Infection of neonatal mice with sindbis virus results in a systemic inflammatory response syndrome

Laboratory strains of viruses may contain cell culture-adaptive mutations w hich result in significant quantitative and qualitative alterations in path ogenesis compared to natural virus isolates. This report suggests that this is the case with Sindbis virus strain AR339. A cDNA clone comprising a con sensus sequence of Sindbis virus strain AR339 has been constructed (W. B. K limstra, K. D. Ryman, and R. E. Johnston, J. Virol. 72:7357-7366, 1998). Th is clone (pTR339) regenerates a sequence predicted to be very close to that of the original AR339 isolate by eliminating several cell culture-adaptive mutations present in individual laboratory strains of the virus (K. L. McK night et al., J. Virol. 70:1981-1989, 1996). It thus provides a unique reag ent for study of the pathogenesis of Sindbis virus strain AR339 in mice. Ne onatal mouse pathogenesis of virus (TR339) generated from the pTR339 clone was compared with that of virus from a cDNA clone of the cell culture-passa ged laboratory AR339 strain, TRSB, and virus from a clone of a more highly cell culture-adapted strain, HRsp (Toto 50). The sequence of TRSB differs f rom the consensus at three coding positions, while Tote 50 differs at eight codons and one nucleotide in the 5' nontranslated region. Both cell cultur e-adapted strains contain mutations associated with heparan sulfate (HS)-de pendent attachment to cells (W. B. Klimstra, K. D. Ryman, and R. E. Johnsto n, J. Virol. 72:7357-7366, 1998). TR339 caused 100% mortality with an avera ge survival time (AST) of 1.7 +/- 0.25 days. While TRSB also caused 100% mo rtality, the AST was extended to 2.9 +/- 0.52 days. The more extensively ce ll culture-adapted virus Tote 50 caused only 30% mortality,vith an AST exte nded to 11.0 +/- 4.8 days. TRSB and TR339 induced high serum levels of alph a/beta interferon, gamma interferon, tumor necrosis factor alpha, interleuk in-6, and corticosterone and induced pathology reminiscent of lipopolysacch aride-induced endotoxic shock, a type of systemic inflammatory response syn drome. However, the reduced intensity of this response in TRSB-infected mic e correlated with the increased AST. Tote 50 failed to induce the shock-lik e cytokine cascade. In situ hybridization studies indicated that TR339 and TRSB replicated in identical tissues, but the TRSB signal was less widespre ad at early times postinfection. While Tote 50 also replicated in similar t issues, the extent of replication was severely restricted and mice develope d lesions characteristic of encephalitis. A single mutation in TRSB at E2 p osition 1 (Arg) conferred MS-dependent attachment to cells and was associat ed with reduced cytokine induction and extended AST in vivo.