Moraga E, Climent N, Sánchez-Molina A
… +10 more, Vicens-Artés S, Maleno MJ, Valero López G, Galera Peñaranda C, Ambrosioni J, Miró JM, Mallolas J, Albendín-Iglesias H, Alcamí J, Sánchez-Palomino S
PLoS Pathog
· 2026 Jun · PMID 42234672
·
Full text
BACKGROUND: Fingolimod, a treatment for multiple sclerosis (MS), decreases autoreactive lymphocytes by lymph node sequestration. In vitro, fingolimod decreases HIV-1 infection and viral reservoir (VR) through SAMHD1 phos...BACKGROUND: Fingolimod, a treatment for multiple sclerosis (MS), decreases autoreactive lymphocytes by lymph node sequestration. In vitro, fingolimod decreases HIV-1 infection and viral reservoir (VR) through SAMHD1 phosphorylation inhibition and reducing lymphocyte activation and CD4 expression. We identified an exceptional MS patient infected with HIV-1 (HIV+ MS+) while on fingolimod therapy and we have analyzed its impact on HIV-1 infection in vivo and ex vivo. METHODS: The case was the HIV+ MS+ patient. Controls were 20 PWH (HIV+ MS-), five HIV-negative donors (HIV-MS) and three HIV-negative MS patients treated with fingolimod (HIV-MS+), as the case reported. VR was quantified by IPDA and HIV-1 intracellular RNAs (icRNAs) by ddPCR in peripheral blood CD4+ T-cells. CD4+ T-cells were infected in vitro with an NL4.3-Renilla strain. Immunophenotype, activation markers and phosphorylated SAMHD1 levels were determined by flow cytometry. FINDINGS: At diagnosis, HIV+ MS+ viral load was nine-fold lower than HIV+ MS- treated at similar Fiebig stage. One year after ART, HIV+ MS+ showed lower intact and defective VR than the HIV+ MS- control group (28-and six-fold decrease respectively). After three years on ART no intact proviruses were detected in HIV+ MS+ . HIV-1 in vitro infection was decreased in HIV+ MS+ and HIV- MS + vs HIV+ MS- and HIV-MS-. CD4+ T-cells levels from fingolimod treated patients were lower and showed decreased CD4 expression, lymphocyte activation and SAMHD1 phosphorylation vs HIV- MS-. icRNAs were significantly increased after T-cell activation in the HIV+ MS-, while they were barely detected at resting and activated HIV+ MS+ CD4+ T-cells. CONCLUSIONS: We describe a strong restriction to HIV-1 infection and replication in vivo and ex vivo leading to indetectable intact VR in HIV+ MS+ after three years of ART. Potential mechanisms of restriction are CD4 downregulation, T-cell activation inhibition, and SAMHD1 activity enhancement.
PLoS Pathog
· 2026 Jun · PMID 42224368
·
Full text
Seneca Valley Virus (SVV) 3C protease is essential for viral polyprotein processing and virion assembly. Meanwhile, it has evolved to cleave and antagonize the multiple innate immune proteins, enabling viral immune evasi...Seneca Valley Virus (SVV) 3C protease is essential for viral polyprotein processing and virion assembly. Meanwhile, it has evolved to cleave and antagonize the multiple innate immune proteins, enabling viral immune evasion. Inhibitors of 3C protease are therefore powerful antiviral agents. Among these, antiviral peptide inhibitors hold particular promise because of their high specificity, strong efficacy, and broad-spectrum activity, and minimal side effects. Here, we developed a dimerization-dependent red fluorescent protein (ddRFP) biosensor system to screen anti-SVV 3C peptides and identified a substrate-competitive decapeptide (P5) that markedly suppresses 3C protease activity. P5 inhibited 3C-mediated cleavage of multiple key immune proteins, including porcine cGAS (pcGAS), porcine Gasdermin A (pGSDMA) and porcine Pro-IL-1β (sPro-IL-1β). Mechanistically, P5 directly interacted with the catalytic His48 site of 3C protease through hydrogen bonding. Remarkably, P5 restored the formation of cGAS-DNA liquid-liquid phase separation (LLPS) by competitively blocking 3C cleavage activity, thereby enhancing cGAS activity and downstream antiviral interferon signaling. Furthermore, P5 demonstrated favorable cellular permeability, low cytotoxicity, good stability and robust antiviral activity. Our findings establish P5 as a highly promising peptide inhibitor of SVV 3C protease with strong translational potential.
PLoS Pathog
· 2026 Jun · PMID 42224367
·
Full text
Bacterial pathogens that infect host sites beyond their native ecological niche must be equipped to cope with unique challenges across distinct environments. This often manifests in the upregulation of virulence factors...Bacterial pathogens that infect host sites beyond their native ecological niche must be equipped to cope with unique challenges across distinct environments. This often manifests in the upregulation of virulence factors specifically in response to host cues, which enhance pathogen fitness. Extraintestinal pathogenic Escherichia coli (ExPEC) typically colonise the host-gut asymptomatically but can disseminate to infectious sites such as the bladder, kidneys and bloodstream. The molecular basis of urinary tract colonisation by ExPEC is well established, with adhesion via chaperone-usher fimbriae being a critical determinant. However, mechanisms that promote bloodstream infection are poorly understood. Here, we show that several ExPEC fimbriae are upregulated rapidly in response to human serum, mimicking exposure to the bloodstream environment. Yad fimbriae displayed the most significant induction in response to this host cue in two distinct ExPEC isolates, and we show that the gene cluster is prevalent across the E. coli phylogeny, suggesting a common virulence mechanism. Expression of Yad fimbriae was found to be repressed at the transcriptional level by the histone-like nucleoid structuring protein (H-NS). Furthermore, a prolonged elevation in Yad transcription was sustained throughout many generations of growth in serum, suggesting that cue(s) in the bloodstream counteract H-NS repression, triggering cell-surface expression of Yad fimbriae. Finally, Yad transcription was significantly upregulated within systemic tissue in a murine model of bacteremia and we show that deletion of the yad genes significantly attenuated ExPEC colonisation during infection. These data reveal Yad fimbriae as an important ExPEC virulence factor and support the concept of cellular adhesion as a crucial element of bacterial bloodstream pathogenesis.
Mahmoud RM, Hiyoshi M, Abdelnaser RA
… +9 more, Monde K, Monde N, Koma T, Mizuno H, Habash SA, Takahashi N, Maeda Y, Ono A, Suzu S
PLoS Pathog
· 2026 Jun · PMID 42224353
·
Full text
We have demonstrated that the cellular protein M-Sec promotes the transmission of human immunodeficiency virus type 1 (HIV-1) in macrophages. However, the underlying mechanism is not fully understood. Here, we report tha...We have demonstrated that the cellular protein M-Sec promotes the transmission of human immunodeficiency virus type 1 (HIV-1) in macrophages. However, the underlying mechanism is not fully understood. Here, we report that M-Sec promotes the production of infectious HIV-1 virus. The major viral structural protein Gag distributed as many puncta in infected cells, which is one of the indicators of viral particle formation. The knockdown of M-Sec hindered the Gag puncta formation and co-localization of Gag with the viral envelope protein Env in cells, and reduced the amount of Env and infectivity of the produced virus. Consistent with these results, the over-expression of M-Sec induced the accumulation of Gag puncta, Gag/Env co-localization, and Env incorporation into virus and viral infectivity. M-Sec is known to bind phosphatidylinositol 4,5-bisphosphate (PIP2) and a small GTPase Ral, both of which were required for the M-Sec-mediated HIV-1 regulation. The exocyst complex, which is the downstream effector of Ral, was also required for the M-Sec-mediated HIV-1 regulation. Because PIP2, Ral and the exocyst complex are important for the M-Sec-mediated formation of the long plasma membrane protrusions, the present study suggests that M-Sec promotes HIV-1 transmission by acting on both cell structures and viral production through these overlapping components.
Chen J, Fan J, Qin M
… +4 more, Lin Z, Mu S, Dai L, Qin Z
PLoS Pathog
· 2026 Jun · PMID 42224297
·
Full text
Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiologic agent of several human cancers, including Kaposi's sarcoma (KS) and primary effusion lymphoma (PEL), both of which still lack effective treatment options. M...Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiologic agent of several human cancers, including Kaposi's sarcoma (KS) and primary effusion lymphoma (PEL), both of which still lack effective treatment options. Members of the bromodomain and extra-terminal domain (BET) family, especially bromodomain-containing protein 4 (BRD4), play important roles in RNA polymerase II-mediated transcriptional regulation and are required for the expression of many tumor-driving oncogenes in various cancer cells. Therefore, BET proteins have become attractive targets for anticancer drug development. Previous studies have demonstrated the high sensitivity of PEL cells to BET inhibitors, and BRD4 silencing effectively blocks tumor cell proliferation. In contrast, KSHV-infected immortalized endothelial cells display strong resistance to BET inhibitors, including (+)-JQ1. To further develop BRD-targeted therapies for KSHV-infected immortalized endothelial cells, we identified MZ-1 and SIM-1, two BRD4 PROTAC degraders, as effective inhibitors of cell growth in these cells. Mechanistically, these inhibitory effects depend on suppression of LANA translation through increased eIF2α phosphorylation in KSHV-infected cells. Similar LANA suppression was also observed following RNAi-mediated silencing of BRD2 or BRD4. Proteomic analysis identified unique protein candidates altered in MZ-1- and SIM-1-treated KSHV-infected immortalized endothelial cells compared with (+)-JQ1-treated cells. In summary, our study develops an effective strategy against KSHV-infected immortalized endothelial cells using selective BRD PROTACs, which may help improve therapeutic outcomes for KSHV-related malignancies in the future.
Shu H, Ludäscher JM, Sharma S
… +12 more, Alam S, Frank L, Hutchinson ES, Tampere M, Lévêque C, van Kuilenburg ABP, Valerie NCK, Altun M, Chabes A, Stenmark P, Rudd SG, Zhang SM
PLoS Pathog
· 2026 May · PMID 42213735
·
Full text
Molnupiravir is a nucleoside analogue antiviral drug against RNA viruses, including its clinical indication SARS-CoV-2. Whilst its mechanism-of-action is well defined, host factors that regulate its therapeutic responses...Molnupiravir is a nucleoside analogue antiviral drug against RNA viruses, including its clinical indication SARS-CoV-2. Whilst its mechanism-of-action is well defined, host factors that regulate its therapeutic responses have not been thoroughly deciphered and characterized. Here we show that uridine cytidine kinases (UCKs), key enzymes in pyrimidine salvage, effectively phosphorylate and thereby bioactivate N4-hydroxycytidine (NHC) - the active compound of molnupiravir, thus dictating its anti-SARS-CoV-2 efficacy and furthermore selectivity. In vitro, both isoforms of UCKs (UCK1 and UCK2) effectively phosphorylated NHC, where the structural basis of the catalysis was further deciphered via the first complete substrate bound co-crystal structure of UCK, i.e., UCK1-NHC-AMPPNP. In SARS-CoV-2-infected cells, UCK2 knockdown via siRNA hampered the intracellular accumulation of the tri-phosphorylated antiviral metabolite of NHC, resulting in a 10-fold reduction of the antiviral efficacy, and surprisingly, 2-fold reduction of its selectivity, which were critically recapitulated in a dose-dependent manner using a pan-UCK inhibitor. Altogether, this work underscores UCKs as pivotal players in upholding molnupiravir efficacy and therapeutic window, and furthermore as pharmacologically tractable targets for tailoring the drug response.
Drewes S, Wyszkowska J, Jaromin E
… +9 more, Hajduk J, Onik I, Konczal M, Lach K, Bober-Sowa B, Baliga-Klimczyk K, Sadowska ET, Ulrich RG, Koteja P
PLoS Pathog
· 2026 May · PMID 42213706
·
Full text
Bank voles (Myodes glareolus syn. Clethrionomys glareolus) are frequently used as an animal model in ecological and biomedical studies and are an important reservoir of viral and bacterial zoonotic pathogens, e.g., Puuma...Bank voles (Myodes glareolus syn. Clethrionomys glareolus) are frequently used as an animal model in ecological and biomedical studies and are an important reservoir of viral and bacterial zoonotic pathogens, e.g., Puumala hantavirus (PUUV). Here we describe an accidental PUUV outbreak in a large bank vole laboratory colony caused by an accidental introduction of infected wild-trapped bank voles, and the successful eradication of the virus. The eradication plan was based on results of previous studies showing that maternal antibodies (MatAb) protect the young from infection for up to 40 days after weaning, four weeks longer than the estimated duration of PUUV infectivity in the environment. After ensuring that most animals were infected, 620 pairs were mated on the same day. Only females that showed PUUV-specific antibodies and produced offspring within 26 days after mating were retained. All individuals of the parental generation were euthanized before the last weaning. The weaned offspring were moved to individually ventilated cages (IVC) and repeatedly tested for the presence of PUUV-specific antibodies and RNA. A few infected or suspect animals were euthanized. The animals were then mated (in IVC) and, after producing grand-offspring generation, euthanized and tested for PUUV RNA in the lungs. No PUUV RNA was detected, and no animals showed PUUV-specific antibodies in subsequent generations. The successful clearance confirmed the protective efficiency of PUUV-specific MatAb. The procedure for PUUV clearance in the bank vole colony may represent a blueprint for similar approaches in valuable colonies of other rodents infected by similar pathogens.
Lau LS, Lichtenberger S, Taira CL
… +2 more, Klein BS, Wüthrich M
PLoS Pathog
· 2026 May · PMID 42207808
·
Full text
Innate lymphocytes and myeloid cells communicate and play an essential part in activating neutrophils and other effector cells to kill fungi. Here, we identified that Signaling Lymphocytic Activation Molecule 1 (SLAMF1)...Innate lymphocytes and myeloid cells communicate and play an essential part in activating neutrophils and other effector cells to kill fungi. Here, we identified that Signaling Lymphocytic Activation Molecule 1 (SLAMF1) orchestrates a cellular and molecular signaling network that activates phagocytes. We uncovered innate lymphocytes including innate CD4+ or TCRγδ+ T cells augment neutrophil killing of Blastomyces dermatitidis (Bd) in a SLAMF1 dependent manner. SLAMF1 expression on neutrophils enabled homotypic SLAMF1:SLAMF1 interactions with innate CD4+ T cells, which released soluble factors that activated neutrophils to kill fungi. Our work furnishes new mechanistic insight about the role of SLAMF1 in mobilizing innate immune cells to induce phagocyte-driven killing of inhaled fungi.
Singh A, Nair AV, Aroli S
… +6 more, Das S, Karmakar S, Rajmani RS, Mukherjee S, Varshney U, Chakravortty D
PLoS Pathog
· 2026 May · PMID 42207781
·
Full text
The intestinal milieu is largely characterized by the complex array of chemical compounds produced through the metabolic activity of resident microbiota. Enteric pathogens like Salmonella, which have evolved refined mech...The intestinal milieu is largely characterized by the complex array of chemical compounds produced through the metabolic activity of resident microbiota. Enteric pathogens like Salmonella, which have evolved refined mechanisms to persist within this environment, utilize these microbial metabolites and self-produce quorum molecules as molecular cues to identify ecological niches and modulate their survival and virulence strategies. Salmonella quorum sensing involves producing and detecting universal Autoinducer-2 (AI-2) signaling molecules. Our research reveals that Salmonella Typhimurium enhances AI-2 biosynthesis and transport under acidic conditions, aiding environmental adaptation and facilitating pathogenesis in macrophages. AI-2 signaling regulates the pH-sensing two-component system genes, phoP/phoQ, ensuring cytosolic pH homeostasis, survival, and acid tolerance. It also involves regulating the lysine/cadaverine-mediated acid tolerance response and maintaining bacterial cytosolic pH. Furthermore, we investigated the mechanism of AI-2-mediated gene regulation and demonstrated that, in addition to the lsr promoter, the repressor LsrR binds the phoP promoter via its Y25 and R43 residues, thereby negatively regulating phoP expression. Additionally, this signaling ameliorates the intracellular survival by modulating Salmonella Pathogenicity Island-2 (SPI-2) regulators (ssrA/ssrB) and SPI-2 effector expression via PhoP. Mouse models demonstrate that AI-2 signaling is essential for colonizing the primary and secondary infection sites. Therefore, quorum sensing facilitates survival in hostile host environments by modulating multiple genetic targets through the AI-2/LsrR-mediated feedback loop in pathogenic bacteria.
Rajaram K, Sievert ML, Elahi R
… +4 more, Blauwkamp J, Dillard LB, Absalon S, Prigge ST
PLoS Pathog
· 2026 May · PMID 42201985
·
Full text
The malaria parasite Plasmodium falciparum depends entirely on de novo pyrimidine synthesis, as it is unable to salvage these essential nucleotides. This reliance makes the pyrimidine biosynthesis pathway a compelling ta...The malaria parasite Plasmodium falciparum depends entirely on de novo pyrimidine synthesis, as it is unable to salvage these essential nucleotides. This reliance makes the pyrimidine biosynthesis pathway a compelling target for antimalarial drugs, with several inhibitors targeting its rate-limiting enzyme, dihydroorotate dehydrogenase (PfDHODH), already in clinical development. In this study, we investigated the roles of three other pathway enzymes: aspartate transcarbamoylase (PfATC), carbamoyl phosphate synthetase II (PfCPSII), and dihydroorotase (PfDHO). PfATC features a unique N-terminal extension predicted to serve as an apicoplast trafficking peptide. However, using antibodies against the native protein and epitope-tagged versions, we found no evidence of apicoplast localization. Knockdown of PfATC expression proved lethal and could not be rescued by an apicoplast metabolic bypass. Complementation assays further revealed that truncation of the N-terminal domain impaired parasite growth, suggesting that this region is important for PfATC function or stability in vivo. PfCPSII, which harbors large Plasmodium-specific insertions between its catalytic domains, was likewise found to be essential for parasite proliferation. To assess the role of PfDHO, we engineered parasites to salvage uracil via heterologous expression of a yeast enzyme. Deletion of PfDHO in this parasite line resulted in uracil auxotrophy, confirming the enzyme's essential function in pyrimidine synthesis. Together, these findings reveal multiple vulnerable nodes within the pyrimidine biosynthesis pathway.
Akanksha, Bouzeyen R, Watson A
… +7 more, Wiseglass G, Sithole N, Abramovitz L, Ben-Shalom N, Rubinstein R, Javid B, Freund NT
PLoS Pathog
· 2026 May · PMID 42201939
·
Full text
The role of antibodies in the host response against Mycobacterium tuberculosis (M. tb) bacteria is still poorly understood. We previously isolated two monoclonal antibodies (mAbs), p4-36 and p4-163, from an M. tb infecte...The role of antibodies in the host response against Mycobacterium tuberculosis (M. tb) bacteria is still poorly understood. We previously isolated two monoclonal antibodies (mAbs), p4-36 and p4-163, from an M. tb infected donor that target two non-overlapping epitopes on PstS1, a subunit of the M. tb phosphate transporter. Although these antibodies reduced lung bacterial burden in mice (30-40% reduction in CFU), their efficacy remained modest for therapeutic application. Here, we employed a rational antibody engineering approach to further enhance their anti-M. tb potency. Affinity maturation of p4-163 yielded p4-163LR, a variant with superior binding to PstS1 and improved recognition of live, attenuated M. tb. Surprisingly, p4-163LR alone did not confer enhanced protection against virulent M. tb in vivo. However, the generation of a bispecific antibody combining p4-36 and p4-163LR (Bi-S 36/163LR) significantly improved bacterial binding and antibody-dependent cellular phagocytosis (ADCP). Notably, prophylactic administration of Bi-S 36/163LR led to a ~ 1 log reduction in lung bacterial burden compared to control animals treated with isotype control. These findings define a novel, structure-guided strategy to amplify the functional capacity of natural anti-M. tb antibodies and highlight bispecific antibody platforms as promising candidates for host-directed tuberculosis immunotherapy.
PLoS Pathog
· 2026 May · PMID 42189918
·
Full text
Enterovirus D68 (EV-D68) is an emerging pathogen associated with severe respiratory diseases and central nervous system complications. This pearl summarizes the roles of glycan receptors, such as sialic acid, and protein...Enterovirus D68 (EV-D68) is an emerging pathogen associated with severe respiratory diseases and central nervous system complications. This pearl summarizes the roles of glycan receptors, such as sialic acid, and protein receptors like ICAM-5 and MFSD6 in EV-D68 infection. MFSD6 serves as a primary receptor due to its widespread distribution in tissues, while sialic acid and ICAM-5 play a synergistic role in facilitating invasion across various tissues. We have elaborated on the correlation between receptor distribution, tissue tropism, and pathogenicity. The complex receptor system of EV-D68 enhances its pathogenicity by facilitating multi-tissue invasion and allowing the virus to adapt to various microenvironments. This adaptability provides insights into distinct receptor preferences and their associations with pathogenic outcomes, where specific receptor binding can influence the severity of infection. Additionally, we discuss the effectiveness of receptor-targeted inhibitors and the potential for therapeutic interventions aimed at disrupting receptor-virus interactions. Our pearl underscores the multifaceted nature of EV-D68 receptors and their implications for the development of novel antiviral strategies.
Silva HGS, Nascimento JF, Braga MS
… +5 more, Menezes APJ, Silber AM, Waldor MK, da Cunha JPC, Kimura S
PLoS Pathog
· 2026 May · PMID 42189901
·
Full text
Trypanosoma cruzi, the etiological agent of Chagas disease, infects millions of people in the Americas. This parasite undergoes drastic changes in its morphology and metabolism between infective and noninfective forms th...Trypanosoma cruzi, the etiological agent of Chagas disease, infects millions of people in the Americas. This parasite undergoes drastic changes in its morphology and metabolism between infective and noninfective forms through global remodeling of its proteome. Chemical modification of tRNA (tRNA modification) contributes to the control of protein expression by modulating the codon decoding process. However, knowledge of tRNA modification profiles, the enzymes that create modifications and their regulation in different cellular conditions is largely restricted to relatively few model organisms. Here, we profile tRNA modifications in both infective and noninfective forms of T. cruzi to probe their dynamic changes. Genome mining of tRNA modifying enzymes identified 65 putative tRNA-modifying enzymes in T. cruzi for 27 species of tRNA modifications, most of which were detected in T. cruzi tRNA by liquid chromatography mass spectrometry analyses. tRNA sequencing detected reverse transcription-derived signatures at 170 sites in T. cruzi tRNAs that are likely derived from 19 tRNA modifications. tRNA modifications and tRNA modification enzymes are differentially modulated across the life stages of T. cruzi. We found that hydroxywybutosine (OHyW) at position 37 on tRNAPhe(GAA) had a reduced level in the infective form (metacyclic trypomastigote) and the associated modification enzyme Tyw1a exhibited reduced expression in this stage. Knockout of Tyw1a increased the differentiation from epimastigote (noninfective form) to metacyclic trypomastigote, suggesting that changes in OHyW37 modification levels alter the rate of metacyclogenesis. Overall, our findings suggest that tRNA modification changes during the life stages of T. cruzi contribute to the differentiation of this parasite.
MacNair CR, Tiku V, Cao S
… +5 more, Sanchez AD, Udayasuryan B, Kroll KT, Singh A, Tan MW
PLoS Pathog
· 2026 May · PMID 42189882
·
Full text
Outer membrane vesicles (OMVs) are nanoscale proteoliposomes shed by Gram-negative bacteria that mediate host-pathogen interactions and hold promise as platforms for vaccines and targeted drug delivery. Despite their bio...Outer membrane vesicles (OMVs) are nanoscale proteoliposomes shed by Gram-negative bacteria that mediate host-pathogen interactions and hold promise as platforms for vaccines and targeted drug delivery. Despite their biological and translational significance, the cellular mechanisms governing OMV entry into host cells remain poorly understood. Here, we demonstrate that E. coli OMVs are internalized by epithelial cells via clathrin-mediated, receptor-dependent endocytosis. Using a high-throughput screen of over 1,500 human single-pass transmembrane proteins, we identify T-cell immunoglobulin and mucin-domain 1 (TIM-1) as a strong OMV-binding receptor. Functional validation revealed that TIM-1 overexpression markedly increased OMV uptake, whereas TIM-1 knockout and antibody-mediated blockade significantly impaired internalization across multiple cell lines. Mechanistic studies demonstrate that TIM-1 binds to lipopolysaccharide (LPS) on the OMV surface via its phosphatidylserine-binding domain. Uptake of OMVs by TIM-1 triggers proinflammatory cytokine production which can be reduced by preventing this interaction. Additionally, OMVs from multiple bacterial species hijack TIM-1 for entry, making it an intriguing antivirulence strategy. Our findings establish TIM-1 as a critical host receptor mediating OMV uptake and provide a novel approach to modulate vesicle-driven pathogenesis and enhance OMV-based therapies.
Arya D, Jaggi U, Oh JJ
… +2 more, Wang S, Ghiasi H
PLoS Pathog
· 2026 May · PMID 42189879
·
Full text
Herpes simplex virus type 1 (HSV-1) glycoprotein D (gD) engages herpesvirus entry mediator (HVEM) and other cellular receptors to mediate efficient viral attachment. We recently identified gD amino acids (aa) Q27-T29 as...Herpes simplex virus type 1 (HSV-1) glycoprotein D (gD) engages herpesvirus entry mediator (HVEM) and other cellular receptors to mediate efficient viral attachment. We recently identified gD amino acids (aa) Q27-T29 as critical to completely block gD binding to HVEM, while the single Q27P mutation in gD reduced its binding to HVEM by approximately 80%. Thus, we constructed two mutant viruses: one with a single gD aa mutation (v27) and the other with three gD aa mutations (v27-29) in the HSV-1 strain GFP-McKrae background. These mutant viruses clearly demonstrated the consequences of disrupting gD binding to HVEM, which reduced HVEM expression and altered the expression of other receptors. To determine whether these mutations also affected viral replication, ocular disease severity, latency levels, and reactivation kinetics, mice were ocularly infected with WT, v27, or v27-29 viruses. Both mutant viruses exhibited significantly reduced viral replication in tears compared with the WT virus, even after corneal scarification. The v27-29 virus showed a greater reduction in viral replication than the v27 virus. Mice infected with both mutant viruses had significantly lower levels of eye disease, latency, and T cell exhaustion than in WT virus-infected mice. In the absence of scarification, significantly fewer trigeminal ganglia (TG) were reactivated by mutant viruses than by the WT virus. In contrast, after scarification, all TG from WT-, v27-, and v27-29-infected mice were reactivated, and the time to reactivate was similar between the two mutant viruses, but reactivation was significantly less delayed than in WT-infected mice. Together, these findings demonstrate that disrupting gD-HVEM binding reduces viral virulence and limits latency, reactivation, and T cell exhaustion. Thus, the Q27-T29 region of gD is a critical determinant of infection dynamics and a potential therapeutic or vaccine target.
Harima H, Sasaki M, Ariizumi T
… +16 more, Kawaguchi N, Kobayashi H, Intaruck K, Kobayashi T, Kawagishi T, Kanai Y, Nao N, Qiu Y, Kajihara M, Orba Y, Ito N, Ishihara K, Saijo M, Hall WW, Hang'ombe BM, Sawa H
PLoS Pathog
· 2026 May · PMID 42189872
·
Full text
Pteropine orthoreovirus (PRV) is an emerging zoonotic virus that causes pneumonia in humans. We previously isolated the PRV strain Nachunsulwe-57 (N57) from a Zambian fruit bat and demonstrated its low virulence in labor...Pteropine orthoreovirus (PRV) is an emerging zoonotic virus that causes pneumonia in humans. We previously isolated the PRV strain Nachunsulwe-57 (N57) from a Zambian fruit bat and demonstrated its low virulence in laboratory mice. Here, we have attempted to identify factors responsible for differences in the virulence between strain N57 and the human-derived clinical strain Miyazaki-Bali/2007 (MB). Characterization of the virulence of recombinant monoreassortant PRVs derived from highly virulent MB and low virulent N57 strains in mice revealed that compared with wild-type (WT) MB, MB-based monoreassortants carrying the L1, S1, or S2 segment from N57 exhibited attenuated virulence. Among these, the monoreassortants carrying the S1 or S2 segment exhibited reduced viral loads and reduced cytokine gene expression levels in the lungs. Genetic mapping of virulence determinants using the reciprocal monoreassortant viruses with increased virulence demonstrated that N57-based monoreassortants carrying the S1 or S2 segment of MB exhibited enhanced virulence, resulting in lower survival rate compared with WT N57. Unlike the S1 segment, the functions of the S2 segment in pathogenesis are unclear. Thus, we further investigated the functional region of the inner-capsid σA protein encoded by the S2 segment. Notably, Ser-46 of σA was identified as a key amino acid determinant of PRV virulence and is present in strains derived from humans, monkeys, and bat flies, but not those identified from bats (their natural host). Collectively, these findings demonstrate that PRV σA is one factor that regulates virulence, and that σA Ser-46 may be related to potential interspecies transmission events from bats.