High frequency of hepatitis B virus infection in patients with β-thalassemia receiving multiple transfusions
Article first published online: 20 MAY 2003
Volume 84, Issue 4, pages 292–299, May 2003
How to Cite
Singh, H., Pradhan, M., Singh, R. L., Phadke, S., Naik, S. R., Aggarwal, R. and Naik, S. (2003), High frequency of hepatitis B virus infection in patients with β-thalassemia receiving multiple transfusions. Vox Sanguinis, 84: 292–299. doi: 10.1046/j.1423-0410.2003.00300.x
- Issue published online: 20 MAY 2003
- Article first published online: 20 MAY 2003
- Received: 28 May 2002, revised 17 November 2002, accepted 6 January 2003
- anti-HBs response;
- HBV vaccine;
- S-gene mutant
Background and Objectives Hepatitis B virus (HBV) may occasionally be transmitted through transfusion of blood units that are hepatitis B surface antigen (HBsAg) negative but HBV DNA positive. Children with β-thalassemia are particularly susceptible to HBV because they receive multiple blood transfusions. These children have high infection rates despite vaccination against HBV. Post-vaccination infections may be a result of viruses harbouring surface (S)-gene mutations (e.g. G587A) in a region critical for reactivity to antibody to hepatitis B surface antigen (anti-HBs). The true prevalence of HBV in individuals with β-thalassemia has not been studied previously.
Patients and Methods Seventy patients with β-thalassemia (median age 6 years; range 8 months to 22 years; 49 male), who had received seven to 623 (median 61) units of blood each and three doses (10/20 µg) of HBV vaccine (Engerix B) before presentation to us, were included in the study; 50 of the 70 patients had received transfusions prior to vaccination. Enzyme-linked immunoassay for serological markers [HBsAg, antibody to hepatitis B core antigen (anti-HBc) and quantitative anti-HBs] and polymerase chain reaction (PCR) followed by Southern hybridization for molecular detection of hepatitis B, was performed on all samples. The PCR-amplified product was cloned, sequenced and the nucleotide and deduced amino acid sequences for the HBV S and polymerase (P) genes were analysed for mutations.
Results Four of 70 (5·7%) individuals with β-thalassemia were HBsAg positive and 14 (20%) were anti-HBc positive. The prevalence of serological markers increased with number of transfusions (P < 0·01). Of 70 patients, 53 (75·7%) had an anti-HBs titre of > 10 IU/l following vaccination and 17 (24·3%) were non-responders (< 10 IU/l); 22 (31·4%) of the 70 were DNA positive. The frequency of HBV infection in β-thalassemia was similar in vaccine responders and non-responders. The virus was of subtype ayw (genotype D) in the five DNA-positive samples in which a 388-nucleotide region of the S gene was sequenced. Mutations occurred at 13 positions in the S gene and at 10 positions in the P gene. Hydrophobicity plots revealed differences in amino acid regions 117–165 and 195–211. Some of these amino acid substitutions coincided with the putative cytotoxic T-lymphocyte epitopes of both S and P proteins.
Conclusions A high frequency of HBV infection was seen using molecular methods in thalassemic patients. The frequency of infection was similar in vaccine responders and non-responders. A number of mutations were observed in the S gene, which could have implications for viral replication as well as virus–host cell interaction.