Molecular comparisons of full length metapneumovirus (MPV) genomes, including newly determined French AMPV-C and -D isolates, further supports possible subclassification within the MPV Genus

Surveillance of Avian Metapneumovirus in Non-Vaccinated Chickens and Co-Infection with Avian Pathogenic Escherichia coli

Brazil is the second largest producer of broiler chicken in the world, and the surveillance of avian pathogens is of great importance for the global economy and nutrition. Avian metapneumovirus (aMPV) infection results in high rates of animal carcass losses due to aerosacculitis and these impacts can be worsened through co-infection with pathogenic bacteria, particularly Escherichia coli (APEC). The present study evaluated the seroprevalence of the main aMPV subtypes in unvaccinated broiler chickens from poultry farms in Brazil, as well as the clinical effects of co-infection with APEC. Blood samples, respiratory swabs, femurs, liver, and spleen of post-mortem broiler chickens were collected from 100 poultry production batches, totaling 1000 samples. The selection of the production batch was based on the history of systemic and respiratory clinical signs. The results indicated that 20% of the lots showed serological evidence of the presence of aMPV, with two lots being positive for aMPV-B. A total of 45% of batches demonstrated co-infection between aMPV and APEC. The results point to the need for viral surveillance, targeted vaccination, and vaccination programs, which could reduce clinical problems and consequently reduce the use of antibiotics to treat bacterial co-infections.

Avian metapneumovirus: A five-plex digital droplet RT-PCR method for identification of subgroups A, B, C, and D

End-point and real-time avian metapneumovirus (AMPV) RT-PCRs have been developed to detect one or two of the four recognized subgroups (A,B,C, and D) simultaneously or for broad range AMPV detection. Current subgroup specific tests target variable areas of the genome which makes these PCRs sensitive to specificity defects as recently documented. In the current study, a single five-plex digital droplet RT-PCR targeting the conserved viral polymerase gene of AMPV, which is less prone to genetic drift, has been designed. This digital droplet RT-PCR was capable of identifying each of the four AMPV subgroups. Each subgroup was identified according to a specifically assigned fluorescent amplitude. Specificity, which was tested including 31 AMPV strains, non-AMPV avian viruses and closely related human respiratory viruses, was 100%. The specific limit of detection for extracted viral RNA was estimated between 1 and 3 copies/μl. This tool simplifies the number of tests required for AMPV genotype diagnostics and should be theoretically less effected by viral genome evolution due to its target region. Ultimately, application of this test will contribute to an improved understanding of the global geographic distribution and subgroup host range of field strains.

Evolutionary Trajectories of Avian Avulaviruses and Vaccines Compatibilities in Poultry

Newcastle disease virus (NDV) causes one of the highly infectious avian diseases in poultry leading to genuine financial misfortunes around the world. Recently, there has been an increasing trend in the number of ND-associated outbreaks in commercial Jordanian poultry flocks indicating a possible complex evolutionary dynamic of NDV infections in the country. To underpin the dynamics of circulating NDV strains and to assess the vaccine-escape potential, a total of 130 samples were collected from different poultry flocks in six Jordanian Governorates during 2019-2021. Twenty positive isolates, based on real-time reverse transcriptase PCR, were used for further genetic characterization and evolutionary analysis. Our results showed that there is a high evolutionary distance between the newly identified NDV strains (genotype VII.1.1) in this study and the commercially used vaccines (genotypes I and II), suggesting that circulating NDV field strains are under constant evolutionary pressure. These mutations may significantly affect flocks that have received vaccinations as well as flocks with insufficient immunity in terms of viral immunity and disease dynamics. To assess this further, we investigated the efficacy of the heterologous inactivated LaSota or homologous genotype VII.1.1 vaccine for their protection against virulent NDV in chicken. Vaccine-induced immunity was evaluated based on the serology, and protection efficacy was assessed based on clinical signs, survival rates, histopathology, and viral shedding. Chickens vaccinated with the inactivated genotype VII.1.1 based vaccine showed 100% protection with a significant reduction in virus shedding, and ameliorated histopathology lesions compared to LaSota vaccinated chicks that showed 60% protection. These results revealed that the usage of NDV inactivated vaccine from the circulating field strains can successfully ameliorate the clinical outcome and virus pathobiology in vaccinated chicks and will serve as an effective vaccine against the threat posed by commonly circulating NDV strains in the poultry industry.

Molecular characterization of avian metapneumovirus subtype C detected in wild mallards (Anas platyrhynchos) in The Netherlands

Avian metapneumovirus (AMPV) represents a long-term threat to the poultry industry due to its etiological role in the induction of acute respiratory disease and/or egg drop syndrome in domestic turkeys, chickens, and ducks. Although this disease is commonly referred to as turkey rhinotracheitis, the host range of AMPV encompasses many avian species. We have screened 1323 oropharyngeal- and cloacal swab samples obtained from wild mallards in the Netherlands from 2017 to 2019 by RT-PCR using a degenerate primer pair to detect all members of the Paramyxoviridae and Pneumoviridae or an avian metapneumovirus subtype C (AMPV-C)-specific RT-qPCR assay. We identified a total of seven cases of AMPV-C infections in wild, healthy mallards (Anas platyrhynchos), of which two AMPV-C positive samples were further processed using next-generation sequencing. Phylogenetic analysis of the two complete genomes showed that the newly identified AMPV-C strains share closest sequence identity (97%) with Eurasian lineage AMPV-C strains identified in Muscovy ducks in China that presented with severe respiratory disease and egg production loss in 2011. Further analysis of G protein amino acid sequences showed a high degree of variability between the newly identified AMPV-C variants. PONDR scoring of the G protein has revealed the ectodomain of AMPV-C to be partitioned into a long intrinsically disordered and short ordered region, giving insights into AMPV G protein structural biology. In summary, we provide the first report of full-length AMPV-C genome sequences derived from wild birds in Europe. This emphasizes the need for further surveillance efforts to better characterize the host range, epidemiologic distribution, and pathogenicity of AMPV-C to determine the risk posed by cross-species jumps from wildfowl to domesticated avian species.

Characterization of avain metapneumovirus subgroup C isolated from chickens in Beijing, China

Avian metapneumovirus (aMPV) is an important causative agent that causes acute respiratory disease and egg-dropping in chickens and turkeys. Here, we characterized an aMPV subgroup C (aMPV/C) from 320-day-old broiler breeder chickens with severe respiratory diseases in Beijing, China, as evidenced by RT-PCR typing and confirmation of the nucleoprotein (N) gene sequence. The N gene sequence of the aMPV/C strain (designated BJ17) exhibited no deletions or insertions and possessed 94.6% to 99.6% identity to those of published aMPV/C isolates. The phylogenetic tree of the nucleotide sequences constructed using the neighbor-joining clustering method showed that the BJ17 strain formed one cluster with other aMPV/C viruses and formed one subcluster with published Chinese aMPV/C isolates regardless of Muscovy duck or chicken origins. Comparative analysis of the N proteins showed that a unique amino acid residue D at position 110 might be associated with regional distribution due to its occurrence in all the Chinese aMPV/C isolates only. Strain BJ17 was successfully isolated by cultured Vero cell passage and further inoculated in 3-wk-old specific-pathogen-free chickens for the examination of pathogenicity. Animal experimental results showed that BJ17-inoculated chickens had severe respiratory diseases and inflammatory lesions, as demonstrated by pathological changes and aMPV antigen in the nasal turbinate, tracheae, and lung tissues. These results enrich the available information regarding the epidemiology and pathogenicity of aMPV/C in chickens, which may facilitate the development of effective measures against aMPV/C infection in China.

Detection and Genome Sequence Analysis of Avian Metapneumovirus Subtype A Viruses Circulating in Commercial Chicken Flocks in Mexico

Avian metapneumoviruses (aMPV subtypes A-D) are respiratory and reproductive pathogens of poultry. Since aMPV-A was initially reported in Mexico in 2014, there have been no additional reports of its detection in the country. Using nontargeted next-generation sequencing (NGS) of FTA card-spotted respiratory samples from commercial chickens in Mexico, seven full genome sequences of aMPV-A (lengths of 13,288-13,381 nucleotides) were de novo assembled. Additionally, complete coding sequences of genes N (n = 2), P and M (n = 7 each), F and L (n = 1 each), M2 (n = 6), SH (n = 5) and G (n = 2) were reference-based assembled from another seven samples. The Mexican isolates phylogenetically group with, but in a distinct clade separate from, other aMPV-A strains. The genome and G-gene nt sequences of the Mexican aMPVs are closest to strain UK/8544/06 (97.22-97.47% and 95.07-95.83%, respectively). Various amino acid variations distinguish the Mexican isolates from each other, and other aMPV-A strains, most of which are in the G (n = 38), F (n = 12), and L (n = 19) proteins. Using our sequence data and publicly available aMPV-A data, we revised a previously published rRT-PCR test, which resulted in different cycling and amplification conditions for aMPV-A to make it more compatible with other commonly used rRT-PCR diagnostic cycling conditions. This is the first comprehensive sequence analysis of aMPVs in Mexico and demonstrates the value of nontargeted NGS to identify pathogens where targeted virus surveillance is likely not routinely performed.

Zoonotic Origins of Human Metapneumovirus: A Journey from Birds to Humans

Metapneumoviruses, members of the family Pneumoviridae, have been identified in birds (avian metapneumoviruses; AMPV’s) and humans (human metapneumoviruses; HMPV’s). AMPV and HMPV are closely related viruses with a similar genomic organization and cause respiratory tract illnesses in birds and humans, respectively. AMPV can be classified into four subgroups, A–D, and is the etiological agent of turkey rhinotracheitis and swollen head syndrome in chickens. Epidemiological studies have indicated that AMPV also circulates in wild bird species which may act as reservoir hosts for novel subtypes. HMPV was first discovered in 2001, but retrospective studies have shown that HMPV has been circulating in humans for at least 50 years. AMPV subgroup C is more closely related to HMPV than to any other AMPV subgroup, suggesting that HMPV has evolved from AMPV-C following zoonotic transfer. In this review, we present a historical perspective on the discovery of metapneumoviruses and discuss the host tropism, pathogenicity, and molecular characteristics of the different AMPV and HMPV subgroups to provide increased focus on the necessity to better understand the evolutionary pathways through which HMPV emerged as a seasonal endemic human respiratory virus.

First detection of Avian metapneumovirus subtype C Eurasian Lineage in a Eurasian wigeon (Mareca penelope) wintering in Northeastern Italy: an additional hint on the role of migrating birds in the viral epidemiology

Avian metapneumovirus (aMPV) economically affects the global poultry industry causing respiratory and reproductive disorders. Considering the paucity of data on the aMPV occurrence in European free-ranging avifauna, a molecular survey was conducted on wild birds of 23 species belonging to the orders Anseriformes, Charadriiformes or Passeriformes, captured alive and sampled in Northeast Italy as part of the national Avian influenza virus (AIV) surveillance activities. A total of 492 oropharyngeal swabs, collected from 2007 to 2010, all AIV negative, were screened from aMPV by subtype-specific qRT-PCR. An aMPV-C strain, named aMPV/C/IT/Wigeon/758/07, was found in a wintering young Eurasian wigeon (Mareca penelope) sampled in November 2007. The matrix, fusion, and attachment glycoprotein genes of the detected strain were subsequently amplified by specific independent RT-PCRs, then sequenced, and compared in a phylogenetic framework with known aMPV homologous sequences retrieved from GenBank. Close genetic relationships were found between the aMPV/C/IT/Wigeon/758/07 strain and subtype C Eurasian lineage strains isolated in the late 1990s in French domestic ducks, suggesting epidemiological links. Eurasian wigeons are indeed medium to long-range migrant dabbling ducks that move along the Black Sea/Mediterranean flyway, our finding might therefore be related to migratory bridges between countries. To our knowledge, this is the first molecular evidence of the occurrence of a subtype C in Italy and backdates the aMPV-C circulation to 2007. Moreover, results suggest the susceptibility of Eurasian wigeons to aMPV. Broader investigations are needed to assess the role of wild ducks and the significance of the wildfowl/poultry interface in the aMPV-C epidemiology.

First report of Avian metapneumovirus type B in Iraqi broiler flocks with swollen head syndrome

Background and Aim:

Swollen head syndrome (SHS) is a complex disease caused by various agents, including bacterial and viral pathogens, as well as environmental factors. Avian metapneumovirus (aMPV) is one of the most important causes of respiratory diseases and SHS in poultry and one of the most widespread viruses worldwide; however, it has not been recorded in Iraq. This study aimed at the molecular identification and subtyping of aMPV in poultry, with the objectives of investigating the prevalence of aMPV in infected broiler flocks with SHS and molecular typing using primers specific to the study of the prevalence of subtypes A, B, and C of aMPV.

Materials and Methods:

This study was performed on 67 broiler farms that reported typical SHS from September 2018 to August 2019. Swabs were collected from the trachea, infraorbital sinuses, and lung, then uploaded on FTA cards and subjected to an RNA extraction protocol.

Results:

aMPV was detected in 16 (23.8%) samples. Molecular typing using primers specific to the attachment glycoprotein (G) gene showed that all positive samples belonged to subtype B, as assessed using the real-time polymerase chain reaction technique.

Conclusion:

aMPV may be the main etiological factor causing SHS in poultry. Moreover, this was the first report of the prevalence of subtype B aMPV strains in broiler farms in Iraq.

Development of A recombinant nucleocapsid based indirect ELISA for the detection of antibodies to avian metapneumovirus subtypes, A, B, and C

Nucleocapsid (N) protein is the most highly expressed of all avian metapneumovirus (aMPV) viral proteins and stimulates a substantial immune response in infected animals. Codon optimized recombinant N (rec-N) protein from aMPV subtypes A, B, and C were expressed using the baculoviral expression system in Trichoplusia ni (Tni) insect cells. A mixture of purified rec-N antigens from each subtype was used as a coating antigen and was evaluated in indirect ELISA (iELISA) to assess antibody response in serum samples collected from experimentally infected chickens and turkeys with different aMPV subtypes. Also, archived field serum samples that were collected from different poultry submissions were used. Receiver operating characteristic (ROC) analysis was performed using chicken and turkey serum samples that were confirmed by indirect fluorescent antibody (IFA) test for serostatus (positive n = 270, negative n = 610). The ROC analysis showed sensitivity and specificity of 97 % at a cut-off value of 0.25. The rec-N iELISA was compared with a commercial whole virus-based APV kit. The rec-N iELISA showed comparable results in detecting antibody response in aMPV infected chicken sera but was more sensitive in detecting early antibody response in aMPV infected turkey serum samples. Our results further confirm the presence of aMPV antibodies in Canadian domestic poultry populations. The developed aMPV-rec N iELISA offers a safe and valuable alternative to whole virus-based iELISA for serodiagnosis and seroepidemiological surveillance of the disease in domestic poultry.

Proteome Analysis in a Mammalian Cell line Reveals that PLK2 is Involved in Avian Metapneumovirus Type C (aMPV/C)-Induced Apoptosis

Avian metapneumovirus subtype C (aMPV/C) causes an acute respiratory disease that has caused serious economic losses in the Chinese poultry industry. In the present study, we first explored the protein profile in aMPV/C-infected Vero cells using iTRAQ quantitative proteomics. A total of 921 of 7034 proteins were identified as significantly altered by aMPV/C infection. Three selected proteins were confirmed by Western blot analysis. Bioinformatics GO analysis revealed multiple signaling pathways involving cell cycle, endocytosis, and PI3K-Akt, mTOR, MAPK and p53 signaling pathways, which might participate in viral infection. In this analysis, we found that PLK2 expression was upregulated by aMPV/C infection and investigated whether it contributed to aMPV/C-mediated cellular dysfunction. Suppressing PLK2 attenuated aMPV/C-induced reactive oxygen species (ROS) production and p53-dependent apoptosis and reduced virus release. These results in a mammalian cell line suggest that high PLK2 expression correlates with aMPV/C-induced apoptosis and viral replication, providing new insight into the potential avian host cellular response to aMPV/C infection and antiviral targets.

Single reaction, real time RT-PCR detection of all known avian and human metapneumoviruses

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Detection of all known avian and human MPV subgroups in a single reaction rRT-PCR.

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Highly sensitive and specific method using SYBR Green I technology.

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Complete validation of the method for detection of avian metapneumoviruses.

Current molecular methods for the detection of avian and human metapneumovirus (AMPV, HMPV) are specifically targeted towards each virus species or individual subgroups of these. Here a broad range SYBR Green I real time RT-PCR was developed which amplified a highly conserved fragment of sequence in the N open reading frame. This method was sufficiently efficient and specific in detecting all MPVs. Its validation according to the NF U47-600 norm for the four AMPV subgroups estimated low limits of detection between 1000 and 10 copies/μL, similar with detection levels described previously for real time RT-PCRs targeting specific subgroups. RNA viruses present a challenge for the design of durable molecular diagnostic test due to the rate of change in their genome sequences which can vary substantially in different areas and over time. The fact that the regions of sequence for primer hybridization in the described method have remained sufficiently conserved since the AMPV and HMPV diverged, should give the best chance of continued detection of current subgroups and of potential unknown or future emerging MPV strains.

Immunization with avian metapneumovirus harboring chicken Fc induces higher immune responses

In this study, we evaluated the immune responses of avian metapneumovirus harboring chicken Fc molecule. Stable Vero cells expressing chicken Fc chimera on its surface (Vero-cFc) were established, and we confirmed that aMPV grown in Vero-cFc incorporated host derived chimera Fc into the aMPV virions. Immunization of chicken with aMPV-cFc induced higher level of antibodies and inflammatory cytokines; (Interferon (IFN)-γ and Interleukin (IL)-1β) compared to those of aMPV. The increased levels of antibodies and inflammatory cytokines in chicken immunized with aMPV-cFc were statistically significantly (p<0.05) to that of aMPV and control. The aMPV-cFc group also generated the highest neutralizing antibody response. After challenges, chickens immunized with aMPV-cFc showed much less pathological signs in nasal turbinates and trachea so that we could confirm aMPV-cFc induced higher protection than that of aMPV. The greater ability of aMPV harboring chicken Fc to that of aMPV presented it as a possible vaccine candidate.

Trypsin- and low pH-mediated fusogenicity of avian metapneumovirus fusion proteins is determined by residues at positions 100, 101 and 294

Avian metapneumovirus (aMPV) and human metapneumovirus (hMPV) are members of the genus Metapneumovirus in the subfamily Pneumovirinae. Metapneumovirus fusion (F) protein mediates the fusion of host cells with the virus membrane for infection. Trypsin- and/or low pH-induced membrane fusion is a strain-dependent phenomenon for hMPV. Here, we demonstrated that three subtypes of aMPV (aMPV/A, aMPV/B, and aMPV/C) F proteins promoted cell-cell fusion in the absence of trypsin. Indeed, in the presence of trypsin, only aMPV/C F protein fusogenicity was enhanced. Mutagenesis of the amino acids at position 100 and/or 101, located at a putative cleavage region in aMPV F proteins, revealed that the trypsin-mediated fusogenicity of aMPV F proteins is regulated by the residues at positions 100 and 101. Moreover, we demonstrated that aMPV/A and aMPV/B F proteins mediated cell-cell fusion independent of low pH, whereas the aMPV/C F protein did not. Mutagenesis of the residue at position 294 in the aMPV/A, aMPV/B, and aMPV/C F proteins showed that 294G played a critical role in F protein-mediated fusion under low pH conditions. These findings on aMPV F protein-induced cell-cell fusion provide new insights into the molecular mechanisms underlying membrane fusion and pathogenesis of aMPV.