| Research Abstract |
cDNAs encoding human parainfluenza virus type 4B (hPIV-4B) haemagglutinin-neuraminidase (HN) protein were cloned and the nucleotide sequences were determined. A high degree of identity (81.4%) was observed between the nucleotide sequences of hPIV -4A and 4B HN proteins, and 87.3% identity was found between the deduced amino acid sequences. This degree of identity is considered to be greater than the immunological similarity between hPIV -4A and -4B HN proteins determined using mAbs. To elucidate the causes of the antigenic difference between HN proteins of hPIV-4A and -4B, we constructed three cDNAs of hPIV -4B HN whose potential N-glycosylation sites were partially or completely the same as in hPIV -4A HN cDNA. We compared the antigenicity of the expressed wild type and mutant proteins, and found that the antigenicities of the mutant hPIV -4B HN proteins were more similar to the hPIV -4A HN protein than to the non-mutant hPIN -4B HN protein. This study indicated that the antigenic div
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ersity between hPIV -4A and -4B was partly caused by deletion or creation of glycosylation sites, showing that the point mutations resulting in deletion or creation of glycosylation sites in one of the initial steps leading to the division of virus into subtypes.
Human parainfluemza virus type 4A (hPIV -4A) and type 4B (hPIV -4B) were tested for their ability to replicate in the monkey kidney LLC-MK2 cell line (MK2 cells) and the murine L929 cell line (L929 cells). Both MK2 cells and L929 cell line(L929 cells). Both MK2 cells and L929 cells were non-permissive for replication of hPIV -4. Acetylated trypsin was effective for the virus replication in MK2 cells, but less effective in L929 cells. Interferon (IFN) produced endogeneously played no role in their replication in L929 cells. Synthesis of virus specific polypeptides was suppressed in L929 cells HN -mTNA was not detected. These results indicate that hPIV -4 can infect both MK2 cells and L929 cells. In MK2 cells, when protease exists in the extracellular medium, hPIV -4 exhibits multistep growth. In L929 cells, however, the cause of incomplete replication might be lack of other unknown factors. Less
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