Retention of antigen specificity of murine sarcoma viruses grown in hamster cells in vitro.

Abstract

TUMOURS can be induced in hamsters by the various strains of murine sarcoma virus (MSV)1–6. Tumours differ, however, in the antigens which are expressed. Whereas the cell line HT-1, derived from early passages of a hamster tumour induced by the Moloney strain of MSV (M-MSV), contains no trace of infectious virus or virion antigen2,7, tumours induced by the Harvey (H), Kirsten (Ki) and later passages of the M-MSV-(GLV) viruses have yielded sarcoma viruses with a hamster-specific host range3–6,8 which do not share envelope4–6,9 or group specific10 antigens with murine viruses. The HT-1 cell does retain the MSV genome which can be rescued by murine leukaemia viruses2. Such rescued viruses are termed pseudo-types and contain the envelope and group-specific antigens of the rescuing virus. The virus preparation from tumours induced by M-MSV(GLV) differed from the other hamster-specific viruses in that a non-sarcomagenic C-type virus could be isolated from cultures infected beyond the cell transformation end point6. This virus was also hamster-specific in host range and antigenic properties and specifically interfered with cell transformation by the various hamster-specific virus strains9. This virus also shared an ether-stable virion-antigen with a C-type virus found in a lymphoma which occurred spontaneously in a hamster10. This shared antigen seems to be the principal structural polypeptide of hamster C-type viruses and is structurally similar but antigenically distinct from its mouse homologue (unpublished work of S. O., C. Foreman, G. K. and R. V. G.). These findings led us to propose that the hamster-specific non-sarcomagenic C-type virus was a hamster leukaemia virus (in the generic but not necessarily the pathological sense) and the virus is therefore designated HaLV9,10. The hamster-specific sarcoma viruses are considered to be pseudotypes of MSV rescued in vivo by HaLV and are abbreviated accordingly; for example, M-MSV(HaLV) represents the hamster-specific sarcoma virus rescued from M-MSV induced tumours. This is plausible because HaLV is able to rescue the MSV genome from HT-1 cells6. (This change in the nomenclature has been made in order to reflect the antigenic composition of the hamster-specific virus more accurately. In addition, to indicate the virus rescued from M-MSV(GLV)-induced hamster tumours, a terminal G is added after the parentheses. This has been done only to distinguish it from the virus obtained from M-MSV induced hamster tumours, for there is no evidence of residual activity from GLV.)