Dynamics of virus-host interplay in HIV-1 replication.

HIV-1, the causative agent of AIDS, is an obligate intracellular parasite that has both evolved to invade the complex human system and adapted to utilize the host machinery for its own propagation. A dynamic interaction between the virus and the host systems can be observed at every step of HIV-1 life cycle. Host factors are involved not only for mounting antiviral responses but are also hijacked by the virus to assist in its replication. The host factors are necessary for viral replication during entry, reverse transcription, nuclear import, integration, transcription, nuclear export, translation, assembly and budding. All retroviruses including HIV-1, are species-specific and the replication of the retroviruses is blocked in the restrictive host by the action of "host restriction factors". These restriction factors act as barriers to retroviral replication at various stages within the infected cell of a restrictive host. Nevertheless, HIV-1 virus has learned to subvert these antiviral responses and successfully propagate within the permissive host environment. This review article describes identification and mechanism of action of several pro- and anti-HIV-1 host factors. It is likely that we are just beginning to get a glimpse of an ongoing complex battle between the HIV-1 and the host, understanding of which should provide valuable information for the development of novel therapeutic strategies against HIV-1.