The In Vitro and In Vivo Analysis of Mammalian Tumour Viruses

ONE of the basic problems in the viral origin of tumours is the mode of virus transmission. Such transmission may take place from one generation to another to give the appearance of a hereditary transmission, and between animals belonging to the same generation. Either of these factors may determine the spread of a tumour virus in a population, and the relative importance of one or the other may, of course, vary with different viruses. Information on the spread of virus correlated with the occurrence of tumours in the infected animals, can furthermore show to what extent animals may be infected with virus, fail to develop tumours, and yet transmit the virus in a way that will produce tumours in their progeny. Such studies can also show whether natural selection in an animal population can modify the virus's tumour inducing properties. The polyoma virus (Stewart, Eddy and Borgese, 1958) is particularly favourable for such epidemiological studies. We have previously shown (Sachs et al., 1959) that this virus can be transmitted between litter mates, from an infected mother to her litter, and from an infected litter to their mother. This virus can therefore be transmitted both from one generation to the next and between animals belonging to the same generation. In addition, since the presence of virus can be determined by the development of haemagglutination inhibition antibodies after virus infection of either newborn, young or adult animals (Sachs et al., 1959; Fogel and Sacbs, 1959), a rapid in vitro test is available for epidemiological investigations. The present studies are concerned with some further experiments on the epidemiology of the polyoma virus, with particular reference to transmission between animals belonging to the same generation; transmission during pregnancy and lactation, by sperm, and by tumour transplants; and virus excretion in the urine, faeces and saliva.