A New Method for Concentrating Influenza Virus from Allantoic Fluid

Abstract

In a recent communication from this laboratory 1 a number of different influenza vaccines were described, and their relative antigenicity in man was compared. The highest mean post-vaccination antibody levels were obtained with those preparations which because of concentration contained the greatest amounts of virus. The concentrated virus was obtained from allantoic fluid by centrifugation at 11,000 rpm for 2 hours. In the present paper another method of virus concentration is described, together with the data showing the antigenic potency of such concentrates when given to man.

Preparation of Virus Suspensions. All of the virus suspensions used, both for concentration experiments and for testing of sera, were prepared from the allantoic fluid of eggs infected with either the PR8 strain of influenza A virus 2 or the Lee strain of influenza B virus. 3 The method of preparation used was described in the previous report on the series of vaccinations. 1

Virus titrations in mice, measurements of red cell agglutination titer, and agglutination inhibition antibody titrations in human sera were all done as described in the previous report. 1 The only change in the method was that the degree of agglutination in the red cell tests was determined by means of a photoelectric cell rather than by comparison with visual standards. In order that the antibody levels of the human sera in this series might be compared directly with those previously reported, the same standard ferret immune sera for each virus (PR8 and Lee) which had been used as controls in the former tests were again titrated. Seven duplicate titrations of each standard serum were distributed throughout the tests as a check on the uniformity of the technic.