Relevance of proteins which are coded by the phosphoprotein gene of Newcastle disease virus for the virulence in the natural host

• Applicant: Dr. Angela Römer-Oberdörfer
• Subject Area: Veterinary Medical Science ; Parasitology and Biology of Tropical Infectious Disease Pathogens
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 262594682

Newcastle disease viruses differ in their virulence. However, the molecular basis of these differences is not completely understood. It is known that the amino acid sequence around the proteolytic cleavage site of the fusion protein is an important virulence determinant, but it has also been shown that other determinants contribute to NDV virulence. The different translation products from the P gene (P, V, W protein) are further potential virulence determinants which we want to investigate within this project. V and W proteins result from an editing process during transcription of the P gene. The V protein is an interferon antagonist and may, consequently, affect virus virulence. The W protein that is predicted on basis of sequence analyses and detected mRNA has not been demonstrated so far. Therefore, it is planned to produce W protein specific antisera. To analyze W protein function in the viral context, recombinant virus shall be generated that express P and V from single, separate open reading frames lacking the editing site, resulting in lack of W mRNA transcription. A resulting virus that is comparable in replication and virulence would indicate that W protein is not essential. Moreover, only few investigations are known that studied relative amount of each possible editing product dependent on virus strain and virulence. Now it is possible to find very small amounts of individual sequence motifs (< 0.5 %) within a population by deep sequencing which shall be used to analyze whether there is a correlation between relative amounts of P, V or W and virus virulence or not. A correlation has to be confirmed by protein detection and protein quantitation using specifically generated antisera. Since all three proteins of the RNP are necessary for transcription, influence not only of P sequence but also of NP and L sequences on editing shall be investigated. P protein has the function to connect NP and L, and is therefore in a key position within the RNP. Since phosphorylation may affect protein structure as well as function, we want to elucidate potential differences in P as well as in V protein from NDV with different pathogenicity. Furthermore, it has been shown that V protein of a mesogenic NDV induced a stronger IFN response than a lentogenic one. The connection between V protein sequence and virulence has to be confirmed by investigations with V proteins of different pathogenic strains to learn more about the molecular mechanism of IFN inhibition in avian cells.

• DFG Programme: Research Grants