Altered Esterase Zymograms associated with Infection with Leukaemia Virus

Abstract

THE study of leukaemia viruses was until recently greatly hampered by the lack of cell cultures capable of propagating such viruses, but several cultures have now been found which support the replication of murine leukaemia virus. One of these cultures (JLS V6) originated from a mixture of BALB/c mouse spleen and thymus cells. Exposure of this culture to a cell free extract of leukaemic spleen from mice infected with Rauscher leukaemia virus (RLV) has resulted in a chronically infected culture (JLS V5) which continually propagates Rauscher virus¹. In our laboratory, gross cytopathic effects are seen in such infected cells². The infected cultures (JLS V5) also show a marked increase in mucopolysaccharide and a concomitant loss of contact inhibition, which results in a transformed “criss-cross” growth pattern. Such infected transformed cells have an enhanced tumorigenicity when they are injected into newborn BALB/c mice. The resultant tumours are rich in mucopolysaccharide and are classified as myxofibrosarcomata³. Tests to detect the presence in the infected cultures of other murine viruses to which the observed alterations might be attributable have been negative³. Moreover, newborn mice from mothers immunized with formalized extracts of spleen infected with RLV are resistant to challenge with the transplantable myxofibrosarcoma cells, whereas newborn mice from mothers immunized with extracts of normal spleen tissue show no such resistance⁴. The uninfected control cells (JLS V6) do not show gross cytopathic effects or transformation and are much less tumorigenic. Furthermore, the tumours that do result from injection of non-infected control cells are classified as spindle-cell sarcomata³.