Immunoglobulin transfer from immune-reconstituted SCID mice to nursing neonates: blood distribution of antibody and association with perinatal virus protection.

ABSTRACT

Previous work in our laboratory has shown that fetal protection from maternal transmission of the murine lactate dehydrogenase-elevating virus (LDV) infection is mediated by adoptive transfer of maternal anti-viral immunity. In the present report, we have characterized reconstitution of immunity in immunodeficient SCID mice following transplantation with BALB/c spleen cells, and studied the fate and distribution of maternally-derived antibodies after passage to neonatal SCID mice by nursing. Immune-reconstituted SCID mice maintained stable immunity for up to 7 months post-transplantation, during which time they produced nonneutralizing IgG anti-LDV antibodies and protected their offspring from maternally-derived LDV infection. Using IgG isotype and allotype assays, it was found that maternal IgG antibodies transferred from breast milk to nursing neonatal mice and appeared in their circulation. Weaning of SCID mice from immunocompetent mothers permitted the determination of blood immunoglobulin isotype half-lives (3.6-10.6 days) in the absence of endogenous antibody production. LDV infection was transferred to nursing mice by nonimmune LDV-infected mothers, but protection from nursing-acquired LDV infection was associated with maternal viral immunity, breast milk transfer of IgG anti-LDV to nursing mice, and reduced breast milk virus titers. These findings show a nursing pathway for LDV infection, and demonstrate the potential of immune protection from this infection pathway.