Human monoclonal antibodies to cytomegalovirus recognize viral epitopes on the surface of virus-infected cells

Abstract

Four human monoclonal antibodies directed against human cytomegalovirus were produced by fusing Sp2/HPT heteromyeloma cells with peripheral blood lymphocytes, after stimulation in vitro for 6 days. The human hybridomas have been maintained in culture for one year and secrete, when cultured in serum-free medium, between 3.1 and 8.1 μg/ml of antibodies/10⁶ cells/24 hours. HCV-1 and HCV-2 are IgG₂κ, while HCV-3 and HCV-4 are JgG₃λ. The four monoclonal antibodies immunoprecipitate a viral protein of 64 kD. Kinetic studies using indirect immunofluorescence indicate that this antigen appears late in the viral infectious cycle. All four monoclonal antibodies recognize human cytomegalovirus prototype strains AD-169, Davis and Towne, and 14 clinical isolates collected between 1984 and 1987. No reactivity was observed with other human herpesviruses. While no neutralizing activity could be observed with the human monoclonal antibodies, binding assays on unfixed infected cells showed that they recognized viral epitopes located on the cell surface membrane. These hybridomas may be useful for future therapy of immunocompromised patients.