An unusual transmissible agent--MaTu.

MaTu is an agent, believed to be derived from a human mammary carcinoma, which displayed several extraordinary properties. These were: RIP and PAGE revealed in MaTu-infected cells only a single protein band of Mr 58 k, the gp 58. This gp 58 was immunoprecipitated by antibodies present in some human sera as well as in some sera of rabbits, sheep, and cattle. MaTu had an extremely restricted host range: it was transmissible only to HeLa cells, but not to human embryo fibroblasts, to three human tumour cell lines (T 47 D, T 24, and HMB 2) or to monkey Vero and rabbit SIRC cells. A retrovirus with a broad host range, used as a helper (X-MLV) enabled the transmission of MaTu to human fibroblasts, but not to Vero or SIRC, which are also permissive for X-MLV. These observations, together with our previous reports, support the view that MaTu might either be a novel type of defective virus, or even a non-viral autonomous genetic element.