[Detection of influenza B virus antibodies in different age groups using hemagglutination inhibition tests]

Antibody levels against influenza B virus were investigated by using hemagglutination-inhibition (HA-I) tests in 402 sera obtained from different age groups. Hemagglutination antigens were obtained by production of influenza B virus (B/Singapur/LLC 6201) in trypsinized Madin Darby Bovine Kidney (MDBK) cell cultured and they were used in tests. In 355 out of 402 sera (88.3%) antibodies against influenza B virus were detected at titers varying between 1/20 and 1/1280. However in 47 sera (11.7%) no antibodies were detected at 1/20 titer. High titers of antibody (1/640-1/1280) were not detected in none of the sera obtained from an age group between 1 and 14. However high titer antibodies were detected in 15.6% of the sera from an age group between 26 and 35, in the 17.3% of the sera from a group above 50 years of age. Our findings suggest that the increase in the rates of seropositivity against influenza B virus depends on getting older and, that the infections by this virus may be widely seen in our country.