PLoS Pathogens最新文献

[This corrects the article DOI: 10.1371/journal.ppat.1013054.].

SARS-CoV-2 infection elicits both neutralizing and non-neutralizing monoclonal antibodies (mAbs), primarily targeting to the N-terminal domain (NTD), receptor-binding domain (RBD), and S2 subunit of the spike protein. Notably, a unique subset of NTD-targeting mAbs isolated from prototype Wuhan-Hu-1 strain infected donors displayed a capacity of facilitating the viral infection independent of the fragment crystallizable (Fc) region in vitro. However, the rapid evolution of SARS-CoV-2 variants, particularly with NTD mutations, has led to widespread immune evasion. Whether SARS-CoV-2 variants could still induce NTD-targeting infection-enhancing antibodies (NIEAs) remains unclear. Here, we identified a distinctive NIEA, ConD-854, from a Delta variant primarily infected donor, with broad infection-enhancing activities against most pre-Omicron variants but not against post-Omicron variants. Structural and functional analysis revealed that ConD-854 enhanced the viral infection through an Fc-independent bivalent binding mechanism with a largely shared recognition epitope, but its heavy-light chain orientation was nearly perpendicular relative to the reported prototype strain-induced NIEAs. Collectively, our findings demonstrated that the primary infection of Delta variant could still induce the NIEAs targeting the similar epitope as those elicited by prototype strain infection. Mutations in Delta NTD were located outside the infection-enhancing epitope and did not affect the induction of NIEAs. Remarkably, we defined a distinctive structural paradigm for an NIEA to recognize the viral epitope. These results enriched our understanding of antiviral antibodies and provided insights for future vaccine design.

Advanced plant disease management strategies are essential to sustainable agriculture and global food security. Advances in plant immunity have given rise to a variety of innovative disease control strategies, such as NLR gene transfer, RNA silencing technology, and CRISPR/Cas9-based gene disruption, as well as the use of immunity inducers. Recently, several novel resistance strategies, including the bioengineering of immunoreceptors, protease-triggered resistance design, and the sentinel approach, have enabled the customized development of disease resistance traits. These new approaches envisage a new paradigm of precision-targeted, artificially engineered resistance to enhance crop protection.

Leishmaniasis is a major public health problem, causing diseases ranging from self-healing skin lesions to life-threatening chronic infections. Understanding how Leishmania parasites evade the host defense system is crucial for understanding the different manifestations of the disease and for improving diagnostic tools and drug development. We performed high-resolution proteome profiling of Leishmania spp. across three species during macrophage infection and identified distinct temporal expression patterns. Clustering analysis revealed unique protein expression profiles for each Leishmania species, whereas pairwise enrichment analysis revealed specific up- and downregulation patterns at different infection stages. Our results confirmed known virulence factors and highlighted new ones, demonstrating how our dataset could be used. We validated the dataset by showing that deletion of putative L. mexicana virulence factors resulted in reduced stage differentiation capacity and infectivity.

Acinetobacter baumannii poses a substantial global health threat, causing severe multi-drug-resistant infections in hospitalized patients. Circulating clinical isolates present remarkable diversity, with a proportion capable of establishing a transient intracellular niche suitable for persistence, multiplication, and spread. Yet, it remains unknown which bacterial factors mediate the formation and maintenance of this niche, especially within non-phagocytic cells, nor what host responses are elicited. This work demonstrates that the invasive A. baumannii ABC141 strain does not secrete ammonia in endothelial cells as previously shown for other A. baumannii strains multiplying within macrophages but resides in an acidic vacuole devoid of active lysosomal degradative enzymes. This compartment mediates bacterial egress and infection of neighboring cells, promoting dissemination. Using a Dual-RNAseq approach, we mapped the host and bacterial gene expression during the replicative stage of the infection. An atypical hypoxia cell response was observed without significant induction of the HIF1 pathway, with no metabolic shift or disturbance of mitochondria. Surprisingly, ABC141 efficiently grew in hypoxic conditions in culture and within host cells. In addition, we found a bacterial signature reflective of an adaptation to a nutrient-deprived environment. Our work also highlights a differential role for ABC141 secretion systems, with the T1SS assisting intracellular multiplication and the T2SS required for host cell invasion, implicating for the first time the T2SS in the intracellular lifecycle of invasive ABC141 in endothelial cells.

Legionella pneumophila is a facultative intracellular bacterial pathogen capable of surviving and replicating within host cells, including macrophages and protozoans. It employs the Dot/Icm type IV secretion system (T4SS) to inject over 330 effector proteins into host cells, manipulating various cellular processes to facilitate infection. Characterizing the functions of these effectors is crucial to deciphering the pathogenesis of L. pneumophila. In this study, we identified SidG as an effector containing a Cys-His-Asp triad, whose functional state is strictly gated by its interaction with the cellular GTPase Rac1, particularly via its C-terminal domain. Rac1-activated SidG then utilizes an acidic (A) domain to target the Arp2/3 complex, the key regulator of actin nucleation. Importantly, SidG disrupts cytoskeletal architecture via both Rac1- and Arp2/3-dependent mechanisms. During L. pneumophila infection, SidG is crucial to promote efficient bacterial invasion of host cells in a Cys-His-Asp motif-dependent manner. Together, our study elucidates a sophisticated pathogenic mechanism where a bacterial effector co-opts a host GTPase to allosterically regulate its function towards the Arp2/3 complex, thereby facilitating bacterial entry into host cells.

Capsid assembly modulators (CAMs) represent a promising antiviral strategy against hepatitis B virus (HBV), but their effects on pre-formed capsids remain incompletely understood. Here, all-atom molecular dynamics (MD) simulations of intact HBV capsids complexed with prototypical CAM-As (HAP1, HAP18) and CAM-Es (AT130), reveal how structural changes induced by small molecule binding in the interdimer interfaces propagate through the shell lattice to yield global morphological consequences. Each quasi-equivalent interface exhibits a unique response: A sites, located within the pentameric capsomers, are unfilled in these systems and altered marginally by the presence of CAMs in neighboring interfaces. B sites are the most open and "CAM-ready," suggesting uptake requires minimal conformational perturbation on the local or global level. C sites emerge as hubs of allosteric control and the key drug target, as their occupancy creates local distortion that is broadcast to adjacent sites, driving capsid faceting and - in the case of CAM-As - the destabilization that precedes dissociation in favor of aberrant assembly. D sites, unfilled in these systems, act as structural sinks, absorbing distortions from adjacent interfaces within the hexameric capsomers. The extent of C site adjustment and the nature of D site counterbalance varies with CAM chemotype, highlighting the divergent effects of CAM-As versus CAM-Es. The tensegrity relationship between the four quasi-equivalent interfaces couples them into a global network for strain redistribution that is functionally allosteric, with CAM binding sites displaying signs of both positive and negative cooperativity. These new insights into HBV capsid dynamics clarify how CAMs alter them on the microsecond timescale and suggest that targeting strain redistribution in mature core particles could be leveraged therapeutically.

Oropouche fever is a re-emerging global viral threat caused by infection with Oropouche virus (OROV). While disease is generally self-limiting, historical and recent reports of neurologic involvement highlight the importance of understanding the neuropathogenesis of OROV. In this study, we characterize viral replication kinetics in neurons, microglia, and astrocytes derived from immortalized, primary, and induced pluripotent stem cell-derived cells, which are all permissive to infection with the prototypic OROV BeAn19991. We demonstrate cell-type dependent replication kinetics with both historic and recently emerged viral strains. Further, we show that ex vivo rat brain slice cultures can be infected by all OROV strains and produce antiviral cytokines and chemokines, which introduces an additional model to study OROV kinetics and tropism in the central nervous system. These findings provide insight into OROV neuropathogenesis and an initial assessment of newly emerged strains.

Enteroviruses comprise a large group of mammalian pathogens that often utilize two open reading frames (ORFs) to encode their proteins: the upstream protein (UP) and the main polyprotein. In some enteroviruses, in addition to the canonical upstream AUG (uAUG), there is another AUG that may represent an alternative upstream initiation site. An analysis of enterovirus sequences containing additional upstream AUGs identified several clusters, including strains of pathogenic Enterovirus alphacoxsackie and E. coxsackiepol. Using ribosome profiling on coxsackievirus CVA13 (E. coxsackiepol), we demonstrate that both upstream AUG codons can be used for translation initiation in infected cells. Moreover, we confirm translation from both upstream AUGs using a reporter system. Mutating the additional upstream AUG in the context of CVA13 did not result in phenotypic changes in immortalized cell lines. However, the wild-type virus outcompeted this mutant in human intestinal organoids and differentiated neuronal systems, representing an advantage in physiologically relevant infection sites. Mutation of the stop codon of the shorter upstream ORF led to dysregulated translation of the other ORFs in the reporter system, suggesting a potential role for the additional uORF in modulating the expression level of the other ORFs. Additionally, we demonstrate regulation of uORF translation in response to stress. These findings reveal the remarkable plasticity of enterovirus IRES-mediated initiation and the competitive advantage of double-upstream-AUG-containing viruses in terminally differentiated intestinal organoids and neuronal systems.

The innate immune response to viral infection needs to be tightly regulated to ensure effective pathogen clearance while avoiding excessive immune activation. During SARS-CoV-2 infection, however, the immune system often fails to elicit appropriate responses, resulting in cytokine-release syndrome in patients with COVID-19. In this study, we show that reduced expression of Regnase-1, an RNase that negatively regulates immune cell activation, confers resistance to infection with the mouse-adapted SARS-CoV-2 MA10 strain. In Regnase-1+/- mice, altered neutrophil function contributed to the amelioration of MA10-induced pneumonia. Single-cell RNA sequencing of lung tissue during MA10 infection revealed four distinct neutrophil subsets, and among these, a subset characterized by an interferon-stimulated gene (ISG) signature was decreased in Regnase-1+/- mice. Furthermore, Regnase-1+/- neutrophils exhibited reduced ISG expression without corresponding changes in proinflammatory gene expression. Regnase-1 was found to repress the expression of Tsc22d3, a gene involved in the negative regulation of interferon responses, through its 3' untranslated region. Collectively, these findings suggest that Regnase-1 attenuates resistance to SARS-CoV-2 MA10 infection by promoting excessive interferon responses in neutrophils.