Two neutralizing human anti-RSV antibodies: Cloning, expression, and characterization

Background: Respiratory syncytial virus (RSV) infection is a major problem in the newborn and aging populations. Fully human monoclonal antibodies with the ability to neutralize RSV could have a major impact on the immunotherapy of the disease. The generation of human antibodies has been difficult because there exists no general way to activate B cells against an antigen of choice in vitro. Materials and Methods: Human spleen cells from individuals exposed to RSV were used to repopulate SCID mice. Hu-SCID mice were boosted with RSV fusion (F)protein and subsequently developed B cell tumors. The tumors were removed and cultured and subcloned in vitro, using a feeder layer of CD154-expressing T cells. Two of these tumors produced the antibodies designated RF-1 and RF-2. VL genes were isolated by standard PCR techniques, however, it was necessary to use high-temperature reverse transcriptase to clone the VH genes. Results: RF-1 and RF-2 VH genes were both found to be closely related members of the VH2 family. Vk genes originated from the VI( III family. RF-1 and RF-2 recombinant antibodies expressed in CHO cells (cRF-1 and cRF-2) were found to have affinities for RSV F-protein of 0.1 nM and 0.07 nM, respectively, and both were able to neutralize several A and B subtypes of RSV. Conclusion: The technique of immortalizing human B lymphocytes, by passage in sCID mice and expression as recombinant antibodies in CHO cells, provides a method by which high-affinity human antibodies can be developed for immunotherapy of viral diseases.