Newcastle disease virus: virus replication in the harderian gland stimulates lacrimal IgA; the yolk sac provides early lacrimal IgG.

An indirect immunoperoxidase monolayer assay was used to measure the location of virus and class-specific antibodies to Newcastle disease virus (NDV) of chickens. The intra-ocular vaccination of chicks with the Ulster and Hitchner B1 strains of NDV resulted in the highest titre of virus being recovered from the Harderian gland (HG) at 10(6) iu/0.1 g tissue without any accompanying virus in the faeces. Maternal IgG antibody which was detected in the lacrimal fluid at 1/50 of serum levels of IgG antibody could prevent this replication. Lacrimal IgA antibody to NDV was shown to be absolutely dependent on local virus replication for its production because it reached titres of 10(3) after local intra-ocular infection compared with < 10(1.5) after two intravenous inoculations of inactivated virus. Biliary IgA, by contrast, reached 10(3.5) after either immunisation schedule. Lacrimal IgG and IgM antibody to NDV occurred at 1-9% of the titres of serum antibody to NDV after immunisation with inactivated virus or the passive transfer of NDV-immune serum between chickens. This percentage increased to 13-33% of serum titres after intra-ocular infection with NDV as if the local replication of NDV in the HG stimulated lacrimal antibody of all classes. This is the first report of NDV replication in the HG and of virus-specific IgM in the lacrimal fluid.