Coxsackie B virus pathogenesis in mice

Abstract

Coxsackie B virus (CVB) belongs to the enterovirus (EV) genera of the Picornaviridae family. These infections range from asymptomatic, mild infections to serious diseases such as myocarditis, pancreatitis, paralysis, aseptic meningitis and encephalitis. CVB has also been implicated as an etiological agent in chronic diseases such as Type 1 diabetes (T1D). In addition to host factors, the outcome of a CVB infections have been shown to depend on the specific strains ability to utilize specific receptors, cause a persistent infection or promote specific immune responses. Charachterization and study of viral isolates in vitro as well as in vivo may unravel the mechanisms by which CVB causes diseases.

In our first study we infected CBA/J mice with the in vitro well characterized CVB4 strains E2 and VD292 1, CVB3 strain Nancy and CVB4/5 recombinant strain V89 4557. These strains have been shown to utilize different receptors in vitro and been shown to replicate in isolated human Langerhans islets with various outcomes. The CVB strains V894557, Nancy and E2 strains caused rapid cytolysis of islet cells but the VD2921 strain induced a persistent infection without cytolysis. Infections of CBA/J mice revealed different viral phenotypes also in vivo. Even though all strains could be equally well isolated from the pancreas, the CVB3 Nancy and the CVB4 E2 induced more severe acute pancreatitis compared with the CVB4/5 strain V89 4557 and the CVB4 strain VD2921. In addition the VD2921 and V89 4557 strains induced a pre-diabetic state in CBA/J mice.

In the second study virus isolations from a mother (T1) and son (T2) with simultaneous T I D onset were performed. EV-RT-PCR revealed that both T l and T2 belonged to the EV genera. The T1 strain was genotyped as CVB5 but the T2 isolate could not be genotyped. Infections with T1/T2 in mice did not cause any obvious symptoms or inflammation in the heart or pancreas. However both strains replicated in a rat insulinoma cell line cultured as cell clusters. CVB-5 have been associated to diabetes before but this was the first time that infection with P-cell tropic strains have been documented to have occurred in two members of the same family who were diagnosed with T1D on the same day, which strongly suggests a causal relationship between the infection and the T1D.

In the third study mice lacking the IFN receptor alpha/beta or gamma (alpha/betaR and gammaR-/-) and 129SV/EV (control) mice were infected with the CVB4 strains VD2921 or E2 which revealed different phenotypes in vitro and in vivo (first study). During recent years evidence has been growing for the case that the cytokines such as interferons may impact on coxsackie viral replication and pathogenesis. The outcome of E2 and VD2921 infections differed also in IFN-deficient mice. In contrast to the VD2921-infected IFNalpha/betaR-/- mice, to the CVB-infected IFNgammaR-/- mice, and controls, the E2-infected IFNalpha/betaR-/- mice died early after infection and those still living on day 7 pi suffered from severe pancreatitis. Preliminary data from in vitro E2- and VD292 1-inocculated spleen cell cultures revealed that there might be viral strain differences in. cytokine induction which may possibly contribute to differences in tissue destruction and death. The VD2921-infected IFNalpha/betaR-/- and CVB infected IFNgammaR-/mice and controls resolved the acute infection and the pancreatic inflammation. Thus for the first time it was shown that the ability to survive, resolve the infection and the severity of acute pancreatitis in IFNalpha/betaR-/- mice is dependent on the viral phenotype. In addition, adequate IFNalpha and/or beta but not IFNgamma seemed to be more essential for preventing early death and for resolving the infection with the E2 strain.