Podstawowe wlasciwosci biologiczne szczepu M-PI3 wirusa parainfluenzy bydla pasazowanego w komorkach MDBK i FLK

It was found that M-PI3 virus could be propagated both in MDBK and FLK cells. TCID₅₀ in the MDBK cell line was 10⁶‧³⁵—10⁷‧⁵ per 0.2 ml in the course of 10 consecutive passages and haemagglutination titer ranged from 80 to 320 using a 0.75 per cent solution of goose erythrocytes. There was observed many mitotic divisions of cells revealed by Pappenheim’s staining. The M-PI3 virus passaged through FLK cells displayed changed biological properties compared with that propagated in MDBK cells. TCID₅₀ and haemagglutination titers of M-PI3 virus depended on the number of passages and infective dose. In the first four passages its TCID₅₀ titer was 10⁵‧³³—10⁶‧⁶⁰ per 0.2 ml, in the 5th — 10³‧³² and in the 6th — 10¹‧⁵. The virus was not found in the next four passages. Similar observations were done with respect to haemagglutination titer; in the first passage its titer was 320, in the 4th — 20 and later no virus was stated. By means of Pappenheim’s method the FLK cells formed syncytia containing 20—40 nuclei. The mean geometric titer of antibodies in sera taken from calves infected with BLV and M-PI3 viruses were 507 and in the group II i.e. infected only with M-PI3 virus — 226. The highest titer of HI antibodies in the group I was found at week 3 p.i. and in the group II at week 4 p.i.