Evaluation of Zika Virus-specific T-cell Responses in Immunoprivileged Organs of Infected Ifnar1<sup>-/-</sup> Mice

The Zika virus (ZIKV) can induce inflammation in immunoprivileged organs (e.g., the brain and testis), leading to the Guillain-Barr&#233; syndrome and ...

Chinese Academy of Sciences

Using a Guelph Permeameter, the soil water infiltration processes were analyzed in the Babao River of the Qilian Mountain in China. The results showed that the average soil initial infiltration and the steady infiltration rates in the upstream reaches of the Babao River are 1.93 and 0.99 cm/min, whereas those of the middle area are 0.48 cm/min and 0.21 cm/min, respectively. The infiltration processes can be divided into three stages: the rapidly changing stage (0-10 min), the slowly changing stage (10-30 min) and the stabilization stage (after 30 min). We used field data collected from lawn soils and evaluated the performances of the infiltration models of Philip, Kostiakov and Horton with the sum of squared error, the root mean square error, the coefficient of determination, the mean error, the model efficiency and Willmott's index of agreement. The results indicated that the Kostiakov model was most suitable for studying the infiltration process in the alpine lawn soils. 

Research on the infiltration processes of lawn soils of the Babao River in the Qilian Mountain.

E-proteins are TCR-sensitive transcription factors essential for intrathymic T cell transitions. Here, we show that deletion of E-proteins leads to both enhanced peripheral TGF-β-induced regulatory T (iT reg) cell and thymic naturally arising T reg cell (nT reg cell) differentiation. In contrast, deletion of Id proteins results in reduced nT reg cell differentiation. Mechanistic analysis indicated that decreased E-protein activity leads to de-repression of signaling pathways that are essential to Foxp3 expression. Decreased E-protein binding to an IL-2Rα enhancer locus facilitated TCR-induced IL-2Rα expression. Similarly, decreased E-protein activity facilitated TCR-induced NF-κB activation and generation of c-Rel. Consistent with this, microarray analysis indicated that cells with E-protein depletion that are not yet expressing Foxp3 exhibit activation of the IL-2 and NF-κB signaling pathways as well as enhanced expression of many of the genes associated with Foxp3 induction. Finally, studies using Nur77-GFP mice to monitor TCR signaling showed that TCR signaling strength sufficient to induce Foxp3 differentiation is accompanied by down-regulation of E-protein levels. Collectively, these data suggest that TCR stimulation acts in part through down-regulation of E-protein activity to induce T reg cell lineage development. 

Dynamic changes in E-protein activity regulate T reg cell development.

The functions of MAIT cells at the site of Mycobacterium tuberculosis infection in humans are still largely unknown. In this study, the phenotypes and immune response of MAIT cells from tuberculous pleural effusions and peripheral blood were investigated. MAIT cells in tuberculous pleural effusions had greatly enhanced IFN-γ, IL-17F and granzyme B response compared with those in peripheral blood. The level of IFN-γ response in MAIT cells from tuberculous pleural effusions was inversely correlated with the extent of tuberculosis infection (p = 0.0006). To determine whether cytokines drive the immune responses of MAIT cells at the site of tuberculosis infection, the role of IL-1β, IL-2, IL-7, IL-12, IL-15 and IL-18 was investigated. Blockade of IL-2, IL-12 or IL-18 led to significantly reduced production of IFN-γ and/or granzyme B in MAIT cells from tuberculous pleural effusions. Majority of IL-2-producing cells (94.50%) in tuberculous pleural effusions had phenotype of CD3(+)CD4(+), and most IL-12p40-producing cells (91.39%) were CD14(+) cells. MAIT cells had significantly elevated expression of γc receptor which correlated with enhanced immune responses of MAIT cells. It is concluded that MAIT cells from tuberculous pleural effusions exhibited highly elevated immune response to Mtb antigens, which are controlled by cytokines produced by innate/adaptive immune cells.

Enhanced immune response of MAIT cells in tuberculous pleural effusions depends on cytokine signaling.

The basis of the increased risk for Crohn's disease conferred by the  polymorphism is incompletely understood. An important step forward came from the recent demonstration that the murine equivalent of Atg16L1T300A (Atg16L1T316A) exhibits increased susceptibility to caspase 3-mediated cleavage and resulting decreased levels of full-length Atg16L1 in macrophages. However, although this finding showed that this polymorphism is a loss-of-function abnormality, it did not address the possibility that this polymorphism also affects the function of a normal  allele in heterozygous mice. Therefore, we evaluated the function of the  polymorphism heterozygote and homozygote in knock-in (KI) mice. Surprisingly, we found that macrophages from both types of KI mice exhibit defective autophagic induction; accordingly, both types of mice exhibit defects in bacterial clearance coupled with increased inflammasome cytokine (IL-1β) responses. Furthermore, macrophages from both types of KI mice displayed defects in TNF-α-induced Atg16L1T300A cleavage, increased retention of bacteria, bacterial dissemination, and induced colitis. These studies suggested that chromosomes bearing the  polymorphism can interfere with the function of the wild-type (WT)  allele and, thus, that the Crohn's disease risk polymorphism is a dominant-negative variant with the potential to act as a disease factor, even when present on only one chromosome. This conclusion was supported by the finding that mice bearing a WT  allele and a null allele (Atg16L1 mice) exhibit normal autophagic function equivalent to that of WT mice.

The Inflammatory Bowel Disease-Associated Autophagy Gene  Acts as a Dominant Negative Variant in Mice.

Zika virus (ZIKV) infection causees neurologic complications, including Guillain-Barré syndrome in adults and central nervous system (CNS) abnormalities in fetuses. We investigated the immune response, especially the CD8 T cell response in C57BL/6 (B6) wild-type (WT) mice, during ZIKV infection. We found that a robust CD8 T cell response was elicited, major histocompatibility complex class I-restricted CD8 T cell epitopes were identified, a tetramer that recognizes ZIKV-specific CD8 T cells was developed, and virus-specific memory CD8 T cells were generated in these mice. The CD8 T cells from these infected mice were functional, as evidenced by the fact that the adoptive transfer of ZIKV-specific CD8 T cells could prevent ZIKV infection in the CNS and was cross protective against dengue virus infection. Our findings provide comprehensive insight into immune responses against ZIKV and further demonstrate that WT mice could be a natural and easy-access model for evaluating immune responses to ZIKV infection. ZIKV infection has severe clinical consequences, including Guillain-Barré syndrome in adults, microcephaly, and congenital malformations in fetuses and newborn infants. Therefore, study of the immune response, especially the adaptive immune response to ZIKV infection, is important for understanding diseases caused by ZIKV infection. Here, we characterized the CD8 T cell immune response to ZIKV in a comprehensive manner and identified ZIKV epitopes. Using the identified immunodominant epitopes, we developed a tetramer that recognizes ZIKV-specific CD8 T cells , which simplified the detection and evaluation of ZIKV-specific immune responses. In addition, the finding that tetramer-positive memory CD8 T cell responses were generated and that CD8 T cells can traffic to a ZIKV-infected brain greatly enhances our understanding of ZIKV infection and provides important insights for ZIKV vaccine design.

CD8 T Cell Immune Response in Immunocompetent Mice during Zika Virus Infection.

A new type of highly pathogenic avian influenza virus, H7N9, has been a great threat to public health since its 2013 outbreak. The humoral immune response plays a critical role in protection from the influenza virus, but its role and kinetics in H7N9-infected patients remain to be determined. In this study, we performed a retrospective investigation of the antibody response in plasma samples from 37 cases of hospitalized patients and analysed the relationship between the antibody response and the clinical outcomes. Our results showed that the HA7-binding antibody was generated earlier than the neutralizing antibody. Higher titer of HA7-binding antibody during the first 14 days after disease onset were associated with a shorter virus-positive continuation period, which is an important risk predictor (<0.05). Additionally, the titers of HA7-binding antibody were consistently and significantly lower in patients who died than those who recovered from the severe disease. Unexpectedly, no correlation between the titer of neutralizing antibody and the resulting clinical outcomes was found, suggesting that a neutralizing antibody-independent mechanism also contributed to virus control. In summary, our data suggests that an early antibody response against H7N9 influenza virus contributes to the eradication of the virus. A higher, early HA7-binding antibody response is associated with better clinical outcomes in H7N9 patients.

Early Antibody Response Contributes to the Virus Eradication and Clinical Recovery of H7N9 Influenza Infection.

Although TLR signaling in B cells has been implicated in the germinal center (GC) responses during viral infections and autoimmune diseases, the underlying mechanism is unclear. Bacterial phage Qβ-derived virus-like particle (Qβ-VLP) contains TLR ligands, which can enhance Qβ-VLP-induced Ab response, including GC response, through TLR/MyD88 signaling in B cells. In this study, by examining Ag-specific B cell response to Qβ-VLP, we found that lack of B cell MyD88 from the beginning of the immune response led to a more severe defect in the GC scale than abolishing MyD88 at later time points of the immune response. Consistently, B cell-intrinsic MyD88 signaling significantly enhanced the initial proliferation of Ag-specific B cells, which was accompanied with a dramatic increase of plasma cell generation and induction of Bcl-6 GC B cell precursors. In addition, B cell-intrinsic MyD88 signaling promoted strong T-bet expression independent of IFN-γ and led to the preferential isotype switching to IgG2a/c. Thus, by promoting the initial Ag-specific B cell proliferation and differentiation, B cell-intrinsic MyD88 signaling enhanced both T-independent and T-dependent Ab responses elicited by Qβ-VLP. This finding will provide additional insight into the role of TLR signaling in antiviral immunity, autoimmune diseases, and vaccine design.

B Cell-Intrinsic MyD88 Signaling Promotes Initial Cell Proliferation and Differentiation To Enhance the Germinal Center Response to a Virus-like Particle.

The maintenance of autoreactive B cells in a quiescent state is crucial for preventing autoimmunity. Here, we identify a variant of human IgG1 (hIgG1-G396R), which positively correlates with systemic lupus erythematosus. In induced lupus models, murine homolog G390R knock-in mice generate excessive numbers of plasma cells, leading to a burst of broad-spectrum autoantibodies. This enhanced production of antibodies is also observed in hapten-immunized G390R mice, as well as in influenza-vaccinated human G396R homozygous carriers. This variant potentiates the phosphorylation of IgG1 immunoglobulin tail tyrosine (ITT) motif. This, in turn, alters the availability of phospho-ITT to trigger longer Grb2 dwell times in immunological synapses, leading to hyper-Grb2-Btk signaling upon antigen binding. Thus, the hIgG1-G396R variant is important for both lupus pathogenesis and antibody responses after vaccination.

An autoimmune disease variant of IgG1 modulates B cell activation and differentiation.

B cells can present antigens to CD4 T cells, but it is thought that dendritic cells (DCs) are the primary initiators of naive CD4 T cell responses. Nanoparticles, including virus-like particles (VLPs), are attractive candidates as carriers for vaccines and drug delivery. Using RNA phage Qβ-derived VLP (Qβ-VLP) as a model antigen, we found that antigen-specific B cells were the dominant antigen-presenting cells that initiated naive CD4 T cell activation. B cells were sufficient to induce T follicular helper cell development in the absence of DCs. Qβ-specific B cells promoted CD4 T cell proliferation and differentiation via cognate interactions and through Toll-like receptor signaling-mediated cytokine production. Antigen-specific B cells were also involved in initiating CD4 T cell responses during immunization with inactivated influenza virus. These findings have implications for the rational design of nanoparticles as vaccine candidates, particularly for therapeutic vaccines that aim to break immune tolerance.

Fuping Zhang

CAS Key Laboratory of Pathogenic Microbiology and Immunology,
Institute of Microbiology,
CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology

Chinese Academy of Sciences

Evaluation of Zika Virus-specific T-cell Responses in Immunoprivileged Organs of Infected Ifnar1^-/- Mice

Fuping Zhang

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}CAS Key Laboratory of Pathogenic Microbiology and Immunology,Institute of Microbiology,CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology

Chinese Academy of Sciences

Evaluation of Zika Virus-specific T-cell Responses in Immunoprivileged Organs of Infected Ifnar1-/- Mice

CAS Key Laboratory of Pathogenic Microbiology and Immunology,
Institute of Microbiology,
CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology

Evaluation of Zika Virus-specific T-cell Responses in Immunoprivileged Organs of Infected Ifnar1^-/- Mice