Immunoglobulins Produced in Response to Japanese Encephalitis Virus Infections of Man

Abstract

Thirty serum specimens were collected at intervals over the course of illness and during convalescence from six human cases of infection with Japanese encephalitis virus diagnosed by serologic tests. These sera were fractionated by gel filtration on Sephadex G 200 and the antibody activities present in the various fractions were determined. HI and neutralizing antibody activities occurred in both IgM and IgG classes of immunoglobulins, but CF activity was present only in the IgG class. These findings would explain why HI and neutralizing antibodies appear earlier in the course of infection than do CF antibodies. The time at which antibody initially appeared in the IgG serum fractions differed between individual patients, and ranged from the first week to the fifth week after onset of infection. A relatively high proportion of the total antibody was found in IgM fractions in sera taken 4 weeks after onset, and some IgM was present as late as 6 months after onset. CF antibody (representing IgG) was shown to appear early in the course of infection in patients with a previous history of JE vaccination and in some older patients who might have experienced prior JE infection; this was considered to indicate a secondary antibody response to the JE virus.