Antibody mediated suppression of secondary IgM response in nude mice against vesicular stomatitis virus

Nude mice immunized with either of the two serotypes of vesicular stomatitis virus (VSV), VSV Indiana (VSV-Ind) or VSV-New Jersey (VSV-NJ), showed an early T cell independent immunoglobulin (Ig) M antibody response comparable with normal euthymic mice. Unlike euthymic mice, however, nude mice reinjected with the homologous serotype were unable to mount a second measurable serum neutralizing (SN) antibody response; a second injection with the heterologous serotype induced a normal primary type of SN antibody response. The serotype-specific refractoriness to a second challenge recovered at about 10 wk after primary infection. When antibody responses were assayed by enzyme-linked immunoabsorbent assay (ELISA), suppressive effects by previous immunization could be observed even after challenge with the heterologous serotypes; this finding probably reflects the known existence of common nonneutralizing determinants shared between the two serotypes. A weak 2-mercaptoethanol (2-ME)-resistant anti-VSV IgG SN antibody response was noticed during the primary response in nude mice and was also found in ELISA; after second infections, this 2-ME-resistant response did not develop. Serum transfer studies in nude and +/+ mice confirmed that the serotype-specific transitory refractoriness of a second response in nude mice was mediated through the anti-VSV-specific IgM antibodies.