Datta Sibnarayan, Banerjee Arup, Chandra Partha K, Chakraborty Subhasis, Basu Subir Kumar, Chakravarty Runu
ICMR Virus Unit, Kolkata, ID and BG Hospital Campus, Kolkata, West Bengal, India.
J Clin Virol. 2007 Nov;40(3):255-8. doi: 10.1016/j.jcv.2007.08.003. Epub 2007 Sep 14.
In blood donors, HBV infection is detected by the presence of serum hepatitis B surface antigen (HBsAg). However, some mutations in the surface gene region may result in altered or truncated HBsAg that can escape from immunoassay-based diagnosis. Such diagnostic escape mutants pose a potential risk for blood transfusion services.
In the present study, we report a blood donor seronegative for HBsAg and antiHBc, but positive for antiHBs who was HBV DNA positive by PCR. Sequencing of the HBsAg gene revealed presence of a point mutation (T-A) at 207th nucleotide of the HBsAg ORF, which resulted in a premature stop codon at position 69. This results in a truncated HBsAg gene lacking the entire 'a' determinant region. However, follow-up of the donor after 2 years revealed clearance of HBV DNA from the serum.
The case illustrates an unusual mutation, which causes HBsAg negativity. The finding emphasizes the importance of molecular assays in reducing the possibility of HBV transmission through blood transfusion. However, developing more sensitive serological assays, capable of detecting HBV mutants, is an alternative to expensive and complex amplification-based assays for developing countries.
在献血者中，通过血清乙肝表面抗原（HBsAg）的存在来检测HBV感染。然而，表面基因区域的一些突变可能导致HBsAg改变或截短，从而逃避基于免疫测定的诊断。这种诊断逃逸突变体给输血服务带来潜在风险。
在本研究中，我们报告了一名献血者，其HBsAg和抗-HBc血清学阴性，但抗-HBs阳性，PCR检测显示其HBV DNA阳性。HBsAg基因测序显示，在HBsAg开放阅读框第207个核苷酸处存在一个点突变（T-A），导致在第69位出现提前终止密码子。这导致截短的HBsAg基因缺失整个“a”决定簇区域。然而，对该献血者随访2年后发现其血清中HBV DNA清除。
该病例说明了一种导致HBsAg阴性的不寻常突变。这一发现强调了分子检测在降低HBV通过输血传播可能性方面的重要性。然而，对于发展中国家而言，开发更敏感的能够检测HBV突变体的血清学检测方法是替代昂贵且复杂的基于扩增的检测方法的一种选择。
