Effects of immunization with the p12 proteins of LP-BM5 defective and ecotropic viruses on development of MAIDS

Delayed progression of murine AIDS in C57BL/6 mice pre-immunized with a highly antigenic 10-mer peptide encoded by the murine AIDS defective virus gag p12 gene

C57BL/6 (B6) mice were immunized with a highly antigenic 10-mer peptide (P12-10), which is encoded by the murine AIDS (MAIDS) defective virus gag p12 gene, emulsified in incomplete Freund's adjuvant (ICFA). One week later, the mice were inoculated with the MAIDS virus to see if the immunization affects progression of MAIDS. It was demonstrated that the immunization significantly delayed progression of MAIDS, although it failed to induce appreciable cytotoxic T lymphocyte (CTL) responses against the P12-10 antigen. In contrast, immunization of B6 mice with the P12-10 coupled with liposome induced substantial CTL responses but failed to protect the mice against MAIDS development. This segregation between CTL activity and in vivo protection efficacy might be worth considering when we exploit vaccines for augmenting cellular immunity mediated by CD8+ T cells.

Retrovirus-induced lymphoproliferative disease in mice: role of humoral immunity in perinatally exposed mice

The mice born to female mice infected with LP-BM5 MuLV, the etiologic agent for lymphoproliferative disease and nursed for 4-6 weeks by them were less susceptible upon reinfection by i.v. transfusion of blood or plasma from infected donors with fully developed disease. Sera of 7 week or older perinatally exposed mice were capable of a complete in vitro neutralization of virus in plasma or blood from mice with fully developed disease. In contrast, sera from 3-week old perinatally exposed mice were ineffective. The neutralizing ability of the sera was drastically reduced or abrogated after their absorption with anti-mouse IgM. These observations are consistent with the notion that perinatally exposure results ina moderate form of the disease of the offspring. This perinatal infection is followed by a production of neutralizing antibodies of predominantly the IgM class that significantly alters the course of the lymphoproliferative disease and, in some instances, even prevents its development.

The significance of the pre-challenge immune status of mice for development of retrovirus-induced immunodeficiency syndrome (MAIDS)

The effects of vaccination with RNA-free viral pseudoparticles, preinfection with non-pathogenic ecotropic virus, and induction of tolerance to viral proteins in newborns on the outcome of murine immunodeficiency syndrome (MAIDS) were studied. The parameters used to follow disease progression were: lymphopenia, circulating B and T8 cells, serum IgG and IgM levels, lymphoproliferation and skin graft rejection. Immunization with RNA-free viral pseudoparticles had no effect on any of these parameters. Preinfection of adults with ecotropic virus and the induction of tolerance in newborns to virus antigens both attenuated the early symptoms of viral infection and delayed the onset of immunodeficiency and lymphoproliferation in some mice, but did not significantly alter the number of deaths due to MAIDS. Failure of immune-based therapy to produce successful protection against MAIDS suggests that immune destruction caused by the persistent virus rather than hyperimmune activity is the main pathogenic factor in this disease.