PLoS Pathogens最新文献

Arginine metabolism plays a key role in the energy metabolism of the intestinal parasite Giardia duodenalis, an amitochondrial protozoan that infects humans and animals and causes significant morbidity. Despite that an arginine deiminase (ADI) has been implicated in virulence, it remains unknown if ADI allele variants from the different genetic G. duodenalis subgroups (assemblages) differ in function. Here, the hypothesis was tested that sequence variation detected between G. duodenalis ADI alleles from the two G. duodenalis assemblage types found in humans affects functional parameters of the enzyme with potential consequences in life cycle progression. The ADI enzyme's affinity for arginine was ~ 5fold reduced in sub-assemblage AII isolates, a human specific assemblage, in comparison to zoonotic sub-assemblage AI and B isolates. We identified the two amino acid residues responsible for the lower substrate affinity of ADIAII variant. By combining genetic ADI-knockout mutants, biochemical assays of substrate affinity, and cellular analyses of life-cycle progression, we demonstrate that ADI is required for efficient parasite encystation and that the lower substrate affinity in ADIAII correlates with reduced encystation efficiency. We further demonstrate that arginine is required for efficient encystation, and use an ADI knockout strain to confirm that ADI mediates this arginine dependence. Thus, we suggest that ADI is a quantitative trait that affects life cycle progression of G. duodenalis with putative clinical and epidemiological relevance.

Kaposi sarcoma-associated herpesvirus (KSHV) is an oncogenic virus that causes Kaposi sarcoma, primary effusion lymphoma and multicentric Castleman disease. A vaccine that prevents KSHV infection or serves in the treatment of KSHV-related diseases represents a critical unmet need, however, the types of immune responses a vaccine should elicit have not been well defined. The gH/gL glycoprotein complex is an important target of KSHV-neutralizing antibodies, but the epitope specificities targeted by these antibodies remain unknown. Here, we isolated 12 gH/gL-specific monoclonal antibodies (mAbs) from KSHV-infected donors and performed structure/function analyses. These mAbs bind recombinant gH/gL with nanomolar affinities and epitope binning analyses revealed that the mAbs bind to 5 epitope clusters on gH/gL. Seven mAbs were able to neutralize KSHV infection of epithelial cell lines. Two potent neutralizing mAbs mapped to the EphA2 binding site as determined by inhibition of the receptor-ligand interaction and negative stain electron microscopy (nsEM) of the mAb/gH/gL complex. The epitopes of other neutralizing mAbs targeting novel sites of vulnerability were determined by a combination of cryogenic electron microscopy and nsEM. Together, these mAbs help to define the relevant epitope targets for KSHV vaccine design, have utility in understanding the role of antibodies in preventing KSHV infection, enable the development of immunotherapy approaches, and provide valuable tools to understand the molecular details of the KSHV entry process.

A previous controlled human influenza transmission trial produced minimal transmission using nasal inoculation of an egg adapted virus. Therefore, we implemented a new trial with naturally infected Donors. We recruited healthy Recipients for four, two-week hotel quarantine cohorts and naturally infected, qRT-PCR confirmed Donors for two cohorts. Five Donors (mean age: 21; 80% female; two H1N1, three H3N2, one for cohort 24b and 4 for 24c, Jan-Feb 2024) exposed Recipients (mean age: 36; 54% female, eight in cohort 24b and 3 in 24c) in a hotel room with limited ventilation but a high air recirculation rate. We collected exhaled breath, ambient and personal bioaerosols, fomite swabs, and sera, and analyzed samples using dPCR and fluorescent focus assays, hemagglutination inhibition (HAI) assay, and enzyme-linked immunosorbent assay (ELISA). Compared with previously studied community-acquired influenza cases, we detected viral RNA (44%) and culturable virus (6%) less frequently and measured fewer viral RNA copies (79 - 8.9 × 103 copies/30-min) in Donors' exhaled fine aerosols. One of 23 surface swab samples was culture positive. At admission, 8 of 11 Recipients had HAI titers ≤10 but 9 of 11 had stronger binding antibody responses than Donors against vaccine strains corresponding to Donor viruses. No Recipient developed influenza-like illness, PCR-positive respiratory samples, or serological evidence of infection. Potential explanations and insights regarding lack of transmission include importance of cough and seasonal variation in viral aerosol shedding by Donors, of potential cross-reactive immunity in middle-aged Recipients with decades of exposure, and of exposure to concentrated exhaled breath plumes limited by rapid air mixing from environmental controls that distributed aerosols evenly. Future trials over multiple seasons, Donors that cough, younger recipients, and environments that preserve normal exhaled breath plumes will be required to observe transmission from naturally infected Donors under controlled conditions and generate new insights into influenza transmission dynamics.

Microsporidia, as opportunistic parasitic pathogens, constitute a formidable threat to human health. Although the regulatory circuitry of the nucleus-targeted effector EnP1 remains highly intricate and only partially characterized, our study identifies histone H2A as a novel binding partner of EnP1. Furthermore, we demonstrate that both EnP1 overexpression and microsporidia infection induce monoubiquitination of H2A (H2Aub) through downregulation of BAP1 expression. Subsequent mechanistic analyses revealed that elevated H2Aub levels positively correlate with enhanced microsporidian proliferation, whereas attenuation of H2Aub markedly suppresses pathogen expansion. Furthermore, EnP1 orchestrates the enrichment of H2Aub at the SLC7A11 promoter, driving its transcriptional upregulation. Collectively, these findings underscore that EnP1 modulates the ferroptosis state of host cells through H2Aub-mediated epigenetic reprogramming, ultimately facilitating pathogen propagation. This study endeavors to elucidate the critical survival strategies of microsporidia within host cells mediated by EnP1 and to unravel the multifaceted interplay between these pathogens and their hosts.

Leptospira interrogans is the major causative agent of leptospirosis. Humans, canines and agricultural animals are susceptible to Leptospira species and can develop fulminant disease. Rodents serve as reservoir hosts in which the bacteria colonize the renal tubules and are excreted in the urine. The host immune response to Leptospira spp. remains poorly defined. We show that L. interrogans induces a robust type I interferon (IFN) response in human and murine macrophages that is dependent on the cytosolic dsDNA sensor Cyclic GMP-AMP Synthase (cGAS) and the Stimulator of IFN Genes (STING) signaling pathway. Further, we show that mice deficient in the IFNα/β receptor subunit 1 (IFNAR1) or STING had higher bacterial burdens and increased renal colonization following infection in vivo suggesting that cGAS-STING-driven type I IFN is required for the host defense against L. interrogans. These findings demonstrate the significance of cGAS-STING- dependent type I IFN signaling in mammalian innate immune responses to L. interrogans.

Since its emergence in 2012, Middle East respiratory syndrome coronavirus (MERS-CoV) has posed a significant threat to human health. Recently, novel MERS-like coronaviruses with the potential for cross-species transmission have been identified. In this study, we focused on two newly isolated bat strains with putative health concern: BatCoV/Ii/GD/2014-422 (2014-422) and BtTp-BetaCoV/GX2012 (GX2012). We determined the cryo-EM structures of the spike glycoprotein trimer in the closed state for these two viruses. These structures display a more compact conformation compared to MERS-CoV spike. Biochemical characterization demonstrates that the spike receptor-binding domains (RBDs) of 2014-422 and GX2012 can bind to human dipeptidyl peptidase 4 (hDPP4). To investigate the structural determinants of pseudovirus infection, we solved the cryo-EM structures of 2014-422 RBD-hDPP4 and GX2012 RBD-hDPP4 complexes. The binding mode of the complex is conserved, but the angle of the RBD binding undergoes significant tilting. Detailed structural analysis reveals that an additional residue at position 514 interacts with the N321 glycan in hDPP4, altering the binding angle and thus influencing receptor recognition. These findings offer valuable insights into the receptor utilization of Merbecovirus and provide a structural basis for future surveillance efforts.

PIWI-interacting RNAs (piRNAs), a class of 23-31 nucleotide non-coding RNAs, are known for silencing transposons and endogenous retroviruses that reside in animal genomes. However, the mechanisms by which host piRNAs affect exogenous viral infections, particularly those by DNA viruses, remain poorly understood. Here, we demonstrated that infection by Bombyx mori nucleopolyhedrovirus (BmNPV), a large DNA virus, induced significant upregulation of silkworm host piR-bmo-796514, which facilitated viral proliferation by suppressing the expression of E3 ubiquitin ligase RNF181. We further revealed that RNF181 exerted antiviral activity through ubiquitin-mediated degradation of Integrin α2b-like, a cellular membrane protein that interacted with viral GP64 protein to mediate BmNPV entry. This study unveiled a previously unrecognized regulatory axis connecting host derived piRNAs with exogenous DNA virus infection, providing further mechanistic insights into the modulation of exogenous viral pathogenesis through the reprogramming of the piRNA pathway. Our findings not only advance the understanding of the immune escape mechanism of exogenous viruses but also provide new insights for the development of oligonucleotide antiviral drugs that target proviral piRNAs.

[This corrects the article DOI: 10.1371/journal.ppat.1004581.].