Hiding in Plain Sight: HIV-1 Membraneless Organelles as Nuclear Hubs-Host Hijacking, Replication, Immune Evasion, and...

Theories on the early steps of the HIV-1 life cycle have been radically revised over the past five years. The long-held assumption that the capsid fully disassembles in the cytoplasm has given way to a more nuanced view: Cytoplasmic disassembly does occur and, in several myeloid systems, is increasingly linked to cytosolic cDNA sensing and to abortive infection. However, a substantial fraction of intact or nearly intact capsid cores instead traverse the nuclear pore complex (NPC) and, upon interacting with the host factor CPSF6, induce liquid-liquid phase separation. This leads to the formation of biomolecular condensates, termed HIV-1 membraneless organelles (HIV-1-MLOs), which subsequently merge with nuclear speckles (NSs). In this Perspective we read these condensates along five interlocking axes. First, the virus drives the host phase separation of cleavage and polyadenylation specificity factor 6 (CPSF6), which quickly fuses with another MLO: the NS composed of the speckle scaffold factors, SON and SRRM2. Second, the resulting condensate behaves as a catalytic site that concentrates the reverse-transcription machinery and thereby promotes integration of the viral DNA into speckle-associated chromatin (SPADs). Third, the same compartment is the final layer of a stratified programme of innate immune evasion, shielding nascent double-stranded DNA from cGAS-STING after cytoplasmic restriction factors and sensors have been outmanoeuvred. Fourth, although demonstrated only in vitro, stable HIV-1-MLOs can maintain the viral RNA genome in the presence of a reverse-transcription inhibitor. Upon removal of the inhibitor, reverse transcription resumes, mirroring, to some extent, the situation in individuals undergoing interruption of antiretroviral therapy and suggesting that these structures may act as a pre-integration reservoir. Fifth, and still largely unexplored, the sanctuary has a pharmacological dimension: anatomical lymphoid compartments, and possibly the condensate itself through selective small-molecule partitioning, may limit antiretroviral drug access. We situate HIV-1-MLOs within the convergent condensate strategies of SARS-CoV-2 and other viruses, and we discuss the clinical, diagnostic, therapeutic, and vaccine implications, including capsid inhibitors as "block-and-expose" tools.