Immunological properties of a type C retrovirus isolated from cultured human T-lymphoma cells and comparison to other mammalian retroviruses

Abstract

HTLV strain CR (HTLVCR) is a retrovirus which was isolated from a human T-cell lymphoma cell line. A protein of MW 24,000, p24, was purified from this virus. Several results indicate that this p24 is an internal core protein of HTLVCR. The p24 copurified with viral cores. It was labeled with 125I after disruption of the virus but not when undisrupted virus was iodinated. The amount of p24 was directly proportional to the amount of HTLVCR. In chromatographic properties, the HTLVCR p24 behaved similarly to the major structural protein (24,000- to 30,000-MW protein) of other retroviruses. A rabbit antiserum raised against disrupted HTLVCR precipitated the labeled p24; the precipitation was competed for by unlabeled HTLVCR and by cytoplasmic proteins from cells producing HTLVCR but not by proteins from normal human cells, including normal growing human T-cells and several cultured human cutaneous T-cell lymphoma lines. Proteins from several mammalian type B [murine mammary tumor virus], type C [Rauscher murine leukemia, simian sarcoma, baboon endogenous, feline leukemia, owl monkey, deer kidney and bovine leukemia viruses] and type D [Mason-Pfizer monkey virus and squirrel monkey retrovirus] viruses also failed to compete in this precipitation. HTLVCR did not react in homologous and interspecies assays for p30 antigens of several mammalian type C and type D viruses. These observations agree with immunological comparisons between reverse transcriptase of HTLVCR and other retroviruses and nucleic acid sequence homology studies which indicate that the various HTLVCR isolates represent new retroviruses found in some human T-cell neoplasias.