G. C. Schild

INTERFERON INDUCTION AND INCREASED NATURAL KILLER-CELL ACTIVITY IN INFLUENZA INFECTIONS IN MAN

Abstract Influenza infection increased the level of natural killer-cell activity in association with induction of interferon. The severity of symptoms and signs of illness correlated with virus shedding, induction of interferon, and enhancement of natural killer-cell activity in a double-blind study in volunteers who received A/Munich/1/79 (H1N1) virus.

THE HONG KONG/68 INFLUENZA A2 VARIANT

Abstract A new influenza variant has been associated with an extensive outbreak of influenza in Hong Kong during July, 1968. Representative isolates have been classified in the A2 subtype because of antigenic overlapping with previous human A2 strains. However, their behaviour under laboratory conditions, reciprocal haemagglutination-inhibition reactions with other influenza-A-virus strains, and measurements of immunological responses all support the conclusion that the haemagglutinin of Hong Kong/68 variants has undergone considerable antigenic change from that of earlier A2 influenza strains. The neuraminidase of the new variants was similar to that of 1964 and 1967 strains of A2 virus.

Prevalence of Antibody to Current Influenza Viruses and Effect of Vaccination on Antibody Response

The extent of antibody to the influenza virus A/Hong Kong/68 (H3N2) after four years of prevalence was investigated in Britain and in the U.S.A. The results indicated a high incidence in both populations. The prevalence of antibody to a variant A/England/42/72 (H3N2) which has been causing epidemics of influenza in the southern hemisphere during the middle months of 1972 was also investigated. The differences reflect the shift in antigenic content of this variant, and although the overall proportion of the sera with antibody at > 1/40 was 37%, some age groups had an incidence of only 20% or less with antibody at this level. A commercial inactivated A/Hong Kong/68 influenza vaccine was given to a group of volunteers in Britain to see how effective it might be in stimulating antibody to the variant A/England/42/72. The antibody responses were better than expected from earlier vaccine studies, and 63% of the vaccinees developed antibody to the A/England/42/72 to levels thought likely to be protective. This suggested that until a vaccine made with the variant A/England/42/72 becomes available the present A/Hong Kong/68 vaccine would be of use to protect those at special risk this winter.

Antigenic Variants of Influenza B Virus

From 1967 to 1971 little antigenic variation was detected in the prevalent influenza B viruses but in December 1972 a new antigenic variant of influenza B was isolated in Hong Kong from sporadic cases of influenza. The new variant, B/Hong Kong/5/72, possessed a haemagglutinin antigen which showed considerable antigenic differences from that of former influenza B strains while its neuraminidase antigen was closely related to that of the earlier, 1967-71, isolates. The B/Hong Kong/5/72 variant became the predominant influenza B strain in the United Kingdom by early summer 1973, and in both the United Kingdom and Japan this strain was associated with outbreaks of influenza. Strains antigenically intermediate between the 1967-71 isolates and B/Hong Kong/5/72 were isolated in a number of countries, often concurrently with B/Hong Kong/5/72-like strains. Serological studies indicated that antibody to B/Hong Kong/5/72 was infrequent in the populations in the United Kingdom and the U.S.A., suggesting the possibility of future epidemic activity associated with the new variant. In addition, conventional inactivated influenza vaccines containing the older influenza B isolates given to volunteers stimulated poor antibody responses to B/Hong Kong/5/72 virus. These studies indicate the desirability of immunizing high risk patients against B/Hong Kong/5/72-like viruses before the coming influenza season. Vaccine containing the new variant influenza B strain are currently available in the United Kingdom.

THERAPEUTIC EFFECT OF 1-ADAMANTANAMINE HYDROCHLORIDE IN NATURALLY OCCURRING INFLUENZA A2/HONG KONG INFECTION: A Controlled Double-blind Study

Abstract The therapeutic activity of 1-adamant-anamine hydrochloride (amantadine) was investigated in a double-blind study of patients with clinically and serologically confirmed influenza A 2 /Hong Kong/68 infections who continued to live in their normal domestic environment. There was a significant reduction (P