Detection Of Lamivudine-resistant HBV YMDD Mutants And Investigation Of Factors On Clinical Treatment With Lamivudine Correlated With Development Of HBV YMDD Mutants

Objective: To detect lamivudine-resistant HBV YMDD mutants in patients with CHB who were treated with lamivudine and investigate factors on clinical treatment with lamivudine correlated with development of HBV YMDD mutants such as the period of lamivudine monotherapy and the project of applying lamivudine(only using lamivudine or combination with lamivudine and interferon or not using lamivudine). Methods: Draw HBV DNA from serum of CHB patients, amplified the 3 00 - 790 nucleoside of HBV DNA polymerase gene which include YMDD motif, cleaved PCR products with restriction endonuclease which is specific to mutation site, cleaved fragments were analysed by 6% polypropylene acidemide gel electrophoresis and HBV YMDD mutants were identified by PCR restrction fragment length polymophism. Results: In the total 152 patients with CHB, 45 cases HBV YMDD mutants were found, the total mutations rates were 29.6%. in 72 cases who received lamivudine monotherapy, 41 cases who received combination therapy with lamivudine / IFN-a and 39 cases who were not treated with lamivudine, the figure of cases of HBV YMDD mutation occurring were respectively 34 cases, 8 cases and 3 cases; the rates of HBV YMDD mutations were respectively 47.2%, 19.5% and 7.7%. Furtherly , in 72 cases who received lamivudine monotherapy, the periods of applying lamivudine in 36 cases, 20 cases and 16 cases were repectively from 2 weeks to 6 months, 7 months to 12 months ,13 months to 27 months, the figure of the cases who were observed with HBV YMDD mutants were respectively 9 cases, 11 cases and 14 cases; the rates of HBV YMDD mutations were respectively 25%, 55% and 87.5%. the rate of HBV YMDD mutations in the lamivudine monotherapy group was significantly higher than that in the not using lamivudine group and in the combination treatment group respectively(47.2% vs 7.7%,19.5%,P<0.01); but there was no significant difference between the rate of HBV YMDD mutations in the not using lamivudine group and the combination treatment group(x2=2.35, P>0.05). the rate of HBV YMDD mutations in the 13m-27m group of lamivudine monotherapy was significantly higher than that in the 2w-6m group and 7m - 12m group of lamivudine monotherapy respectively(87.5% vs 25%, 55%,P<0.05), the rate of HBV YMDD mutations in the 7m - 12m group of lamivudine monotherapy was significantly higher than that in the 2w -6m group of lamivudine monotherapy(55% vs 25%,P<0.05), with the period of lamivudine monotherapy being prolonged, the rate of HBV YMDD mutations increase and were 25%, 55%, 87.5%, respectively. Conclusion: The therapy with lamivudine may result in the development of HBV YMDD mutants and the prolonged lamivudine therapy would increase the incidence of HBV YMDD mutants, while combination therapy with lamivudine and IFN-a would delay the development of HBV YMDD mutants, the gender, age and nation of patients with CHB were not correlated with the rates of HBV YMDD mutations; it was predicted that HBV YMDD mutants may exist before lamivudine therapy or occur naturally; it was also predicted that the mutation outside the YMDD motif may contribute to clinical viral resistance to lamivudine.