Gene polymorphisms of esxA, esxH and fbpB in clinical Mycobacterium tuberculosis isolates from tuberculosis children / 第三军医大学学报

ABSTRACT

Objective To sequence the antigen-encoding genes esxA,fbpB and Rv2660c from clinical isolates of Mycobacterium tuberculosis (MTB) in tuberculosis children and study the polymorphisms.Methods A total of 135 isolated strains were amplified for gene sequences of esxA,fbpB and Rv2660c by PCR,and the products were sequenced respectively.The results of sequencing were compared with the corresponding gene sequences of standard strain H37Rv and human T and B cell epitope sequences from immune epitope database (IEDB).The genetic diversities of the gene sequences of esxA,fbpB and Rv2660c were analyzed.Results Among the 135 strains,no gene polymorphisms were found in esxA and Rv2660c.But fbpB had genetic diversities in 66 clinical isolates (48.89％).The 5 single nucleotide polymorphism (SNP) mutations in fbpB affected 8 (14.81％) T cell epitopes and 9 (24.32％) B cell epitopes.The dN and dS values of whole fbpB gene were 0.000 120 and 0.002 126,respectively.The dN and dS values of T epitopes areas were 0.000 067 and 0.002 382 respectively,those of non-T epitopes area were 0.000 408 and 0.000 470,respectively,those of B epitopes areas were 0.000 063 and 0.00 2380,and those of non-B epitopes areas were 0.Conclusion The gene sequences of esxA and Rv2660c are conservative,and that of fbpB contains genetic diversities.Its polymorphisms may influence the function of antigen Ag85B,and thus affect the efficacy of vaccine H56.