I. W. Mclean

Antibody response of swine to repeated vaccination with formalin-inactivated, purified swine influenza virus.

Summary The antibody response of swine to second vaccination with formalin-inactivated swine influenza virus was greatly influenced by the period between vaccinations. Second vaccination at intervals of one to four weeks resulted in antibody titers and amounts progressively greater in direct relation to the length of the interval. In parallel higher antibody levels were maintained for longer periods in those animals receiving the second vaccination after the longer intervals. Considering the height of titer after the second vaccination, together with the rapid loss of antibody after the first injection, the interval between vaccinations optimum for maintenance of the highest antibody levels appeared to be about three weeks.

pH of the Chorio-allantoic Fluid of Chick Embryos Infected with Influenza Virus B.

Summary Influenza virus B (Lee strain) increases to small degree in the chorio-allantoic fluid of 11-day-old chick embryos incubated for 60 hours at 39°C after inoculation with the virus. Increase was great at 37°C and still greater at 35°C. The pH of the chorio-allantoic fluid of the same embryos descended into the acid region at 39°C; at 37° C the pH remained essentially above 7.0; and at 35°C the reaction was maintained well in the alkaline region. These relations suggest the possibility that the extent of increase of the virus in the chorio-allantoic fluid may be influenced more by the pH of the fluid at the various temperatures than by the temperature per se.