Development of transgenic mice expressing a coronavirus-specific public CD4 T cell receptor

Virus-Specific Regulatory T Cells Persist as Memory in a Neurotropic Coronavirus Infection

Regulatory T cells (Tregs) are critical for regulating immunopathogenic responses in a variety of infections, including infection of mice with JHM strain of mouse hepatitis virus (JHMV), a neurotropic coronavirus that causes immune-mediated demyelinating disease. Although virus-specific Tregs are known to mitigate disease in this infection by suppressing pathogenic effector T cell responses of the same specificity, it is unclear whether these virus-specific Tregs form memory populations and persist similar to their conventional T cell counterparts of the same epitope specificity. Using congenically labeled JHMV-specific Tregs, we found that virus-specific Tregs persist long-term after murine infection, through at least 180 d postinfection and stably maintain Foxp3 expression. We additionally demonstrate that these cells are better able to proliferate and inhibit virus-specific T cell responses postinfection than naive Tregs of the same specificity, further suggesting that these cells differentiate into memory Tregs upon encountering cognate Ag. Taken together, these data suggest that virus-specific Tregs are able to persist long-term in the absence of viral Ag as memory Tregs.

Roles of regulatory T cells and IL-10 in virus-induced demyelination

Neurotropic viruses are important causes of morbidity and mortality in human populations. Some of these viruses preferentially infect oligodendrocytes in the white matter, causing either direct lysis of infected cells, or more commonly myelin damage as a consequence of the host immune response to the virus. Virus-induced demyelination has similarities to the human disease multiple sclerosis. To study this disease process in experimental animals, mice are infected, most commonly, with neurotropic strains of mouse hepatitis virus, a coronavirus or Theiler's murine encephalomyelitis, a picornavirus. While the diseases caused by these two viruses differ in some aspects, in both cases demyelination is a major consequence of the infection. As in autoimmune disease, therapeutic interventions that diminish an overactive immune response would be useful. However, unlike autoimmune disease, complete suppression would result in unchecked virus replication, generally leading to more severe disease. Here we discuss two approaches that dampen but do not fully suppress the host immune response. Regulatory T cells, especially those that are specific for antigens recognized by pathogenic T cells, and IL-10 are two anti-inflammatory/pro-resolution factors that demonstrate efficacy in experimental models of virus-induced demyelination and may be useful in patients infected with viruses that cause demyelination.

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MHV and TMEV are common causes of virus-induced demyelination in mice

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Virus-induced demyelination is often host cell-mediated.

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Virus-specific Treg dampen pathogenic T cells responding to cognate epitope

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IL-10 expressed by Tregs and Tr1 cells dampens pathogenic T cell responses

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Tregs and IL-10 suppress pathogenic T cells without broad immunosuppression

Virus-specific regulatory T cells ameliorate encephalitis by repressing effector T cell functions from priming to effector stages

Several studies have demonstrated the presence of pathogen-specific Foxp3+ CD4 regulatory T cells (Treg) in infected animals, but little is known about where and how these cells affect the effector T cell responses and whether they are more suppressive than bulk Treg populations. We recently showed the presence of both epitope M133-specific Tregs (M133 Treg) and conventional CD4 T cells (M133 Tconv) in the brains of mice with coronavirus-induced encephalitis. Here, we provide new insights into the interactions between pathogenic Tconv and Tregs responding to the same epitope. M133 Tregs inhibited the proliferation but not initial activation of M133 Tconv in draining lymph nodes (DLN). Further, M133 Tregs inhibited migration of M133 Tconv from the DLN. In addition, M133 Tregs diminished microglia activation and decreased the number and function of Tconv in the infected brain. Thus, virus-specific Tregs inhibited pathogenic CD4 T cell responses during priming and effector stages, particularly those recognizing cognate antigen, and decreased mortality and morbidity without affecting virus clearance. These cells are more suppressive than bulk Tregs and provide a targeted approach to ameliorating immunopathological disease in infectious settings.