T-cell exhaustion is a phenomenon of dysfunction or physical elimination of antigen-specific T cells reported in human immunodeficiency virus (HIV), hepatitis B virus (HBV), and hepatitis C virus (HCV) infections as well as cancer. Exhaustion appears to be often restricted to CD8+ T cells responses in the literature, although CD4+ T cells have also been reported to be functionally exhausted in certain chronic infections. Although our understanding of the molecular mechanisms associated with the transcriptional regulation of T-cell exhaustion is advancing, it is imperative to also explore the central mechanisms that control the altered expression patterns. Targeting metabolic dysfunctions with mitochondrion-targeted antioxidants are also expected to improve the antiviral functions of exhausted virus-specific CD8+ T cells. In addition, it is crucial to consider the contributions of mitochondrial biogenesis on T-cell exhaustion and how mitochondrial metabolism of T cells could be targeted whilst treating chronic viral infections. Here, we review the current understanding of cardinal features of T-cell exhaustion in chronic infections, and have attempted to focus on recent discoveries, potential strategies to reverse exhaustion and reinvigorate optimal protective immune responses in the host.
Hand, foot and mouth disease (HFMD), caused by enterovirus A71 (EV-A71), presents mild to severe disease, and sometimes fatal neurological and respiratory manifestations. However, reasons for the severe pathogenesis remain undefined. To investigate this, infection and viral kinetics of EV-A71 isolates from clinical disease (mild, moderate and severe) from Sarawak, Malaysia, were characterised in human rhabdomyosarcoma (RD), neuroblastoma (SH-SY5Y) and peripheral blood mononuclear cells (PBMCs). High resolution transcriptomics was used to decipher EV-A71-host interactions in PBMCs. Ingenuity analyses revealed similar pathways triggered by all EV-A71 isolates, although the extent of activation varied. Importantly, several pathways were found to be specific to the severe isolate, including triggering receptor expressed on myeloid cells 1 (TREM-1) signalling. Depletion of TREM-1 in EV-A71-infected PBMCs with peptide LP17 resulted in decreased levels of pro-inflammatory genes for the moderate and severe isolates. Mechanistically, this is the first report describing the transcriptome profiles during EV-A71 infections in primary human cells, and the potential involvement of TREM-1 in the severe disease pathogenesis, thus providing new insights for future treatment targets.
In Malaysia, co-circulation of CRF01_AE and subtype B has resulted in the emergence of the second generation derivative; CRF33_01B in approximately 20% of its HIV-1 infected individuals. Our objective was to identify possible biological advantages that CRF33_01B possesses over its progenitors. Biological and molecular comparisons of CRF33_01B against its parental subtypes clearly show that CRF33_01B replicated better in activated whole peripheral blood mononuclear cells (PBMCs) and CD4+ T-lymphocytes, but not monocyte-derived macrophages (MDMs). Also, its acquired fitness was greater than CRF01_AE but not subtype B. Moreover, CRF33_01B has higher rate of apoptotic cell death and syncytia induction compared to subtype B. These adaptive and survival abilities could have been acquired by CRF33_01B due to the incorporation of subtype B fragments into the gag-RT region of its full-length genome. Our studies confirm the previously held belief that HIV-1 strains may harbor enhanced biological fitness upon recombination. We therefore estimate a possible gradual replacement of the current predominance of CRF01_AE, as well as wider dissemination of CRF33_01B, together with the identification of other new CRF01_AE/B inter-subtype recombinants in Malaysia.
Simian immunodeficiency virus (SIV) infection models in cynomolgus macaques are important for analysis of the pathogenesis of immunodeficiency virus and for studies on the efficacy of new vaccine candidates. However, very little is known about the pathogenesis of SIV or simian human immunodeficiency virus (SHIV) in cynomolgus macaques from different Asian countries. In the present study, we analysed the infectivity and pathogenicity of CCR5-tropic SIVmac and those of dual-tropic SHIV89.6P inoculated into cynomolgus macaques in Indonesian, Malaysian or Philippine origin. The plasma viral loads in macaques infected with either SIVmac239 or SHIV89.6P were maintained at high levels. CD4+ T cell levels in macaques infected with SIVmac239 gradually decreased. All of the macaques infected with SHIV89.6P showed greatly reduced CD4+ T-cell numbers within 6 weeks of infection. Eight of the 11 macaques infected with SIVmac239 were killed due to AIDS symptoms after 2-4.5 years, while four of the five macaques infected with SHIV89.6P were killed due to AIDS symptoms after 1-3.5 years. We also analysed cynomolgus macaques infected intrarectally with repeated low, medium or high doses of SIVmac239, SIVmac251 or SHIV89.6P. Infection was confirmed by quantitative RT-PCR at more than 5000, 300 and 500 TCID50 for SIVmac239, SIVmac251 and SHIV89.6P, respectively. The present study indicates that cynomolgus macaques of Asian origin are highly susceptible to SIVmac and SHIV infection by both intravenous and mucosal routes. These models will be useful for studies on virus pathogenesis, vaccination and therapeutics against human immunodeficiency virus/AIDS.
Systemic Epstein-Barr virus-positive T-cell lymphoproliferative childhood disease is an extremely rare disorder and classically arises following primary acute or chronic active Epstein-Barr virus infection. It is characterized by clonal proliferation of Epstein-Barr virus-infected T-cells with an activated cytotoxic phenotype. This disease has a rapid clinical course and is more frequent in Asia and South America, with relatively few cases being reported in Western countries. The clinical and pathological features of the disease overlap with other conditions including infectious mononucleosis, chronic active Epstein-Barr virus infection, hemophagocytic lymphohistiocytosis and natural killer cell malignancies. We describe the rare case of systemic Epstein-Barr virus-positive T-cell lymphoproliferative childhood disease in a 16-year-old Malay boy.
This study evaluates the immune responses of single avian influenza virus (AIV) HA DNA vaccine immunization using attenuated Salmonella enterica sv. Typhimurium as an oral vaccine carrier and intramuscular (IM) DNA injection. One-day-old specific-pathogen-free (SPF) chicks immunized once by oral gavage with 10(9) Salmonella colony-forming units containing plasmid expression vector encoding the HA gene of A/Ck/Malaysia/5858/04 (H5N1) (pcDNA3.1.H5) did not show any clinical manifestations. Serum hemagglutination inhibition (HI) titer samples collected from the IM immunized chickens were low compared to those immunized with S. typhimurium.pcDNA3.1.H5. The highest average antibody titers were detected on day 35 post immunization for both IM and S. typhimurium.pcDNA3.1.H5 immunized groups, at 4.0±2.8 and 51.2±7.5, respectively. S. typhimurium.pcDNA3.1.H5 also elicited both CD4(+) and CD8(+) T cells from peripheral blood mononuclear cells (PBMCs) of immunized chickens as early as day 14 after immunization, at 20.5±2.0 and 22.9±1.9%, respectively. Meanwhile, the CD4(+) and CD8(+) T cells in chickens vaccinated intramuscularly were low at 5.9±0.9 and 8.5±1.3%, respectively. Immunization of chickens with S. typhimurium.pcDNA3.1.H5 enhanced IL-1β, IL-12β, IL-15 and IL-18 expressions in spleen although no significant differences were recorded in chickens vaccinated via IM and orally with S. typhimurium and S. typhimurium.pcDNA3.1. Hence, single oral administrations of the attenuated S. typhimurium containing pcDNA3.1.H5 showed antibody, T cell and Th1-like cytokine responses against AIV in chickens. Whether the T cell response induced by vaccination is virus-specific and whether vaccination protects against AIV infection requires further study.
Newcastle disease (ND) is a highly contagious avian disease and one of the major causes of economic losses in the poultry industry. The emergence of virulent NDV genotypes and repeated outbreaks of NDV in vaccinated chickens have raised the need for fundamental studies on the virus-host interactions. In this study, the profiles of B and T lymphocytes and macrophages and differential expression of 26 immune-related genes in the spleen of specific-pathogen-free (SPF) chickens, infected with either the velogenic genotype VII NDV strain IBS002 or the genotype VIII NDV strain AF2240, were evaluated. A significant reduction in T lymphocyte population and an increase in the infiltration of IgM+ B cells and KUL01+ macrophages were detected in the infected spleens at 1, 3 and 4 days post-infection (dpi) (P<0.05). The gene expression profiles showed an up-regulation of CCLi3, CXCLi1, CXCLi2 (IL-8), IFN-γ, IL-12α, IL-18, IL-1β, IL-6, iNOS, TLR7, MHCI, IL-17F and TNFSF13B (P<0.05). However, these two genotypes showed different cytokine expression patterns and viral load. IBS002 showed higher viral load than AF2240 in spleen at 3 and 4dpi and caused a more rapid up-regulation of CXCLi2, IFN-γ, IL-12α, IL-18, IL-1β, iNOS and IL-10 at 3dpi. Meanwhile, the expression levels of CCLI3, CXCLi1, IFN-γ, IL-12α, IL-1β and iNOS genes were significantly higher in AF2240 at 4dpi. In addition, the expression levels of IL-10 were significantly higher in the IBS002-infected chickens at 3 and 4dpi. Hence, infection with velogenic genotype VII and VIII NDV induced different viral load and production of cytokines and chemokines associated with inflammatory reactions.
Hepatitis C virus (HCV)-specific CD4+ and CD8+ T cells are key to successful viral clearance in HCV disease. Accumulation of exhausted HCV-specific T cells during chronic infection results in considerable loss of protective functional immune responses. The role of T-cell exhaustion in chronic HCV disease remains poorly understood. Here, we studied the frequency of HCV peptide-stimulated T cells expressing negative immune checkpoints (PD-1, CTLA-4, TRAIL, TIM-3 and BTLA) by flow cytometry, and measured the levels of Th1/Th2/Th17 cytokines secreted by T cells by a commercial Multi-Analyte ELISArray™ following in vitro stimulation of T cells using HCV peptides and phytohemagglutinin (PHA). HCV peptide-stimulated CD4+ and CD8+ T cells of chronic HCV (CHC) patients showed significant increase of CTLA-4. Furthermore, HCV peptide-stimulated CD4+ T cells of CHC patients also displayed relatively higher levels of PD-1 and TRAIL, whereas TIM-3 was up-regulated on HCV peptide-stimulated CD8+ T cells. Whereas the levels of IL-10 and TGF-β1 were significantly increased, the levels of pro-inflammatory cytokines IL-2, TNF-α, IL-17A and IL-6 were markedly decreased in the T cell cultures of CHC patients. Chronic HCV infection results in functional exhaustion of CD4+ and CD8+ T cells likely contributing to viral persistence.