Effect of Environmental pH on Rescue of Simian Virus 40

Rescue of SV40 virus after Sendai virus-mediated fusion of transformed mouse or hamster cell lines with permissive monkey cells was strikingly dependent on pH in the range 6.4-8.8, with a maximum at pH 8.4. The titer of virus recovered at pH 8.4 was 2 logs higher than that at pH 7.6, and 4 logs higher than that at pH 6.4. The pH-sensitive step was neither the number of heterokaryocytes formed, which was essentially the same at pH 7.6 and 8.4, nor the degree of SV40 replication in the monkey cells, which was also unaffected by pH variation in the range 7.2-8.4.