The human antibody response to porcine xenoantigens is encoded by IGHV3-11and IGHV3-74 IgV(H) germline progenitors

Preformed and induced Ab responses present a major immunological barrier to the use of pig organs for human xenotransplantation, We generated IgM and IgG gene libraries established from lymphocytes of patients treated with a bioartificial liver (BAL) containing pig hepatocytes and used these librari es to identify IgV(H) genes that encode human Ab responses to pig xenoantig ens. Genes encoded by the V(H)3 family are increased in expression in patie nts following BAL treatment. cDNA libraries representing the V(H)3 gene fam ily were generated, and the relative frequency of expression of genes used to encode the Ab response was determined at days 0, 10, and 21, Ig genes de rived from the IGHV3-11 and IGHV3-74 germline progenitors increase in frequ ency post-Brit. The IGHV3-11 gene encodes 12% of V(H)3 cDNA clones expresse d as Igh I Abs at day 0 and 32.4-39.0% of cDNA clones encoding IgM Abs in t wo patients at day 10, IGHV3-11 and IGHV3-74 genes encoding IgM Abs in thes e patients are expressed without evidence of somatic mutation. By day 21, a n isotype switch occurs and 1GHV3-11 IgV(H) progenitors encode IgG Abs that demonstrate somatic mutation. We cloned these genes into a phagemid vector , expressed these clones as single-chain Abs, and demonstrated that the IGH V3-11 gene encodes Abs with the ability to bind to the gal alpha (1,3) gal epitope, Our results demonstrate that the senoantibody response in humans i s encoded by IgV(H) genes restricted to 1GHV3-11 and IGHV3-74 germline prog enitors. IgM Abs are expressed in germline configuration and IgG Abs demons trate somatic mutations by day 21.