of disease relapse, and its relationship to organ involvement in retrospective cohorts. The aims of this study were to ascertain conditions that are associated with an elevated serum IgG4 and to investigate the role of IgG4 in diagnosis, relapse, and organ involvement in a prospective cohort of patients with IgG4-RD. METHODS: We evaluated serum IgG4 measurements in the Oxford Immunology Laboratory over 6 years. Patients in whom serum IgG4 was requested to differentiate IgG4-RD from other diseases were recruited into a longitudinal follow-up study to determine final diagnosis. In a prospective cohort of IgG4-RD patients, organ involvement, response to therapy, and disease relapse were determined. RESULTS: Two thousand and sixty-seven samples from 1,510 patients had serum IgG4 measured. Of these, IgG4 was elevated (≥1.4 g l(-1)) in 243 (16.1%) patients. The main indication (85.6%) was to distinguish between IgG4-RD and non-IgG4-RD conditions. Only 5.1% of patients who had serum IgG4 measured for this purpose had a final diagnosis of IgG4-RD. Of those with an elevated serum IgG4, 22.4% met IgG4-RD diagnostic criteria. Serum IgG4 was elevated in 48 (82.8%) of IgG4-RD patients. An IgG4 cutoff of 1.4 g l(-1) gave a sensitivity of 82.8% and specificity of 84.7% to diagnose IgG4-RD. Increasing this to 2.8 g l(-1) increased specificity to 96.2% and negative predictive value to 97.7%, with a lower sensitivity of 56.9% and positive predictive value of 44.5%. Serum IgG4 levels fell with corticosteroid therapy, but this was not disease-specific. A serum IgG4 of ≥2.8 g l(-1) at diagnosis was associated with multi-organ involvement and risk of relapse. CONCLUSIONS: Serum IgG4 levels are elevated in multiple non-IgG4-RD inflammatory and malignant conditions, with less than one-quarter of those with an elevated IgG4 meeting IgG4-RD diagnostic criteria. A serum IgG4 of ≥2.8 g l(-1) is useful in distinguishing between IgG4-RD and non-IgG4-RD diagnoses, predicting multiple-organ involvement and risk of relapse in IgG4-RD.

CD161(int)CD8+ T cells: a novel population of highly functional, memory CD8+ T cells enriched within the gut.

The C-type lectin-like receptor CD161 is expressed by lymphocytes found in human gut and liver, as well as blood, especially natural killer (NK) cells, T helper 17 (Th17) cells, and a population of unconventional T cells known as mucosal-associated invariant T (MAIT) cells. The association of high CD161 expression with innate T-cell populations including MAIT cells is established. Here we show that CD161 is also expressed, at intermediate levels, on a prominent subset of polyclonal CD8+ T cells, including antiviral populations that display a memory phenotype. These memory CD161(int)CD8+ T cells are enriched within the colon and express both CD103 and CD69, markers associated with tissue residence. Furthermore, this population was characterized by enhanced polyfunctionality, increased levels of cytotoxic mediators, and high expression of the transcription factors T-bet and eomesodermin (EOMES). Such populations were induced by novel vaccine strategies based on adenoviral vectors, currently in trial against hepatitis C virus. Thus, intermediate CD161 expression marks potent polyclonal, polyfunctional tissue-homing CD8+ T-cell populations in humans. As induction of such responses represents a major aim of T-cell prophylactic and therapeutic vaccines in viral disease and cancer, analysis of these populations could be of value in the future.

Safety and immunogenicity of novel respiratory syncytial virus (RSV) vaccines based on the RSV viral proteins F, N and M2-1 encoded by simian adenovirus (PanAd3-RSV) and MVA (MVA-RSV); protocol for an open-label, dose-escalation, single-centre, phase 1 clinical trial in healthy adults.

INTRODUCTION: Respiratory syncytial virus (RSV) infection causes respiratory disease throughout life, with infants and the elderly at risk of severe disease and death. RSV001 is a phase 1 (first-in-man), open-label, dose-escalation, clinical trial of novel genetic viral-vectored vaccine candidates PanAd3-RSV and modified vaccinia virus Ankara (MVA)-RSV. The objective of RSV001 is to characterise the (primary objective) safety and (secondary objective) immunogenicity of these vaccines in healthy younger and older adults. METHODS AND ANALYSIS: Heterologous and homologous 'prime'/boost combinations of PanAd3-RSV and single-dose MVA-RSV are evaluated in healthy adults. 40 healthy adults aged 18-50 years test one of four combinations of intramuscular (IM) or intranasal (IN) PanAd3-RSV prime and IM PanAd3 or IM MVA-RSV boost vaccination, starting at a low dose for safety. The following year an additional 30 healthy adults aged 60-75 years test either a single dose of IM MVA-RSV, one of three combinations of IN or IM PanAd3-RSV prime and PanAd3-RSV or MVA-RSV boost vaccination used in younger volunteers, and a non-vaccinated control group. Study participants are self-selected volunteers who satisfy the eligibility criteria and are assigned to study groups by sequential allocation. Safety assessment includes the daily recording of solicited and unsolicited adverse events for 1 week after vaccination, as well as visit (nursing) observations and safety bloods obtained at all scheduled attendances. Laboratory measures of RSV-specific humoral and cellular immune responses after vaccination will address the secondary end points. All study procedures are performed at the Centre for Clinical Vaccinology and Tropical Medicine (CCVTM), Oxford, UK. ETHICS AND DISSEMINATION: RSV001 has clinical trial authorisation from the Medicines and Healthcare Products Regulatory Agency (MHRA) and ethics approval from NRES Berkshire (reference 13/SC/0023). All study procedures adhere to International Conference on Harmonisation (ICH) Good Clinical Practice guidelines. The results of the trial are to be published in peer-reviewed journals, conferences and academic forums. TRIAL REGISTRATION NUMBER: NCT01805921.

T- and B-cell responses and previous exposure to hepatitis B virus in 'anti-HBc alone' patients.

A serologic response to hepatitis B virus (HBV) defined as 'anti-HBc alone' is commonly observed, but its significance remains unclear. This study aimed to define the relationship between 'anti-HBc alone' serostatus and HBV infection, including HBV-specific T- and B-cell memory responses. We enrolled 31 'anti-HBc alone' patients. Total HBV DNA and cccDNA were tested by nested polymerase chain reaction (PCR) analysis in liver samples from 22 'anti-HBc alone' patients vs controls (chronic or resolved HBV infection), followed by HBsAg/HBcAg immunohistochemical (IHC) staining. IFN-γ secretion by HBV-specific T cells was compared in individuals who were 'anti-HBc alone' (n = 27), resolved HBV (n = 21), chronic HBV (n = 24) and 12 healthy controls using enzyme-linked immunospot (ELISpot) assays. An HBsAg-IgG B-cell ELISpot assay was performed in 'anti-HBc alone' patients before and after one dose of recombinant HBsAg vaccine. The majority (23/31, 74.2%) of the 'anti-HBc alone' individuals were co-infected with HCV. Infrequent intrahepatic total HBV DNA (2/22, 9.1%) and cccDNA (1/22, 4.5%) were detected in biopsies; HBsAg and HBcAg IHC staining was negative. HBV-specific T-cell responses were similar between 'anti-HBc alone' individuals and HBV resolvers. Circulating HBV-memory B-cell responses were detected in all 'anti-HBc alone' individuals, consistent with an HBsAg-specific memory pool. After one HBV vaccine dose, increased anti-HBs antibody levels were observed, accompanied by an expansion of HBsAg-specific memory B cells (P = 0.0226). 'Anti-HBc alone' individuals showed HBV-specific T-cell and memory B-cell responses typical of previous viral exposure and protective memory, suggesting a resolved infection.

Current knowledge and future perspectives on acute hepatitis C infection.

Acute hepatitis C virus (HCV) infections are frequently seen worldwide in certain risk groups, with an annual incidence rate varying between 0.08% and 66%. Although this incidence is substantial, a delayed diagnosis during chronic infection is most often made in the absence of clinical symptoms in the acute phase of the infection. Currently used methods to diagnose acute HCV infection are IgG antibody seroconversion and repeated HCV RNA measurements, although no definitive diagnostic test is currently available. Progress in the field of adaptive and innate immune responses has aided both advances in the field of HCV vaccine development and a more basic understanding of viral persistence. The rapid changes in the treatment of chronic HCV infection will affect therapeutic regimens for acute HCV infection in the coming years, leading to shorter treatment courses and pegylated interferon-free modalities. This review gives an overview of the current knowledge and uncertainties, together with some future perspectives on acute hepatitis C epidemiology, virology, immunology, and treatment.

MAIT cells are licensed through granzyme exchange to kill bacterially sensitized targets.

Mucosal-associated invariant T (MAIT) cells are an innate-like T-cell population restricted by the non-polymorphic, major histocompatibility complex class I-related protein 1, MR1. MAIT cells are activated by a broad range of bacteria through detection of riboflavin metabolites bound by MR1, but their direct cytolytic capacity upon recognition of cognate target cells remains unclear. We show that resting human MAIT cells are uniquely characterized by a lack of granzyme (Gr) B and low perforin expression, key granule proteins required for efficient cytotoxic activity, but high levels of expression of GrA and GrK. Bacterial activation of MAIT cells rapidly induced GrB and perforin, licensing these cells to kill their cognate target cells. Using a novel flow cytometry-based killing assay, we show that licensed MAIT cells, but not ex vivo MAIT cells from the same donors, can efficiently kill Escherichia coli-exposed B-cell lines in an MR1- and degranulation-dependent manner. Finally, we show that MAIT cells are highly proliferative in response to antigenic and cytokine stimulation, maintaining high expression of GrB, perforin, and GrA, but reduced expression of GrK following antigenic proliferation. The tightly regulated cytolytic capacity of MAIT cells may have an important role in the control of intracellular bacterial infections, such as Mycobacterium tuberculosis.

A mutation in X-linked inhibitor of apoptosis (G466X) leads to memory inflation of Epstein-Barr virus-specific T cells.

Mutations in the X-linked inhibitor of apoptosis (XIAP) gene have been associated with XLP-like disease, including recurrent Epstein-Barr virus (EBV)-related haemophagocytic lymphohystiocytosis (HLH), but the immunopathogenic bases of EBV-related disease in XIAP deficiency is unknown. We present the first analysis of EBV-specific T cell responses in functional XIAP deficiency. In a family of patients with a novel mutation in XIAP (G466X) leading to a late-truncated protein and varying clinical features, we identified gradual hypogammaglobulinaemia and large expansions of T cell subsets, including a prominent CD4(+) CD8(+) population. Extensive ex-vivo analyses showed that the expanded T cell subsets were dominated by EBV-specific cells with conserved cytotoxic, proliferative and interferon (IFN)-γ secretion capacity. The EBV load in blood fluctuated and was occasionally very high, indicating that the XIAP(G466X) mutation could impact upon EBV latency. XIAP deficiency may unravel a new immunopathogenic mechanism in EBV-associated disease.

Quantification of hepatic FOXP3+ T-lymphocytes in HIV/hepatitis C coinfection.

Coinfection with HIV adversely impacts every stage of hepatitis C (HCV) infection. Liver damage in HCV infection results from host antiviral responses rather than direct viral pathogenesis. Despite depressed cellular immunity, coinfected patients show accelerated hepatic fibrosis compared with HCV monoinfected patients. This paradox is poorly understood. T-regulatory (Treg) cells (CD4+ and FOXP3+) are hypothesized to limit hepatic damage in HCV. Our hypothesis was that reduced frequency of hepatic Treg in HIV/HCV coinfection compared with HCV monoinfection may explain poorer outcomes. We quantified FOXP3+, CD4+, CD8+ and CD20+ cells in liver biopsies of 35 male subjects matched by age and ISHAK fibrosis score, 12 HIV monoinfected, 11 HCV monoinfected and 12 HIV/HCV coinfected. Cell counts were performed using indirect immunohistochemical staining and light microscopy. HIV/HCV coinfected subjects had fewer hepatic FOXP3+ (P = 0.031) and CD4+ cells (P = 0.001) than HCV monoinfected subjects. Coinfected subjects had more hepatic CD8+ cells compared with HCV monoinfected (P = 0.023), and a lower ratio of FOXP3+ to CD8+ cells (0.08 vs 0.27, P < 0.001). Multivariate analysis showed number of CD4+ cells controlled for differences in number of FOXP3+ cells. Fewer hepatic FOXP3+ and CD4+ cells in HIV/HCV coinfection compared with HCV monoinfection suggests lower Treg activity, driven by an overall loss of CD4+ cells. Higher number of CD8+ cells in HIV/HCV coinfection suggests higher cytotoxic activity. This may explain poorer outcomes in HIV/HCV coinfected patients and suggests a potential mechanism by which highly active antiretroviral therapy may benefit these patients.