Virus Protein-Specific Immune Responses in Selective Depletion of Lymphocyte Populations Using Monoclonal Antibodies in Bolivian Squirrel Monkeys (Saimiri boliviensis boliviensisv).

The increasing use of immune suppressive monoclonal antibodies in the treatment of organ transplant recipients and patients with oncologic, neurological, and autoimmune diseases can lead to serious morbidity and mortality from the reactivation of viral agents that persist in humans. The squirrel monkey polyomaviruses are naturally found in Bolivian squirrel monkeys (SQM) and may be a useful model for the study of polyomavirus-associated pathogenesis and experimental treatment and prevention strategies. Two diverse groups of squirrel monkeys were given, a single dose of an anti-B cell antibody (rituximab) resulting in complete depletion of B cells (CD20+), while an anti-CD8 monoclonal antibody (7 pt-3F9) resulted in a transient depletion of CD8+ lymphocytes compared with control animals (group with no infusion with either of the monoclonal antibodies). The animals remained clinically healthy, with no pathological symptoms suggesting that the intensity and/or duration of immune suppression were inadequate to trigger pathogenic reactivation of the latent polyoma and herpes viruses. We observed a transient reduction in circulating plasma cytokines, IL-2, IFN-γ, and IL-12 reduced JC and BK viral protein-specific proliferative responses in both the CD8 and CD20 depletion groups. This study clearly elucidates the consequences of the use of depletion monoclonal antibodies in immune suppression modalities in the treatment of human malignancies and during transplantation, and SQM acts as a good model in the selection of dosage at which activation of latent viruses is at a minimum, with no pathological consequences.