Recent evidence indicates that inhibition of HIV-1 integrase (IN) binding to the viral RNA genome by allosteric integrase inhibitors (ALLINIs) or through mutations within IN yields aberrant particles in which the viral ribonucleoprotein complexes (vRNPs) are eccentrically localized outside the capsid lattice. These particles are noninfectious and are blocked at an early reverse transcription stage in target cells. However, the basis of this reverse transcription defect is unknown. Here, we show that the viral RNA genome and IN from ALLINI-treated virions are prematurely degraded in target cells, whereas reverse transcriptase remains active and stably associated with the capsid lattice. The aberrantly shaped cores in ALLINI-treated particles can efficiently saturate and be degraded by a restricting TRIM5 protein, indicating that they are still composed of capsid proteins arranged in a hexagonal lattice. Notably, the fates of viral core components follow a similar pattern in cells infected with eccentric particles generated by mutations within IN that inhibit its binding to the viral RNA genome. We propose that IN-RNA interactions allow packaging of both the viral RNA genome and IN within the protective capsid lattice to ensure subsequent reverse transcription and productive infection in target cells. Conversely, disruption of these interactions by ALLINIs or mutations in IN leads to premature degradation of both the viral RNA genome and IN, as well as the spatial separation of reverse transcriptase from the viral genome during early steps of infection.IMPORTANCE Recent evidence indicates that HIV-1 integrase (IN) plays a key role during particle maturation by binding to the viral RNA genome. Inhibition of IN-RNA interactions yields aberrant particles with the viral ribonucleoprotein complexes (vRNPs) eccentrically localized outside the conical capsid lattice. Although these particles contain all of the components necessary for reverse transcription, they are blocked at an early reverse transcription stage in target cells. To explain the basis of this defect, we tracked the fates of multiple viral components in infected cells. Here, we show that the viral RNA genome and IN in eccentric particles are prematurely degraded, whereas reverse transcriptase remains active and stably associated within the capsid lattice. We propose that IN-RNA interactions ensure the packaging of both vRNPs and IN within the protective capsid cores to facilitate subsequent reverse transcription and productive infection in target cells.KEYWORDS ALLINIs, capsid, HIV-1, integrase, maturation, protein-RNA interaction, RNA packaging, TRIM5, reverse transcriptase

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The role of natural killer (NK) cells against HIV-1 infections remains to be elucidated in vivo.While humanized mouse models potentially could be used to directly evaluate humans NK cell responses during HIV-1 infection, improved functional development of human NK cells in these hosts is needed. Here we report the humanized MISTRG-6-15 mouse model, in which NK cells were quick to expand and exhibit degranulation, cytotoxicity, and pro-inflammatory cytokine production in non-lymphoid organs upon HIV-1 infection, but had reduced functionality in lymphoid organs. Although HIV-1 infection induced functional impairment of NK cells, antiretroviral therapy reinvigorated NK cells in response to HIV-1 rebound after analytic treatment interruption. Moreover, a broadly neutralizing antibody PGT121 enhanced NK cell function in vivo, consistent with antibody-dependent cellular cytotoxicity. Monoclonal antibody depletion of NK cells resulted in higher viral loads in multiple non-lymphoid organs. Overall, our results in humanized MISTRG-6-15 mice demonstrated that NK cells provided direct anti-HIV-1 responses in vivo but were limited in their responses in lymphoid organs.

Neutrophil responses against pathogens must be balanced between protection and immunopathology. Factors that determine these outcomes are not well-understood. In a mouse model of genital herpes simplex virus-2 (HSV-2) infection, which results in severe genital inflammation, antibody-mediated neutrophil depletion reduced disease. Comparative single-cell RNA-sequencing analysis of vaginal cells against a model of genital HSV-1 infection, which results in mild inflammation, demonstrated sustained expression of interferon-stimulated genes (ISGs) only after HSV-2 infection primarily within the neutrophil population. Both therapeutic blockade of IFNα/β receptor 1 (IFNAR1) and genetic deletion of IFNAR1 in neutrophils concomitantly decreased HSV-2 genital disease severity and vaginal IL-18 levels. Therapeutic neutralization of IL-18 also diminished genital inflammation, indicating an important role for this cytokine in promoting neutrophil-dependent immunopathology. Our study reveals that sustained type I interferon (IFN) signaling is a driver of pathogenic neutrophil responses and identifies IL-18 as a novel component of disease during genital HSV-2 infection.

The complement component C3 is a fundamental plasma protein for host defense, produced largely by the liver. However, recent work has demonstrated the critical importance of tissue-specific C3 expression in cell survival. Here, we analyzed the effects of local versus peripheral sources of C3 expression in a model of acute bacterial pneumonia induced by Pseudomonas aeruginosa . Whereas mice with global C3 deficiency had severe pneumonia-induced lung injury, those deficient only in liver-derived C3 remained protected, comparable to wild-type mice. Human lung transcriptome analysis showed that secretory epithelial cells, such as club cells, express high levels of C3 mRNA. Mice with tamoxifen-induced C3 gene ablation from club cells in the lung had worse pulmonary injury compared with similarly treated controls, despite maintaining normal circulating C3 levels. Last, in both the mouse pneumonia model and cultured primary human airway epithelial cells, we showed that stress-induced death associated with C3 deficiency parallels that seen in Factor B deficiency rather than C3a receptor deficiency. Moreover, C3-mediated reduction in epithelial cell death requires alternative pathway component Factor B. Thus, our findings suggest that a pathway reliant on locally derived C3 and Factor B protects the lung mucosal barrier.