Failure to detect antibody to turkey rhinotracheitis virus in Australian poultry flocks

Avian Metapneumovirus circulation in Italian broiler farms

With increasing frequency, avian Metapneumovirus (aMPV) is reported to induce respiratory signs in chickens. An adequate knowledge of current aMPV prevalence among Italian broilers is lacking, with little information available on its economical and health impact on the poultry industry. In order to collect preliminary data on the epidemiological context of aMPV in broiler flocks, a survey was performed in areas of Northern Italy with high poultry density from 2014 to 2016. Upper respiratory tract swabs were collected and processed by A and B subtype-specific multiplex real-time reverse transcription PCR (RT-PCR). Samples were also screened for infectious bronchitis virus (IBV) by generic RT-PCR and sequencing. Productive data and respiratory signs were detailed where possible. The high prevalence of aMPV was confirmed in broilers older than 26 d and also attested in IBV-negative farms. All aMPV detections belonged to subtype B. Italian strain genetic variability was evaluated by the partial attachment (G) gene sequencing of selected strains and compared with contemporary turkey strains and previously published aMPV references, revealing no host specificity and the progressive evolution of this virus in Italy.

Avian metapneumoviruses expressing Infectious Bronchitis virus genes are stable and induce protection

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Foreign viral genes can be inserted into the AMPV genome.

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Resultant recombinant viruses express the inserted genes and are stable in cell culture.

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Both S1 and N genes from IBX QX induced protection against QX challenge.

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Induced seroconversion after recombinant inoculation was minimal.

The study investigates the ability of subtype A Avian metapneumovirus (AMPV) to accept foreign genes and be used as a vector for delivery of Infectious bronchitis virus (IBV) QX genes to chickens. Initially the GFP gene was added to AMPV at all gene junctions in conjunction with the development of cassetted full length DNA AMPV copies. After recombinant virus had been recovered by reverse genetics, GFP positions supporting gene expression while maintaining virus viability in vitro, were determined. Subsequently, either S1 or nucleocapsid (N) genes of IBV were positioned between AMPV M and F genes, while later a bivalent recombinant was prepared by inserting S1 and N at AMPV MF and GL junctions respectively. Immunofluorescent antibody staining showed that all recombinants expressed the inserted IBV genes in vitro and furthermore, all recombinant viruses were found to be highly stable during serial passage. Eyedrop inoculation of chickens with some AMPV-IBV recombinants at one-day-old induced protection against virulent IBV QX challenge 3 weeks later, as assessed by greater motility of tracheal cilia from chickens receiving the recombinants. Nonetheless evidence of AMPV/IBV seroconversion, or major recombinant tracheal replication, were largely absent.

Avian and human metapneumovirus

Pneumovirus infection remains a significant problem for both human and veterinary medicine. Both avian pneumovirus (aMPV, Turkey rhinotracheitis virus) and human metapneumovirus (hMPV) are pathogens of birds and humans, which are associated with respiratory tract infections. Based on their different genomic organization and low level of nucleotide (nt) and amino acid (aa) identity with paramyxoviruses in the genus Pneumovirus, aMPV and hMPV have been classified into a new genus referred to as Metapneumovirus. The advancement of our understanding of pneumovirus biology and pathogenesis of pneumovirus disease in specific natural hosts can provide us with strategies for vaccine formulations and combined antiviral and immunomodulatory therapies.

Subgroup C avian metapneumovirus (MPV) and the recently isolated human MPV exhibit a common organization but have extensive sequence divergence in their putative SH and G genes

The genes encoding the putative small hydrophobic (SH), attachment (G) and polymerase (L) proteins of the Colorado isolate of subgroup C avian pneumovirus (APV) were entirely or partially sequenced. They all included metapneumovirus (MPV)-like gene start and gene end sequences. The deduced Colorado SH protein shared 26.9 and 21.7 % aa identity with its counterpart in human MPV (hMPV) and APV subgroup A, respectively, but its only significant aa similarities were to hMPV. Conserved features included a common hydrophobicity profile with an unique transmembrane domain and the conservation of most extracellular cysteine residues. The Colorado putative G gene encoded several ORFs, the longer of which encoded a 252 aa long type II glycoprotein with aa similarities to hMPV G only (20.6 % overall aa identity with seven conserved N-terminal residues). The putative Colorado G protein shared, at best, 21.0 % aa identity with its counterparts in the other APV subgroups and did not contain the extracellular cysteine residues and short aa stretch highly conserved in other APVs. The N-terminal end of the Colorado L protein exhibited 73.6 and 54.9 % aa identity with hMPV and APV subgroup A, respectively, with four aa blocks highly conserved among Pneumovirus: Phylogenetic analysis performed on the nt sequences confirmed that the L sequences from MPVs were genetically related, whereas analysis of the G sequences revealed that among MPVs, only APV subgroups A, B and D clustered together, independently of both the Colorado isolate and hMPV, which shared weak genetic relatedness at the G gene level.

Metapneumoviruses in birds and humans

Avian pneumovirus (APV, Turkey rhinotracheitis virus) and Human metapneumovirus (hMPV) are pathogens of birds and humans, respectively, that are associated with upper respiratory tract infections. Based on their different genomic organization and low level of nucleotide (nt) and amino acid (aa) identity with paramyxoviruses in the genus Pneumovirus, APV and hMPV have been classified into a new genus referred to as Metapneumovirus. First isolated in 1970s, APV strains have since been isolated in Europe, Africa, middle east, and United States (US) and classified in four subgroups, APV/A, APV/B, APV/C, and APV/D based on nt and predicted aa sequence identity. Although it was first isolated in 2001, serological evidence indicates that hMPV may have been present in human population from as early as the 1950s. There is only one subgroup of hMPV so far, whose nt and aa sequence identity indicates that it is more closely related to APV/C than to APV/A, APV/B, or APV/D.

Detection and differentiation of avian pneumoviruses (metapneumoviruses)

The available detection methods for avian pneumoviruses (turkey rhinotracheitis virus; genus Metapneumovirus) in turkeys, domestic fowl and other species are reviewed. The advantages and disadvantages of virus isolation techniques, virus or genome (polymerase chain reaction) detection and serology are discussed. Some of the problems likely to be encountered are considered, including the detection of yet to be discovered subtypes, as are the factors that are likely to influence the outcome of the work.

Efficacy of avian pneumovirus vaccines against an avian pneumovirus/Escherichia coli O2:K1 dual infection in turkeys

The clinical, pathological and microbiological outcome of a challenge with avian pneumovirus (APV) and Escherichia coli O2:K1 was evaluated in turkeys vaccinated with an attenuated APV vaccine and with or without maternally derived antibodies. Two groups of two-week-old poults, one with and one without maternally derived antibodies against APV, were vaccinated oculonasally with attenuated APV subtype A or B. A third group remained unvaccinated. Eleven weeks later, the turkeys were inoculated intranasally with either virulent APV subtype A, or E. coli O2:K1, or with both agents three days apart. After the dual infection, birds vaccinated with attenuated subtype A or B, and with or without maternally derived antibodies, had lower mean clinical scores than the unvaccinated birds. In the vaccinated birds, virus replication was significantly reduced and no bacteria were isolated, except from the birds vaccinated with attenuated subtype B. In the unvaccinated turkeys, large numbers of E. coli O2:K1 were isolated from the turbinates of the dually infected birds between one-and-a-half and seven days after they were inoculated.

Sequence analysis of the nucleocapsid and phosphoprotein genes of avian pneumoviruses circulating in the US

Avian pneumovirus (APV) has recently been described as the cause of a new respiratory syndrome in turkey flocks in the United States. We here describe the complete sequence of the nucleocapsid (N) and phosphoprotein (P) genes of this emerging APV (APV/US). Our results show 59 and 61% nucleotide sequence identity of the APV/US N gene with N genes of previously described European APV subgroups A and B, respectively. The P gene of APV/US showed only 53% nucleotide sequence identity with the ortholog from APV subgroup A. Phylogenetic analyses of both N and P genes clearly demonstrate that the APV/US lineage is evolutionarily related but distinct from European APVs. Moreover, sequence analysis of the N and P genes from two laboratory adapted isolates of APV/US (APV/MN-1a and APV/MN-1b) and from ten clinical samples from APV-infected turkeys suggests only modest level of amino acid divergence in the N (0-0.3%) and P (0-1.4%) proteins. Taken together, the results of this study indicate support that APV/US represents a new subgroup (subgroup C) of APV and show that there is limited heterogeneity in the N and P genes of APV/US isolates.

Avian pneumovirus infections of turkeys and chickens

Avian pneumoviruses (APVs) cause major disease and welfare problems in many areas of the world. In turkeys the respiratory disease and the effect on egg laying performance are clearly defined. However, in chickens, the role of APV as a primary pathogen is less clear, although it is widely believed to be one of the factors involved in Swollen Head Syndrome. The mechanisms of virus transmission over large distances are not understood, but wild birds have been implicated. APV has recently been reported in the USA for the first time and the virus isolated was a different type or possibly a different serotype from the APVs found elsewhere. Good biosecurity is crucial for controlling infection and highly effective vaccines are available for prophylaxis. Although different subtypes and possibly different serotypes exist, there is good cross protection between them. Diagnosis is usually based on serology using ELISAs, but the available kits give variable results, interpretation is difficult and improved diagnostic tests are required.

Isolation of avian pneumovirus from an outbreak of respiratory illness in Minnesota turkeys

Antibodies to avian pneumovirus (APV) were first detected in Minnesota turkeys in 1997. Virus isolation was attempted on 32 samples (28 tracheal swabs, 4 pools of trachea and turbinates) that were positive for APV by reverse transcriptase polymerase chain reaction (RT-PCR). The cell cultures used were chicken embryo fibroblast (CEF), Vero cells, and QT-35 cells. Five virus isolates were obtained from these samples, and the identity of the isolates was confirmed by RT-PCR. Four isolates were obtained by inoculation of CEF cells, and 1 isolate was obtained in QT-35 cells after 3-7 blind passages in cell cultures. Vero cells did not yield any isolate on primary isolation; however, all 5 isolates could be adapted to grow in Vero cells following primary isolation in CEF or QT-35 cells. This is the first report of isolation of APV in Minnesota and also the first report of primary isolation of APV in QT-35 cells.