Viruses that carry a positive-sense, single-stranded RNA translate their genomes after entering the host cell to produce viral proteins, with the exception of retroviruses. A distinguishing feature of retroviruses is reverse transcription, where the +ssRNA genome serves as a template to synthesize a double-stranded DNA copy that subsequently integrates into the host genome. As retroviral RNAs are produced by the host transcriptional machinery and are largely indistinguishable from cellular mRNAs, we investigated the potential of incoming retroviral genomes to express proteins. Here we show through various biochemical methods that HIV-1 genomes are translated after entry, in case of minimal or full-length genomes, envelopes using different cellular entry pathways and in diverse cell types. Our findings challenge the dogma that retroviruses require reverse transcription to produce viral proteins. Synthesis of retroviral proteins in the absence of productive infection has significant implications for basic retrovirology, immune responses and gene therapy applications.

Programmed cell death is a regulatory mechanism to eliminate infected or damaged cells. Several programmed cell death pathways exist, including apoptosis, necroptosis and pyroptosis, which can be distinguished by the cellular molecules involved. Here we show that infection of monocytic cells with HIV-1 causes cell death, which is dose- and cell type dependent and occurs independently of nucleic acid sensing or interferon (IFN) signaling. Death is observed in the case of near full-length viruses that produce viral proteins upon infection, but not in case of a minimal lentiviral vector that does not express viral gene products, demonstrating the necessity of viral gene products or a near-full length RNA genome to trigger death. Inhibition of reverse transcription or integration rescues cells, indicating that a step after integration is responsible. Using mutant viruses, we further narrow down the step in the retroviral replication cycle that triggers death. Inhibition of diverse cell death pathways individually cannot rescue cells from death following infection, consistent with PANoptosis, a cellular death process that cannot be accounted for by any single programmed cell death pathway alone. Our results elucidate the viral and cellular determinants of cell death caused by HIV-1 infection and outline cellular responses that result in the depletion of specific cell populations.