The serological differentiation of viruses in the tick-borne encephalitis subgroup by the gel-diffusion method.

A study has been made of the suitability of several modifications of the gel-diffusion test for differentiating between the various arboviruses in the tick-borne encephalitis subgroup and for obtaining indications as to the antigenic structure of these arboviruses.It was found that use of antisera and antigens in a square or hexagonal array in the gel-diffusion test allowed differentiation of the various arboviruses: related arbovirus pairs gave continuous precipitation lines, while less closely related pairs gave spurring. These phenomena could be explained on the assumption of a common precipitinogen for all members of the tick-borne encephalitis subgroup, with immunological modifications specific to the different members of the subgroup.It was further found that various other methods tested were not suitable for the differentiation of the arboviruses in this subgroup-namely, the cross-absorption of immune sera with homologous and heterologous viruses, titration of immune sera in the presence of homologous and heterologous viruses, and determination of the density of precipitation lines.