Abstract
BackgroundThe prevalence of chronic Hepatitis B Virus (HBV) infection is 2–4% in the Pakistani population, defining Pakistan as an intermediate prevalence country. In this study, hepatitis B surface antigen (HBsAg) reactive blood donations were screened using a combination of serological and molecular methods to identify immune escape HBV mutant strains and to determine the HBV genotypes and subtypes present in Pakistan.MethodsBlood donations were collected at the Armed Forces Institute of Transfusion (AFIT) located in northern Pakistan and the Hussaini Blood Bank (HBB) located in the south. From 2009 to 2013 a total of 706,575 donations were screened with 2.04% (14,409) HBsAg reactive. A total of 2055 HBsAg reactive specimens, were collected and screened using a monoclonal antibody based research assay to identify immune escape mutants followed by PCR amplification and DNA sequencing to identify the mutation present. DNA sequences obtained from 192 specimens, including mutant candidates and wild type strains, were analyzed for escape mutations, genotype, and HBsAg subtype.ResultsMutations were identified in approximately 14% of HBsAg reactive donations. Mutations at HBsAg amino acid positions 143–145 are the most common (46%) with the mutation serine 143 to leucine the most frequently occurring change (28%). While regional differences were observed, the most prevalent HBV strains are subgenotypes of D with subgenotype D1/subtype ayw2 accounting for the majority of infections; 90.2% at AFIT and 52.5% at HBB.ConclusionsThe high frequency of immune escape HBV mutants in HBV infected Pakistani blood donors highlights the need for more studies into the prevalence of escape mutants. Differences between vaccinated and unvaccinated populations, the correlation of escape mutant frequency with genotype, and impact of escape mutations in different genotype backgrounds on the performance of commercially available HBsAg assays represent avenues for further investigation.
Highlights
Hepatitis B virus (HBV) is a global public health issue with 15–25% of chronically infected individuals developing severe disease and dying prematurely due to cirrhosis, hepatocellular carcinoma or hepatitis
Mutations were identified in approximately 14% of HBV surface antigen (HBsAg) reactive donations
The high frequency of immune escape HBV mutants in HBV infected Pakistani blood donors highlights the need for more studies into the prevalence of escape mutants
Summary
Hepatitis B virus (HBV) is a global public health issue with 15–25% of chronically infected individuals developing severe disease and dying prematurely due to cirrhosis, hepatocellular carcinoma or hepatitis. Pakistan is classified as an intermediate prevalence country with a prevalence of 2–4% chronic HBV infection and an additional 32% of the population having had exposure to HBV [2]. The prevalence of chronic HBV infection varies between and within provinces, in rural versus urban populations, and by socioeconomic status. In a national survey conducted from 2007– 2008, overall HBV surface antigen (HBsAg) prevalence was 2.5% with provincial rates ranging from 4.3% in the Balochistan province to 1.3% in the northern Khyber Pakhtunkhwa province with the southern province of Sindh and Punjab at 2.5% and 2.4% respectively [3]. The prevalence of chronic Hepatitis B Virus (HBV) infection is 2–4% in the Pakistani population, defining Pakistan as an intermediate prevalence country. Hepatitis B surface antigen (HBsAg) reactive blood donations were screened using a combination of serological and molecular methods to identify immune escape HBV mutant strains and to determine the HBV genotypes and subtypes present in Pakistan
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