Initial Studies On Host Restrictions To HIV-1 Cross-species Transmission And On HIV-1 Susceptible Nonhuman Primate Models

Lacking proper animal models is still a major obstacle for AIDS research. Although non-human primates (NHP), such as macaques, are widely used as animal models for studies on HIV-1 infection and host immune responses, there are multiple species-specific restriction factors existing in these animals, which set up inhibitions to the cross-species transmission of HIV-1 by different ways. Two key restriction factors, TRIM5αand APOBEC3G, which inhibit the proliferation of HIV-1 were identified recently in NHP. Simian TRIM5αbinds HIV-1 capsid protein (CA) and therefore restricts the replication of the human AIDS virus, but has no inhibitions on simian AIDS virus (SIV). Similarly, the Vif protein of HIV-1 antagonizes the restriction of human APOBEC3G but not the simian APOBEC3G, whereas SIV Vif potently blocks the activity of simian APOBEC3G. Therefore, it is hypothesized that HIV-1 will be able to infect monkeys if its genes encoding CA and Vif are substituted by the corresponding regions from SIV. In addition, a TRIM5αvariant TRIMCyp was found in Old world macaques. Differed from TRIM5α, TRIMCyp is a chimera of TRIM5αand CypA, which is encoded by the TRIM5 gene inserted with a CypA peudogene by retrotransposition. TRIMCyp has lost the function of TRIM5αon restricting HIV-1 replication though still potently blocks HIV-2 infection. Therefore, monkeys expressing TRIMCyp are predicted more susceptible to HIV-1 infection than those bearing TRIM5αand are desired candidates for cross-species transmission study of HIV-1 infection.There are three objectives in this study for Ph.D thesis, which includes constructions of simian-tropic HIV-1 infectious clones, screening of TRIMCyp genotype macaque species and individuals and evaluation of simian-tropic HIV-1 infection to target cells from TRIMCyp monkeys. Results for these objectives are summarized as follows:I. To overcome the restrictions imposed by simian TRIM5αand APOBEC3G, a series of recombinant simian-tropic HIV-1 infectious clones were constructed by replacing HIV-1 CA and Vif encoding genes with corresponding regions from SIV. These chimeric viruses are termed as human-simian immunodeficiency virus (HSIV). Analysis of these resultant HSIV clones indicated that these recombinant infectious viral clones were biologically functional in human cell lines.II. Several Chinese macaque species were investigated for individuals of the TRIMCyp genotype. It is the first time that the TRIMCyp genotype was identified in Chinese rhesus monkeys. In addition, TRIMCyp homozygous long-tailed macaques were screened, characterized and used as the source of target cells of HSIV for in vitro studies.III. Confirmed by infections to cells over-expressing monkey TRIMCyp and APOEBC3G, the constructed HSIV viruses were able overcome the restrictions of TRIMCyp and APOEBC3G and successfully replicated in cells mimicking monkey restrictions. The establishment of HSIV and its target monkey cells have provided a solid base for further tests on monkey primary lymphocytes and in vivo cross-species transmission studies. Furthermore, the results of this study present useful data on the cross-species transmission of retroviruses and the antiretroviral innate immunity of hosts.