Meningopneumonitis virusの浮遊L細胞内増殖に関する生化学的研究

抄録

As part of a general investigation of meningopneumonitis virus (MPV) multiplication in L cell, the nucleic acid content of the cells has been studied by direct chemical analysis at successive stage in the growth cycle.
Cal 10 strain of MPV and L cell suspension culture were used. Measurements of virus adsorption rate, distribution of MPV after adsorption and infective center formation indicated that essentially all cells were infected within 1 hour after addition of virus at multiplicity more than 50 PFU per cell.
Growth curves of MPV showed that an increase in intracellular virus began at 18.5 hours after infection and reached levels of 450-500 PFU per infected cell. It should be noted that the amount of intracellular virus titer during lag period dropped extremely below that number of infected cells, showing as low as 10^-3 PFU per infected cell at the lowest point.
In the experiments on the multiplication of infected cells, uninfected control cells multiplied until 25 hours, followed by stationary phase. But infected cell cultures did not show increase in cell number. Infected dead cells which were determined by staining with trypan blue were observed 20 hours after infection and almost all cells were dead within 35 hours after infection.
Nitrogen content in uninfected cells was constant until 40 hours, but in infected cultures decline was observed subsequent after 25 hours of infection. Protein content was constant until 20 hours, followed by dropping down both in infected and uninfected cells.
On the other hand, in analysing RNA and DNA contents per 10⁶ cells, although they were constant during 40 hours in control cultures, significant increase was observed in infected cells. The RNA and DNA increment in infected cells was first detected after 10 and 15 hours of infection, respectively, which proceeded an increase of cell associated virus by 8.5 and 3.5 hours. RNA content reached maximum at 20 hours after infection, followed rapidly decreased. DNA content continued to increase and reached near maximum approximately 25 hours after infection. Maximum increment of RNA and DNA reached levels about 133% and 135% of control cells, respectively.
From the results described above, it appears that both RNA and DNA are synthesized in MPV infected L cells. These polymer increment is demonstrable several hours before a significant increase in intracellular virus is found. The relationship of these increased nucleic acids to virus multiplication has been discussed.