An experiment was carried out to clarify the immunogenicity of recombinant influenza virus vaccines. These vaccines were made from a virus which possessed the hemagglutinin and neuraminidase antigens of current epidemic wild-type influenza A [H3N2] virus and the high virusyielding capacity of egg-adapted A/PR/8/34 [H0N1] virus.
The potency of the vaccines was assayed by the antigen-extinction test, in which the minimal dose capable of eliciting neutralizing antibody responses in mice was determined. This test revealed that recombinant vaccines labelled with KIX-1, KIX-4, KIX-7 and KIX-16 had nearly the same potency as the respective wild-type parental virus vaccines; that is, A/Kumamoto/5/72, A/Aichi/2/68, A/Tokyo/6/73 and A/Kumamoto/22/76, respectively. The equivalent antigen content was measured by the CCA test.
The response of hemagglutination-inhibition (HAI) and neuraminidase-inhibition (NAI) antibodies was studied by injecting intramuscularly with the vaccines into rabbits. The recombinant vaccine was slightly superior or equal to the parental virus vaccine in immunogenic capacity. Its superiority, however, became significant after the second injection was given 28 days later. The response of HAI and NAI antibodies of mice was assayed by intraperitoneal injection with fivefold graded dilutions of the vaccines. When lower dilutions were inoculated, there was a tendency for the recombinant vaccine to produce a higher antibody titer than for the parental virus vaccine. When higher dilutions were inoculated, a detectable amount of antibodies was produced, whereas the same dilutions of the parental virus vaccine failed to produce antibodies.
Forty-eight healthy adult subjects were injected subcutaneously with two doses of 0.5ml each of KIX-16 or A/Kumamoto/22/76 vaccine at 7 days' interval. The rise in mean titers of HAI and NAI antibodies between day 0 and day 42 was slightly higher with KIX-16 vaccine than with A/Kumamoto/22/76 vaccine, but essentially the same number of subjects showed a fourfold or greater increase in each antibody titer, regardless of the type of vaccine. The two vaccines were less potent in man in eliciting antibody against neuraminidase than against hemagglutinin, although they were quite effective in mice in inducing not only HAI but NAI antibody.
The results strongly indicate that the recombinant vaccine is at least as effective as a con ventional wild-type virus vaccine in manifesting immunogenicity in man and laboratory animals.

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The proteins of Salmonella phage P22 were extracted with acetic acid and fractionated on a DEAE-cellulose column. The fractionated proteins were named Fraction 1 (F1), Fraction 2 (F2) and Fraction 3 (F3). F3 protein was suggested to be a main component related to the production of antibody. It was investigated for biochemical characteristics.
1. When P22 protein (P22P) was fractionated on a DEAE-cellulose column with 0.001-0.02M phosphate buffer, a large yield was obtained after the pH of the sample was regulated with 0.001M phosphate buffer before fractionation.
2. The isolated F3 fraction was treated with trypsin and developed by two-dimensional paper chromatography. Sixteen peptides were detected with ninhydrin solution.
3. The N-terminal amino acid sequence of the fraction was determined by the dansyl method. It was suggested that the N-terminal might be the Val-Val or Val-Ile sequence.
4. After citraconylation and tryptic digestion, the fraction was applied to Dowex 50X2 with pyridinium acetate buffer. By the fluorescamine method 9-18 peaks were detected. With 10 of these peaks the N-terminal sequence was determined by the dansyl method.

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