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Recently we demonstrated the induction of a C-type R N A virus ( X C I V ) in tissue culture line XC derived from Wistar random-bred rats. In this article two other rat C-type virus isolates ( NRKA V and RPLA V ) rat major speciesspecific (gs-I) antigen and gs-3 interspecies antigen. Two of the isolates ( N R K A V and RPLAV) were able to rescue mouse sarcoma virus ( M S V ) genome from a rat M S V-transformed non-productive line. The NRK line was assayed for virus release at various in vitro passage levels. In lower passages (43-73) spontaneous virus release was absent or minimal but the virus could be induced by treatment of cells withThe treatment of mouse cells with halogen derivatives of uridine (Lowy et al., 1971) induced endogenous murine type-C virus with high efficiency. Similarly, we and others (Klement et al., 1971b; Aaronson, 1971) had previously demonstrated that a normal rat kidney line (NRK) non-productively transformed by mouse sarcoma virus-Kirsten (Ki-MSV) subsequently released focus-forming virus when treated with 5-bromodeoxyuridine (BrdU), and that this chemically induced virus was serologically different from the transforming virus. It was assumed that the chemical treatment induced latent endogenous rat C-type virus which provided helper function for defective MSV.This paper shows direct evidence of spontaneous in vitro release of such a Gtype virus from NRK cells and compares the biological characteristics of this virus with those of two other rat C-type isolates.

There was 100% agreement between the results of indirect immunofluorescence (IF) and Western blot testing when these methods were used to detect antibodies to the human immunodeficiency virus in sera from 25 patients with acquired immune deficiency syndrome (AIDS), 20 patients with AIDS-related complex, 186 subjects at high risk for AIDS, and 40 healthy heterosexuals. However, there was only an 88.7% correlation between IF and Western blot results for 728 sera from blood and plasma donor centers that were selected on the basis of screening enzyme immunoassay reactivity. IF tests yielded nine false-negatives and were equivocal, yielding a nonspecific pattern of reactivity for both infected and uninfected cells for 73 of these specimens. The IF and Western blot methods were equal in performance for the detection of anti-human immunodeficiency virus antibodies in the high-risk and unselected low-risk groups, proving to be a practical approach for testing specimens from these subjects. However, the Western blot was the most acceptable method for the validation of specimens from groups at low risk for AIDS that were selected based on enzyme immunoassay reactivity.

The major phosphoprotein common to woolly monkey sarcoma virus, gibbon ape lymphosarcoma virus, and type C viruses of the lower mammalian species (mouse, rat, cat), with the exception of the endogenous cat virus (RD-114), is the polypeptide of about 12,000 molecular weight. The protein-phosphate bond in this polypeptide of several viruses is of the phosphoserine variety excepting gibbon ape virus, which contains both phosphoserine and phosphothreonine. The primary phosphoprotein of RD-114 virus and the endogenous baboon type C virus, on the other hand, is the polypeptide of about 15,000 molecular weight which contains phosphothreonine as its phosphoamino acid. A second major phosphoprotein of molecular weight of 10,000 is detected only in viruses genetically related to rat species including those derived from the RPL cell line, from Sprague-Dawley rat embryo cells, and the Kirsten mouse sarcoma virus which was recovered from a mouse erythroblastosis virus after in vivo propagation through rat. These phosphorylated polypeptides of molecular weight 15,000, 12,000, or 10,000 are present in the virion structure in several different but nonrandom phosphorylated states.

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