Tioman virus, a paramyxovirus of bat origin, causes mild disease in pigs and has a predilection for lymphoid tissues

Threat, challenges, and preparedness for future pandemics: A descriptive review of phylogenetic analysis based predictions

For centuries the world has been confronted with many infectious diseases, with a potential to turn into a pandemic posing a constant threat to human lives. Some of these pandemics occurred due to the emergence of new disease or re-emergence of previously known diseases with a few mutations. In such scenarios their optimal prevention and control options were not adequately developed. Most of these diseases are highly contagious and for their timely control, knowledge about the pathogens and disease progression is the basic necessity. In this review, we have presented a documented chronology of the earlier pandemics, evolutionary analysis of the infectious disease with pandemic potential, the role of RNA, difficulties in controlling pandemics, and the likely pathogens that could trigger future pandemics. In this study, the evolutionary history of the pathogens was identified by carrying out phylogenetic analysis. The percentage similarity between different infectious diseases is critically analysed for the identification of their correlation using online sequence matcher tools. The Baltimore classification system was used for finding the genomic nature of the viruses. It was observed that most of the infectious pathogens rise from their animal hosts with some mutations in their genome composition. The phylogenetic tree shows that the single-stranded RNA diseases have a common origin and many of them are having high similarity percentage. The outcomes of this study will help in the identification of potential pathogens that can cause future pandemics. This information will be helpful in the development of early detection techniques, devising preventive mechanism to limit their spread, prophylactic measures, Infection control and therapeutic options, thereby, strengthening our approach towards global preparedness against future pandemics.

Zoonotic and reverse zoonotic transmission of viruses between humans and pigs

Humans and pigs share a close contact relationship, similar biological traits, and one of the highest estimated number of viruses compared to other mammalian species. The contribution and directionality of viral exchange between humans and pigs remain unclear for some of these viruses, but their transmission routes are important to characterize in order to prevent outbreaks of disease in both host species. This review collects and assesses the evidence to determine the likely transmission route of 27 viruses between humans and pigs.

Bats and viruses: a death-defying friendship

Bats have a primeval evolutionary origin and have adopted various survival methods. They have played a central role in the emergence of various viral diseases. The sustenance of a plethora of virus species inside them has been an earnest area of study. This review explains how the evolution of viruses in bats has been linked to their metabolic pathways, flight abilities, reproductive abilities and colonization behaviors. The utilization of host immune response by DNA and RNA viruses is a commencement of the understanding of differences in the impact of viral infection in bats from other mammals. Rabies virus and other lyssa viruses have had long documented history as bat viruses. While many others like Ebola virus, Nipah virus, Hantavirus, SARS-CoV, MERS-CoV and other new emerging viruses like Sosuga virus, Menangle and Tioman virus are now being studied extensively for their transmission in new hosts. The ongoing pandemic SARS-CoV-2 virus has also been implicated to be originated from bats. Certain factors have been linked to spillover events while the scope of entitlement of other conditions in the spread of diseases from bats still exists. However, certain physiological and ecological parameters have been linked to specific transmission patterns, and more definite proofs are awaited for establishing these connections.

Setting the Terms for Zoonotic Diseases: Effective Communication for Research, Conservation, and Public Policy

Many of the world's most pressing issues, such as the emergence of zoonotic diseases, can only be addressed through interdisciplinary research. However, the findings of interdisciplinary research are susceptible to miscommunication among both professional and non-professional audiences due to differences in training, language, experience, and understanding. Such miscommunication contributes to the misunderstanding of key concepts or processes and hinders the development of effective research agendas and public policy. These misunderstandings can also provoke unnecessary fear in the public and have devastating effects for wildlife conservation. For example, inaccurate communication and subsequent misunderstanding of the potential associations between certain bats and zoonoses has led to persecution of diverse bats worldwide and even government calls to cull them. Here, we identify four types of miscommunication driven by the use of terminology regarding bats and the emergence of zoonotic diseases that we have categorized based on their root causes: (1) incorrect or overly broad use of terms; (2) terms that have unstable usage within a discipline, or different usages among disciplines; (3) terms that are used correctly but spark incorrect inferences about biological processes or significance in the audience; (4) incorrect inference drawn from the evidence presented. We illustrate each type of miscommunication with commonly misused or misinterpreted terms, providing a definition, caveats and common misconceptions, and suggest alternatives as appropriate. While we focus on terms specific to bats and disease ecology, we present a more general framework for addressing miscommunication that can be applied to other topics and disciplines to facilitate more effective research, problem-solving, and public policy.

Animal board invited review: Risks of zoonotic disease emergence at the interface of wildlife and livestock systems

The ongoing coronavirus disease 19s pandemic has yet again demonstrated the importance of the human-animal interface in the emergence of zoonotic diseases, and in particular the role of wildlife and livestock species as potential hosts and virus reservoirs. As most diseases emerge out of the human-animal interface, a better understanding of the specific drivers and mechanisms involved is crucial to prepare for future disease outbreaks. Interactions between wildlife and livestock systems contribute to the emergence of zoonotic diseases, especially in the face of globalization, habitat fragmentation and destruction and climate change. As several groups of viruses and bacteria are more likely to emerge, we focus on pathogenic viruses of the Bunyavirales, Coronaviridae, Flaviviridae, Orthomyxoviridae, and Paramyxoviridae, as well as bacterial species including Mycobacterium sp., Brucella sp., Bacillus anthracis and Coxiella burnetii. Noteworthy, it was difficult to predict the drivers of disease emergence in the past, even for well-known pathogens. Thus, an improved surveillance in hotspot areas and the availability of fast, effective, and adaptable control measures would definitely contribute to preparedness. We here propose strategies to mitigate the risk of emergence and/or re-emergence of prioritized pathogens to prevent future epidemics.

Detection of Tioman Virus in Pteropus vampyrus Near Flores, Indonesia

Diverse paramyxoviruses have coevolved with their bat hosts, including fruit bats such as flying foxes (Chiroptera: Pteropodidae). Several of these viruses are zoonotic, but the diversity and distribution of Paramyxoviridae are poorly understood. We screened pooled feces samples from three Pteropus vampyrus colonies and assayed tissues, rectal swabs, and oral swabs from 95 individuals of 23 pteropodid species sampled at 17 sites across the Indonesian archipelago with a conventional paramyxovirus PCR; all tested negative. Samples from 43 individuals were screened with next generation sequencing (NGS), and a single Pteropus vampyrus collected near Flores had Tioman virus sequencing reads. Tioman virus is a bat-borne virus in the genus Pararubulavirus with prior evidence of spillover to humans. This work expands the known range of Tioman virus, and it is likely that this isolated colony likely has sustained intergenerational transmission over a long period.

Swine virome on rural backyard farms in Mexico: communities with different abundances of animal viruses and phages

Domestic swine have been introduced by humans into a wide diversity of environments and have been bred in different production systems. This has resulted in an increased risk for the occurrence and spread of diseases. Although viromes of swine in intensive farms have been described, little is known about the virus communities in backyard production systems around the world. The aim of this study was to describe the viral diversity of 23 healthy domestic swine maintained in rural backyards in Morelos, Mexico, through collection and analysis of nasal and rectal samples. Next-generation sequencing was used to identify viruses that are present in swine. Through homology search and bioinformatic analysis of reads and their assemblies, we found that rural backyard swine have a high degree of viral diversity, different from those reported in intensive production systems or under experimental conditions. There was a higher frequency of bacteriophages and lower diversity of animal viruses than reported previously. In addition, sapoviruses, bocaparvoviruses, and mamastroviruses that had not been reported previously in our country were identified. These findings were correlated with the health status of animals, their social interactions, and the breeding/rearing environment (which differed from intensive systems), providing baseline information about viral communities in backyard swine.

Seroprevalence of three paramyxoviruses; Hendra virus, Tioman virus, Cedar virus and a rhabdovirus, Australian bat lyssavirus, in a range expanding fruit bat, the Grey-headed flying fox (Pteropus poliocephalus)

Habitat-mediated global change is driving shifts in species’ distributions which can alter the spatial risks associated with emerging zoonotic pathogens. Many emerging infectious pathogens are transmitted by highly mobile species, including bats, which can act as spill-over hosts for pathogenic viruses. Over three years, we investigated the seroepidemiology of paramyxoviruses and Australian bat lyssavirus in a range-expanding fruit bat, the Grey-headed flying fox (Pteropus poliocephalus), in a new camp in Adelaide, South Australia. Over six, biannual, sampling sessions, we quantified median florescent intensity (MFI) antibody levels for four viruses for a total of 297 individual bats using a multiplex Luminex binding assay. Where appropriate, florescence thresholds were determined using finite mixture modelling to classify bats’ serological status. Overall, apparent seroprevalence of antibodies directed at Hendra, Cedar and Tioman virus antigens was 43.2%, 26.6% and 95.7%, respectively. We used hurdle models to explore correlates of seropositivity and antibody levels when seropositive. Increased body condition was significantly associated with Hendra seropositivity (Odds ratio = 3.67; p = 0.002) and Hendra virus levels were significantly higher in pregnant females (p = 0.002). While most bats were seropositive for Tioman virus, antibody levels for this virus were significantly higher in adults (p < 0.001). Unexpectedly, all sera were negative for Australian bat lyssavirus. Temporal variation in antibody levels suggests that antibodies to Hendra virus and Tioman virus may wax and wane on a seasonal basis. These findings suggest a common exposure to Hendra virus and other paramyxoviruses in this flying fox camp in South Australia.

Emerging horizon for bat borne viral zoonoses

Bats are the only flying placental mammals that constitute the second largest order of mammals and present all around the world except in Arctic, Antarctica and a few oceanic islands. Sixty percent of emerging infectious diseases originating from animals are zoonotic and more than two-thirds of them originate in wildlife. Bats were evolved as a super-mammal for harboring many of the newly identified deadly diseases without any signs and lesions. Their unique ability to fly, particular diet, roosting behavior, long life span, ability to echolocate and critical susceptibility to pathogens make them suitable host to harbor numerous zoonotic pathogens like virus, bacteria and parasite. Many factors are responsible for the emergence of bat borne zoonoses but the most precipitating factor is human intrusions. Deforestation declined the natural habitat and forced the bats and other wild life to move out of their niche. These stressed bats, having lost foraging and behavioral pattern invade in proximity of human habitation. Either directly or indirectly they transmit the viruses to humans and animals. Development of fast detection modern techniques for viruses from the diseased and environmental samples and the lessons learned in the past helped in preventing the severity during the latest outbreaks.

Characterization of Teviot virus, an Australian bat-borne paramyxovirus

Bats are the reservoir hosts for multiple viruses with zoonotic potential, including coronaviruses, paramyxoviruses and filoviruses. Urine collected from Australian pteropid bats was assessed for the presence of paramyxoviruses. One of the viruses isolated was Teviot virus (TevPV), a novel rubulavirus previously isolated from pteropid bat urine throughout the east coast of Australia. Here, we further characterize TevPV through analysis of whole-genome sequencing, growth kinetics, antigenic relatedness and the experimental infection of ferrets and mice. TevPV is phylogenetically and antigenically most closely related to Tioman virus (TioPV). Unlike many other rubulaviruses, cell receptor attachment by TevPV does not appear to be sialic acid-dependent, with the receptor for host cell entry being unknown. The infection of ferrets and mice suggested that TevPV has a low pathogenic potential in mammals. Infected ferrets seroconverted by 10 days post-infection without clinical signs of disease. Furthermore, infected ferrets did not shed virus in any respiratory secretions, suggesting a low risk of onward transmission of TevPV. No productive infection was observed in the mouse infection study.

Viruses in bats and potential spillover to animals and humans

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Bats are a very important source of emerging viruses.

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Bat coronavirus, filovirus, paramyxovirus and reovirus are known zoonotic viruses.

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Many of the emergent bat viruses are highly lethal in livestock and humans.

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Past incidents and viral genetic features predict bat coronaviruses as the highest risk.

In the last two decades, several high impact zoonotic disease outbreaks have been linked to bat-borne viruses. These include SARS coronavirus, Hendra virus and Nipah virus. In addition, it has been suspected that ebolaviruses and MERS coronavirus are also linked to bats. It is being increasingly accepted that bats are potential reservoirs of a large number of known and unknown viruses, many of which could spillover into animal and human populations. However, our knowledge into basic bat biology and immunology is very limited and we have little understanding of major factors contributing to the risk of bat virus spillover events. Here we provide a brief review of the latest findings in bat viruses and their potential risk of cross-species transmission.

Nipah Virus Infection of Immature Dendritic Cells Increases Its Transendothelial Migration Across Human Brain Microvascular Endothelial Cells

Nipah virus (NiV) can infect multiple organs in humans with the central nervous system (CNS) being the most severely affected. Currently, it is not fully understood how NiV spreads throughout the body. NiV has been shown to infect certain leukocyte populations and we hypothesized that these infected cells could cross the blood-brain barrier (BBB), facilitating NiV entry into the CNS. Here, three leukocyte types, primary immature dendritic cells (iDC), primary monocytes (pMO), and monocytic cell line (THP-1), were evaluated for permissiveness to NiV. We found only iDC and THP-1 were permissive to NiV. Transendothelial migration of mock-infected and NiV-infected leukocytes was then evaluated using an in vitro BBB model established with human brain microvascular endothelial cells (HBMEC). There was approximately a threefold increase in migration of NiV-infected iDC across endothelial monolayer when compared to mock-infected iDC. In contrast, migration rates for pMO and THP-1 did not change upon NiV infection. Across TNF-α-treated endothelial monolayer, there was significant increase of almost twofold in migration of NiV-infected iDC and THP-1 over mock-infected cells. Immunofluorescence analysis showed the migrated NiV-infected leukocytes retained their ability to infect other cells. This study demonstrates for the first time that active NiV infection of iDC and THP-1 increased their transendothelial migration activity across HBMEC and activation of HBMEC by TNF-α further promoted migration. The findings suggest that NiV infection of leukocytes to disseminate the virus via the “Trojan horse” mechanism is a viable route of entry into the CNS.

Hervey virus: Study on co-circulation with Henipaviruses in Pteropid bats within their distribution range from Australia to Africa

In 2011, an unusually large number of independent Hendra virus outbreaks were recorded on horse properties in Queensland and New South Wales, Australia. Urine from bat colonies adjacent to the outbreak sites were sampled and screened for Hendra and other viruses. Several novel paramyxoviruses were also isolated at different locations. Here one of the novel viruses, named Hervey virus (HerPV), is fully characterized by genome sequencing, annotation, phylogeny and in vitro host range, and its serological cross-reactivity and neutralization patterns are examined. HerPV may have ecological and spatial and temporal patterns similar to Hendra virus and could serve as a sentinel virus for the surveillance of this highly pathogenic virus. The suitability of HerPV as potential sentinel virus is further assessed by determining the serological prevalence of HerPV antibodies in fruit-eating bats from Australia, Indonesia, Papua New Guinea, Tanzania and the Gulf of Guinea, indicating the presence of similar viruses in regions beyond the Australian border.

Zoonotic Potential of Emerging Paramyxoviruses: Knowns and Unknowns

The risk of spillover of enzootic paramyxoviruses and the susceptibility of recipient human and domestic animal populations are defined by a broad collection of ecological and molecular factors that interact in ways that are not yet fully understood. Nipah and Hendra viruses were the first highly lethal zoonotic paramyxoviruses discovered in modern times, but other paramyxoviruses from multiple genera are present in bats and other reservoirs that have unknown potential to spillover into humans. We outline our current understanding of paramyxovirus reservoir hosts and the ecological factors that may drive spillover, and we explore the molecular barriers to spillover that emergent paramyxoviruses may encounter. By outlining what is known about enzootic paramyxovirus receptor usage, mechanisms of innate immune evasion, and other host-specific interactions, we highlight the breadth of unexplored avenues that may be important in understanding paramyxovirus emergence.

Isolation of Tioman virus from Pteropus giganteus bat in North-East region of India

Bat-borne viral diseases are a major public health concern among newly emerging infectious diseases which includes severe acute respiratory syndrome, Nipah, Marburg and Ebola virus disease. During the survey for Nipah virus among bats at North-East region of India; Tioman virus (TioV), a new member of the Paramyxoviridae family was isolated from tissues of Pteropus giganteus bats for the first time in India. This isolate was identified and confirmed by RT-PCR, sequence analysis and electron microscopy. A range of vertebrate cell lines were shown to be susceptible to Tioman virus. Negative electron microscopy study revealed the "herringbone" morphology of the nucleocapsid filaments and enveloped particles with distinct envelope projections a characteristic of the Paramyxoviridae family. Sequence analysis of Nucleocapsid gene of TioV demonstrated sequence identity of 99.87% and 99.99% nucleotide and amino acid respectively with of TioV strain isolated in Malaysia, 2001. This report demonstrates the first isolation of Tioman virus from a region where Nipah virus activity has been noticed in the past and recent years. Bat-borne viruses have become serious concern world-wide. A Survey of bats for novel viruses in this region would help in recognizing emerging viruses and combating diseases caused by them.

Zoonotic Viruses and Conservation of Bats

Many of the recently emerging highly virulent zoonotic diseases have a likely bat origin, for example Hendra, Nipah, Ebola and diseases caused by coronaviruses. Presumably because of their long history of coevolution, most of these viruses remain subclinical in bats, but have the potential to cause severe illnesses in domestic and wildlife animals and also humans. Spillovers from bats to humans either happen directly (via contact with infected bats) or indirectly (via intermediate hosts such as domestic or wildlife animals, by consuming food items contaminated by saliva, faeces or urine of bats, or via other environmental sources). Increasing numbers of breakouts of zoonotic viral diseases among humans and livestock have mainly been accounted to human encroachment into natural habitat, as well as agricultural intensification, deforestation and bushmeat consumption. Persecution of bats, including the destruction of their roosts and culling of whole colonies, has led not only to declines of protected bat species, but also to an increase in virus prevalence in some of these populations. Educational efforts are needed in order to prevent future spillovers of bat-borne viruses to humans and livestock, and to further protect bats from unnecessary and counterproductive culling.

Evidence of bat origin for Menangle virus, a zoonotic paramyxovirus first isolated from diseased pigs

Menangle virus (MenPV) is a zoonotic paramyxovirus capable of causing disease in pigs and humans. It was first isolated in 1997 from stillborn piglets at a commercial piggery in New South Wales, Australia, where an outbreak of reproductive disease occurred. Neutralizing antibodies to MenPV were detected in various pteropid bat species in Australia and fruit bats were suspected to be the source of the virus responsible for the outbreak in pigs. However, previous attempts to isolate MenPV from various fruit bat species proved fruitless. Here, we report the isolation of MenPV from urine samples of the black flying fox, Pteropus alecto, using a combination of improved procedures and newly established bat cell lines. The nucleotide sequence of the bat isolate is 94 % identical to the pig isolate. This finding provides strong evidence supporting the hypothesis that the MenPV outbreak in pigs originated from viruses in bats roosting near the piggery.

Henipaviruses: an updated review focusing on the pteropid reservoir and features of transmission

The henipaviruses, Hendra virus and Nipah virus, are pathogens that have emerged from flying foxes in Australia and South-east Asia to infect both livestock and humans, often fatally. Since the emergence of Hendra virus in Australia in 1994 and the identification of Australian flying foxes as hosts to this virus, our appreciation of bats as reservoir hosts of henipaviruses has expanded globally to include much of Asia and areas of Africa. Despite this, little is currently known of the mechanisms by which bats harbour viruses capable of causing such severe disease in other terrestrial mammals. Pteropid bat ecology, henipavirus virology, therapeutic developments and features of henipavirus infection, pathology and disease in humans and other mammals are reviewed elsewhere in detail. This review focuses on bats as reservoir hosts to henipaviruses and features of transmission of Hendra virus and Nipah virus following spillover from these reservoir hosts.

Infection barriers to successful xenotransplantation focusing on porcine endogenous retroviruses

Xenotransplantation may be a solution to overcome the shortage of organs for the treatment of patients with organ failure, but it may be associated with the transmission of porcine microorganisms and the development of xenozoonoses. Whereas most microorganisms may be eliminated by pathogen-free breeding of the donor animals, porcine endogenous retroviruses (PERVs) cannot be eliminated, since these are integrated into the genomes of all pigs. Human-tropic PERV-A and -B are present in all pigs and are able to infect human cells. Infection of ecotropic PERV-C is limited to pig cells. PERVs may adapt to host cells by varying the number of LTR-binding transcription factor binding sites. Like all retroviruses, they may induce tumors and/or immunodeficiencies. To date, all experimental, preclinical, and clinical xenotransplantations using pig cells, tissues, and organs have not shown transmission of PERV. Highly sensitive and specific methods have been developed to analyze the PERV status of donor pigs and to monitor recipients for PERV infection. Strategies have been developed to prevent PERV transmission, including selection of PERV-C-negative, low-producer pigs, generation of an effective vaccine, selection of effective antiretrovirals, and generation of animals transgenic for a PERV-specific short hairpin RNA inhibiting PERV expression by RNA interference.

Menangle virus, a pteropid bat paramyxovirus infectious for pigs and humans, exhibits tropism for secondary lymphoid organs and intestinal epithelium in weaned pigs

This study is the first report of experimental infection and transmission of Menangle virus (MenPV) in pigs. Isolated in 1997 from piglets that were stillborn at a large commercial piggery in New South Wales, Australia, MenPV is a recently identified paramyxovirus of bat origin that causes severe reproductive disease in pigs and an influenza-like illness, with a rash, in humans. Although successfully eradicated from the infected piggery, the virus was only isolated from affected fetuses and stillborn piglets during the period of reproductive disease, and thus the mode of transmission between pigs was not established. To investigate the pathogenesis of MenPV, we undertook time-course studies in 6-week-old pigs following intranasal administration of a low-passage, non-plaque-purified isolate from the lung of an infected stillborn piglet. Viraemia was of short duration and low titre, as determined by real-time RT-PCR and virus isolation. Following an incubation period of 2-3 days, virus was shed in nasal and oral secretions, faeces and urine, typically for less than 1 week. Cessation of shedding correlated with the development of neutralizing antibodies in sera. Secondary lymphoid organs and intestine were identified, using quantitative real-time RT-PCR, as major sites of viral replication and dissemination, and this was confirmed by positive immunolabelling of viral antigen within various lymphoid tissues and intestinal epithelium. These data provide new insights into the pathogenesis of MenPV in weaned pigs, and will facilitate future control and eradication programmes should it ever re-emerge in the pig population.

Evaluation of the human host range of bovine and porcine viruses that may contaminate bovine serum and porcine trypsin used in the manufacture of biological products

Current U.S. requirements for testing cell substrates used in production of human biological products for contamination with bovine and porcine viruses are U.S. Department of Agriculture (USDA) 9CFR tests for bovine serum or porcine trypsin. 9CFR requires testing of bovine serum for seven specific viruses in six families (immunofluorescence) and at least 2 additional families non-specifically (cytopathicity and hemadsorption). 9CFR testing of porcine trypsin is for porcine parvovirus. Recent contaminations suggest these tests may not be sufficient. Assay sensitivity was not the issue for these contaminations that were caused by viruses/virus families not represented in the 9CFR screen. A detailed literature search was undertaken to determine which viruses that infect cattle or swine or bovine or porcine cells in culture also have human host range [ability to infect humans or human cells in culture] and to predict their detection by the currently used 9CFR procedures. There are more viruses of potential risk to biological products manufactured using bovine or porcine raw materials than are likely to be detected by 9CFR testing procedures; even within families, not all members would necessarily be detected. Testing gaps and alternative methodologies should be evaluated to continue to ensure safe, high quality human biologicals.

Interferon production and signaling pathways are antagonized during henipavirus infection of fruit bat cell lines

Bats are natural reservoirs for a spectrum of infectious zoonotic diseases including the recently emerged henipaviruses (Hendra and Nipah viruses). Henipaviruses have been observed both naturally and experimentally to cause serious and often fatal disease in many different mammal species, including humans. Interestingly, infection of the flying fox with henipaviruses occurs in the absence of clinical disease. The extreme variation in the disease pattern between humans and bats has led to an investigation into the effects of henipavirus infection on the innate immune response in bat cell lines. We report that henipavirus infection does not result in the induction of interferon expression, and the viruses also inhibit interferon signaling. We also confirm that the interferon production and signaling block in bat cells is not due to differing viral protein expression levels between human and bat hosts. This information, in addition to the known lack of clinical signs in bats following henipavirus infection, suggests that bats control henipavirus infection by an as yet unidentified mechanism, not via the interferon response. This is the first report of henipavirus infection in bat cells specifically investigating aspects of the innate immune system.

Bats, emerging infectious diseases, and the rabies paradigm revisited

The significance of bats as sources of emerging infectious diseases has been increasingly appreciated, and new data have been accumulated rapidly during recent years. For some emerging pathogens the bat origin has been confirmed (such as lyssaviruses, henipaviruses, coronaviruses), for other it has been suggested (filoviruses). Several recently identified viruses remain to be ‘orphan’ but have a potential for further emergence (such as Tioman, Menangle, and Pulau viruses). In the present review we summarize information on major bat-associated emerging infections and discuss specific characteristics of bats as carriers of pathogens (from evolutionary, ecological, and immunological positions). We also discuss drivers and forces of an infectious disease emergence and describe various existing and potential approaches for control and prevention of such infections at individual, populational, and societal levels.

Novel monoclonal antibodies against Menangle virus nucleocapsid protein

Menangle virus (MenV) is a member of the family Paramyxoviridae isolated in Australia that causes a reproductive disease of pigs. There is a need for specific immunoassays for virus detection to facilitate the diagnosis of MenV infection. Three novel monoclonal antibodies (MAbs) of the IgG1 subtype were generated by immunizing mice with recombinant yeast-expressed MenV nucleocapsid (N) protein self-assembled to nucleocapsid-like structures. One MAb was cross-reactive with recombinant N protein of Tioman virus. The epitopes of MAbs were mapped using a series of truncated MenV N proteins lacking the 29-119 carboxy-terminal amino acid (aa) residues. The epitopes of two MAbs were mapped to aa 430-460 of the MenV N protein, whilst the epitope of one MAb was mapped to residues 460-490. All three MAbs specifically recognized MenV, as indicated by immunohistochemical staining of brain tissue isolated from a field case (a stillborn piglet) of MenV infection. The MAbs against MenV N protein may be a useful tool for immunohistological diagnosis of MenV infection.

Generation of Tioman virus nucleocapsid-like particles in yeast Saccharomyces cerevisiae

Tioman virus (TioV) was isolated from a number of pooled urine samples of Tioman Island flying foxes (Pteropus hypomelanus) during the search for the reservoir host of Nipah virus. Studies have established TioV as a new virus in the family Paramyxoviridae. This novel paramyxovirus is antigenically related to Menangle virus that was isolated in Australia in 1997 during disease outbreak in pigs. TioV causes mild disease in pigs and has a predilection for lymphoid tissues. Recent serosurvey showed that 1.8% of Tioman Islanders had neutralizing antibodies against TioV, indicating probable past infection. For the development of convenient serological tests for this virus, recombinant TioV nucleocapsid (N) protein was expressed in the yeast Saccharomyces cerevisiae. High yields of recombinant TioV N protein were obtained. Electron microscopy demonstrated that purified recombinant N protein self-assembled into nucleocapsid-like particles which were identical in density and morphology to authentic nucleocapsids from paramyxovirus-infected cells. Different size nucleocapsid-like particles were stable and readily purified by CsCl gradient ultracentrifugation. Polyclonal sera raised in rabbits after immunization with recombinant TioV N protein reacted reliably with TioV infected tissues in immunohistochemistry tests. It confirmed that the antigenic properties of yeast derived TioV N protein are identical to authentic viral protein.

Paramyxoviruses infecting humans: the old, the new and the unknown

Prior to the emergence of Hendra virus in Australia in 1994, paramyxoviruses were considered to be a taxonomic group of ubiquitous pathogens, consisting primarily of Biosafety Level 2 agents, which possessed narrow host ranges and often caused only mild or preventable diseases in humans and animals. In recent years, a number of Paramyxoviridae members have emerged, including previously unrecognized human pathogens and highly pathogenic zoonoses. The recent emergence of paramyxoviruses in humans suggests that there is an increased incidence of zoonotic transmission between wildlife, livestock and human hosts. This article explores the current body of scientific knowledge, disease burden and knowledge of reservoirs of these emerging paramyxoviruses and provides a comparative review of both older and emerging viruses that have been shown to infect humans.

Bats and viruses: a brief review

Bats, probably the most abundant, diverse and geographically dispersed vertebrates on earth, have recently been shown to be the reservoir hosts of a number of emerging viruses responsible for severe human and livestock disease outbreaks. Flying foxes have been demonstrated to be the natural reservoir for Hendra and Nipah viruses. Evidence supporting the possibility of bats as potential reservoirs for SARS coronavirus (SARS-CoV) and Ebola virus has also been reported. The recent discovery of these viruses and other viruses occurring naturally in the bat population provides a unique insight into a diverse pool of potentially emergent and pathogenic viruses. The factors which influence the ability of zoonotic viruses to effectively cross the species barrier from bats to other animal populations are poorly understood. A brief review is provided here on the recently emerged bat viruses and on current and future strategies for research in this area.

Emerging and re-emerging viruses in Malaysia, 1997-2007

Over the past decade, a number of unique zoonotic and non-zoonotic viruses have emerged in Malaysia. Several of these viruses have resulted in significant morbidity and mortality to those affected and they have imposed a tremendous public health and economic burden on the state. Amongst the most devastating was the outbreak of Nipah virus encephalitis in 1998, which resulted in 109 deaths. The culling of more than a million pigs, identified as the amplifying host, ultimately brought the outbreak under control. A year prior to this, and subsequently again in 2000 and 2003, large outbreaks of hand-foot-and-mouth disease due to enterovirus 71, with rare cases of fatal neurological complications, were reported in young children. Three other new viruses – Tioman virus (1999), Pulau virus (1999), and Melaka virus (2006) – whose origins have all been linked to bats, have been added to the growing list of novel viruses being discovered in Malaysia. The highly pathogenic H5N1 avian influenza has also been detected in Malaysia with outbreaks in poultry in 2004, 2006, and 2007. Fortunately, no human infections were reported. Finally, the HIV/AIDS epidemic has seen the emergence of an HIV-1 recombinant form (CRF33_01B) in HIV-infected individuals from various risk groups, with evidence of ongoing and rapid expansion.

Viral morphogenesis and morphological changes in human neuronal cells following Tioman and Menangle virus infection

Tioman virus (TioPV) and Menangle virus (MenPV) are two antigenically and genetically related paramyxoviruses (genus: Rubulavirus, family: Paramyxoviridae) isolated from Peninsular Malaysia (2001) and Australia (1997), respectively. Both viruses are potential zoonotic agents. In the present study, the infectivity, growth kinetics, morphology and morphogenesis of these two paramyxoviruses in a human neuronal cell (SK-N-SH) line were investigated. Sub-confluent SK-N-SH cells were infected with TioPV and MenPV at similar multiplicity of infection. These cells were examined by conventional and immunoelectron microscopy, and virus titres in the supernatants were assayed. Syncytia were observed for both infections in SK-N-SH cells and were more pronounced during the early stages of TioPV infection. The TioPV titre increased consistently (10(1)) every 12 h after infection. In MenPV-infected cells, cellular material was frequently observed within budding virions, and microfilaments and microtubules were abundant. Viral budding was common, and extracellular MenPVs tended to be more pleomorphic compared to TioPVs, which appeared to be more spherical in appearance. The MenPV cytoplasmic viral inclusion appeared to be comparatively smaller, loose and interspersed with randomly scattered circle-like particles, whereas huge tubule-like cytoplasmic inclusions were observed in TioPV-infected cells. Both viruses also displayed different cellular pathology in the SK-N-SH cells. The intracellular ultrastructural characteristics of these two viruses in infected neuronal cells may allow them to be differentiated by electron microscopy.