结核分枝杆菌抗原Lppx和MT0322人T细胞抗原表位的多态性研究

Investigation on Human T Cell Eitopes Polymorphisms of Antigens Lppx and MT0322 in Mycobacterium Tuberculosis

目的探讨中国结核分枝杆菌抗原Lppx和MT0322的多态性及对其T细胞抗原表位的影响。方法选取中国多省的173株临床分离株,采用L-J培养基对菌株进行培养,PCR扩增Lppx和MT0322基因序列,Bioedit软件进行比对,比较其T细胞抗原表位区与非表位区的多态性。最后用Mega5软件分别计算同义突变率(d S)和非同义突变率(d N)及其比值。结果在173株菌株中,基因Lppx表现为4个非同义突变和1个同义突变位点,基因MT0322出现了3个非同义突变和1个同义突变位点。其中,有9株菌在Lppx152位的氨基酸和在MT0322的159位分别发生了1个同义突变和1个非同义突变,表现较高的多态性。Lppx有15个T细胞抗原表位中有6个发生了改变,而在MT0322中,2个表位中有1个发生了1个氨基酸的改变。Lppx的d N/d S值为0.19,MT0322的d N/d S值达到了3.69。MT0322的表位区的d N/d S值高于非表位区。结论结核分枝杆菌基因Lppx和MT0322序列具有多态性,并可能反映了这两个抗原参与了逃避宿主免疫的分化选择。

Objective To study polymorphisms of antigens Lppx and MT0322 in mycobacterium tuberculosis and the effect on T cell epitopes of these two genes. Methods We selected 173 strains from China, cultured them by L - J medium and amplified gene se- quences of antigens Lppx and MT0322 by PCR. The sequences were compared and sliced by Bioedit and the dN/dS values were calculated by MEGA5. Results Among 173 strains, there were four nonsynonymous mutations and one synonymous mutation in Lppx, while MT0322 had three nonsynonymous mutations and one synonymous mutation. Nine strains presented higher polymorphism at position 152 in Lppx and pnstion 159 in MT0322. Six of 15 epitopes contained in Lppx and one of two epitopes of MT0322 were altered. The dN/dS value of Lppx was 0. 19, while dN/dS value of MT0322 reached to 3.69. In MT0322, the dN/dS value of the epitope region was higher than that in the non - epitope region. Conclusion The gene sequences of Lppx and MT0322 contain genetic diversity, which may reflect that the antigens are involved in diversifying selection to evade host immunity.