| Research Abstract |
As PreviouslY reported, the M strain of parainfluenza 3 virus causes lethal encephalitis in mice and has intensive syncytium-inducing (SI) ability, while the SC strain is avirulent and has very weak SI ability. However, the fusion (F) protein of both strains is identical in the amino acid sequence. Instead, each of the hemagglu.tinin-neuraminidase (HN) and membrance (M) proteins is different by 1 amino acid between the strains.
In the present study, we determined by using recombinant vaccinia virus technology that the HN protein, but not the M protein, of the M virus is responsible for the intensive SI ability of the M virus. The amino acid substitution site between the HN protein of the M and SC strains is located at the very vicinity of the C terminal, being distant from the active site of the hemagglutinin and neuraminidase activities, and we are analyzing the mechanism by which this substitution influences the SI ability.
Furthermore, from a stock of the M strain, we isolated a mutant which, like the SC strain, showed a very weak SI activity. The HN protein of this mutant was identical to that of the M strain whereas its F protein differed from that of the M strain by 1 amino acid. These results indicate that syncytiun formation of parainfluenza virus requires both F and HN proteins and mutation of each protein exerts effects on the SI ability.
On the other band, we found that Sendai virus, a parainfluenza 1 virus, could be recovered form its ribonucleoprotein-transfected cells by supplying the cells with Sendai virus L and P proteins through recombinant vaccinia viruses. This result will open a way to recover Sendai virus, a negative strand RNA virus, from a complementary DNA clone of its genome RNA.
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