FURTHER STUDIES ON ANTIGENIC RELATIONSHIPS AMONG THE VIRUSES OF THE GROUP B TICK-BORNE COMPLEX.

This paper is a report on further studies of the antigenic relationships among viruses of the Group B tick-borne complex, carried out by the haemagglutination-inhibition (HI), complement-fixation, absorption-HI and diffusion-in-gel techniques. Earlier work has been extended to include Powassan and Negishi viruses.Comparisons of a number of strains of tick-borne viruses have revealed inter-strain variation only in the case of Omsk haemorrhagic fever virus, where two subtypes are distinguishable.This recognition of subtypes of Omsk virus has led the author to review the concept that Central European encephalitis and Russian spring-summer encephalitis viruses are distinct entities. On the basis of their close relationship, as well as new information on vectors and geographical range, she suggests that they be considered variant subtypes of one virus, designated Group B tick-borne encephalitis virus.