[Slowly-sedimenting hemagglutinin of the tick-borne encephalitis virus].

Ring-shaped particles of 5-10 mm in diameter considered by research workers to be a slowly-sedimenting hemagglutinin (SSHA) of flaviviruses (an antigen immunologically related to virions) were detected in the precipitation band formed in immunoelectrophoresis by the non-virion ("soluble") antigen but not in the precipitation band formed by the virion antigen. The slowly sedimenting (SS) virions of tick-borne encephalitis virus previously found in a SSHA fraction did not differ in the set of structural proteins from virions of the main population (rapidly sedimenting). It is concluded from the foregoing that the hemagglutinating activity of the SS-structures is realized not by a hypothetic SSHA ("natural" ring-shaped fragment of virion envelope, precursor or a by-product of virus morphogenesis, according to other workers) but by SS-virus particles.