The immune response to viruses in calves: I. Response to Murray Valley encephalitis virus

Abstract

SummaryFollowing inoculation of Murray Valley encephalitis virus into calves there was an early transient IgM response. The appearance of IgG was only slightly later than the first appearance of IgM in three calves, and in one calf IgG was detected before IgM. The secondary response was characterized by the more rapid appearance of IgG and the virtual absence of IgM. The IgG was of the electrophoretically fast type; there was an almost insignificant amount of antibody activity in electrophoretically slow fractions. IgM and slow IgG had no complement-fixing activity. IgM and IgG showed different cross-reactions to other group B arboviruses. The different cross-reactions, and the appearance of IgG before IgM in one animal suggests that the switch-over from IgM to IgG synthesis in the response is not the result of either a total or a random proportion of cells producing IgM, changing to IgG production. The fact that the IgG was almost exclusively of fast electrophoretic mobility suggested that the virus antigenic components were strongly basic, and as this is contrary to the chromatographic properties of arboviruses, it is suggested that the virus particles must be broken down before making contact with the factors determining the type of immunoglobulin formed.