Nodamura virus, an arthropod-transmissible virus which is resistant to ether and chloroform, was characterized by electron microscopic, physical, and additional immunological studies. Examination of thin sections of limb muscles of infected infant mice revealed extremely large numbers of virus particles (28 nm in diameter) dispersed and in crystalline array within sarcoplasm. Two kinds of viroplasmic inclusions and severe destruction of skeletal muscle cell architecture were associated with the presence of virus. Kupffer cells in the liver of these animals also contained large aggregates of virus particles. Negative contrast preparations contained virus particles 29 nm in diameter with cubic symmetry. The virus was morphologically indistinguishable from picornaviruses. The density of infectious virus was 1.34 g/ml; it was insensitive to pH 3.7, and its sensitivity to heat (50 °) was not stabilized by molar MgCl2. Since serum neutralization tests against 10 swine enteroviruses were negative, as were previously reported attempts at serological identification, Nodamura virus remains a picornavirus unrelated to any known virus, but with a demonstrated capacity for transmission by and multiplication in arthropods.
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