Biology subjects

Ortigoza, M. B.

Publications and source records attributed to Ortigoza, M. B..

8 recordsLinked to original sources

bioRxiv2026

SARS-CoV-2 ORF8 modulates the upper respiratory tract inflammatory response to facilitate transmission

The ability of respiratory viruses to exploit host immune responses to promote transmission is a defining feature of pandemics. SARS-CoV-2 remains a major global public health threat because of its persistent evolution and capacity to counteract evolving immune defenses. Although the immune evasion properties of the SARS-CoV-2 Spike protein are well characterized, the contributions of other viral proteins to transmission remain poorly understood. Here, we used the infant mouse model to define the role of the accessory protein ORF8 in SARS-CoV-2 spread. We demonstrate that ORF8 supports efficient upper respiratory tract (URT) infection, infectious virus shedding, and host-to-host transmission. Mice infected with a recombinant SARS-CoV-2 strain lacking ORF8 (r{Delta}ORF8) had less infectious virus recovered from URT tissues and nasal secretions and transmitted less efficiently than mice infected with the isogenic ancestral strain rWA-1, which contains an intact ORF8. Recombinant viruses encoding naturally occurring ORF8 mutations exhibited distinct transmission phenotypes, with ORF8-deficient viruses resembling r{Delta}ORF8. Infection with ORF8-sufficient viruses induced greater macrophage recruitment, inflammatory cytokine production, and type-I interferon (IFN-I) signaling programs than ORF8-deficient viruses. Intranasal IFN{beta} supplementation partially restored URT shedding by r{Delta}ORF8-infected mice and rescued transmission to contacts, whereas blockade of the type I interferon receptor (IFNAR) in rWA-1-infected index mice reduced contact infection and transmission. Together, these findings demonstrate that ORF8 promotes SARS-CoV-2 transmission by engaging an IFN-I-associated inflammatory and secretory program in the URT that supports virus shedding from the infected host. These data identify ORF8 as a viral determinant of host mucosal responses that promote contagiousness. ImportanceEfficient host-to-host transmission underlies the success of respiratory viruses. Although SARS-CoV-2 research has largely focused on the Spike protein, accessory proteins can also shape viral fitness and spread. We previously identified ORF8 as a determinant of SARS-CoV-2 transmission. Here we show that ORF8 promotes SARS-CoV-2 infectious viral shedding and transmission by engaging IFN-I-associated inflammatory and secretory responses in the URT. These findings reveal how a SARS-CoV-2 accessory protein can exploit mucosal antiviral responses to increase host contagiousness.

microbiology↗

bioRxiv2026

IFNγ-Driven Inflammatory Responses in the Nasal Mucosa Drive Influenza Virus Shedding and Transmission

What determines host infectiousness during influenza A virus (IAV) infection remains a fundamental unanswered question in virology. While upper respiratory tract (URT) replication is necessary for transmission, its insufficient to explain host-to-host variation in contagiousness. Using the infant mouse model of influenza transmission, we show that viruses containing H3 hemagglutinin shed at higher levels than non-H3-containing viruses, despite comparable URT replication. H3-containing virus infection was associated with higher URT inflammation, characterized by increased cytokine production, immune cell recruitment, and mucus hypersecretion, which directly correlated with shedding efficiency. Transcriptomic profiling identified enrichment of interferon-stimulated gene programs, with a dominant interferon gamma (IFN{gamma}) signature during H3 infections. Functional studies demonstrated that IFN{gamma} deficiency reduced mucus production, shedding, and transmission, whereas IFN{gamma} supplementation restored these phenotypes. Together, these findings identify IFN{gamma}-driven mucosal inflammation key host determinant of influenza infectiousness, reframing contagiousness as a consequence of host inflammatory clearance rather than viral replication alone.

microbiology↗

bioRxiv2023

Targeting host sialic acids in the upper respiratory tract with a broadly-acting neuraminidase to inhibit influenza virus transmission

The ongoing transmission of influenza A viruses (IAV) for the past century continues to be a burden to humans. IAV binds terminal sialic acids (SA) of sugar molecules present within the upper respiratory tract (URT) in order to successfully infect hosts. The two most common SA structures that are important for IAV infection are those with 2,3- and 2,6-linkages. While mice were once considered to be an unsuitable system for studying IAV transmission due to their lack of 2,6-SA in the trachea, we have successfully demonstrated that IAV transmission in infant mice is remarkably efficient. This finding led us to reevaluate the SA composition of the URT of mice using in situ immunofluorescence and examine its in vivo contribution to transmission for the first time. We demonstrate that mice express both 2,3- and 2,6-SA in the URT and that the difference in expression between infants and adults contribute to the variable transmission efficiencies observed. Furthermore, selectively blocking 2,3-SA or 2,6-SA within the URT of infant mice using lectins was necessary but insufficient at inhibiting transmission, and simultaneous blockade of both receptors was crucial in achieving the desired inhibitory effect. By employing a broadly-acting neuraminidase (ba-NA) to indiscriminately remove both SA moieties in vivo, we effectively suppressed viral shedding and halted the transmission of different strains of influenza viruses. These results emphasize the utility of the infant mouse model for studying IAV transmission, and strongly indicate that broadly targeting host SA is an effective approach that inhibits IAV contagion. IMPORTANCEInfluenza virus transmission studies have historically focused on viral mutations that alter hemagglutinin binding to sialic acid (SA) receptors in vitro. However, SA binding preference doesnt fully account for the complexities of IAV transmission in humans. Our previous findings reveal that viruses that are known to bind 2,6-SA in vitro have different transmission kinetics in vivo, suggesting that diverse SA interactions may occur during their life-cycle. In this study, we examine the role of host SA on viral replication, shedding, and transmission in vivo. We highlight the critical role of SA presence during virus shedding, such that attachment to SA during virion egress is equally important as detachment from SA during virion release. These insights support the potential of broadly-acting neuraminidases as therapeutic agents capable of restraining viral transmission in vivo. Our study unveils intricate virus-host interactions during shedding, highlighting the necessity to develop innovative strategies to effectively target transmission.

microbiology↗

bioRxiv2022

Molecularly distinct memory CD4+ T cells are induced by SARS-CoV-2 infection and mRNA vaccination

Adaptive immune responses are induced by vaccination and infection, yet little is known about how CD4+ T cell memory differs when primed in these two contexts. Notably, viral infection is generally associated with higher levels of systemic inflammation than is vaccination. To assess whether the inflammatory milieu at the time of CD4+ T cell priming has long-term effects on memory, we compared Spike-specific memory CD4+ T cells in 22 individuals around the time of the participants third SARS-CoV-2 mRNA vaccination, with stratification by whether the participants first exposure to Spike was via virus or mRNA vaccine. Multimodal single-cell profiling of Spike-specific CD4+ T cells revealed 755 differentially expressed genes that distinguished infection- and vaccine-primed memory CD4+ T cells. Spike-specific CD4+ T cells from infection-primed individuals had strong enrichment for cytotoxicity and interferon signaling genes, whereas Spike-specific CD4+ T cells from vaccine-primed individuals were enriched for proliferative pathways by gene set enrichment analysis. Moreover, Spike-specific memory CD4+ T cells established by infection had distinct epigenetic landscapes driven by enrichment of IRF-family transcription factors, relative to T cells established by mRNA vaccination. This transcriptional imprint was minimally altered following subsequent mRNA vaccination or breakthrough infection, reflecting the strong bias induced by the inflammatory environment during initial memory differentiation. Together, these data suggest that the inflammatory context during CD4+ T cell priming is durably imprinted in the memory state at transcriptional and epigenetic levels, which has implications for personalization of vaccination based on prior infection history. One Sentence SummarySARS-CoV-2 infection versus SARS-CoV-2 mRNA vaccination prime durable transcriptionally and epigenetically distinct Spike-specific CD4+ T cell memory landscapes.

immunology↗

bioRxiv2022

A neonatal mouse model characterizes transmissibility of SARS-CoV-2 variants and reveals a role for ORF8

Small animal models have been a challenge for the study of SARS-CoV-2 transmission, with most investigators using golden hamsters or ferrets1, 2. Mice have the advantages of low cost, wide availability, less regulatory and husbandry challenges, and the existence of a versatile reagent and genetic toolbox. However, adult mice do not robustly transmit SARS-CoV-23. Here we establish a model based on neonatal mice that allows for transmission of clinical SARS-CoV-2 isolates. We characterize tropism, respiratory tract replication and transmission of ancestral WA-1 compared to variants Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), Delta (B.1.617.2), Omicron BA.1 and Omicron BQ.1.1. We identify inter-variant differences in timing and magnitude of infectious particle shedding from index mice, both of which shape transmission to contact mice. Furthermore, we characterize two recombinant SARS-CoV-2 lacking either the ORF6 or ORF8 host antagonists. The removal of ORF8 shifts viral replication towards the lower respiratory tract, resulting in significantly delayed and reduced transmission in our model. Our results demonstrate the potential of our neonatal mouse model to characterize viral and host determinants of SARS-CoV-2 transmission, while revealing for the first time a role for an accessory protein in this context.

microbiology↗

bioRxiv2022

Delta-Omicron recombinant SARS-CoV-2 in a transplant patient treated with Sotrovimab

BackgroundThe emergence of recombinant viruses is a threat to public health. Recombination of viral variants may combine variant-specific features that together catalyze viral escape from treatment or immunity. The selective advantages of recombinant SARS-CoV-2 isolates over their parental lineages remain unknown. MethodsMulti-method amplicon and metagenomic sequencing of a clinical swab and the in vitro grown virus allowed for high-confidence detection of a novel recombinant variant. Mutational, phylogeographic, and structural analyses determined features of the recombinant genome and spike protein. Neutralization assays using infectious as well as pseudotyped viruses and point mutants thereof defined the recombinants sensitivity to a panel of monoclonal antibodies and sera from vaccinated and/or convalescent individuals. ResultsA novel Delta-Omicron SARS-CoV-2 recombinant was identified in an unvaccinated, immunosuppressed kidney transplant recipient treated with monoclonal antibody Sotrovimab. The recombination breakpoint is located in the spike N-terminal domain, adjacent to the Sotrovimab quaternary binding site, and results in a 5-Delta AY.45 and a 3-Omicron BA.1 mosaic spike protein. Delta and BA.1 are sensitive to Sotrovimab neutralization, whereas the Delta-Omicron recombinant is highly resistant to Sotrovimab, both with and without the RBD resistance mutation E340D. ConclusionsRecombination between circulating SARS-CoV-2 variants can functionally contribute to immune escape. It is critical to validate phenotypes of mosaic viruses and monitor immunosuppressed COVID-19 patients treated with monoclonal antibodies for the selection of recombinant and immune escape variants. (Funded by NYU, the National Institutes of Health, and others)

microbiology↗

bioRxiv2020

Neuraminidase B controls neuraminidase A-dependent mucus production and evasion

Binding of Streptococcus pneumoniae (Spn) to nasal mucus leads to entrapment and clearance via mucociliary activity during colonization. To identify Spn factors allowing for evasion of mucus binding, we used a solid-phase adherence assay with immobilized mucus of human and murine origin. Spn bound large mucus particles through interactions with carbohydrate moieties. Mutants lacking neuraminidase (nanA) or neuraminidase B (nanB) showed increased mucus binding that correlated with diminished removal of terminal sialic acid residues on bound mucus. The non-additive activity of the two enzymes raised the question why Spn expresses two neuraminidases and suggested they function in the same pathway. Transcriptional analysis demonstrated expression of nanA depends on the enzymatic function of NanB. As transcription of nanA is increased in the presence of sialic acid, our findings suggest that sialic acid liberated from host glycoconjugates by the secreted enzyme NanB induces the expression of the cell-associated enzyme NanA. The absence of detectable mucus desialylation in the nanA mutant, in which NanB is still expressed, suggests that NanA is responsible for the bulk of the modification of host glycoconjugates. Thus, our studies describe a functional role for NanB in sialic acid sensing in the host. The contribution of the neuraminidases in vivo was then assessed in a murine model of colonization. Although mucus-binding mutants showed an early advantage, this was only observed in a competitive infection, suggesting a complex role of neuraminidases. Histologic examination of the upper respiratory tract demonstrated that Spn stimulates mucus production in a neuraminidase-dependent manner. Thus, an increase production of mucus containing secretions appears to be balanced, in vivo, by decreased mucus binding. We postulate that through the combined activity of its neuraminidases, Spn evades mucus binding and mucociliary clearance, which is needed to counter neuraminidase-mediated stimulation of mucus secretions. Author SummaryStreptococcus pneumoniae (Spn) is a leading mucosal pathogen, whose host interaction begins with colonization of the upper respiratory tract. While there has been extensive investigation into bacterial interaction with epithelial cells, there is little understanding of bacterial-mucus interactions. Our study used mucus of human and murine origin and a murine model of colonization to study mucus associations involving Spn. The main findings reveal i) the enzymatic activity of Spns neuraminidases (NanA and NanB) contribute to mucus evasion through removing terminal sialic acid, ii) the enzymatic activity of NanB controls expression of the main neuraminidase, NanA, and iii) Spn induces sialic acid containing mucus secretions in vivo in a neuraminidase-dependent manner. We postulate that during colonization, neuraminidase-dependent reduction in mucus binding enables evasion of mucociliary clearance, which is necessary to counter neuraminidase-mediated stimulation of mucus secretions. Thus, our study provides new insights into the role of Spn neuraminidases on colonization.

microbiology↗

bioRxiv2018

An infant mouse model of influenza virus transmission demonstrates the role of virus-specific shedding, humoral immunity, and sialidase expression by colonizing Streptococcus pneumoniae.

The pandemic potential of influenza A viruses (IAV) depends on the infectivity of the host, transmissibility of the virus, and susceptibility of the recipient. While virus traits supporting IAV transmission have been studied in detail using ferret and guinea pig models, there is limited understanding of host traits determining transmissibility and susceptibility because current animal models of transmission are not sufficiently tractable. Although mice remain the primary model to study IAV immunity and pathogenesis, the efficiency of IAV transmission in adult mice has been inconsistent. Here we describe an infant mouse model which support efficient transmission of IAV. We demonstrate that transmission in this model requires young age, close contact, shedding of virus particles from the upper respiratory tract (URT) of infected pups, the use of a transmissible virus strain, and a susceptible recipient. We characterize shedding as a marker of infectiousness that predicts the efficiency of transmission among different influenza virus strains. We also demonstrate that transmissibility and susceptibility to IAV can be inhibited by humoral immunity via maternal-infant transfer of IAV-specific immunoglobulins, and modifications to the URT milieu, via sialidase activity of colonizing Streptococcus pneumoniae (Spn). Due to its simplicity and efficiency, this model can be used to dissect the hosts contribution to IAV transmission and explore new methods to limit contagion.\n\nIMPORTANCEThis study provides insight into the role of the virus strain, age, immunity, and URT flora on IAV shedding and transmission efficiency. Using the infant mouse model, we found that: (a) differences in viral shedding of various IAV strains is dependent on specific hemagglutinin (HA) and/or neuraminidase (NA) proteins; (b) host age plays a key role in the efficiency of IAV transmission; (c) levels of IAV-specific immunoglobulins are necessary to limit infectiousness, transmission, and susceptibility to IAV; and (d) expression of sialidases by colonizing Spn antagonize transmission by limiting the acquisition of IAV in recipient hosts. Our findings highlight the need for strategies that limit IAV shedding, and the importance of understanding the function of the URT bacterial composition in IAV transmission. This work reinforces the significance of a tractable animal model to study both viral and host traits affecting IAV contagion, and its potential for optimizing vaccines and therapeutics that target disease spread.

microbiology↗