RESUMO
Bovine parainfluenza virus type 3 (bPIV3) is under development as a live virus vaccine vector. The RNA genome of a recombinant bPIV3 harbored four nucleotide changes, one of which resulted in a mutation of the viral polymerase (A. A. Haller et al., 2000, J. Virol. 74, 11626-11635). The contribution of this conservative amino acid substitution (I1103V) in the polymerase to the temperature-sensitive and attenuation phenotypes of r-bPIV3 was investigated by creating a new virus, r-bPIV3(I), that expressed the wild-type polymerase. r-bPIV3(I) was not temperature-sensitive for growth in vitro and the replication of r-bPIV3(I) was no longer restricted in hamsters. The effect of the amino acid substitution in the polymerase was also studied in a chimeric bovine/human PIV3, a virus that displayed temperature-sensitive and attenuated phenotypes (A. A. Haller et al., 2000, J. Virol. 74, 11626-11635). It was not clear whether these defects were due to the impaired polymerase or the replacement of the bPIV3 surface glycoproteins with those of hPIV3. The results showed that the altered polymerase was indeed responsible for the temperature-sensitive phenotype of bovine/human PIV3 but did not appear to play a role in the attenuation phenotype.
Assuntos
Vírus da Parainfluenza 3 Bovina/enzimologia , RNA Polimerase Dependente de RNA/metabolismo , DNA Polimerase Dirigida por RNA/metabolismo , Sequência de Aminoácidos , Substituição de Aminoácidos , Animais , Sequência de Bases , Bovinos , Chlorocebus aethiops , Cricetinae , Células HeLa , Humanos , Mesocricetus , Dados de Sequência Molecular , Vírus da Parainfluenza 3 Bovina/genética , Vírus da Parainfluenza 3 Bovina/fisiologia , Vírus da Parainfluenza 3 Humana/genética , Vírus da Parainfluenza 3 Humana/fisiologia , RNA Polimerase Dependente de RNA/genética , DNA Polimerase Dirigida por RNA/genética , Recombinação Genética , Temperatura , Células Vero , Replicação ViralRESUMO
Bovine parainfluenza virus type 3 (bPIV3) is being evaluated as an intranasal vaccine for protection against human PIV3 (hPIV3). In young infants, the bPIV3 vaccine appears to be infectious, attenuated, immunogenic, and genetically stable, which are desirable characteristics for an RNA virus vector. To test the potential of the bPIV3 vaccine strain as a vector, an infectious DNA clone of bPIV3 was assembled and recombinant bPIV3 (r-bPIV3) was rescued. r-bPIV3 displayed a temperature-sensitive phenotype for growth in tissue culture at 39 degrees C and was attenuated in the lungs of Syrian golden hamsters. In order to test whether r-bPIV3 could serve as a vector, the fusion and hemagglutinin-neuraminidase genes of bPIV3 were replaced with those of hPIV3. The resulting bovine/human PIV3 was temperature sensitive for growth in Vero cells at 37 degrees C. The replication of bovine/human PIV3 was also restricted in the lungs of hamsters, albeit not as severely as was observed for r-bPIV3. Despite the attenuation phenotypes observed for r-bPIV3 and bovine/human PIV3, both of these viruses protected hamsters completely upon challenge with hPIV3. In summary, bPIV3 was shown to function as a virus vector that may be especially suitable for vaccination of infants and children against PIV3 and other viruses.
