Abstract
Improvement was made in the method described in the first report. By using the improved method, called the HEIC method, it was possible to prove HCV constantly in tissue culture, without using swine. The neutralizing antibodies produced after the crystal violet vaccine (CVV) inoculation could also be measured. 1. In the new HEIC method, the period of culture of the first virus was extended to 9 days and bovine serum was removed from the composition of the second culture medium. This method made the demonstration of hog cholera virus (HCV) more practical than the original method. For example, the presence of HCV in the infected blood was proved up to a 10-2 dilution by the original method; the new HEIC method showed a marked difference in sensitiveness and could prove HCV up to a 10-5 dilution of the same sample. 2. By extending the incubation period from one hour to overnight, considerable progress could be made in the measurement of the NAT of swine vaccinated with CVV. The titer was 2.5 on the average by the virus dilution method. The titers of swine surviving after virus challenge were in a range of 3.5 to 5.0 by the serum dilution method. These tests were excellent in reproducibility. These titers were almost the same as the value obtained by the END method. 3. In the potency test of CVV conducted in the authors' laboratory, the relationship between the neutralizing antibody titer and the degrees of post-challenge reaction was examined in 39 swine. On the whole, swine which had a high NAT recovered from a slight clinical reaction. Swine which had a low NAT, however, showed a moderate or severe clinical reaction, and some of them could not survive after the challenge.
