Estimation of heterokaryon formation and hybridoma growth in murine and human cell fusions

Cephalin as an efficient fusogen in hybridoma technology: can it replace poly ethylene glycol?

In this study we set up a simple, fast, and highly efficient protocol to fuse cells and produce human hybridoma using non-toxic cephalin as a fusogenic lipid. We compared our proposed method with PEG-mediated fusion, the well-known conventional method. Human lymphoblastoid cells were fused with an F3B6 heteromyeloma cell line using cephalin or PEG as the fusogenic compound. The viability of the cells and their fusion rate were determined microscopically and hybridoma (antigen-specific and non-specific) production yield was calculated following HAT selection and screening. The fusion rates of cells in cephalin and PEG-mediated methods were comparable (25.9+/-5.73% versus 27.3+/-6.07%) while the viability of the cells immediately and after overnight incubation was obviously greater in the cephalin method than in the PEG (p<0.001). Our proposed cephalin-mediated cell fusion method is about five times more efficient than PEG in production of hybridoma clones; thus it may dismiss PEG as the most generalized fusogen in the future.

Human anti-anthrax protective antigen neutralizing monoclonal antibodies derived from donors vaccinated with anthrax vaccine adsorbed

BACKGROUND: Potent anthrax toxin neutralizing human monoclonal antibodies were generated from peripheral blood lymphocytes obtained from Anthrax Vaccine Adsorbed (AVA) immune donors. The anti-anthrax toxin human monoclonal antibodies were evaluated for neutralization of anthrax lethal toxin in vivo in the Fisher 344 rat bolus toxin challenge model. METHODS: Human peripheral blood lymphocytes from AVA immunized donors were engrafted into severe combined immunodeficient (SCID) mice. Vaccination with anthrax protective antigen and lethal factor produced a significant increase in antigen specific human IgG in the mouse serum. The antibody producing lymphocytes were immortalized by hybridoma formation. The genes encoding the protective antibodies were rescued and stable cell lines expressing full-length human immunoglobulin were established. The antibodies were characterized by; (1) surface plasmon resonance; (2) inhibition of toxin in an in vitro mouse macrophage cell line protection assay and (3) in vivo in a Fischer 344 bolus lethal toxin challenge model. RESULTS: The range of antibodies generated were diverse with evidence of extensive hyper mutation, and all were of very high affinity for PA83~1 x 10-10-11M. Moreover all the antibodies were potent inhibitors of anthrax lethal toxin in vitro. A single IV dose of AVP-21D9 or AVP-22G12 was found to confer full protection with as little as 0.5x (AVP-21D9) and 1x (AVP-22G12) molar equivalence relative to the anthrax toxin in the rat challenge prophylaxis model. CONCLUSION: Here we describe a powerful technology to capture the recall antibody response to AVA vaccination and provide detailed molecular characterization of the protective human monoclonal antibodies. AVP-21D9, AVP-22G12 and AVP-1C6 protect rats from anthrax lethal toxin at low dose. Aglycosylated versions of the most potent antibodies are also protective in vivo, suggesting that lethal toxin neutralization is not Fc effector mediated. The protective effect of AVP-21D9 persists for at least one week in rats. These potent fully human anti-PA toxin-neutralizing antibodies are attractive candidates for prophylaxis and/or treatment against Anthrax Class A bioterrorism toxins.