A prototype avian metapneumovirus (AMPV) vaccine (P20) was previously shown to give variable outcomes in experimental trials. Following plaque purification, three of 12 viruses obtained from P20 failed to induce protection against virulent challenge, whilst the remainder retained their protective capacity. The genome sequences of two protective viruses were identical to the P20 consensus, whereas two non-protective viruses differed only in the SH gene transcription termination signal. Northern blotting showed that the alterations in the SH gene-end region of the non-protective viruses led to enhanced levels of dicistronic mRNA produced by transcriptional readthrough. A synthetic minigenome was used to demonstrate that the altered SH gene-end region reduced the level of protein expression from a downstream gene. The genomes of the remaining eight plaque-purified viruses were sequenced in the region where the P20 consensus sequence differed from the virulent progenitor. The seven protective clones were identical, whereas the non-protective virus retained the virulent progenitor sequence at two positions and contained extensive alterations in its attachment (G) protein sequence associated with a reduced or altered expression pattern of G protein on Western blots. The data indicate that the efficacy of a putative protective vaccine strain is affected by mutations altering the balance of G protein expression.
BassB. L.,
WeintraubH.,
CattaneoR.,
BilleterM. A.1989; Biased hypermutation of viral RNA genomes could be due to unwinding/modification of double-stranded RNA. Cell 56:331[CrossRef]
BiacchesiS.,
PhamQ. N.,
SkiadopoulosM. H.,
MurphyB. R.,
CollinsP. L.,
BuchholzU. J.2005; Infection of nonhuman primates with recombinant human metapneumovirus lacking the SH, G, or M2-2 protein categorizes each as a nonessential accessory protein and identifies vaccine candidates. J Virol 79:12608–12613[CrossRef]
BuchholzU. J.,
FinkeS.,
ConzelmannK. K.1999; Generation of bovine respiratory syncytial virus (BRSV) from cDNA: BRSV NS2 is not essential for virus replication in tissue culture, and the human RSV leader region acts as a functional BRSV genome promoter. J Virol 73:251–259
CatelliE.,
CecchinatoM.,
SavageC. E.,
JonesR. C.,
NaylorC. J.2006; Demonstration of loss of attenuation and extended field persistence of a live avian metapneumovirus vaccine. Vaccine 24:6476–6482[CrossRef]
JohnsonT. R.,
TengM. N.,
CollinsP. L.,
GrahamB. S.2004; Respiratory syncytial virus (RSV) G glycoprotein is not necessary for vaccine-enhanced disease induced by immunization with formalin-inactivated RSV. J Virol 78:6024–6032[CrossRef]
JonesR. C.,
NaylorC. J.,
al-AfaleqA.,
WorthingtonK. J.,
JonesR.1992; Effect of cyclophosphamide immunosuppression on the immunity of turkeys to viral rhinotracheitis. Res Vet Sci 53:38–41[CrossRef]
LingR.,
EastonA. J.,
PringleC. R.1992; Sequence analysis of the 22K, SH and G genes of turkey rhinotracheitis virus and their intergenic regions reveals a gene order different from that of other pneumoviruses. J Gen Virol 73:1709–1715[CrossRef]
NaylorC. J.,
JonesR. C.1994; Demonstration of a virulent subpopulation in a prototype live attenuated turkey rhinotracheitis vaccine. Vaccine 12:1225–1230[CrossRef]
NaylorC. J.,
WorthingtonK. J.,
JonesR. C.1997b; Failure of maternal antibodies to protect young turkey poults against challenge with turkey rhinotracheitis virus. Avian Dis 41:968–971[CrossRef]
NaylorC. J.,
BrownP. A.,
EdworthyN.,
LingR.,
JonesR. C.,
SavageC. E.,
EastonA. J.2004; Development of a reverse-genetics system for Avian pneumovirus demonstrates that the small hydrophobic (SH) and attachment (G) genes are not essential for virus viability. J Gen Virol 85:3219–3227[CrossRef]
RandhawaJ. S.,
WilsonS. D.,
TolleyK. P.,
CavanaghD.,
PringleC. R.,
EastonA. J.1996; Nucleotide sequence of the gene encoding the viral polymerase of avian pneumovirus. J Gen Virol 77:3047–3051[CrossRef]
RandhawaJ. S.,
MarriottA. C.,
PringleC. R.,
EastonA. J.1997; Rescue of synthetic minireplicons establishes the absence of the NS1 and NS2 genes from avian pneumovirus. J Virol 71:9849–9854
TranK. C.,
CollinsP. L.,
TengM. N.2004; Effects of altering the transcription termination signals of respiratory syncytial virus on viral gene expression and growth in vitro and in vivo. J Virol 78:692–699[CrossRef]
van den HoogenB. G.,
BestebroerT. M.,
OsterhausA. D.,
FouchierR. A.2002; Analysis of the genomic sequence of a human metapneumovirus. Virology 295:119–132[CrossRef]
WilliamsR. A.,
SavageC. E.,
WorthingtonK. J.,
JonesR. C.1991b; Further studies on the development of a live attenuated vaccine against turkey rhinotracheitis. Avian Pathol 20:585–596[CrossRef]
YuQ.,
DavisP. J.,
BrownT. D.,
CavanaghD.1992a; Sequence and in vitro expression of the M2 gene of turkey rhinotracheitis pneumovirus. J Gen Virol 73:1355–1363[CrossRef]
YuQ.,
DavisP. J.,
LiJ.,
CavanaghD.1992b; Cloning and sequencing of the matrix protein (M) gene of turkey rhinotracheitis virus reveal a gene order different from that of respiratory syncytial virus. Virology 186:426–434[CrossRef]