OBJECTIVE: To estimate the characteristics of complementarity determining regions (CDRs) in immunoglobulin (Ig) gene which are essential to interact with variable epitopes of HIV-1 proteins. METHODS: Using the data base DDBJ we analyzed CDRs in human and rodent Ig genes by the purine (u)/pyrimidine (y) 6-mers [uuyuuy], which are most variable in the HIV-1 genome (Doi, H., Proc. Natl. Acad. Sci. USA, 1991, 88, 9282-9286), and their complementary 6-mers [uyyuyy]. RESULTS: TABULAR DATA, SEE ABSTRACT VOLUME. The 6-mers [uuyuuy] and/or [uyyuyy] characteristically and differently appeared between in human and rodent Ig genes or in each CDRs of H-chain and L-chain. They most frequently appeared (87.7%) in CDR3 of human H-chain, but infrequently in CDR2 of human H-chain (29.6%). In contrast, they frequently appeared in CDR2 of rodent L-chain (81.3%), and infrequently in CDR1 of rodent H-chain (30.9%). Codon frames in the 6-mers also differed between the two species. DISCUSSION AND CONCLUSIONS: The characteristics of CDRs are different between in human and in rodents Ig. The results suggest that chimeric anti-HIV antibodies having CDRs from rodents would not effectively operate or would cause any side effect in human because of idiotype network.

Animal Base Sequence Epitopes/IMMUNOLOGY *Genes, Immunoglobulin Genome, Viral Human HIV Antibodies/*BIOSYNTHESIS/GENETICS HIV-1/*GENETICS/*IMMUNOLOGY Immunoglobulins, Heavy-Chain/BIOSYNTHESIS/GENETICS Immunoglobulins, Light-Chain/BIOSYNTHESIS/GENETICS Rodentia *Variation (Genetics) ABSTRACT

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