Human monoclonal antibodies isolated from spontaneous Epstein-Barr virus-transformed tumors of Hu-SPL-SCID mice and specific for fusion protein display broad neutralizing activity toward respiratory syncytial virus

Two human monoclonal antibodies, RF-1 and RF-2, specifically recognize the fusion protein of the human respiratory syncytial virus (RSV), These were i solated from spontaneous tumors in SCID mice reconstituted with human splen ocytes and boosted with fusion protein. The tumors consisted of Epstein-Bar r virus-transformed human B cells in animals with antigen-specific antibody titers >10(5). The binding affinity of RF-1 and RF-2 to the fusion protein is 10(10) and 10(9) M-1, respectively. The antibodies bind specifically to a conformational epitope of the fusion protein on RSV-infected HEp-2 cells , Both antibodies display virus-neutralizing properties in vitro at concent rations varying between 8 and 1000 ng/mL, Virus neutralization applies to a broad variety of wild and laboratory-adapted virus strains belonging to bo th virus types A and B, These antibodies are potential candidates for passi ve immunotherapy of severe RSV infections.