Major histocompatibility complex class I as a ligand for natural killer cell recognition

grantor: University of TorontoNatural killer cell (NK)-mediated cytotoxicity involves two families of receptors: activating receptors that trigger lysis of the target cells being recognized and inhibitory receptors specific primarily for Major Histocompatibility Complex Class I (MHC-I) on the target cell surface that can override the activating signal. Cells expressing reduced surface MHC-I have been shown to be targets for NK-mediated cytotoxicity. MHC-I molecules on the cell surface can be classified into molecules made stable by the binding of high affinity peptide (p H-MHC-I) or unstable molecules potentially capable of being stabilized by binding high affinity peptide (peptide receptive, PR-MHC-I). It has been previously shown that the Ly49A inhibitory receptor recognizes pH-D d. Our data suggest the existence of other NK inhibitory receptor(s) recognizing PR-Kb, -Db, -Dd, or -Kd. During the search for such receptor(s), we found that the inhibitory receptor Ly49CB6 recognizes PR-Kb but does not recognize Kb once they have bound high affinity peptide. Furthermore, we have measured the stability of surface pH-K b and PR-Kb molecules in the presence of BFA. p H-Kb has a t1/2 of ~45 ± 3h and surface PR-Kb has a t1/2 of approximately 30 ± 4 min at 37°C. These observations suggest a possible explanation as to why some virus infected cells become targets for syngeneic NK cells even without a major reduction in total surface MHC-I expression. Our recent study on cells infected with adenovirus types 5 (Ad5) or 12 (Ad12) shows that Ad5 infected cells lose surface PR-Kb expression and become sensitive to NK-lysis within 9h post-infection while Ad12 infected cells have normal PR-Kb expression and remain resistant to NK-lysis until 42h post-infection. Furthermore, the total Kb expression remains unaltered on cells infected by either Ad5 or Ad12. These observations agree with our hypothesis and further suggest that recognition of PR-MHC I may be one of the mechanisms employed by NK cells to detect viral infection.Ph.D

The treatment of SARS-CoV2 with antivirals and mitigation of the cytokine storm syndrome: the role of gene expression

In the absence of a vaccine, the treatment of SARS-CoV2 has focused on eliminating the virus with antivirals or mitigating the cytokine storm syndrome (CSS) that leads to the most common cause of death: respiratory failure. Herein we discuss the mechanisms of antiviral treatments for SARS-CoV2 and treatment strategies for the CSS. Antivirals that have shown in vitro activity against SARS-CoV2, or the closely related SARS-CoV1 and MERS-CoV, are compared on the enzymatic level and by potency in cells. For treatment of the CSS, we discuss medications that reduce the effects or expression of cytokines involved in the CSS with an emphasis on those that reduce IL-6 because of its central role in the development of the CSS. We show that some of the medications covered influence the activity or expression of enzymes involved in epigenetic processes and specifically those that add or remove modifications to histones or DNA. Where available, the latest clinical data showing the efficacy of the medications is presented. With respect to their mechanisms, we explain why some medications are successful, why others have failed, and why some untested medications may yet prove useful.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Seroprevalence of hepatitis B virus in Taiwan 30 years after the commencement of the national vaccination program

Background In this study, the long-term efficacy of hepatitis B virus (HBV) vaccination was assessed using seroprevalence and an age–period–cohort (APC) model of HBV seromarkers among university entrants 30 years after the introduction of the national neonatal HBV vaccination program in Taiwan. Methods In total, data of 17,611 university entrants who underwent university entrance health examinations between 2005 and 2016 were included. The seroprevalence of the HBV surface antigen (HBsAg) and the levels of the antibody against the HBV surface antigen (anti-HBs) in each year group and sex were calculated. The levels of the antibody against the HBV core antigen were examined only for 2012 and 2016. The APC model was used to analyze the HBV carrier rates. Results The chronic HBV infection (HBsAg positivity) rate decreased from 9.7% in university students born before June 1974 to <1.0% in students born after 1992. The prevalence of anti-HBs positivity declined, particularly between the 1984–1988 cohort (78.2%–53.2%) and the 1990–1994 cohort (60.6%–44.4%). Our APC model revealed that the chronic HBV carrier rate among the student population was affected significantly by age, period, and cohort (P < 0.001). Conclusions HBV vaccination is one of the most effective strategies for preventing HBV infection. However, for complete eradication of HBV infection, the development of strategies that detect vaccination failure more effectively than current strategies do and early implementation of appropriate treatments are both necessary

Reducing IRF-1 to Levels Observed in HESN Subjects Limits HIV Replication, But Not the Extent of Host Immune Activation

Cells from women who are epidemiologically deemed resistant to HIV infection exhibit a 40–60% reduction in endogenous IRF-1 (interferon regulatory factor-1), an essential regulator of host antiviral immunity and the early HIV replication. This study examined the functional consequences of reducing endogenous IRF-1 on HIV-1 replication and immune response to HIV in natural HIV target cells. IRF-1 knockdown was achieved in ex vivo CD4+ T cells and monocytes with siRNA. IRF-1 level was assessed using flow cytometry, prior to infection with HIV-Bal, HIV-IIIB, or HIV-VSV-G. Transactivation of HIV long terminal repeats was assessed by p24 secretion (ELISA) and Gag expression (reverse transcription–polymerase chain reaction (RT–PCR)). The expression of IRF-1–regulated antiviral genes was quantitated with RT–PCR. A modest 20–40% reduction in endogenous IRF-1 was achieved in >87% of ex vivo–derived peripheral CD4+ T cells and monocytes, resulted in >90% reduction in the transactivation of the HIV-1 genes (Gag, p24) and, hence, HIV replication. Curiously, these HIV-resistant women demonstrated normal immune responses, nor an increased susceptibility to other infection. Similarly, modest IRF-1 knockdown had limited impact on the magnitude of HIV-1–elicited activation of IRF-1–regulated host immunologic genes but resulted in lessened duration of these responses. These data suggest that early expression of HIV-1 genes requires a higher IRF-1 level, compared to the host antiviral genes. Together, these provide one key mechanism underlying the natural resistance against HIV infection and further suggest that modest IRF-1 reduction could effectively limit productive HIV infection yet remain sufficient to activate a robust but transient immune response

Vitamin D treatment of peripheral blood mononuclear cells modulated immune activation and reduced susceptibility to HIV-1 infection of CD4+ T lymphocytes.

IntroductionMucosal immune activation, in the context of sexual transmission of HIV-1 infection, is crucial, as the increased presence of activated T cells enhance susceptibility to infection. In this regard, it has been proposed that immunomodulatory compounds capable of modulating immune activation, such as Vitamin D (VitD) may reduce HIV-1 transmission and might be used as a safe and cost-effective strategy for prevention. Considering this, we examined the in vitro effect of the treatment of peripheral blood mononuclear cells (PBMCs) with the active form of VitD, calcitriol, on cellular activation, function and susceptibility of CD4+ T cells to HIV-1 infection.MethodsWe treated PBMCs from healthy HIV unexposed individuals (Co-HC) and frequently exposed, HIV-1 seronegative individuals (HESNs) from Colombia and from healthy non-exposed individuals from Canada (Ca-HC) with calcitriol and performed in vitro HIV-1 infection assays using X4- and R5-tropic HIV-1 strains respectively. In addition, we evaluated the activation and function of T cells and the expression of viral co-receptors, and select antiviral genes following calcitriol treatment.ResultsCalcitriol reduced the frequency of infected CD4+ T cells and the number of viral particles per cell, for both, X4- and R5-tropic viruses tested in the Co-HC and the Ca-HC, respectively, but not in HESNs. Furthermore, in the Co-HC, calcitriol reduced the frequency of polyclonally activated T cells expressing the activation markers HLA-DR and CD38, and those HLA-DR+CD38-, whereas increased the subpopulation HLA-DR-CD38+. Calcitriol treatment also decreased production of granzyme, IL-2 and MIP-1β by T cells and increased the transcriptional expression of the inhibitor of NF-kB and the antiviral genes cathelicidin (CAMP) and APOBEC3G in PBMCs from Co-HC.ConclusionOur in vitro findings suggest that VitD treatment could reduce HIV-1 transmission through a specific modulation of the activation levels and function of T cells, and the production of antiviral factors. In conclusion, VitD remains as an interesting potential strategy to prevent HIV-1 transmission that should be further explored