Potential role of HTLV-1 Tax-specific cytotoxic t lymphocytes expressing a unique t-cell receptor to promote inflammation of the central nervous system in myelopathy associated with HTLV-1.

Human T-lymphotropic virus 1 (HTLV-1) infection causes two serious diseases: adult T-cell leukemia/lymphoma (ATL) and HTLV-1-associated myelopathy (HAM). Immunological studies have revealed that HTLV-1 Tax-specific CD8+ cytotoxic T-cells (Tax-CTLs) in asymptomatic carriers (ACs) and ATL patients play an important role in the elimination of HTLV-1-infected host cells, whereas Tax-CTLs in HAM patients trigger an excessive immune response against HTLV-1-infected host cells infiltrating the central nervous system (CNS), leading to local inflammation. Our previous evaluation of HTLV-1 Tax301-309 (SFHSLHLLF)-specific Tax-CTLs (Tax301-309-CTLs) revealed that a unique T-cell receptor (TCR) containing amino acid (AA)-sequence motif PDR, was shared among HLA-A*24:02+ ACs and ATL patients and behaved as an eliminator by strong activity against HTLV-1. However, it remains unclear whether PDR+Tax301-309-CTLs also exist in HLA-A*24:02+ HAM patients and are involved in the pathogenesis of HAM. In the present study, by high-throughput TCR repertoire analysis technology, we revealed TCR repertoires of Tax301-309-CTLs in peripheral blood (PB) of HLA-A*24:02+ HAM patients were skewed, and a unique TCR-motif PDR was conserved in HAM patients (10 of 11 cases). The remaining case dominantly expressed (-DR, P-R, and PD-), which differed by one AA from PDR. Overall, TCRs with unique AA-sequence motifs PDR, or (-DR, P-R, and PD-) accounted for a total of 0.3-98.1% of Tax301-309-CTLs repertoires of HLA-A*24:02+ HAM patients. Moreover, TCR repertoire analysis of T-cells in the cerebrospinal fluid (CSF) from four HAM patients demonstrated the possibility that PDR+Tax301-309-CTLs and (-DR, P-R, and PD-)+Tax301-309-CTLs efficiently migrated and accumulated in the CSF of HAM patients fostering increased inflammation, although we observed no clear significant correlation between the frequencies of them in PB and the levels of CSF neopterin, a known disease activity biomarker of HAM. Furthermore, to better understand the potential function of PDR+Tax301-309-CTLs, we performed immune profiling by single-cell RNA-sequencing of Tax301-309-CTLs, and the result showed that PDR+Tax301-309-CTLs up-regulated the gene expression of natural killer cell marker KLRB1 (CD161), which may be associated with T-cell activation and highly cytotoxic potential of memory T-cells. These findings indicated that unique and shared PDR+Tax301-309-CTLs have a potential role in promoting local inflammation within the CNS of HAM patients.

NSG-Mice Reveal the Importance of a Functional Innate and Adaptive Immune Response to Overcome RVFV Infection.

Rift Valley fever (RVF) is a zoonotic disease caused by RVF Phlebovirus (RVFV). The RVFV MP-12 vaccine strain is known to exhibit residual virulence in the case of a deficient interferon type 1 response. The hypothesis of this study is that virus replication and severity of lesions induced by the MP-12 strain in immunocompromised mice depend on the specific function of the disturbed pathway. Therefore, 10 strains of mice with deficient innate immunity (B6-IFNARtmAgt, C.129S7(B6)-Ifngtm1Ts/J, B6-TLR3tm1Flv, B6-TLR7tm1Aki, NOD/ShiLtJ), helper T-cell- (CD4tm1Mak), cytotoxic T-cell- (CD8atm1Mak), B-cell- (Igh-Jtm1DhuN?+N2), combined T- and B-cell- (NU/J) and combined T-, B-, natural killer (NK) cell- and macrophage-mediated immunity (NOD.Cg-PrkdcscidIl2rgtm1WjI/SzJ (NSG) mice) were subcutaneously infected with RVFV MP-12. B6-IFNARtmAgt mice were the only strain to develop fatal disease due to RVFV-induced severe hepatocellular necrosis and apoptosis. Notably, no clinical disease and only mild multifocal hepatocellular necrosis and apoptosis were observed in NSG mice, while immunohistochemistry detected the RVFV antigen in the liver and the brain. No or low virus expression and no lesions were observed in the other mouse strains. Conclusively, the interferon type 1 response is essential for early control of RVFV replication and disease, whereas functional NK cells, macrophages and lymphocytes are essential for virus clearance.

Diminished Peripheral CD29hi Cytotoxic CD4+ T Cells Are Associated With Deleterious Effects During SIV Infection.

Cytotoxic CD4+ T cells (CD4+ CTLs) limit HIV pathogenesis, as evidenced in elite controllers (a subset of individuals who suppress the virus without the need for therapy). CD4+ CTLs have also been shown to kill HIV-infected macrophages. However, little is known about their contribution towards HIV persistence, how they are affected following exposure to immune modulators like morphine, and what factors maintain their frequencies and function. Further, the lack of robust markers to identify CD4+ CTLs in various animal models limits understanding of their role in HIV pathogenesis. We utilized various PBMC samples obtained from SIV infected and cART treated rhesus macaques exposed to morphine or saline and subjected to flow cytometry evaluations. Thereafter, we compared and correlated the expression of CD4+ CTL-specific markers to viral load and viral reservoir estimations in total CD4+ T cells. We found that CD29 could be reliably used as a marker to identify CD4+ CTLs in rhesus macaques since CD29hi CD4+ T cells secrete higher cytotoxic and proinflammatory cytokines following PMA/ionomycin or gag stimulation. In addition, this immune cell subset was depleted during untreated SIV infection. Strikingly, we also observed that early initiation of cART reconstitutes depleted CD29hi CD4+ T cells and restores their function. Furthermore, we noted that morphine exposure reduced the secretion of proinflammatory cytokines/cytotoxic molecules in CD29hi CD4+ T cells. Lastly, increased functionality of CD29hi CD4+ T cells as depicted by elevated levels of either IL-21 or granzyme B hi T Bet+ gag specific responses were linked to limiting the size of the replication-competent reservoir during cART treatment. Collectively, our data suggest that CD4+ CTLs are crucial in limiting SIV pathogenesis and persistence.

Cytotoxic Lymphocytes Target HIV-1 Gag Through Granzyme M-Mediated Cleavage.

Untreated HIV-1 infection leads to a slow decrease in CD4+ T cell lymphocytes over time resulting in increased susceptibility to opportunistic infections (acquired immunodeficiency syndrome, AIDS) and ultimately death of the infected individual. Initially, the host's immune response controls the infection, but cannot eliminate the HIV-1 from the host. Cytotoxic lymphocytes are the key effector cells in this response and can mediate crucial antiviral responses through the release of a set of proteases called granzymes towards HIV-1-infected cells. However, little is known about the immunological molecular mechanisms by which granzymes could control HIV-1. Since we noted that HIV-1 subtype C (HIV-1C) Gag with the tetrapeptide insertion PYKE contains a putative granzyme M (GrM) cleavage site (KEPL) that overlaps with the PYKE insertion, we analyzed the proteolytic activity of GrM towards Gag. Immunoblot analysis showed that GrM could cleave Gag proteins from HIV-1B and variants from HIV-1C of which the Gag-PYKE variant was cleaved with extremely high efficiency. The main cleavage site was directly after the insertion after leucine residue 483. GrM-mediated cleavage of Gag was also observed in co-cultures using cytotoxic lymphocytes as effector cells and this cleavage could be inhibited by a GrM inhibitor peptide. Altogether, our data indicate towards a noncytotoxic immunological mechanism by which GrM-positive cytotoxic lymphocytes target the HIV-1 Gag protein within infected cells to potentially control HIV-1 infection. This mechanism could be exploited in new therapeutic strategies to treat HIV-1-infected patients to improve immunological control of the infection.

A vaccine inducing solely cytotoxic T lymphocytes fully prevents Zika virus infection and fetal damage.

As vaccine-induced non-neutralizing antibodies may cause antibody-dependent enhancement of Zika virus (ZIKV) infection, we test a vaccine that induces only specific cytotoxic T lymphocytes (CTLs) without specific antibodies. We construct a DNA vaccine expressing a ubiquitinated and rearranged ZIKV non-structural protein 3 (NS3). The protein is immediately degraded and processed in the proteasome for presentation via major histocompatibility complex (MHC) class I for CTL generation. We immunize Ifnar1-/- adult mice with the ubiquitin/NS3 vaccine, impregnate them, and challenge them with ZIKV. Our data show that the vaccine greatly reduces viral titers in reproductive organs and other tissues of adult mice. All mice immunized with the vaccine survived after ZIKV challenge. The vaccine remarkably reduces placenta damage and levels of pro-inflammatory cytokines, and it fully protects fetuses from damage. CD8+ CTLs are essential in protection, as demonstrated via depletion experiments. Our study provides a strategy to develop safe and effective vaccines against viral infections.

Complex Interplay Between MAZR and Runx3 Regulates the Generation of Cytotoxic T Lymphocyte and Memory T Cells.

The BTB zinc finger transcription factor MAZR (also known as PATZ1) controls, partially in synergy with the transcription factor Runx3, the development of CD8 lineage T cells. Here we explored the role of MAZR as well as combined activities of MAZR/Runx3 during cytotoxic T lymphocyte (CTL) and memory CD8+ T cell differentiation. In contrast to the essential role of Runx3 for CTL effector function, the deletion of MAZR had a mild effect on the generation of CTLs in vitro. However, a transcriptome analysis demonstrated that the combined deletion of MAZR and Runx3 resulted in much more widespread downregulation of CTL signature genes compared to single Runx3 deletion, indicating that MAZR partially compensates for loss of Runx3 in CTLs. Moreover, in line with the findings made in vitro, the analysis of CTL responses to LCMV infection revealed that MAZR and Runx3 cooperatively regulate the expression of CD8α, Granzyme B and perforin in vivo. Interestingly, while memory T cell differentiation is severely impaired in Runx3-deficient mice, the deletion of MAZR leads to an enlargement of the long-lived memory subset and also partially restored the differentiation defect caused by loss of Runx3. This indicates distinct functions of MAZR and Runx3 in the generation of memory T cell subsets, which is in contrast to their cooperative roles in CTLs. Together, our study demonstrates complex interplay between MAZR and Runx3 during CTL and memory T cell differentiation, and provides further insight into the molecular mechanisms underlying the establishment of CTL and memory T cell pools.

Features of HLA class I expression and its clinical relevance in SARS-CoV-2: What do we know so far?

Modifications in HLA-I expression are found in many viral diseases. They represent one of the immune evasion strategies most widely used by viruses to block antigen presentation and NK cell response, and SARS-CoV-2 is no exception. These alterations result from a combination of virus-specific factors, genetically encoded mechanisms, and the status of host defences and range from loss or upregulation of HLA-I molecules to selective increases of HLA-I alleles. In this review, I will first analyse characteristic features of altered HLA-I expression found in SARS-CoV-2. I will then discuss the potential factors underlying these defects, focussing on HLA-E and class-I-related (like) molecules and their receptors, the most documented HLA-I alterations. I will also draw attention to potential differences between cells transfected to express viral proteins and those presented as part of authentic infection. Consideration of these factors and others affecting HLA-I expression may provide us with improved possibilities for research into cellular immunity against viral variants.

UTX promotes CD8+ T cell-mediated antiviral defenses but reduces T cell durability.

Persistent virus infections can cause pathogenesis that is debilitating or lethal. During these infections, virus-specific T cells fail to protect due to weakened antiviral activity or failure to persist. These outcomes are governed by histone modifications, although it is unknown which enzymes contribute to T cell loss or impaired function over time. In this study, we show that T cell receptor-stimulated CD8+ T cells increase their expression of UTX (ubiquitously transcribed tetratricopeptide repeat, X chromosome) to enhance gene expression. During chronic lymphocytic choriomeningitis virus (LCMV) infection in mice, UTX binds to enhancers and transcription start sites of effector genes, allowing for improved cytotoxic T lymphocyte (CTL)-mediated protection, independent of its trimethylation of histone 3 lysine 27 (H3K27me3) demethylase activity. UTX also limits the frequency and durability of virus-specific CD8+ T cells, which correspond to increased expression of inhibitory receptors. Thus, UTX guides gene expression patterns in CD8+ T cells, advancing early antiviral defenses while reducing the longevity of CD8+ T cell responses.

Stem Cell-Derived Viral Antigen-Specific T Cells Suppress HIV Replication and PD-1 Expression on CD4+ T Cells.

The viral antigen (Ag)-specific CD8+ cytotoxic T lymphocytes (CTLs) derived from pluripotent stem cells (PSCs), i.e., PSC-CTLs, have the ability to suppress the human immunodeficiency virus (HIV) infection. After adoptive transfer, PSC-CTLs can infiltrate into the local tissues to suppress HIV replication. Nevertheless, the mechanisms by which the viral Ag-specific PSC-CTLs elicit the antiviral response remain to be fully elucidated. In this study, we generated the functional HIV-1 Gag epitope SL9-specific CTLs from the induced PSC (iPSCs), i.e., iPSC-CTLs, and investigated the suppression of SL9-specific iPSC-CTLs on viral replication and the protection of CD4+ T cells. A chimeric HIV-1, i.e., EcoHIV, was used to produce HIV replication in mice. We show that adoptive transfer of SL9-specific iPSC-CTLs greatly suppressed EcoHIV replication in the peritoneal macrophages and spleen in the animal model. Furthermore, we demonstrate that the adoptive transfer significantly reduced expression of PD-1 on CD4+ T cells in the spleen and generated persistent anti-HIV memory T cells. These results indicate that stem cell-derived viral Ag-specific CTLs can robustly accumulate in the local tissues to suppress HIV replication and prevent CD4+ T cell exhaustion through reduction of PD-1 expression.

Bromodomain proteins regulate human cytomegalovirus latency and reactivation allowing epigenetic therapeutic intervention.

Reactivation of human cytomegalovirus (HCMV) from latency is a major health consideration for recipients of stem-cell and solid organ transplantations. With over 200,000 transplants taking place globally per annum, virus reactivation can occur in more than 50% of cases leading to loss of grafts as well as serious morbidity and even mortality. Here, we present the most extensive screening to date of epigenetic inhibitors on HCMV latently infected cells and find that histone deacetylase inhibitors (HDACis) and bromodomain inhibitors are broadly effective at inducing virus immediate early gene expression. However, while HDACis, such as myeloid-selective CHR-4487, lead to production of infectious virions, inhibitors of bromodomain (BRD) and extraterminal proteins (I-BETs), including GSK726, restrict full reactivation. Mechanistically, we show that BET proteins (BRDs) are pivotally connected to regulation of HCMV latency and reactivation. Through BRD4 interaction, the transcriptional activator complex P-TEFb (CDK9/CycT1) is sequestered by repressive complexes during HCMV latency. Consequently, I-BETs allow release of P-TEFb and subsequent recruitment to promoters via the superelongation complex (SEC), inducing transcription of HCMV lytic genes encoding immunogenic antigens from otherwise latently infected cells. Surprisingly, this occurs without inducing many viral immunoevasins and, importantly, while also restricting viral DNA replication and full HCMV reactivation. Therefore, this pattern of HCMV transcriptional dysregulation allows effective cytotoxic immune targeting and killing of latently infected cells, thus reducing the latent virus genome load. This approach could be safely used to pre-emptively purge the virus latent reservoir prior to transplantation, thereby reducing HCMV reactivation-related morbidity and mortality.

Hallmarks of the aging T-cell system.

The adaptive immune system has the enormous challenge to protect the host through the generation and differentiation of pathogen-specific short-lived effector T cells while in parallel developing long-lived memory cells to control future encounters with the same pathogen. A complex regulatory network is needed to preserve a population of naïve cells over lifetime that exhibit sufficient diversity of antigen receptors to respond to new antigens, while also sustaining immune memory. In parallel, cells need to maintain their proliferative potential and the plasticity to differentiate into different functional lineages. Initial signs of waning immune competence emerge after 50 years of age, with increasing clinical relevance in the 7th-10th decade of life. Morbidity and mortality from infections increase, as drastically exemplified by the current COVID-19 pandemic. Many vaccines, such as for the influenza virus, are poorly effective to generate protective immunity in older individuals. Age-associated changes occur at the level of the T-cell population as well as the functionality of its cellular constituents. The system highly relies on the self-renewal of naïve and memory T cells, which is robust but eventually fails. Genetic and epigenetic modifications contribute to functional differences in responsiveness and differentiation potential. To some extent, these changes arise from defective maintenance; to some, they represent successful, but not universally beneficial adaptations to the aging host. Interventions that can compensate for the age-related defects and improve immune responses in older adults are increasingly within reach.

Can BCG vaccine protect against COVID-19 via trained immunity and tolerogenesis?

As the number of infections and mortalities from the SARS-CoV-2 pandemic continues to rise, the development of an effective therapy against COVID-19 becomes ever more urgent. A few reports showing a positive correlation between BCG vaccination and reduced COVID-19 mortality have ushered in some hope. BCG has been suggested to confer a broad level of nonspecific protection against several pathogens, mainly via eliciting "trained immunity" in innate immune cells. Secondly, BCG has also been proven to provide benefits in autoimmune diseases by inducing tolerogenicity. Being an acute inflammatory disease, COVID-19 requires a therapy that induces early priming of anti-viral immune responses and regulates aberrant hyperactivity of innate-immune cells. Here, we hypothesize that BCG can offer reliable spatiotemporal protection from COVID-19 by triggering trained immunity and tolerogenesis, through multiple cellular pathways. We propose further research on BCG-mediated immunoprotection, especially in vulnerable individuals, as a strategy to halt the progress of the SARS-CoV-2 pandemic. Also see the video abstract here https://youtu.be/P2D2RXfq6Vg.

A simple and efficient method of generating HCMV pp65-specific T cells using overlapping peptides.

The methods for expansion of human cytomegalovirus (HCMV)-specific T lymphocytes are limited due to the complex culture process, long culture duration, and human leukocyte antigen (HLA) restriction. Here, we report that in vitro stimulation with pp65 kDa phosphoprotein (pp65)-derived overlapping synthetic peptides rapidly generates large numbers of HCMV-specific cytotoxic T lymphocytes from peripheral blood mononuclear cells (PBMCs) regardless of HLA type. Treatment of PBMCs from healthy volunteers expressing HLA-A*02:01 or HLA-A*24:02 with 138 pp65 overlapping peptides (OLP) resulted in an expansion of HCMV pp65 NLVPMVATV (NLV) pentamer-specific CD8+ T lymphocytes that expressed interferon (IFN)-γ, but the pp65 NLV peptide did not generate HCMV-specific CD8+ T lymphocytes in PBMCs obtained from an HLA-A*24:02 donor due to HLA restriction. The OLP-induced T lymphocytes specific for HCMV derived from PBMCs of HLA-A*02:01- and HLA-A*24:02-expressing donors showed effective cytolytic responses against target cells loaded with OLP or the NLV epitope, but pp65 NLV peptide-induced T lymphocytes did not. Phenotypic analyses demonstrated that OLP increased the frequency of CD3+ CD8+ cells, but not CD3+ CD4+, CD14+, or CD56+ cells, in donor PBMCs. Thus, this study provides evidence that in vitro stimulation with OLP efficiently generates sufficient numbers of HCMV pp65-specific cytotoxic T lymphocytes for adoptive cell therapy. Keywords: human cytomegalovirus; cytotoxic T lymphocyte; overlapping peptides; pp65; cytotoxicity.

Mini-Review on the Roles of Vitamin C, Vitamin D, and Selenium in the Immune System against COVID-19.

Low levels of micronutrients have been associated with adverse clinical outcomes during viral infections. Therefore, to maximize the nutritional defense against infections, a daily allowance of vitamins and trace elements for malnourished patients at risk of or diagnosed with coronavirus disease 2019 (COVID-19) may be beneficial. Recent studies on COVID-19 patients have shown that vitamin D and selenium deficiencies are evident in patients with acute respiratory tract infections. Vitamin D improves the physical barrier against viruses and stimulates the production of antimicrobial peptides. It may prevent cytokine storms by decreasing the production of inflammatory cytokines. Selenium enhances the function of cytotoxic effector cells. Furthermore, selenium is important for maintaining T cell maturation and functions, as well as for T cell-dependent antibody production. Vitamin C is considered an antiviral agent as it increases immunity. Administration of vitamin C increased the survival rate of COVID-19 patients by attenuating excessive activation of the immune response. Vitamin C increases antiviral cytokines and free radical formation, decreasing viral yield. It also attenuates excessive inflammatory responses and hyperactivation of immune cells. In this mini-review, the roles of vitamin C, vitamin D, and selenium in the immune system are discussed in relation to COVID-19.

Dynamics of SARS-CoV-2 infection model with two modes of transmission and immune response.

In this paper, we propose a new within-host model which describes the interactions between SARS-CoV-2, host pulmonary epithelial cells and cytotoxic T lymphocyte (CTL) cells. Furthermore, the proposed model takes into account the lytic and nonlytic immune responses and also incorporates both modes of transmission that are the virus-to-cell infection through extracellular environment and the cell-to-cell transmission via virological synapses. The well-posedness of the model as well as the existence of equilibria are established rigorously. Moreover, the dynamical behaviour of the model is further examined by two threshold parameters, and the biological aspects of the analytical results are further presented.

Concanamycin A counteracts HIV-1 Nef to enhance immune clearance of infected primary cells by cytotoxic T lymphocytes.

Nef is an HIV-encoded accessory protein that enhances pathogenicity by down-regulating major histocompatibility class I (MHC-I) expression to evade killing by cytotoxic T lymphocytes (CTLs). A potent Nef inhibitor that restores MHC-I is needed to promote immune-mediated clearance of HIV-infected cells. We discovered that the plecomacrolide family of natural products restored MHC-I to the surface of Nef-expressing primary cells with variable potency. Concanamycin A (CMA) counteracted Nef at subnanomolar concentrations that did not interfere with lysosomal acidification or degradation and were nontoxic in primary cell cultures. CMA specifically reversed Nef-mediated down-regulation of MHC-I, but not CD4, and cells treated with CMA showed reduced formation of the Nef:MHC-I:AP-1 complex required for MHC-I down-regulation. CMA restored expression of diverse allotypes of MHC-I in Nef-expressing cells and inhibited Nef alleles from divergent clades of HIV and simian immunodeficiency virus, including from primary patient isolates. Lastly, we found that restoration of MHC-I in HIV-infected cells was accompanied by enhanced CTL-mediated clearance of infected cells comparable to genetic deletion of Nef. Thus, we propose CMA as a lead compound for therapeutic inhibition of Nef to enhance immune-mediated clearance of HIV-infected cells.

Rhesus Cytomegalovirus-Specific CD8+ Cytotoxic T Lymphocytes Do Not Become Functionally Exhausted in Chronic SIVmac239 Infection.

CD8+ cytotoxic T lymphocytes (CTLs) exert potent antiviral activity after HIV/SIV infection. However, efforts to harness the antiviral efficacy of CTLs for HIV/SIV prophylaxis and therapy have been severely hindered by two major problems: viral escape and exhaustion. By contrast, CTLs directed against human cytomegalovirus (HCMV), a ubiquitous chronic herpesvirus, seldom select for escape mutations and remain functional and refractory to exhaustion during chronic HCMV and HIV infection. Recently, attempts have been made to retarget HCMV-specific CTLs for cancer immunotherapy. We speculate that such a strategy may also be beneficial in the context of HIV/SIV infection, facilitating CTL-mediated control of HIV/SIV replication. As a preliminary assessment of the validity of this approach, we investigated the phenotypes and functionality of rhesus CMV (RhCMV)-specific CTLs in SIVmac239-infected Indian rhesus macaques (RMs), a crucial HIV animal model system. We recently identified two immunodominant, Mamu-A∗02-restricted CTL epitopes derived from RhCMV proteins and sought to evaluate the phenotypic and functional characteristics of these CTL populations in chronic SIVmac239 infection. We analyzed and directly compared RhCMV- and SIVmac239-specific CTLs during SIVmac239 infection in a cohort of Mamu-A∗01+ and Mamu-A∗02+ RMs. CTL populations specific for at least one of the RhCMV-derived CTL epitopes were detected in ten of eleven Mamu-A∗02+ animals tested, and both populations were detected in five of these animals. Neither RhCMV-specific CTL population exhibited significant changes in frequency, memory phenotype, granzyme B expression, exhaustion marker (PD-1 and CTLA-4) expression, or polyfunctionality between pre- and chronic SIVmac239 infection timepoints. In chronic SIVmac239 infection, RhCMV-specific CTLs exhibited higher levels of granzyme B expression and polyfunctionality, and lower levels of exhaustion marker expression, than SIVmac239-specific CTLs. Additionally, compared to SIVmac239-specific CTLs, greater proportions of RhCMV-specific CTLs were of the terminally differentiated effector memory phenotype (CD28- CCR7-) during chronic SIVmac239 infection. These results suggest that, in contrast to SIVmac239-specific CTLs, RhCMV-specific CTLs maintain their phenotypes and cytolytic effector functions during chronic SIVmac239 infection, and that retargeting RhCMV-specific CTLs might be a promising SIV immunotherapeutic strategy.

The «moonlighting protein¼ able to explain the Th1 immune lockdown in severe COVID-19.

COVID-19 is a major public health issue around the world and new data about its etiological agent, SARS-CoV-2, are urgently necessary, also translating the scientific knowledge acquired on its more similar predecessors, SARS-CoV-1 and MERS-CoV, the coronaviruses responsible for SARS and MERS, respectively. Like SARS-CoV-1, SARS-CoV-2 exploits the ACE2 receptors to enter the host cells; nevertheless, recent bioinformatics insights suggest a potential interaction of SARS-CoV-2 with the «moonlighting protein¼ CD26/DPP4, exactly how MERS-CoV works. CD26/DPP4 is overexpressed on T-helper type 1 (Th1) cells and its expression increases with aging, all factors which could well explain the Th1 immune lockdown, especially in the elderly, during fatal SARS-CoV-2 infections. Facing with this scenario, it is possible that Th1 and T-cytotoxic lymphocytes are the immune cells most affected by SARS-CoV-2, and that the immune system is forced to mount a T-helper type 2 (Th2) response, the only one still mountable, in the attempt to counteract the viral load. However, in this way, the symptomatic patient experiences all the negative effects of the Th2 response, which can seriously aggravate the clinical picture.

Human T-lymphotropic virus type 1 (HTLV-1) and cellular immune response in HTLV-1-associated myelopathy/tropical spastic paraparesis.

Human T-lymphotropic virus type 1 (HTLV-1) is associated with adult T cell leukemia/lymphoma and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). HAM/TSP is an inflammatory disease of the spinal cord and clinically characterized by progressive spastic paraparesis, urinary incontinence, and mild sensory disturbance. The interaction between the host immune response and HTLV-1-infected cells regulates the development of HAM/TSP. HTLV-1 preferentially infects CD4+ T cells and is maintained by proliferation of the infected T cells. HTLV-1-infected cells rarely express viral antigens in vivo; however, they easily express the antigens after short-term culture. Therefore, such virus-expressing cells may lead to activation and expansion of antigen-specific T cell responses. Infected T cells with HTLV-1 and HTLV-1-specific CD8+ cytotoxic T lymphocytes invade the central nervous system and produce various proinflammatory cytokines and chemokines, leading to neuronal damage and degeneration. Therefore, cellular immune responses to HTLV-1 have been considered to play important roles in disease development of HAM/TSP. Recent studies have clarified the viral strategy for persistence in the host through genetic and epigenetic changes by HTLV-1 and host immune responses including T cell function and differentiation. Newly developed animal models could provide the opportunity to uncover the precise pathogenesis and development of clinically effective treatment. Several molecular target drugs are undergoing clinical trials with promising efficacy. In this review, we summarize recent advances in the immunopathogenesis of HAM/TSP and discuss the perspectives of the research on this disease.