Investigation of herpes simplex virus type 1 genes encoding multiply inserted membrane proteins.

The herpes simplex virus type 1 genome contains four open reading frames (ORFs) which are predicted to encode hydrophobic proteins with the potential to cross a membrane several times. The products of these genes (genes UL10, UL20, UL43 and UL53) have not previously been identified. To investigate the role of these proteins in the virus life cycle, we attempted to inactivate the genes individually by inserting the lacZ gene from Escherichia coli within the ORFs. Using this approach we have isolated insertion mutants for UL10 and UL43, as well as a deletion mutant lacking the majority of the UL43 ORF. The growth of the UL10-lacZ virus was slightly impaired in tissue culture compared to that of the wild-type virus parent, whereas the growth of the UL43 mutants was indistinguishable from that of wild-type virus. Furthermore, deletion of the majority of the UL43 ORF did not impair the ability of the virus to replicate in vivo at the periphery, or to spread to and replicate within the nervous system, in a mouse ear model. Repeated attempts to isolate lacZ insertion mutants for UL20 and UL53 were unsuccessful, suggesting that these genes may be essential for virus growth, at least in tissue culture. Using antipeptide sera, the products of genes UL10 and UL20 have been detected.