Identification of a truncated nucleoprotein in avian metapneumovirus-infected cells encoded by a second AUG, in-frame to the full-length gene

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.

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.

Deduced amino acid sequences surrounding the fusion glycoprotein cleavage site and of the carboxyl-terminus of haemagglutinin-neuraminidase protein of the avirulent thermostable vaccine strain I-2 of Newcastle disease virus

A single-tube RT-PCR technique generated a 387 bp or 300 bp cDNA amplicon covering the F(0) cleavage site or the carboxyl (C)-terminus of the HN gene, respectively, of Newcastle disease virus (NDV) strain I-2. Sequence analysis was used to deduce the amino acid sequences of the cleavage site of F protein and the C-terminus of HN protein, which were then compared with sequences for other NDV strains. The cleavage site of NDV strain I-2 had a sequence motif of (112) RKQGRLIG(119), consistent with an avirulent phenotype. Nucleotide sequencing and deduction of amino acids at the C-terminus of HN revealed that strain I-2 had a 7-amino-acid extension (VEILKDGVREARSSR. This differs from the virulent viruses that caused outbreaks of Newcastle disease in Australia in the 1930s and 1990s, which have HN extensions of 0 and 9 amino acids, respectively. Amino acid sequence analyses of the F and HN genes of strain I-2 confirmed its avirulent nature and its Australian origin.

Production and Characterization of Monoclonal Antibodies That React to the Nucleocapsid Protein of Avian Metapneumovirus Subtype C

Monoclonal antibodies (MAbs) were prepared against avian metapneumovirus (aMPV) subtype C (aMPV/ Minnesota/turkey/1a/97). Six MAbs were selected based on enzyme-linked immunosorbent assay activities and characterized by isotyping, neutralization test, western blot analysis, and immunohistochemistry assay. The results showed that three MAbs (3E, 9D, and 12C) belonged to the IgG1 subclass, whereas the other three (5D, 8E, and 16E) were of the IgG2a subclass. None of the six MAbs neutralized aMPV infectivity at a detectable level, but all reacted with both denatured and nondenatured forms of the nucleocapsid (N) protein of aMPV, suggesting that these MAbs may recognize structurally independent epitopes of the N protein. These MAbs provide new tools and methods for investigating aMPV infection and pathogenesis, as well as diagnosis of aMPV disease.