Herpes Simplex Virus Types 1 and 2 Completely Help Adenovirus-Associated Virus Replication

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Abstract
In addition to adenoviruses, which are capable of completely helping adenovirus-associated virus (AAV) multiplication, only herpesviruses are known to provide any AAV helper activity, but this activity has been thought to be partial (i.e., AAV DNA, RNA, and protein syntheses are induced, but infectious particles are not assembled). In this study, however, we show that herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) are in fact complete AAV helpers and that AAV type 2 (AAV2) infectivity yields can approach those obtained when coinfections are carried out with a helper adenovirus. AAV helper activity was demonstrated in KB cells with two HSV-1 strains (11124 and 17MP) and an HSV-2 strain (HG52). Each herpesvirus supported AAV2 multiplication with comparable efficiency. AAV2 multiplication was similarly efficient in HSV-1 coinfections of HeLa cells, whereas lower yields were obtained in HEp-2 and primary human embryonic kidney cells. HSV-1 also supported AAV1 multiplication in HeLa cells but, at corresponding multiplicities of infection, AAV1 grew less efficiently than AAV2. Comparisons of the time courses of AAV2 DNA, RNA, and protein syntheses after coinfection with either adenovirus type 5 or HSV-1 revealed that, in each case, the onset of synthesis and attainment of maximal synthesis rate occurred earlier in coinfections with HSV-1. These findings demonstrate the linkage of AAV macromolecular synthesis to an event(s) in the helper virus cycle. Aside from this temporal association, helper-related differences in AAV macromolecular synthesis were not apparent.