Characterisation of a block to HIV-1 infection in rabbit cells as a model to study HIV-1 trafficking

This thesis focuses mainly on the analysis of the restriction to HIV-1 infection using rabbit cells as a model. Rabbit cells are poorly permissive to HIV-1 infection and the nature of this block is not well understood. This work shows that the restriction is independent of the cell receptor used by the virus for entry, as shown by infection of cells with HIV-1 pseudotyped with different types of envelopes and that it occurs mainly at the level of reverse transcription. It cannot be effectively saturated with high doses of virus or virus-like particles and has a recessive phenotype in human-rabbit heterokaryons. These results point to the existence of a factor required for HIV-1 infection that is absent in SIRC cells but can be complemented by human cells. The reverse transcription complexes extracted from human and rabbit cells have been analysed biochemically and found to have different densities but to be competent for reverse transcription in both cases in an in vitro endogenous assay. Cell fractionation of infected cells showed that HIV-1 is trafficked in a different way in human and rabbit cells and that correct intracellular trafficking is related to efficient reverse transcription and high infectivity in vivo. It is shown as well that viral DNA accumulates in rabbit cell nuclei only at a later stage of infection and fails to associate with chromatin, suggesting a further block prior to integration in SIRC cells Finally, chimeric viruses are used to determine the viral components responsible for the block. Viral chimeras formed by HIV-1 and SIV or MLV are used to infect the human cell line HeLa and SIRC cells. It is found that HIV-1 capsid is the determinant of the block in SIRC cells. Our data point to the existence of cellular factors regulating the early stages of intracytoplasmic and possibly intranuclear HIV-1 trafficking