762. Inhibition of HIV-1 Replication by Simian Intrinsic Restriction Factors, TRIM5alpha and APOBEC3G

Abstract

Top of pageAbstract The gene therapy approach for AIDS using therapeutic sequences that block viral replication has been extensively studied. The inhibitory effects of HIV-1 replication by anti-HIV ribozymes, decoys or antisense constructs are rather mild. Although sequence-specific degradation of viral mRNA by siRNA constructs strongly inhibit HIV-1 replication, the emergence of escape mutants with few mutations in the siRNA target region can avoid the antiviral activity of viral siRNA. Recently, two intrinsic cellular factors, which control HIV-1 permissivity in primate cells, were identified as TRIM5alpha and APOBEC3 proteins. Old World monkey TRIM5alpha targets incoming HIV-1 viral capsid (CA) and blocks viral reverse transcription, whereas the APOBEC3 family hypermutate or degrade viral sequences. Here we examined the impacts of simian TRIM5alpha and APOBEC3G expression on HIV-1 replication. First we examined the effects of HIV-1 Gag/CA substations on simian TRIM5alpha-mediated restriction in human cells. We demonstrated that both rhesus (rh)- and African green monkey (agm)-derived TRIM5alpha could efficiently restrict HIV-1 vectors with divergent, naturally occurring Gag/CA substitutions from different HIV-1 subtypes. HIV-1 vectors with H87Q CA substitution, which are less sensitive to Lv1 restriction in monkey cells, were also blocked by the simian TRIM5alpha. Human T cells genetically engineered to express rh- or agm-TRIM5alpha could block or delay HIV-1 replication and were more protected from viral cytopathic effects. Although agm-APOBEC3G expression alone could only transiently suppress HIV-1 replication, co-expression of agm-APOBEC3G and agm-TRIM5a significantly enhanced the antiviral effects of agm-TRIM5a and successfully blocked the virus replication for more than 5 weeks. Therefore, the intrinsic restriction factors are promising candidates as therapeutic genes for AIDS gene therapy.