Background
HIV-1 establishes unique biomolecular condensates known as HIV-1 membraneless organelles (HIV-1-MLOs) within the nucleus of infected cells. It has been observed that these organelles localize in some nuclear speckles during the early steps of HIV-1 infection. Despite their identification in vitro, questions remain regarding their persistence, composition, function, and formation in vivo.
Methods
We investigated HIV-1-MLO formation in vitro and in vivo during acute infection using an animal model. We used advanced imaging techniques such as double immunogold labeling, electron microscopy, and tomography to analyze viral core structures within HIV-1-MLOs. Functional assays were performed to assess the stability of HIV-1-MLOs under reverse transcriptase (RT) inhibitor treatment and to determine their role in viral genome maturation and immune evasion.
Results
Our study demonstrated that HIV-1-MLOs persist for several weeks in infected cells and are essential for canonical post-nuclear entry steps. Within HIV-1-MLOs, we identified distinct categories of viral cores, likely representing different stages of nuclear RT. Importantly, we investigated whether HIV-1-MLOs form in vivo during physiological infection. For the first time, our research using humanized mice revealed that HIV-1 induces biomolecular condensates during acute infection in vivo. HIV-1-MLOs play a critical role in viral genome maturation and immune evasion, either preserving viral infectivity or promoting dormancy in the presence of RT inhibitors by sequestering the viral RNA genome in a stable, inactive state that can later be reactivated. Notably, the restoration of nuclear RT occurs exclusively within these organelles. When HIV-1-MLOs are disassembled, there is a complete loss of viral infectivity, even after the removal of RT inhibitors. During canonical infection, in the absence of drugs, dismantling HIV-1-MLOs exposes newly synthesized vDNA, triggering innate immune responses.
Conclusions
HIV-1-MLOs play a critical role in viral genome maturation and immune evasion, maintaining viral infectivity and dormancy in the presence of RT inhibitors by holding the viral RNA genome in a stable, inactive state. These nuclear sites are essential for shielding the newly formed viral dsDNA from host immune responses, ensuring the virus’s ability to persist. Disrupting HIV-1-MLOs presents a potential therapeutic target that could alter latent HIV-1 reservoirs, which are established early during infection.
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