STAT1-cooperative DNA binding distinguishes type 1 from type 2 interferon signaling.

STAT1 is an indispensable component of a heterotrimer (ISGF3) and a STAT1 homodimer (GAF) that function as transcription regulators in type 1 and type 2 interferon signaling, respectively. To investigate the importance of STAT1-cooperative DNA binding, we generated gene-targeted mice expressing cooperativity-deficient STAT1 with alanine substituted for Phe77. Neither ISGF3 nor GAF bound DNA cooperatively in the STAT1F77A mouse strain, but type 1 and type 2 interferon responses were affected differently. Type 2 interferon-mediated transcription and antibacterial immunity essentially disappeared owing to defective promoter recruitment of GAF. In contrast, STAT1 recruitment to ISGF3 binding sites and type 1 interferon-dependent responses, including antiviral protection, remained intact. We conclude that STAT1 cooperativity is essential for its biological activity and underlies the cellular responses to type 2, but not type 1 interferon.

Unique Evolution of Antiviral Tetherin in Bats.

Bats are recognized as important reservoirs of viruses deadly to other mammals, including humans. These infections are typically nonpathogenic in bats, raising questions about host response differences that might exist between bats and other mammals. Tetherin is a restriction factor which inhibits the release of a diverse range of viruses from host cells, including retroviruses, coronaviruses, filoviruses, and paramyxoviruses, some of which are deadly to humans and transmitted by bats. Here, we characterize the tetherin genes from 27 bat species, revealing that they have evolved under strong selective pressure, and that fruit bats and vesper bats express unique structural variants of the tetherin protein. Tetherin was widely and variably expressed across fruit bat tissue types and upregulated in spleen tissue when stimulated with Toll-like receptor agonists. The expression of two computationally predicted splice isoforms of fruit bat tetherin was verified. We identified an additional third unique splice isoform which includes a C-terminal region that is not homologous to known mammalian tetherin variants but was functionally capable of restricting the release of filoviral virus-like particles. We also report that vesper bats possess and express at least five tetherin genes, including structural variants, more than any other mammal reported to date. These findings support the hypothesis of differential antiviral gene evolution in bats relative to other mammals. IMPORTANCE Bats are an important host of various viruses which are deadly to humans and other mammals but do not cause outward signs of illness in bats. Furthering our understanding of the unique features of the immune system of bats will shed light on how they tolerate viral infections, potentially informing novel antiviral strategies in humans and other animals. This study examines the antiviral protein tetherin, which prevents viral particles from escaping their host cell. Analysis of tetherin from 27 bat species reveals that it is under strong evolutionary pressure, and we show that multiple bat species have evolved to possess more tetherin genes than other mammals, some of which encode structurally unique tetherins capable of activity against different viral particles. These data suggest that bat tetherin plays a potentially broad and important role in the management of viral infections in bats.

Whole-genome sequencing and gene sharing network analysis powered by machine learning identifies antibiotic resistance sharing between animals, humans and environment in livestock farming.

Anthropogenic environments such as those created by intensive farming of livestock, have been proposed to provide ideal selection pressure for the emergence of antimicrobial-resistant Escherichia coli bacteria and antimicrobial resistance genes (ARGs) and spread to humans. Here, we performed a longitudinal study in a large-scale commercial poultry farm in China, collecting E. coli isolates from both farm and slaughterhouse; targeting animals, carcasses, workers and their households and environment. By using whole-genome phylogenetic analysis and network analysis based on single nucleotide polymorphisms (SNPs), we found highly interrelated non-pathogenic and pathogenic E. coli strains with phylogenetic intermixing, and a high prevalence of shared multidrug resistance profiles amongst livestock, human and environment. Through an original data processing pipeline which combines omics, machine learning, gene sharing network and mobile genetic elements analysis, we investigated the resistance to 26 different antimicrobials and identified 361 genes associated to antimicrobial resistance (AMR) phenotypes; 58 of these were known AMR-associated genes and 35 were associated to multidrug resistance. We uncovered an extensive network of genes, correlated to AMR phenotypes, shared among livestock, humans, farm and slaughterhouse environments. We also found several human, livestock and environmental isolates sharing closely related mobile genetic elements carrying ARGs across host species and environments. In a scenario where no consensus exists on how antibiotic use in the livestock may affect antibiotic resistance in the human population, our findings provide novel insights into the broader epidemiology of antimicrobial resistance in livestock farming. Moreover, our original data analysis method has the potential to uncover AMR transmission pathways when applied to the study of other pathogens active in other anthropogenic environments characterised by complex interconnections between host species.

Infectious KoRV-related retroviruses circulating in Australian bats.

Bats are reservoirs of emerging viruses that are highly pathogenic to other mammals, including humans. Despite the diversity and abundance of bat viruses, to date they have not been shown to harbor exogenous retroviruses. Here we report the discovery and characterization of a group of koala retrovirus-related (KoRV-related) gammaretroviruses in Australian and Asian bats. These include the Hervey pteropid gammaretrovirus (HPG), identified in the scat of the Australian black flying fox (Pteropus alecto), which is the first reproduction-competent retrovirus found in bats. HPG is a close relative of KoRV and the gibbon ape leukemia virus (GALV), with virion morphology and Mn2+-dependent virion-associated reverse transcriptase activity typical of a gammaretrovirus. In vitro, HPG is capable of infecting bat and human cells, but not mouse cells, and displays a similar pattern of cell tropism as KoRV-A and GALV. Population studies reveal the presence of HPG and KoRV-related sequences in several locations across northeast Australia, as well as serologic evidence for HPG in multiple pteropid bat species, while phylogenetic analysis places these bat viruses as the basal group within the KoRV-related retroviruses. Taken together, these results reveal bats to be important reservoirs of exogenous KoRV-related gammaretroviruses.

Re-Routing Persuasion: How Conversion Messages Boost Attitudes and Reduce Resistance Among Holdouts Unvaccinated for COVID-19.

This study examined the persuasive effects of two-sided refutational conversion messages compared to one-sided advocacy messages in increasing pro-COVID-19 vaccination attitudes and reducing resistance to getting vaccinated among U.S. adults who self-reported as unvaccinated. Results showed that main effects of conversion messages led to significantly higher attitudes but failed to directly reduce resistance toward vaccination. Predicted mediation effects between conversion messages and the dependent variables were found for homophily but were not supported for argument strength. Significant group differences were detected between participants who self-reported as high or low in vaccine hesitancy, for structural equation models that significantly and indirectly led to decreased resistance. Findings show the potential for two-sided conversion messages to be used by public health message designers to affect pro-health outcomes. Implications and limitations of these results and future directions are discussed.

Facing the Strain: The Persuasive Effects of Conversion Messages on COVID-19 Vaccination Attitudes and Behavioral Intentions.

This study examined two-sided conversion messages in relation to one-sided advocacy messages in reducing vaccine hesitancy related to COVID-19 vaccine uptake. Results demonstrated that, for vaccine-hesitant participants, conversion messages increased pro-COVID-19 vaccination attitudes and behavioral intentions. For high vaccine-hesitant participants, the relationship between conversion messages and attitudes toward COVID-19 vaccinations was mediated through source credibility. For low vaccine-hesitant participants, mediation occurred through counterarguing. Findings have implications for health message tailoring related to COVID-19 vaccine uptake.

Detection of filovirus-reactive antibodies in Australian bat species.

Bats have been implicated as the reservoir hosts of filoviruses in Africa, with serological evidence of filoviruses in various bat species identified in other countries. Here, serum samples from 190 bats, comprising 12 different species, collected in Australia were evaluated for filovirus antibodies. An in-house indirect microsphere assay to detect antibodies that cross-react with Ebola virus (Zaire ebolavirus; EBOV) nucleoprotein (NP) followed by an immunofluorescence assay (IFA) were used to confirm immunoreactivity to EBOV and Reston virus (Reston ebolavirus; RESTV). We found 27 of 102 Yinpterochiroptera and 19 of 88 Yangochiroptera samples were positive to EBOV NP in the microsphere assay. Further testing of these NP positive samples by IFA revealed nine bat sera that showed binding to ebolavirus-infected cells. This is the first report of filovirus-reactive antibodies detected in Australian bat species and suggests that novel filoviruses may be circulating in Australian bats.

Novel SCCmec type XV (7A) and two pseudo-SCCmec variants in foodborne MRSA in China.

BACKGROUND: Staphylococcal cassette chromosome mec (SCCmec) elements are highly diverse and have been classified into 14 types. Novel SCCmec variants have been frequently detected from humans and animals but rarely from food. OBJECTIVES: To characterize a novel SCCmec type and two SCCmec variants identified from food-associated MRSA in China. METHODS: Three MRSA (NV_1, NT_611 and NT_8) collected from retail foods in China were subjected to WGS and the SCCmec elements were determined. RESULTS: The novel SCCmecXV identified in NV_1 carried the mec gene complex class A (mecI-mecR1-mecA-IS431) and the ccr gene complex 7 (ccrA1B6), and a Tn558-mediated phenicol exporter gene fexA was detected in this SCCmecXV cassette. The pseudo-SCCmec elements ΨSCCmecNT_611 and ΨSCCmecNT_8 showed a truncated SCCmec pattern, carrying the class C2 mec gene complex but missing the ccr genes. The ΨSCCmecNT_611 element shared more similarities with those of Staphylococcus haemolyticus (AB478934.1) and carried a heavy metal resistance gene cluster cadD-cadX-arsC-arsB-arsR-copA. The ΨSCCmecNT_8 MRSA exhibited a highly resistant phenotype, showing the absence of a 19.3 kb segment compared with the reference SCCmecXII element (CP019945.1). Notably, a 46 kb region containing multiple transposons encoding antimicrobial or metal resistance genes flanked by IS431 or IS256 was identified ∼30 kb downstream from the mec gene complex in ΨSCCmecNT_8, which might explain such high resistance in MRSA NT_8. CONCLUSIONS: Our finding of novel and pseudo-SCCmec elements reflected the ongoing intra/interspecies genetic rearrangements in staphylococci. Further study will be needed to investigate the biological significance and prevalence of those SCCmec variants along the food chain.

Acute experimental infection of bats and ferrets with Hendra virus: Insights into the early host response of the reservoir host and susceptible model species.

Bats are the natural reservoir host for a number of zoonotic viruses, including Hendra virus (HeV) which causes severe clinical disease in humans and other susceptible hosts. Our understanding of the ability of bats to avoid clinical disease following infection with viruses such as HeV has come predominantly from in vitro studies focusing on innate immunity. Information on the early host response to infection in vivo is lacking and there is no comparative data on responses in bats compared with animals that succumb to disease. In this study, we examined the sites of HeV replication and the immune response of infected Australian black flying foxes and ferrets at 12, 36 and 60 hours post exposure (hpe). Viral antigen was detected at 60 hpe in bats and was confined to the lungs whereas in ferrets there was evidence of widespread viral RNA and antigen by 60 hpe. The mRNA expression of IFNs revealed antagonism of type I and III IFNs and a significant increase in the chemokine, CXCL10, in bat lung and spleen following infection. In ferrets, there was an increase in the transcription of IFN in the spleen following infection. Liquid chromatography tandem mass spectrometry (LC-MS/MS) on lung tissue from bats and ferrets was performed at 0 and 60 hpe to obtain a global overview of viral and host protein expression. Gene Ontology (GO) enrichment analysis of immune pathways revealed that six pathways, including a number involved in cell mediated immunity were more likely to be upregulated in bat lung compared to ferrets. GO analysis also revealed enrichment of the type I IFN signaling pathway in bats and ferrets. This study contributes important comparative data on differences in the dissemination of HeV and the first to provide comparative data on the activation of immune pathways in bats and ferrets in vivo following infection.

Predator Versus Pathogen: How Does Predatory Bdellovibrio bacteriovorus Interface with the Challenges of Killing Gram-Negative Pathogens in a Host Setting?

Bdellovibrio bacteriovorus is a small deltaproteobacterial predator that has evolved to invade, reseal, kill, and digest other gram-negative bacteria in soils and water environments. It has a broad host range and kills many antibiotic-resistant, clinical pathogens in vitro, a potentially useful capability if it could be translated to a clinical setting. We review relevant mechanisms of B. bacteriovorus predation and the physiological properties that would influence its survival in a mammalian host. Bacterial pathogens increasingly display conventional antibiotic resistance by expressing and varying surface and soluble biomolecules. Predators coevolved alongside prey bacteria and so encode diverse predatory enzymes that are hard for pathogens to resist by simple mutation. Predators do not replicate outside pathogens and thus express few transport proteins and thus few surface epitopes for host immune recognition. We explain these features, relating them to the potential of predatory bacteria as cellular medicines.

An argument for pandemic risk management using a multidisciplinary One Health approach to governance: an Australian case study.

The emergence of SARS-CoV-2 and the subsequent COVID-19 pandemic has resulted in significant global impact. However, COVID-19 is just one of several high-impact infectious diseases that emerged from wildlife and are linked to the human relationship with nature. The rate of emergence of new zoonoses (diseases of animal origin) is increasing, driven by human-induced environmental changes that threaten biodiversity on a global scale. This increase is directly linked to environmental drivers including biodiversity loss, climate change and unsustainable resource extraction. Australia is a biodiversity hotspot and is subject to sustained and significant environmental change, increasing the risk of it being a location for pandemic origin. Moreover, the global integration of markets means that consumption trends in Australia contributes to the risk of disease spill-over in our regional neighbours in Asia-Pacific, and beyond. Despite the clear causal link between anthropogenic pressures on the environment and increasing pandemic risks, Australia's response to the COVID-19 pandemic, like most of the world, has centred largely on public health strategies, with a clear focus on reactive management. Yet, the span of expertise and evidence relevant to the governance of pandemic risk management is much wider than public health and epidemiology. It involves animal/wildlife health, biosecurity, conservation sciences, social sciences, behavioural psychology, law, policy and economic analyses to name just a few.The authors are a team of multidisciplinary practitioners and researchers who have worked together to analyse, synthesise, and harmonise the links between pandemic risk management approaches and issues in different disciplines to provide a holistic overview of current practice, and conclude the need for reform in Australia. We discuss the adoption of a comprehensive and interdisciplinary 'One Health' approach to pandemic risk management in Australia. A key goal of the One Health approach is to be proactive in countering threats of emerging infectious diseases and zoonoses through a recognition of the interdependence between human, animal, and environmental health. Developing ways to implement a One Health approach to pandemic prevention would not only reduce the risk of future pandemics emerging in or entering Australia, but also provide a model for prevention strategies around the world.

Examining the Effects of Celebrity (Vs. Noncelebrity) Narratives on Opioid Addiction Prevention: Identification, Transportation, and the Moderating Role of Personal Relevance.

Celebrity disclosures and narratives are popular strategies in health promotion. However, less is known about their joint effects and the mechanisms through which they function. A 2 (narrative type: celebrity vs. layperson) x 2 (personal relevance: low vs. high) online experiment (N = 248) tested the impact of different narrative types in increasing awareness about prescription opioid abuse. Results indicated that a celebrity narrative is more persuasive than its layperson counterpart. Also, personal relevance toward opioid addiction moderated the influence of narrative type. Celebrity narratives evoked more positive attitudes toward opioid prevention and greater behavioral compliance intentions with the recommended action for low-relevance individuals. Transportation and identification mediated the effects of celebrity narratives on participants' issue attitudes and behavioral intentions, but only for low-relevance individuals. Practically, the data suggest that incorporating celebrities in health narratives about opioid addiction prevention facilitates behavioral compliance, especially for individuals to whom a pressing health issue like opioid misuse is currently of low relevance.

Stream Dissolved Organic Matter in Permafrost Regions Shows Surprising Compositional Similarities but Negative Priming and Nutrient Effects.

Permafrost degradation is delivering bioavailable dissolved organic matter (DOM) and inorganic nutrients to surface water networks. While these permafrost subsidies represent a small portion of total fluvial DOM and nutrient fluxes, they could influence food webs and net ecosystem carbon balance via priming or nutrient effects that destabilize background DOM. We investigated how addition of biolabile carbon (acetate) and inorganic nutrients (nitrogen and phosphorus) affected DOM decomposition with 28-day incubations. We incubated late-summer stream water from 23 locations nested in seven northern or high-altitude regions in Asia, Europe, and North America. DOM loss ranged from 3% to 52%, showing a variety of longitudinal patterns within stream networks. DOM optical properties varied widely, but DOM showed compositional similarity based on Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis. Addition of acetate and nutrients decreased bulk DOM mineralization (i.e., negative priming), with more negative effects on biodegradable DOM but neutral or positive effects on stable DOM. Unexpectedly, acetate and nutrients triggered breakdown of colored DOM (CDOM), with median decreases of 1.6% in the control and 22% in the amended treatment. Additionally, the uptake of added acetate was strongly limited by nutrient availability across sites. These findings suggest that biolabile DOM and nutrients released from degrading permafrost may decrease background DOM mineralization but alter stoichiometry and light conditions in receiving waterbodies. We conclude that priming and nutrient effects are coupled in northern aquatic ecosystems and that quantifying two-way interactions between DOM properties and environmental conditions could resolve conflicting observations about the drivers of DOM in permafrost zone waterways.

Dual Predation by Bacteriophage and Bdellovibrio bacteriovorus Can Eradicate Escherichia coli Prey in Situations where Single Predation Cannot.

Bacteria are preyed upon by diverse microbial predators, including bacteriophage and predatory bacteria, such as Bdellovibrio bacteriovorus While bacteriophage are used as antimicrobial therapies in Eastern Europe and are being applied for compassionate use in the United States, predatory bacteria are only just beginning to reveal their potential therapeutic uses. However, predation by either predator type can falter due to different adaptations arising in the prey bacteria. When testing poultry farm wastewater for novel Bdellovibrio isolates on Escherichia coli prey lawns, individual composite plaques were isolated containing both an RTP (rosette-tailed-phage)-like-phage and a B. bacteriovorus strain and showing central prey lysis and halos of extra lysis. Combining the purified phage with a lab strain of B. bacteriovorus HD100 recapitulated haloed plaques and increased killing of the E. coli prey in liquid culture, showing an effective side-by-side action of these predators compared to their actions alone. Using approximate Bayesian computation to select the best fitting from a variety of different mathematical models demonstrated that the experimental data could be explained only by assuming the existence of three prey phenotypes: (i) sensitive to both predators, (ii) genetically resistant to phage only, and (iii) plastic resistant to B. bacteriovorus only. Although each predator reduces prey availability for the other, high phage numbers did not abolish B. bacteriovorus predation, so both predators are competent to coexist and are causing different selective pressures on the bacterial surface while, in tandem, controlling prey bacterial numbers efficiently. This suggests that combinatorial predator therapy could overcome problems of phage resistance.IMPORTANCE With increasing levels of antibiotic resistance, the development of alternative antibacterial therapies is urgently needed. Two potential alternatives are bacteriophage and predatory bacteria. Bacteriophage therapy has been used, but prey/host specificity and the rapid acquisition of bacterial resistance to bacteriophage are practical considerations. Predatory bacteria are of interest due to their broad Gram-negative bacterial prey range and the lack of simple resistance mechanisms. Here, a bacteriophage and a strain of Bdellovibrio bacteriovorus, preyed side by side on a population of E. coli, causing a significantly greater decrease in prey numbers than either alone. Such combinatorial predator therapy may have greater potential than individual predators since prey surface changes selected for by each predator do not protect prey against the other predator.

Differential Evolution of Antiretroviral Restriction Factors in Pteropid Bats as Revealed by APOBEC3 Gene Complexity.

Bats have attracted attention in recent years as important reservoirs of viruses deadly to humans and other mammals. These infections are typically nonpathogenic in bats raising questions about innate immune differences that might exist between bats and other mammals. The APOBEC3 gene family encodes antiviral DNA cytosine deaminases with important roles in the suppression of diverse viruses and genomic parasites. Here, we characterize pteropid APOBEC3 genes and show that species within the genus Pteropus possess the largest and most diverse array of APOBEC3 genes identified in any mammal reported to date. Several bat APOBEC3 proteins are antiviral as demonstrated by restriction of retroviral infectivity using HIV-1 as a model, and recombinant A3Z1 subtypes possess strong DNA deaminase activity. These genes represent the first group of antiviral restriction factors identified in bats with extensive diversification relative to homologues in other mammals.

Short-Term Mediterranean Diet Improves Endurance Exercise Performance: A Randomized-Sequence Crossover Trial.

Objective: Healthful dietary patterns have constituents that are known to improve exercise performance, such as antioxidants, nitrates, and alkalizing effects. However, ergogenic effects of such diets have not been evaluated. We hypothesized that a short-term Mediterranean diet results in better exercise performance, as compared to a typical Western diet. Methods: Eleven recreationally active women (n = 7) and men (n = 4) (body mass index, 24.6 ± 3.2 kg/m2; age 28 ± 3 years) were studied in a randomized-sequence crossover study, in which they underwent exercise performance testing on one occasion after 4 days of a Mediterranean diet and on another occasion after 4 days of a Western diet. A 9- to 16-day washout period separated the two trials. Endurance exercise performance was evaluated with a 5-km treadmill time trial. Anaerobic exercise performance tests included a Wingate cycle test, a vertical jump test, and hand grip dynamometry. Results: Five-kilometer run time was 6% ± 3% shorter (faster) in the Mediterranean diet trial than in the Western diet trial (27.09 ± 3.55 vs 28.59 ± 3.21 minutes; p = 0.030) despite similar heart rates (160 ± 5 vs 160 ± 4 beats/min; p = 0.941) and ratings of perceived exertion (14.6 ± 0.5 vs 15.0 ± 0.5; p = 0.356). No differences between the diet conditions were observed for anaerobic exercise tests, including peak and mean power from the Wingate test (both p ≥ 0.05), the vertical jump test (p = 0.19), and the hand grip strength test (p = 0.69). Conclusions: Our findings extend existing evidence of the health benefits of the Mediterranean diet by showing that this diet is also effective for improving endurance exercise performance in as little as 4 days. Further studies are warranted to determine whether a longer-term Mediterranean diet provides greater benefits and whether it might also be beneficial for anaerobic exercise performance and muscle strength and power.

Contraction of the type I IFN locus and unusual constitutive expression of IFN-α in bats.

Bats harbor many emerging and reemerging viruses, several of which are highly pathogenic in other mammals but cause no clinical signs of disease in bats. To determine the role of interferons (IFNs) in the ability of bats to coexist with viruses, we sequenced the type I IFN locus of the Australian black flying fox, Pteropus alecto, providing what is, to our knowledge, the first gene map of the IFN region of any bat species. Our results reveal a highly contracted type I IFN family consisting of only 10 IFNs, including three functional IFN-α loci. Furthermore, the three IFN-α genes are constitutively expressed in unstimulated bat tissues and cells and their expression is unaffected by viral infection. Constitutively expressed IFN-α results in the induction of a subset of IFN-stimulated genes associated with antiviral activity and resistance to DNA damage, providing evidence for a unique IFN system that may be linked to the ability of bats to coexist with viruses.

Comparative Transcriptomics Highlights the Role of the Activator Protein 1 Transcription Factor in the Host Response to Ebolavirus.

Ebolavirus and Marburgvirus comprise two genera of negative-sense single-stranded RNA viruses that cause severe hemorrhagic fevers in humans. Despite considerable research efforts, the molecular events following Ebola virus (EBOV) infection are poorly understood. With the view of identifying host factors that underpin EBOV pathogenesis, we compared the transcriptomes of EBOV-infected human, pig, and bat kidney cells using a transcriptome sequencing (RNA-seq) approach. Despite a significant difference in viral transcription/replication between the cell lines, all cells responded to EBOV infection through a robust induction of extracellular growth factors. Furthermore, a significant upregulation of activator protein 1 (AP1) transcription factor complex members FOS and JUN was observed in permissive cell lines. Functional studies focusing on human cells showed that EBOV infection induces protein expression, phosphorylation, and nuclear accumulation of JUN and, to a lesser degree, FOS. Using a luciferase-based reporter, we show that EBOV infection induces AP1 transactivation activity within human cells at 48 and 72 h postinfection. Finally, we show that JUN knockdown decreases the expression of EBOV-induced host gene expression. Taken together, our study highlights the role of AP1 in promoting the host gene expression profile that defines EBOV pathogenesis.IMPORTANCE Many questions remain about the molecular events that underpin filovirus pathophysiology. The rational design of new intervention strategies, such as postexposure therapeutics, will be significantly enhanced through an in-depth understanding of these molecular events. We believe that new insights into the molecular pathogenesis of EBOV may be possible by examining the transcriptomic response of taxonomically diverse cell lines (derived from human, pig, and bat). We first identified the responsive pathways using an RNA-seq-based transcriptomics approach. Further functional and computational analysis focusing on human cells highlighted an important role for the AP1 transcription factor in mediating the transcriptional response to EBOV infection. Our study sheds new light on how host transcription factors respond to and promote the transcriptional landscape that follows viral infection.

Characterization of the Antigen Processing Machinery and Endogenous Peptide Presentation of a Bat MHC Class I Molecule.

Bats are a major reservoir of emerging and re-emerging infectious diseases, including severe acute respiratory syndrome-like coronaviruses, henipaviruses, and Ebola virus. Although highly pathogenic to their spillover hosts, bats harbor these viruses, and a large number of other viruses, with little or no clinical signs of disease. How bats asymptomatically coexist with these viruses is unknown. In particular, little is known about bat adaptive immunity, and the presence of functional MHC molecules is mostly inferred from recently described genomes. In this study, we used an affinity purification/mass spectrometry approach to demonstrate that a bat MHC class I molecule, Ptal-N*01:01, binds antigenic peptides and associates with peptide-loading complex components. We identified several bat MHC class I-binding partners, including calnexin, calreticulin, protein disulfide isomerase A3, tapasin, TAP1, and TAP2. Additionally, endogenous peptide ligands isolated from Ptal-N*01:01 displayed a relatively broad length distribution and an unusual preference for a C-terminal proline residue. Finally, we demonstrate that this preference for C-terminal proline residues was observed in Hendra virus-derived peptides presented by Ptal-N*01:01 on the surface of infected cells. To our knowledge, this is the first study to identify endogenous and viral MHC class I ligands for any bat species and, as such, provides an important avenue for monitoring and development of vaccines against major bat-borne viruses both in the reservoir and spillover hosts. Additionally, it will provide a foundation to understand the role of adaptive immunity in bat antiviral responses.