Ether-treated, subunit Hsw1N1 influenza vaccines: response of immunologically primed subjects to two antigenic variants.

Two bivalent, ether-treated, subunit influenza vaccines were compared in adults greater than or equal to 45 years old. Both vaccines contained 200 chick cell-agglutinating (CCA) units of A/Victoria/3/75 antigen/dose. The Hsw1N1 components, also at a level of 200 CCA units/dose and designated A/Shope and A/X-53, were antigenically representative of the A/swine/1976/31 and A/New Jersey/8/76 viruses, respectively. A/Shope virus possessed about 100 times more neuraminidase activity than A/X-53 virus. The two vaccine groups had equivalent geometric mean titers (GMTs) of antibody to A/NJ virus, with about 95% of each group having titers of greater than or equal to 1:40 after vaccination. Group GMTs of antibody to A/Vic virus were also equivalent. Failure of the A/X-53 vaccinees to respond according to the dogma of original antigenic sin and a highly significant between-group difference in response to A/PR/8/34 antigen are interpreted as due to a difference in vaccine neuraminidase levels. It is suggested that, although A/Shope was as serologically effective against A/NJ virus as A/X-53 in this age group, under similar conditions a recombinant with the A/NJ hemagglutinin and the stable A/swine neuraminidase antigens might be more effective against A/NJ than either of the present vaccines.

Automated procedure for measuring antigenicity of extracted and intact influenza virus.

An automated serum-blocking (S-B) technique was developed in an attempt to find an in vitro test for the determination of the antigenicity of extracted influenza vaccines. The S-B test depends on the ability of an antigen to combine with (or block) specific (in this case, hemagglutination-inhibiting) antibodies. After mixing the test virus with a constant amount of specific antiserum and hemagglutinating virus in an Auto Analyzer, chicken erythrocytes were pumped into the system and the mixture was incubated by passing through coils. The hemagglutinated cells were removed and the residual cells were lysed. The optical density was read and recorded automatically. The S-B test was much more reproducible than the chicken cell agglutination (CCA) test. There was good correlation between the S-B and CCA titers of intact influenza virus, but not of ether-extracted influenza virus. The CCA titer of influenza strains of type A was reduced significantly during ether-extraction. The S-B titers indicated that there was no significant loss in specific antigenicity when influenza strains of types A and B were extracted with ether and Tween-80 according to the described procedure. The S-B test seemed to be a true measurement of the total antigens present in influenza vaccines.

Induction of an inhibitor of influenza virus hemagglutination by treatment of serum with periodate.

Serum is commonly treated with potassium periodate to destroy nonspecific inhibitors of influenza virus hemagglutination. We have observed, however, that such treatment of serum without pre-existing inhibitor produced high titers of inhibitor against certain strains of influenza virus. Inhibitor was induced in the serum from several different animal species but not in hamster or mouse serum. Periodate treatment of serum albumin, fraction V, from several animals, including man, creates this inhibitor. Our data indicate that the inhibitor induced in the serum of various animal species differs in its mechanism of induction and in its resistance to receptor-destroying enzyme and trypsin. Hemagglutination by B/Singapore/3/64, B/Colorado/2/65, B/Georgia/1/65, and B/Massachusetts/3/66 strains of influenza virus is inhibited by periodate-treated human serum at dilutions as high as 1:5,120. The routine use of periodate treatment of serum in diagnostic and surveillance studies of influenza virus infections is not recommended.

Preservation of influenza virus infectivity by lyophilization.

A method of lyophilizing influenza virus in allantoic fluid with retention of high-titer of egg infectivity is described. Five strains of virus were lyophilized, and all were much more stable than fluid virus preparations, retaining 2 to 3 logs of infectivity after storage at 37 C for 60 to 95 days. Statistical analysis of an accelerated storage test by extrapolation of viral degradation indicates that the lyophilized viruses are stable indefinitely at or below room temperature.

Inactivation of adenovirus and simian virus 40 tumorigenicity in hamsters by vaccine processing methods.

The effectiveness of the adenovirus vaccine inactivation process in destroying the tumorigenic potential for hamsters of adenoviruses, simian virus 40 (SV-40), and adenovirus-SV-40 hybrids was studied. Baby hamsters injected with untreated virus and with samples subjected to the complete inactivation process and to portions of the process were observed for tumor development for periods in excess of 300 days. Over 20,000 hamsters were injected. From 1 to 7 hr of exposure to formaldehyde at a concentration of 0.031 m at 37 C was sufficient to destroy the tumorigenicity observed in the nontreated preparations. Since the inactivation process included 48 hr of exposure at 37 C to 0.031 m formaldehyde plus treatment with ultraviolet (UV) and with beta-propiolactone (BPL), it was concluded that the process has a large margin of safety. Adenovirus isolates free from tumorigenic potential are difficult, if not impossible, to obtain. Therefore, a proven inactivation process appears to provide the best assurance for obtaining adenovirus vaccines free from such potential. Data presented suggest that the tumorigenic property of the viruses studied might be independent of the infectivity of the preparation. The tumorigenic property was found to be highly susceptible to formaldehyde, but less sensitive to BPL or UV treatment. In contrast, treatment with UV or BPL decreased viral infectivity more readily than tumorigenicity. The three-stage inactivation process (formaldehyde, UV, and BPL) inactivated both tumorigenicity and infectivity.