A theoretical analysis of codon adaptation index of the Boophilus microplus bm86 gene directed to the optimization of a DNA vaccine

DNA vaccines utilize host cell molecules for gene transcription and translation to proteins, and the interspecific difference of codon usage is one of the major obstacles for effective induction of specific and strong immune response. In an attempt to improve codon usage effects of DNA vaccine on protein expression, a quantitative study was conducted to clarify the relationship of codon usage in the tick gene bm86 and its potential expression in bovine cells. The calculated relative synonymous codon usage (RSCU) and codon adaptation index (CAI) values of bm86 from Boophilus microplus and a set of 14 highly expressed genes from Bos taurus indicated that some codons utilized frequently in bm86 are rarely used in B. taurus genes and vice versa. The different translational efficiencies obtained suggested that after DNA vaccination using the wild bm86 gene, the protein Bm86 would be expressed in bovines, but it would not be the optimum sequence. However, using the codon-optimized bm86 gene to bovines, whose sequence was theoretically designed, would probably improve the level of the immune response generated against ticks.