Factors affecting the growth and titration by immunofluorescence of simian foamy virus

This paper presents some observations concerned with the growth of simian foamy virus and some modifications which should be introduced to the fluorescence assay of foamy virus. The modified procedure is the most sensitive method described for the titration of foamy virus. Examination of the optimal conditions for the growth and titration by fluorescence assay of simian foamy virus showed that the virus was particularly sensitive to changes in virus and cell concentration. At the low cell concentrations employed previously a "saturation-type" response was obtained with high titre virus and virus adsorption efficiency was decreased as input virus was diluted. Maximum virus production was obtained with high cell concentrations at input multiplicities of 5 and 10. At high multiplicities of infection more than 90 per cent of the cells adsorbed virus but only 45 per cent became infected, this appeared to be related to cell DNA synthesis.