Simple serological diagnosis of arboviruses: a simplified diluent system for Japanese encephalitis virus hemagglutination-inhibition tests using formalinized chick erythrocytes.

Formalinized chick erythrocytes agglutinated with Japanese encephalitis virus antigens over a wider range of pH (6.0-7.2) than fresh erythrocytes (pH 6.4-6.8). The virus antigens were unstable below pH 7.0 and therefore the use of the formalinized erythrocytes made it possible for a one-diluent system of the hemagglutination-inhibition tests to be used. In these tests phosphate-buffered saline at pH 7.0 was used throughout as a diluent for serum, antigen and erythrocytes, although the conventional system, using fresh erythrocytes, requires two buffers of different pHs, one an alkaline diluent for serum and antigen and the other an acidic diluent for erythrocytes.