SIMIAN-VIRUS-40 AS A VECTOR - RECOMBINANT VIRUSES EXPRESSING INDIVIDUAL POLYOMA T-ANTIGENS

We constructed simian virus 40 (SV40)/polyomavirus recombinants by rep lacing in SV40 the T antigen coding region with polyoma early region s equences, either cDNAs encoding small, middle or large T antigen or th e wild-type sequence coding all three proteins. The recombinants maint ained the SV40 late region and origin of replication and were propagat ed in COS cells yielding recombinant virus preparations with titers of 10(6)-10(7) infectious particles per milliliter. These viruses were c haracterized in productive infections of COS cells by analyzing early and late mRNA levels and by following synthesis of polyoma early prote ins. In the absence of viral DNA replication, i.e. in infected monkey or mouse cells, expression of the polyoma T antigens was weak. Further experiments indicated that this was mostly due to high genomic instab ility during amplification, to lower levels of cDNA transcripts as com pared to spliced mRNA, and possibly also to lower infectivity of the r ecombinant virions. It remains to be determined, whether these handica ps are unique to SV40/polyoma recombinants or whether SV40 is in gener al inadequate as a viral vector. (C) 1998 Elsevier Science B.V. All ri ghts reserved.