Analysis of T-cell receptor Vbeta gene from infiltrating T cells in insulitis and myocarditis in encephalomyocarditis virus-infected BALB/C mice

Sex chromosome complement contributes to sex differences in coxsackievirus B3 but not influenza A virus pathogenesis

BACKGROUND

Both coxsackievirus B3 (CVB3) and influenza A virus (IAV; H1N1) produce sexually dimorphic infections in C57BL/6 mice. Gonadal steroids can modulate sex differences in response to both viruses. Here, the effect of sex chromosomal complement in response to viral infection was evaluated using four core genotypes (FCG) mice, where the Sry gene is deleted from the Y chromosome, and in some mice is inserted into an autosomal chromosome. This results in four genotypes: XX or XY gonadal females (XXF and XYF), and XX or XY gonadal males (XXM and XYM). The FCG model permits evaluation of the impact of the sex chromosome complement independent of the gonadal phenotype.

METHODS

Wild-type (WT) male and female C57BL/6 mice were assigned to remain intact or be gonadectomized (Gdx) and all FCG mice on a C57BL/6 background were Gdx. Mice were infected with either CVB3 or mouse-adapted IAV, A/Puerto Rico/8/1934 (PR8), and monitored for changes in immunity, virus titers, morbidity, or mortality.

RESULTS

In CVB3 infection, mortality was increased in WT males compared to females and males developed more severe cardiac inflammation. Gonadectomy suppressed male, but increased female, susceptibility to CVB3. Infection with IAV resulted in greater morbidity and mortality in WT females compared with males and this sex difference was significantly reduced by gonadectomy of male and female mice. In Gdx FCG mice infected with CVB3, XY mice were less susceptible than XX mice. Protection correlated with increased CD4+ forkhead box P3 (FoxP3)+ T regulatory (Treg) cell activation in these animals. Neither CD4+ interferon (IFN)γ (T helper 1 (Th1)) nor CD4+ interleukin (IL)-4+ (Th2) responses differed among the FCG mice during CVB3 infection. Infection of Gdx FCG mice revealed no effect of sex chromosome complement on morbidity or mortality following IAV infection.

CONCLUSIONS

These studies indicate that sex chromosome complement can influence pathogenicity of some, but not all, viruses.

Spontaneous focal activation of invariant natural killer T (iNKT) cells in mouse liver and kidney

BACKGROUND

Invariant natural killer T (iNKT) cells differ from other T cells by their hyperactive effector T-cell status, in addition to the expression of NK lineage receptors and semi-invariant T-cell receptors. It is generally agreed that the immune phenotype of iNKT cells is maintained by repeated activation in peripheral tissues although no explicit evidence for such iNKT cell activity in vivo has so far been reported.

RESULTS

We used an interferon (IFN)-γ-inducible cytoplasmic protein, Irga6, as a histological marker for local IFN-γ production. Irga6 was intensely expressed in small foci of liver parenchymal cells and kidney tubular epithelium. Focal Irga6 expression was unaffected by germ-free status or loss of TLR signalling and was totally dependent on IFN-γ secreted by T cells in the centres of expression foci. These were shown to be iNKT cells by diagnostic T cell receptor usage and their activity was lost in both CD1 d and Jα-deficient mice.

CONCLUSIONS

This is the first report that supplies direct evidence for explicit activation events of NKT cells in vivo and raises issues about the triggering mechanism and consequences for immune functions in liver and kidney.

The significance of T cells, B cells, antibodies and macrophages against encephalomyocarditis (EMC)-D virus-induced diabetes in mice

In order to clarify the significance of protective mechanisms against encephalomyocarditis (EMC) virus-induced diabetes in mice, we studied the relative importance of T cells, B cells, antibodies and macrophages in the prevention of virus-induced diabetes. Neither T cell-deficient athymic nude mice nor B cell-deficient microMT/microMT mice showed an enhanced clinical course of EMC-D virus-induced diabetes, indicating that neither T cells nor B cells played a major role in the protection against EMC-D-virus-induced diabetes. Transfer of a large amount of antiserum to EMC-D-virus-infected mice protected the development of diabetes only when transferred within 36 h of infection, the timing of which was earlier than that for the production of natural neutralizing antibodied. Since pretreatment of mice with the macrophage-activating immunopotentiator Corynebacterium parvum (CP) completely prevented the development of diabetes, we studied the clinical outcome of EMC-D-virus-infected mice pretreated with CP. Mice treated with CP showed reduced proliferation of EMC-D virus in the affected organs, including the pancreas, while the levels of development of neutralizing antibody and serum interferon were not enhanced compared with the controls. Finally, we studied the macrophages derived from mice pretreated with CP and found that they inhibited the growth of EMC-D virus in vitro more than those derived from non-treated and thioglycolate-treated mice. Taken together, it can be suggested that neither T cells nor B cells, which have to do with adaptive immunity, play a significant role in the pathogenesis of EMC-D-virus-induced diabetes, while innate immunity, which is dependent on activated macrophages, contributes to in vivo resistance against EMC-D-virus-induced diabetes.

Elimination of CD4+ CD25+ regulatory T cells breaks down reovirus type 2-triggered and CpG ODN-induced prolonged mild autoimmune insulitis in DBA/1 mice

We have reported previously that subclinical prolonged mild T helper (Th) 1-dependent autoimmune insulitis with impaired glucose tolerance in wealing DBA/1J mice, which is induced by the combined effects of reovirus type 2 (Reo-2) and synthetic 20-base oligodeoxynucleotides with CpG motifs (CpG ODN) (control mice). Compared with the control mice, newborn mice treated with monoclonal antibody (MoAb) against mouse CD25(+) CD4(+) T cells together with Reo-2 and CpG ODN greatly reduced the absolute number of splenic CD25(+) T cells and resulted in the development of severe insulitis, leading to an overt early diabetes. Moreover, the treatment of the MoAb increased production of interferon-gamma (IFN-gamma) and decreased that of interleukin-4 (IL-4) and transforming growth factor-beta1 (TGF-beta1) and developed high titre of autoantibodies against pancreatic islet cells. These evidences suggest that CD4(+) CD25(+) T cell may, at least in part, maintain tolerance to Reo-2-triggered and CpG ODN-induced prolonged mild Th1-dependent autoimmune insulitis, leading to the overt disease. This system may give a novel model to elucidate the mechanisms of the development of overt diabetes from borderline subclinical diabetes in virus-triggered autoimmune type I diabetes in human.