Early clearance of Chikungunya virus in children is associated with a strong innate immune response

Chikungunya fever (CHIKF) is a global infectious disease which can affect a wide range of age groups. The pathological and immunological response upon Chikungunya virus (CHIKV) infection have been reported over the last few years. However, the clinical profile and immune response upon CHIKV infection in children remain largely unknown. In this study, we analyzed the clinical and immunological response, focusing on the cytokine/chemokine profile in a CHIKV-infected pediatric cohort from Sarawak, Malaysia. Unique immune mediators triggered upon CHIKV infection were identified through meta-analysis of the immune signatures between this pediatric group and cohorts from previous outbreaks. The data generated from this study revealed that a broad spectrum of cytokines/chemokines is up-regulated in a sub-group of virus-infected children stratified according to their viremic status during hospitalization. Furthermore, different immune mediator profiles (the levels of pro-inflammatory cytokines, chemokines and growth and other factors) were observed between children and adults. This study gives an important insight to understand the immune response of CHIKV infection in children and would aid in the development of better prognostics and clinical management for children

Persistent Arthralgia Induced by Chikungunya Virus Infection is Associated with Interleukin-6 and Granulocyte Macrophage Colony-Stimulating Factor

Background. Chikungunya virus (CHIKV) infection induces arthralgia. The involvement of inflammatory cytokines and chemokines has been suggested, but very little is known about their secretion profile in CHIKV-infected patients

THE ROLE OF INNATE IMMUNE DEFENSE IN THE PATHOGENESIS OF CHIKUNGUNYA VIRUS INFECTION

Ph.DDOCTOR OF PHILOSOPH

Humanized Mouse Models for the Study of Hepatitis C and Host Interactions

Hepatitis C virus (HCV) infection is commonly attributed as a major cause of chronic hepatotropic diseases, such as, steatosis, cirrhosis and hepatocellular carcinoma. As HCV infects only humans and primates, its narrow host tropism hampers in vivo studies of HCV-mammalian host interactions and the development of effective therapeutics and vaccines. In this context, we will focus our discussion on humanized mice in HCV research. Here, these humanized mice are defined as animal models that encompass either only human hepatocytes or both human liver and immune cells. Aspects related to immunopathogenesis, anti-viral interventions, drug testing and perspectives of these models for future HCV research will be discussed

Myeloid Cell Arg1 Inhibits Control of Arthritogenic Alphavirus Infection by Suppressing Antiviral T Cells

<div><p>Arthritogenic alphaviruses, including Ross River virus (RRV) and chikungunya virus (CHIKV), are responsible for explosive epidemics involving millions of cases. These mosquito-transmitted viruses cause inflammation and injury in skeletal muscle and joint tissues that results in debilitating pain. We previously showed that arginase 1 (Arg1) was highly expressed in myeloid cells in the infected and inflamed musculoskeletal tissues of RRV- and CHIKV-infected mice, and specific deletion of Arg1 from myeloid cells resulted in enhanced viral control. Here, we show that Arg1, along with other genes associated with suppressive myeloid cells, is induced in PBMCs isolated from CHIKV-infected patients during the acute phase as well as the chronic phase, and that high Arg1 expression levels were associated with high viral loads and disease severity. Depletion of both CD4 and CD8 T cells from RRV-infected Arg1-deficient mice restored viral loads to levels detected in T cell-depleted wild-type mice. Moreover, Arg1-expressing myeloid cells inhibited virus-specific T cells in the inflamed and infected musculoskeletal tissues, but not lymphoid tissues, following RRV infection in mice, including suppression of interferon-γ and CD69 expression. Collectively, these data enhance our understanding of the immune response following arthritogenic alphavirus infection and suggest that immunosuppressive myeloid cells may contribute to the duration or severity of these debilitating infections.</p></div

Loss of myeloid cell Arg1 results in activation of virus-specific CD8⁺ T cells in inflamed muscle tissue.

<p>Three-to-four week-old WT (n = 8) and LysMcre;Arg1^F/F (n = 10) mice were inoculated with 10³ PFU of RRV-LCMV. At 10 dpi, leukocytes from quadriceps muscles (following enzymatic digestion) were isolated for flow cytometric analysis of CD11a and CD69 expression on virus-specific CD8⁺ T cells. Muscle-infiltrating leukocytes that were left unstained were utilized as a control for CD11a and CD69 staining. (A) Representative histograms demonstrating CD11a (left) and CD69 (right) expression on CD44⁺gp33⁺CD8⁺CD4^- T cells at 10 dpi. (B) Frequency of CD11a⁺ or CD69⁺ cells (of CD44⁺gp33⁺CD8⁺CD4^- T cells) in the muscle tissue of RRV-LCMV-inoculated WT mice and LysMcre;Arg1^F/F mice at 10 dpi. Data are represented as the arithmetic mean ± SEM and combined from two independent experiments. * <i>P</i> < 0.05 as determined by two-way ANOVA followed by a Bonferroni multiple comparison test.</p

Muscle-infiltrating CD4⁺ and CD8⁺ T cells isolated from LysMcre;Arg1^F/F mice express enhanced IFN-γ transcript.

<p>(A) Representative flow plots demonstrating the gating strategy to FACS-sort CD19^-CD3⁺CD4⁺CD8^- and CD19^-CD3⁺CD8⁺CD4^- T cells isolated from quadriceps muscles of RRV-infected WT or LysMcre;Arg1^F/F mice at 10 dpi and the post-sort purities. RT-qPCR analysis of (B) IFN-γ, (C) TNF-α, (D) IL-10, and (E) IL-2 expression in FACS-sorted T cells from the spleen of a mock-inoculated mouse (n = 1) or from the quadriceps muscle of RRV-infected WT (n = 3) or LysMcre;Arg1^F/F mice (n = 3) at 10 dpi. Data are normalized to 18S rRNA levels and are expressed as the relative expression (<i>n</i>-fold increase) over expression in spleen T cells from a mock-inoculated mouse. Data are represented as the arithmetic mean ± SEM. Data are representative of two independent experiments. <i>P</i>-values determined by two-tailed, unpaired <i>t</i>-tests with or without Welch’s correction. nd, not detected.</p

Similar frequencies and total number of CD4⁺ and CD8⁺ T cells in inflamed muscle tissues of WT and LysMcre;Arg1^F/F mice at 7, 10, and 14 dpi.

<p>Three-to-four week-old WT and LysMcre;Arg1^F/F mice were mock-inoculated (n = 3) or inoculated with 10³ PFU of RRV (n = 7–8 per time point per genotype). At 7, 10, and 14 dpi, quadriceps muscles were dissected, enzymatically digested, and the infiltrating leukocytes were isolated for FACS analysis. (A) Representative flow plots indicating the gating strategy to identify lymphocytes, CD3⁺CD8⁺ T cells versus CD3⁺CD8^- T cells, and CD3⁺CD4⁺ T cells in the muscle tissue of mock (top panel), RRV-inoculated WT (middle panel), and RRV-inoculated LysMcre;Arg1^F/F (bottom panel) mice at 10 dpi. Frequency (top panel) and total number (bottom panel) of (B) CD3⁺CD4⁺ T cells and (C) CD3⁺CD8⁺ T cells in muscle tissue of RRV-inoculated WT and LysMcre;Arg1^F/F mice compared with mock-inoculated mice. Data are represented as the arithmetic mean ± SEM and combined from two independent experiments. Each time point was individually evaluated for statistical difference by a two-tailed, unpaired <i>t</i>-test, and all were found to be not significant (<i>P</i> > 0.05).</p