In recent years, the emergence of several highly pathogenic zoonotic diseases in humans has led to a renewed emphasis on the interconnectedness of human, animal, and environmental health, otherwise known as One Health. For example, Hendra virus (HeV), a zoonotic paramyxovirus, was discovered in 1994, and since then, infections have occurred in 7 humans, each of whom had a strong epidemiologic link to similarly affected horses. As a consequence of these outbreaks, eradication of bat populations was discussed, despite their crucial environmental roles in pollination and reduction of the insect population. We describe the development and evaluation of a vaccine for horses with the potential for breaking the chain of HeV transmission from bats to horses to humans, thereby protecting horse, human, and environmental health. The HeV vaccine for horses is a key example of a One Health approach to the control of human disease.

The henipaviruses, Hendra virus (HeV) and Nipah virus (NiV), are two deadly zoonotic viruses for which no vaccines or therapeutics have yet been approved for human or livestock use. In 14 outbreaks since 1994 HeV has been responsible for multiple fatalities in horses and humans, with all known human infections resulting from close contact with infected horses. A vaccine that prevents virus shedding in infected horses could interrupt the chain of transmission to humans and therefore prevent HeV disease in both. Here we characterise HeV infection in a ferret model and show that it closely mirrors the disease seen in humans and horses with induction of systemic vasculitis, including involvement of the pulmonary and central nervous systems. This model of HeV infection in the ferret was used to assess the immunogenicity and protective efficacy of a subunit vaccine based on a recombinant soluble version of the HeV attachment glycoprotein G (HeVsG), adjuvanted with CpG. We report that ferrets vaccinated with a 100 μg, 20 μg or 4 μg dose of HeVsG remained free of clinical signs of HeV infection following a challenge with 5,000 TCID50 of HeV. In addition, and of considerable importance, no evidence of virus or viral genome was detected in any tissues or body fluids in any ferret in the 100 and 20 μg groups, while genome was detected in the nasal washes only of one animal in the 4 μg group. Together, our findings indicate that 100 μg or 20 μg doses of HeVsG vaccine can completely prevent a productive HeV infection in the ferret, suggesting that vaccination to prevent the infection and shedding of HeV is possible.

Hendra virus and Nipah virus are bat-borne paramyxoviruses that are the prototypic members of the genus Henipavirus. The henipaviruses emerged in the 1990s, spilling over from their natural bat hosts and causing serious disease outbreaks in humans and livestock. Hendra virus emerged in Australia and since 1994 there have been 7 human infections with 4 case fatalities. Nipah virus first appeared in Malaysia and subsequent outbreaks have occurred in Bangladesh and India. In total, there have been an estimated 582 human cases of Nipah virus and of these, 54% were fatal. Their broad species tropism and ability to cause fatal respiratory and/or neurologic disease in humans and animals make them important transboundary biological threats. Recent experimental findings in animals have demonstrated that a human monoclonal antibody targeting the viral G glycoprotein is an effective post-exposure treatment against Hendra and Nipah virus infection. In addition, a subunit vaccine based on the G glycoprotein of Hendra virus affords protection against Hendra and Nipah virus challenge. The vaccine has been developed for use in horses in Australia and is the first vaccine against a Biosafety Level-4 (BSL-4) agent to be licensed and commercially deployed. Together, these advances offer viable approaches to address Hendra and Nipah virus infection of livestock and people.

Hendra virus and Nipah virus, two zoonotic paramyxoviruses in the genus

BackgroundNipah virus (NiV) is a zoonotic virus belonging to the henipavirus genus in the family Paramyxoviridae. Since NiV was first identified in 1999, outbreaks have continued to occur in humans in Bangladesh and India on an almost annual basis with case fatality rates reported between 40% and 100%.MethodsFerrets were vaccinated with 4, 20 or 100 μg HeVsG formulated with the human use approved adjuvant, CpG, in a prime-boost regime. One half of the ferrets were exposed to NiV at 20 days post boost vaccination and the other at 434 days post vaccination. The presence of virus or viral genome was assessed in ferret fluids and tissues using real-time PCR, virus isolation, histopathology, and immunohistochemistry; serology was also carried out. Non-immunised ferrets were also exposed to virus to confirm the pathogenicity of the inoculum.ResultsFerrets exposed to Nipah virus 20 days post vaccination remained clinically healthy. Virus or viral genome was not detected in any tissues or fluids of the vaccinated ferrets; lesions and antigen were not identified on immunohistological examination of tissues; and there was no increase in antibody titre during the observation period, consistent with failure of virus replication. Of the ferrets challenged 434 days post vaccination, all five remained well throughout the study period; viral genome – but not virus - was recovered from nasal secretions of one ferret given 20 μg HeVsG and bronchial lymph nodes of the other. There was no increase in antibody titre during the observation period, consistent with lack of stimulation of a humoral memory response.ConclusionsWe have previously shown that ferrets vaccinated with 4, 20 or 100 μg HeVsG formulated with CpG adjuvant, which is currently in several human clinical trials, were protected from HeV disease. Here we show, under similar conditions of use, that the vaccine also provides protection against NiV-induced disease. Such protection persists for at least 12 months post-vaccination, with data supporting only localised and self-limiting virus replication in 2 of 5 animals. These results augur well for acceptability of the vaccine to industry.

c Hendra virus is a highly pathogenic zoonotic paramyxovirus in the genus Henipavirus. Thirty-nine outbreaks of Hendra virus have been reported since its initial identification in Queensland, Australia, resulting in seven human infections and four fatalities. Little is known about cellular host factors impacting Hendra virus replication. In this work, we demonstrate that Hendra virus makes use of a microRNA (miRNA) designated miR-146a, an NF-B-responsive miRNA upregulated by several innate immune ligands, to favor its replication. miR-146a is elevated in the blood of ferrets and horses infected with Hendra virus and is upregulated by Hendra virus in human cells in vitro. Blocking miR-146a reduces Hendra virus replication in vitro, suggesting a role for this miRNA in Hendra virus replication. In silico analysis of miR-146a targets identified ring finger protein (RNF)11, a member of the A20 ubiquitin editing complex that negatively regulates NF-B activity, as a novel component of Hendra virus replication. RNA interference-mediated silencing of RNF11 promotes Hendra virus replication in vitro, suggesting that increased NF-B activity aids Hendra virus replication. Furthermore, overexpression of the IB superrepressor inhibits Hendra virus replication. These studies are the first to demonstrate a host miRNA response to Hendra virus infection and suggest an important role for host miRNAs in Hendra virus disease.

Intertypic recombinant fowl adenoviruses (FAVs) were generated to determine regions of the viral genome involved in virulence. Recombinants were produced with two serotype 8 FAVs, mildly virulent CFA 3 and hypervirulent CFA 40. Restriction endonuclease fragments from the genomes of the two FAVs were used to transfect primary chicken kidney cells. Virulence testing of these recombinants located the region responsible for differences in virulence to an 8.4-kb fragment of the genome located between kb 26.6 and 35.0. According to data available for a serotype 10 FAV that had been partially characterized in the laboratory, this segment of the genome contained three genes of known identity (100K, 33K, and pVIII) and a region between kb 31 and 35 with unknown coding potential (although this information subsequently became available for a serotype 1 FAV, CELO). Therefore, the region between kb 30.5 and 34.5 was sequenced. The results revealed that the unknown region encoded a fiber gene on the right strand and several small open reading frames of unknown identity on the left strand. Further recombinant viruses containing defined exchanges within the 4-kb fragment were constructed, and virulence testing of these viruses indicated that the fiber was responsible for differences in virulence for CFA 40 and CFA 3.

The marine toad Bufo marinus is native to northern South America, parts of Central America and Southern Texas. It was deliberately introduced into Australia's tropical north-east in 1935 in an unsuccessful attempt to control the cane beetle, a damaging insect pest of sugarcane crops. The toads quickly established in the new environment and began to spread. Today, they inhabit most of the Australian tropics and sub-tropics and have reached Western Australia. Models predict that global warming will enable the toads to extend their range further south. They cause severe environmental impacts, as all life stages of B. marinus contain bufadienolides, alkaloid substances toxic to vertebrates, resulting in death of the predators ingesting it. The continental scale of this biological invasion in combination with the remoteness of the areas affected, poses a specific set of challenges to potential control approaches for cane toads. This review covers different biocontrol strategies pursued over the past 8 years, with particular focus on an immunological approach aiming at the disruption of toad metamorphosis. So far, research efforts have failed to produce a tool for large-scale reduction of toad populations. Considerations of future research priorities and efforts are also discussed.