Pteropus Alecto Research Articles

Structural Analysis of Virus Regulatory N6-Methyladenosine (m6A) Machinery of the Black Flying Fox (Pteropus alecto) and the Egyptian Fruit Bat (Rousettus aegyptiacus) Shows Evolutionary Conservation Amongst Mammals

Background: N6-methyladenosine (m6A) is an abundant RNA epitranscriptomic modification in eukaryotes. The m6A machinery includes cellular writer, eraser and reader proteins that regulate m6A. Pteropus alecto (P. alecto) (the Australian black flying fox) and Rousettus aegyptiacus (R. aegyptiacus) (the Egyptian fruit bat) are bats associated with several viral zoonoses yet neglected in the field of m6A epigenetics studies. Objectives: This study utilises various bioinformatics and in silico tools to genetically identify, characterise and annotate the m6A machinery in P. alecto and R. aegyptiacus. Methods: A range of bioinformatic tools were deployed to comprehensively characterise all known m6A-associated proteins of P. alecto and R. aegyptiacus. Results: Phylogenetically, the m6A fat mass and obesity-associated protein (FTO) eraser placed the order Chiroptera (an order including all bat species) in a separate clade. Additionally, it showed the lowest identity matrices in P. alecto and R. aegyptiacus when compared to other mammals (74.1% and 72.8%) and Homo sapiens (84.0% and 76.1%), respectively. When compared to humans, genetic loci-based analysis of P. alecto and R. aegyptiacus showed syntenic conservation in multiple flanking genes of 8 out the 10 m6A-associated genes. Furthermore, amino acid alignment and protein tertiary structure of the two bats’ m6A machinery demonstrated conservation in the writers but not in erasers and readers, compared to humans. Conclusions: These studies provide foundational annotation and genetic characterisation of m6A machinery in two important species of bats which can be exploited to study bat–virus interactions at the interface of epitranscriptomics.

Native and non-native winter foraging resources do not explain Pteropus alecto winter roost occupancy in Queensland, Australia

Anthropogenic land use change concurrent with introductions of non-native species alters the abundance and distribution of foraging resources for wildlife. This is particularly concerning when resource bottlenecks for wildlife are linked to spillover of infectious diseases to humans. Hendra virus is a bat-borne pathogen in eastern Australia. Spillovers align with winter food shortages for flying foxes and flying foxes foraging in agriculture or peri-urban lands, as opposed to native forests. It is believed the increased abundance and spatiotemporal reliability of non-native species planted in anthropogenically modified areas compared to native, ephemeral diet species may be a key draw for flying foxes into urban and peri-urban areas. We investigate the explanatory power of environmental factors on the winter roost occupancy of the reservoir for Hendra virus, the black flying fox Pteropus alecto, from 2007-2020 in Queensland, Australia. We measured the extent, spatial aggregation, and annual reliability of typical (i.e. native) and atypical (i.e. non-native) winter habitat species in 20km foraging areas around roosts surveyed by the National Flying Fox Monitoring Program. We find that neither the extent nor the spatial distribution of winter habitats explained black flying fox winter roost presence. Although the establishment of roosts was associated with high reliability for typical winter diet species, the reliability of frequently listed winter diet species surrounding surveyed roosts was not different between roosts that were occupied versus unoccupied in the winter. Significant interactions between lagged weather conditions and winter habitats identified by the best model did not reflect observable differences in patterns of occupancy upon scrutiny. Static measures of winter habitat and weather conditions poorly explained the winter roost occupancy of black flying foxes. Understanding the drivers of flying fox movement and presence requires further investigation before they can be thoughtfully integrated into Hendra spillover prevention efforts and flying fox management.

Identification and epidemiological analysis of a putative novel hantavirus in Australian flying foxes.

In July 2017, an investigation into the cause of neurological signs in a black flying fox (Pteropus alecto, family Pteropodidae) identified a putative novel hantavirus (Robina virus, ROBV, order Bunyavirales, family Hantaviridae, genus Mobatvirus) in its brain. Analysis of the evolutionary relationship between other hantaviruses using maximum-likelihood, a systematic Bayesian clustering approach, and a minimum spanning tree, all suggest that ROBV is most closely related to another Mobatvirus, Quezon virus, previously identified in the lung of a Philippine frugivorous bat (Rousettus amplexicaudatus, also family Pteropodidae). Subsequently, between March 2018 and October 2023, a total of 495 bats were opportunistically screened for ROBV with an experimental qRT-PCR. The total prevalence of ROBV RNA detected in Pteropus spp. was 4.2% (95% CI 2.8-6.4%). Binomial modelling identified that there was substantial evidence supporting an increase (P = 0.033) in the detection of ROBV RNA in bats in 2019 and 2020 suggesting of a possible transient epidemic. There was also moderate evidence to support the effect of season (P = 0.064), with peak detection in the cooler seasons, autumn, and winter, possibly driven by physiological and ecological factors similar to those already identified for other bat-borne viruses. This is Australia's first reported putative hantavirus and its identification could expand the southern known range of hantaviruses in Australasia.

Going it alone: observations of solitary roosting in two Australian flying-foxes (Pteropus alecto and P. poliocephalus)

Unlike some flying-fox species that exhibit solitary roosting, all flying-fox species of the Australian mainland are strongly colonial, though some extent of solitary roosting in these species is anecdotally known. This note reports on five accounts of solitary roosting in black flying-foxes (Pteropus alecto) and grey-headed flying-foxes (Pteropus poliocephalus), herein referred to as 'singletons'. These accounts are potentially the first published detailed observations of singletons in Australian flying-foxes outside of visible periods of food shortages. In particular, one account involved solitary roosting recorded over multiple days. The frequency and extent of singletons in Australian flying-foxes remain completely unknown. In terms of deriving population sizes in these species from counts at communal roosts, these individuals represent an addition to those estimates.

Multi-omic analysis of bat versus human fibroblasts reveals altered central metabolism.

Bats have unique characteristics compared to other mammals, including increased longevity and higher resistance to cancer and infectious disease. While previous studies have analyzed the metabolic requirements for flight, it is still unclear how bat metabolism supports these unique features, and no study has integrated metabolomics, transcriptomics, and proteomics to characterize bat metabolism. In this work, we performed a multi-omics data analysis using a computational model of metabolic fluxes to identify fundamental differences in central metabolism between primary lung fibroblast cell lines from the black flying fox fruit bat (Pteropus alecto) and human. Bat cells showed higher expression levels of Complex I components of electron transport chain (ETC), but, remarkably, a lower rate of oxygen consumption. Computational modeling interpreted these results as indicating that Complex II activity may be low or reversed, similar to an ischemic state. An ischemic-like state of bats was also supported by decreased levels of central metabolites and increased ratios of succinate to fumarate in bat cells. Ischemic states tend to produce reactive oxygen species (ROS), which would be incompatible with the longevity of bats. However, bat cells had higher antioxidant reservoirs (higher total glutathione and higher ratio of NADPH to NADP) despite higher mitochondrial ROS levels. In addition, bat cells were more resistant to glucose deprivation and had increased resistance to ferroptosis, one of the characteristics of which is oxidative stress. Thus, our studies revealed distinct differences in the ETC regulation and metabolic stress responses between human and bat cells.

Fruit bats trade in the traditional markets of South Minahasa, North Sulawesi, Indonesia

Abstract. Ransaleleh TA, Kawatu M, Wahyuni I, Onibala J, Nangoy MJ, Umboh S, Rembet UNWJ, Saputro S, Wiantoro S. 2024. Fruit bats trade in the traditional markets of South Minahasa, Sulawesi, Indonesia. Biodiversitas 25: 716-725. The hunting and trading of fruit bats are significant sources of income for several communities in North Sulawesi, Indonesia. Therefore, this research aimed to map the market locations and identify the species of traded bats, along with their conservation status in South Minahasa District. Surveys of markets, hunters, and sellers were conducted for 5 months from May to September 2023. Morphological examinations were carried out on the traded bats, focusing on several parameters such as body weight, morphometric and description of the morphological characters. We identified the traditional markets which sell fruit bats (family Pteropodidae), Acerodon celebensis and Pteropus alecto meat, namely Berdikari Tumpaan, 54 Amurang, 45 Langsot Tareran, Tenga, Pakuure, Ongkaw, Soko Raanan Baru, Motoling, Poigar, Poopo, Pinaesaan Tompaso Baru, and Pinasungkulan Modoinding. Furthermore, two markets, namely Pakuure and Pinaesaan Tompaso Baru, were identified selling the small fruit bats (family Pteropodidae), Cynopterus minutus, Dobsonia exoleta, Nyctimene cephalotes, Rousettus amplexicaudatus, and Thoopterus nigrescens. According to the International Union for Conservation of Nature (IUCN) Red List, A. celebensis and D. exoleta are endemic bat species in Sulawesi with a conservation status of vulnerable and least concern, respectively. Fostering education and advocacy program is crucial to promote awareness and conservation strategy, especially for the 12 traditional markets which trade seven fruit bat species in South Minahasa, Sulawesi.

Interferon-induced protein with tetratricopeptide repeats 5 of black fruit bat (Pteropus alecto) displays a broad inhibition of RNA viruses.

Bats are natural host reservoirs and have adapted a unique innate immune system that permits them to host many viruses without exhibiting symptoms. Notably, bat interferon stimulated genes (ISGs) have been shown to play antiviral roles. Interferon induced protein with tetratricopeptide repeats 5 (IFIT5) is a well-characterised ISG in humans with antiviral activities against negative-sense RNA viruses via inhibiting viral transcription. Here, we aim to investigate if Pteropus alecto (pa) IFIT5 (paIFIT5) possess the ability to inhibit negative-sense RNA viruses. Initially, gene syntenic and comparative structural analyses of multiple animals highlighted a high level of similarity between Pteropus alecto and human IFIT5 proteins. Our results showed that paIFIT5 was significantly inducible by viral and dsRNA stimulation. Transient overexpression of paIFIT5 inhibited the replication of vesicular stomatitis virus (VSV). Using minireplicon and transcription reporter assays, we demonstrated the ability of paIFIT5 specifically to inhibit H17N10 polymerase activity. Mechanistically, we noticed that the antiviral potential of paIFIT5 against negative sense RNA viruses was retributed to its interaction with 5'ppp containing RNA. Taken together, these findings highlight the genetic and functional conservation of IFIT5 among mammals.

Applications of VirScan to broad serological profiling of bat reservoirs for emerging zoonoses.

Bats are important providers of ecosystem services such as pollination, seed dispersal, and insect control but also act as natural reservoirs for virulent zoonotic viruses. Bats host multiple viruses that cause life-threatening pathology in other animals and humans but, themselves, experience limited pathological disease from infection. Despite bats' importance as reservoirs for several zoonotic viruses, we know little about the broader viral diversity that they host. Bat virus surveillance efforts are challenged by difficulties of field capture and the limited scope of targeted PCR- or ELISA-based molecular and serological detection. Additionally, virus shedding is often transient, thus also limiting insights gained from nucleic acid testing of field specimens. Phage ImmunoPrecipitation Sequencing (PhIP-Seq), a broad serological tool used previously to comprehensively profile viral exposure history in humans, offers an exciting prospect for viral surveillance efforts in wildlife, including bats. Here, for the first time, we apply PhIP-Seq technology to bat serum, using a viral peptide library originally designed to simultaneously assay exposures to the entire human virome. Using VirScan, we identified past exposures to 57 viral genera-including betacoronaviruses, henipaviruses, lyssaviruses, and filoviruses-in semi-captive Pteropus alecto and to nine viral genera in captive Eonycteris spelaea. Consistent with results from humans, we find that both total peptide hits (the number of enriched viral peptides in our library) and the corresponding number of inferred past virus exposures in bat hosts were correlated with poor bat body condition scores and increased with age. High and low body condition scores were associated with either seropositive or seronegative status for different viruses, though in general, virus-specific age-seroprevalence curves defied assumptions of lifelong immunizing infection, suggesting that many bat viruses may circulate via complex transmission dynamics. Overall, our work emphasizes the utility of applying biomedical tools, like PhIP-Seq, first developed for humans to viral surveillance efforts in wildlife, while highlighting opportunities for taxon-specific improvements.

Presence of Multiple Herpesvirus Variants in Australian Flying Foxes (Pteropus spp.).

Herpesviruses have been detected in bat species from several countries, with a limited number of studies examining herpesviruses in Pteropus spp. (flying foxes) and no investigation of herpesviruses in Australian flying foxes. We examined the presence and prevalence of herpesviruses in the four mainland Australian flying fox species. A nested PCR targeting highly conserved amino acid motifs in the DNA polymerase (DPOL) gene of herpesviruses was used to analyze 564 samples collected from 514 individual Pteropus scapulatus, Pteropus poliocephalus, Pteropus alecto, and Pteropus conspicillatus. The prevalence of herpesvirus DNA in blood, urine, oral, and fecal swabs from the four species was 17% in P. scapulatus, 11% in P. poliocephalus, 10% in P. alecto, and 9% in P. conspicillatus (31% in P. conspicillatus spleen tissue). Five putative novel herpesviruses were detected. Following PCR amplicon sequence analysis, four of the herpesviruses grouped phylogenetically with the gammaherpesviruses, with nucleotide identities between 79% and 90% to gammaherpesviruses from Asian megabats. A betaherpesvirus was detected in P. scapulatus with 99% nucleotide identity to the partial DPOL gene sequence of an Indonesian fruit bat betaherpesvirus. This study lays the foundation for future epidemiology research of herpesviruses in Australian Pteropus spp. and adds to the discussion of hypotheses surrounding the evolutionary epidemiology of bat-borne viruses on a global scale.

Population genomic analysis reveals distinct demographics and recent adaptation in the black flying fox (Pteropus alecto)

As the only mammalian group capable of powered flight, bats have many unique biological traits. Previous comparative genomic studies in bats have focused on long-term evolution. However, the micro-evolutionary processes driving recent evolution are largely under-explored. Using resequencing data from 50 black flying foxes (Pteropus alecto), one of the model species for bats, we find that black flying fox has much higher genetic diversity and lower levels of linkage disequilibrium than most of the mammalian species. Demographic inference reveals strong population fluctuations (>100 fold) coinciding with multiple historical events including the last glacial change and Toba super eruption, suggesting that the black flying fox is a very resilient species with strong recovery abilities. While long-term adaptation in the black flying fox is enriched in metabolic genes, recent adaptation in the black flying fox has a unique landscape where recently selected genes are not strongly enriched in any functional category. The demographic history and mode of adaptation suggest that black flying fox might be a well-adapted species with strong evolutionary resilience. Taken together, this study unravels a vibrant landscape of recent evolution for the black flying fox and sheds light on several unique evolutionary processes for bats comparing to other mammalian groups.

Habitat loss for black flying foxes and implications for Hendra virus

ContextEnvironmental change impacts natural ecosystems and wildlife populations. In Australia, native forests have been heavily cleared and the local emergence of Hendra virus (HeV) has been linked to land-use change, winter habitat loss, and changing bat behavior.ObjectivesWe quantified changes in landscape factors for black flying foxes (Pteropus alecto), a reservoir host of HeV, in sub-tropical Queensland, Australia from 2000–2020. We hypothesized that native winter habitat loss and native remnant forest loss were greatest in areas with the most human population growth.MethodsWe measured the spatiotemporal change in human population size and native ‘remnant’ woody vegetation extent. We assessed changes in the observed P. alecto population and native winter habitats in bioregions where P. alecto are observed roosting in winter. We assessed changes in the amount of remnant vegetation across bioregions and within 50 km foraging buffers around roosts.ResultsHuman populations in these bioregions grew by 1.18 M people, mostly within 50 km foraging areas around roosts. Remnant forest extent decreased overall, but regrowth was observed when policy restricted vegetation clearing. Winter habitats were continuously lost across all spatial scales. Observed roost counts of P. alecto declined.ConclusionNative remnant forest loss and winter habitat loss were not directly linked to spatial human population growth. Rather, most remnant vegetation was cleared for indirect human use. We observed forest loss and regrowth in response to state land clearing policies. Expanded flying fox population surveys will help better understand how land-use change has impacted P. alecto distribution and Hendra virus spillover.

Growth of Pteropus alecto bats (Chiroptera: Pteropodidae) in cages

Abstract. Ransaleleh TA, Wahyuni I, Kawatu M, Laatung S, Lambey L, Rembet UNWJ. 2022. Growth of Pteropus alecto bats (Chiroptera: Pteropodidae) in cages. Biodiversitas 23: 6313-6319. Black Flying Fox (Pteropus alecto), known as Paniki yaki, is widely consumed by the residents of Minahasa, North Sulawesi, Indonesia. It is imported from outside the provinces of Gorontalo, Central Sulawesi, and South Sulawesi. The peak of selling bats in Sulawesi is during Thanksgiving Day and religious holidays such as Easter, Christmas, and New Year. Even though the conservation status of this species, according to the International Union for Conservation of Nature (IUCN), is of Least Concern, this species will one day become extinct due to continuous exploration without control. Conservation or cultivation is one of the efforts to preserve this type of bat. Cultivation will be successful when the growth of this mammal is outside the habitat. Therefore, research has been conducted on breeding this animal in cages using five bats. The bats had been taken from the captivity in Wanea Sub-district, Manado city, 58-533 days old. The fruits given as food are papaya, banana, and mango, and the variables measured were the amount of consumption, body weight gain, and morphometry. Furthermore, the data obtained were tabulated and narrated descriptively. The results showed that consumption of P. alecto 1,2,3,4 and 5 fruits were 110.64, 147.86, 192.61, 249.18, and 331.61 g/day, with body weight gain of 0.50, 0.53, 0.96, 1, 17, 1, and 50 g/day. The morphometric growth of P. alecto 1 was total body length 0.10, forearm 0.06, tibia 0.03, ear 0.01 and wingspan 0.08 mm/day. Sequentially, the morphometric growth of P. alecto 2 was 0.11, 0.07, 0.05, 0.01 and 0.12 mm/day, while P. alecto 3 was 0.29, 0.13, 0.06, 0.03, and 0.89 mm/day. The growth of P. alecto 4 was 0.19, 0.02, 0.02.0.01 and 0.89 mm/day, while P. alecto 5 was 0.20, 0.01, 0.01, 0.01 and 0.85 mm/day. In conclusion, the 1st and 2nd P. alecto were in early bone growth, while the 3rd P. alecto was in bone and meat growth, meanwhile, the 4th and 5th P. alecto were in meat and slow bone growth.

Landscape and age dynamics of immune cells in the Egyptian rousette bat.

Bats harbor high-impact zoonotic viruses often in the absence of disease manifestation. This restriction and disease tolerance possibly rely on specific immunological features. In-depth molecular characterization of cellular immunity and imprinting of age on leukocyte compartments remained unexplored in bats. We employ single-cell RNA sequencing (scRNA-seq) and establish immunostaining panels to characterize the immune cell landscape in juvenile, subadult, and adult Egyptian rousette bats (ERBs). Transcriptomic and flow cytometry data reveal conserved subsets and substantial enrichments of CD79a+ B cells and CD11b+ Tcells in juvenile animals, whereas neutrophils, CD206+ myeloid cells, and CD3+ Tcells dominate as bats reach adulthood. Despite differing frequencies, phagocytosis of circulating and tissue-resident myeloid cells and proliferation of peripheral and splenic lymphocytes are analogous in juvenile and adult ERBs. We provide a comprehensive map of the immune landscape in ERBs and show age-imprinted resilience progression and find that variability in cellular immunity only partly recapitulates mammalian archetypes.

Morphological and quantitative analysis of leukocytes in free-living Australian black flying foxes (Pteropus alecto)

The black flying fox (Pteropus alecto) is a natural reservoir for Hendra virus, a paramyxovirus that causes fatal infections in humans and horses in Australia. Increased excretion of Hendra virus by flying foxes has been hypothesized to be associated with physiological or energetic stress in the reservoir hosts. The objective of this study was to explore the leukocyte profiles of wild-caught P. alecto, with a focus on describing the morphology of each cell type to facilitate identification for clinical purposes and future virus spillover research. To this end, we have created an atlas of images displaying the commonly observed morphological variations across each cell type. We provide quantitative and morphological information regarding the leukocyte profiles in bats captured at two roost sites located in Redcliffe and Toowoomba, Queensland, Australia, over the course of two years. We examined the morphology of leukocytes, platelets, and erythrocytes of P. alecto using cytochemical staining and characterization of blood films through light microscopy. Leukocyte profiles were broadly consistent with previous studies of P. alecto and other Pteropus species. A small proportion of individual samples presented evidence of hemoparasitic infection or leukocyte morphological traits that are relevant for future research on bat health, including unique large granular lymphocytes. Considering hematology is done by visual inspection of blood smears, examples of the varied cell morphologies are included as a visual guide. To the best of our knowledge, this study provides the first qualitative assessment of P. alecto leukocytes, as well as the first set of published hematology reference images for this species.

Behavior of the black flying fox, Pteropus alecto (Chiroptera: Pteropodidae) in cages

Abstract. Ransaleleh TA, Wahyuni I, Kawatu M, Nangoy MJ, Wiantoro S. 2021. Behavior of the black flying fox, Pteropus alecto (Chiroptera: Pteropodidae) in cages. Biodiversitas 22: 5657-5665. Hunting and illegal trading have become a common thread for the black flying fox in Sulawesi, Indonesia. However, information on its biology and behavior as a baseline for conservation and management program is still lacking. Therefore, this study aims to examine the behavioral activities of black flying fox, Pteropus alecto (Temminck, 1837) kept in cages through direct observation. The results showed that feeding was carried out by descending to the bottom of the cage before picking up fruits with the mouth and wings. Furthermore, the time associated with this process ranged from 06.01 to 10.00, while agonistic behavior performed using claws and wings took place from 10.01 to 14.00 in the daytime and 22.01 to 02.00 at night. Grooming was carried out using the tongue and wings, from 14.01 to 18.00 during the day and 22.01 to 02.00 during the night. Subsequently, the bats slept by perching with the eyes closed and the whole body wrapped with the wings from 02.01 to 10.00, while locomotion and stationary behaviors were performed by perching with eyes open and flying around the cage with the wings spread apart from 10.01 to 14.00 during the day and 22.01 to 02.00 at night. The percentage of day and night behavior activities consist of agonistic 0.12%, grooming 6.14%, eating 19.36%, sleeping 56.33%, and stationary and locomotive 17.76%. The results improve the understanding of P. alecto's daily activities in the cage which are difficult to observe in the wild and provide insight for conservation and wildlife management. Furthermore, information from this study is useful for future bat captivity programs.

“Someday we will all learn anew through hands that love us”: Protecting a key insular population of the Sulawesi Fruit Bat Acerodon celebensis

“Someday we will all learn anew through hands that love us”: Protecting a key insular population of the Sulawesi Fruit Bat <i>Acerodon celebensis</i>

Genomic landscape of mitochondrial DNA insertions in 23 bat genomes: characteristics, loci, phylogeny, and polymorphism.

The transfer of mitochondrial DNA to the nuclear genome gives rise to the nuclear DNA sequences of mitochondrial origin (NUMTs), considered as a driving force in genome evolution. In this study, NUMTs in 23 bat genomes were investigated and compared systematically. The results showed that NUMTs existed in 22 genomes except for Noctilio leporinus, suggesting that mitochondrial fragment insertion in the nuclear genome was a common event in bat genomes. However, remarkable variations in NUMTs number, cumulative length, and proportion in the nuclear genome were discovered across bat species. Further orthologous NUMT loci analysis of the Phyllostomidae family indicated that the NUMTs insertion events in bat genomes were homoplasy-free. The NUMTs were mainly inserted into the intergenic regions, particularly, co-localized with repetitive sequences (especially transposable elements). However, several NUMTs were inserted into genes, some of which were in the exon region of functional genes. One NUMT in the genome of Pteropus alecto surprisingly matched with cDNA of ATP8B3 that provided evidence of NUMTs with coding function. Phylogenic analysis on NUMTs originating from COXI and COXII loci highlighted 2 clusters of Yinpterochiroptera and Yangochiroptera for Chiroptera. Seven NUMTs from Rhinolophus ferrumequinum were amplified, and the sequencing results confirmed the reliability of the NUMT analysis. One of them was polymorphic for the presence or absence of the NUMT insertion, and each genotype of NUMT loci showed a distinct regional distribution pattern. The information obtained in this study provides novel insights into the NUMT organization and features in bat genomes and establishes a basis for further studying of the evolution of bat species.

Orthogonal genome-wide screens of bat cells identify MTHFD1 as a target of broad antiviral therapy

Bats are responsible for the zoonotic transmission of several major viral diseases, including those leading to the 2003 SARS outbreak and likely the ongoing COVID-19 pandemic. While comparative genomics studies have revealed characteristic adaptations of the bat innate immune system, functional genomic studies are urgently needed to provide a foundation for the molecular dissection of the viral tolerance in bats. Here we report the establishment of genome-wide RNA interference (RNAi) and CRISPR libraries for the screening of the model megabat, Pteropus alecto. We used the complementary RNAi and CRISPR libraries to interrogate P. alecto cells for infection with two different viruses: mumps virus and influenza A virus, respectively. Independent screening results converged on the endocytosis pathway and the protein secretory pathway as required for both viral infections. Additionally, we revealed a general dependence of the C1-tetrahydrofolate synthase gene, MTHFD1, for viral replication in bat cells and human cells. The MTHFD1 inhibitor, carolacton, potently blocked replication of several RNA viruses, including SARS-CoV-2. We also discovered that bats have lower expression levels of MTHFD1 than humans. Our studies provide a resource for systematic inquiry into the genetic underpinnings of bat biology and a potential target for developing broad-spectrum antiviral therapy.

Effects of Waning Maternal Immunity on Infection Dynamics in Seasonally Breeding Wildlife.

Increasing outbreaks of emerging infectious diseases originating from wildlife have intensified interests in understanding their dynamics in reservoir hosts. The effect of waning maternally derived antibodies on epidemics in a seasonally breeding wild mammal population is unclear. We examined how the population structure, influenced by seasonal breeding and maternally derived immunity, affects viral invasion and persistence using a hypothetical system based on Hendra virus infection in black flying foxes (Pteropus alecto). A deterministic Hendra virus epidemic model with uncertainty in parameter values was used to simulate transient epidemics following viral introduction into an infection-free population, including various timings within a year and differences in pre-existing seroprevalence. Additionally, we applied different modelling methods of waning maternal immunity to examine whether different models notably affected modelling outputs. The waning of maternally derived immunity temporally dispersed the supply of susceptible individuals in seasonally breeding populations, diminishing the effect of birth pulses generating the temporally synchronised supply of susceptible newborns. Thus, even in a population with seasonal births, a considerable level of probabilities of viral invasion and persistence could occur no matter when infectious individuals were introduced into the population. Viral invasion and persistence were substantially influenced by the modelling method of maternally derived immunity, emphasising the need to select an appropriate method and further investigate the waning pattern of maternally derived antibodies.

Zinc transporter mutations linked to acrodermatitis enteropathica disrupt function and cause mistrafficking

ZIP4 is a representative member of the Zrt-/Irt-like protein (ZIP) transporter family and responsible for zinc uptake from diet. Loss-of-function mutations of human ZIP4 (hZIP4) drastically reduce zinc absorption, causing a life-threatening autosomal recessive disorder, acrodermatitis enteropathica (AE). These mutations occur not only in the conserved transmembrane zinc transport machinery, but also in the extracellular domain (ECD) of hZIP4, which is only present in a fraction of mammalian ZIPs. How these AE-causing ECD mutations lead to ZIP4 malfunction has not be fully clarified. In this work, we characterized all seven confirmed AE-causing missense mutations in hZIP4-ECD and found that the variants exhibited completely abolished zinc transport activity in a cell-based transport assay. Although the variants were able to be expressed in HEK293T cells, they failed to traffic to the cell surface and were largely retained in the ER with immature glycosylation. When the corresponding mutations were introduced in the ECD of ZIP4 from Pteropus Alecto, a close homolog of hZIP4, the variants exhibited structural defects or reduced thermal stability, which likely accounts for intracellular mistrafficking of the AE-associated variants and as such a total loss of zinc uptake activity. This work provides a molecular pathogenic mechanism for AE.