ABSTRACT
Objective To analyze the mutation of PreS-S region in occult hepatitis B virus(OHBV) in HBV infected persons with positive HBsAb and investigate the biological mechanisms of the special infectious model.Methods A total of 38 HB-sAb positive OBI serum samples were amplified by Nested PCR and sequenced,HBV genotype and serotype were determined.The amino acid sequences of OHBV were compared to the corresponding sequence of wild-type strains of similar genotype obtained from the GenBank database.Results PreS-S segment of 11 samples were obtained and 8 samples were sequenced successfully.Among which,5 were genotype C and 3 were genotype B.Genotype B were all serotype adw,while genotype C were 1 adw and 4 adr.The mutation rates of PreS-S region,the immunoreactive area and the major hydrophilic region (MHR) were higher in OHBV than the wild-type strains (2.6％ vs 0.8％,x2 =40.23,3.2％ vs 0.3％,x2 =52.13,3.6％ vs 0.6％,x2 =13.25,all P＜0.01) and the substitutions of I126T,Q129R,M133T,F134I,D144E,G145K in α determinant were found in OBI samples.The mutation rate of amino acids in PreS-S region was higher in genotype C than genotype B (3.5％ vs 1.2％,x2--15.98,P＜0.01),meanwhile,the mutation rates in MHR,α determinant and immunoreactive region were higher in genotype C too,but no statistical significance was attained (4.7％ vs 1.7 ％,x2 =2.96,3.6 ％ vs 2.9％,x2 =0.25,4.1％ vs 2.3％,x2 =3.59,all P ＞0.05).Conclusion Mutations in PreS-S region,especially in immunoepitope,might change the virus'immunogenicity leading to escape from immune response and cause OBI with HBsAb positive.
ABSTRACT
Objective To assess the sequence variations in preS/S regions of occult hepatitis B virus (OHB) and their relationship to severe chronic hepatic injury. MethodsWe collected samples from HBsAg negative patients, and evaluated their HBV-DNA by nest-PCR. HBV-DNA positive samples were used for analysis of preS/S region by PCR sequencing. Results Sixty-nine cases with HBV-DNA were identified in 468 cases without HBsAg. The positive percents were 16％, 8.7％, 36.4％, 18.3％ and 0％in group of only HBcAb positive, only HBeAb positive, only HBeAg positive, both HBcAb and HBsAb positive and all indexes negative, respectively. The level of HBV-DNA of OHB was significant lower than that in HBsAg positive patients. Compared with HBsAg positive controls, preS/S deletion, M1I and Q2K in preS2 region, Q129N/R/P,G185R and S210R in S region were more common in OHB. Moreover, M1I and Q2K in preS2 region, G185R and S210R in S region in OHB with severe chronic hepatic injury were more common that those in OHB without severe chronic hepatic injury. Compared with HBsAg positive patients with severe chronic hepatic injury, the level of HBV-DNA was lower, while the frequency of M1I and Q2K mutation in preS2 region, G185R and S210R in S region were more common in OHB patients with severe chronic hepatic injury. ConclusionThe virological factors were different between OHB and HBsAg positive patients. The M1I and Q2K in preS2 region, G185R and S210R in S region might be useful for prognosis evaluation of OHB patients.