Hepatitis B virus genotypes.

Epidemiology of hepatitis B virus in Africa, its genotypes and clinical associations of genotypes.

Geographical and genetic diversity of the human hepatitis B virus.

Genetic variability of the S gene of hepatitis B virus: clinical and diagnostic impact.

Prevention of transfusion-transmitted infections.

The significance of 'anti-HBc only' in the clinical virology laboratory.

Hepatitis B virus (HBV) genotypes in three different communities in the Republic of Yemen with and without significant African links were studied. The subjects included indigenous Yemeni blood donors (n = 987), Africans who had settled down in Yemen for several generations (n = 97) and Soqotrans living on an island in the Indian Ocean close to the African coast (n = 99). Phylogenetic analysis of HBV surface region sequences showed the presence of two major genotypes; A and D: sequences from the blood donors were all genotype D (17/17); those from Africans residing in Yemen were predominantly genotype D (7/8) although one sequence was genotype A; whereas a mixture of genotype A and D was found among the Soqotrans (5/8 and 3/8 respectively). Genotype A sequences were associated with higher viral load, but the difference was not statistically significant. Human migration and international travel, may lead to an interaction between HBV genotypes. The Republic of Yemen is at a location where genotypes A and D meet. The results from this study suggest that genotype A is found only in communities with continuing African links and that genotype D remains the dominant genotype in settled populations. More studies are needed to examine possible long-term changes in HBV genotypes in this region. J. Med. Virol. 73:23–28, 2004. © 2004 Wiley-Liss, Inc.

African links and hepatitis B virus genotypes in the Republic of Yemen

Genetic variations in the basic core promoter (BCP) region of hepatitis B virus (HBV) occur during the natural history of chronic HBV infection. This study investigates the presence of basic core promoter variations in 28 asymptomatic Yemeni blood donors, correlating variations with HBeAg phenotype and viral load. The core promoter/precore and surface gene region of HBV DNA were amplified using nested PCRs and the PCR products were sequenced either directly or after cloning. HBeAg and viral load were measured when HBV DNA was detectable. Sequencing of 18 surface PCR products indicated that all were of genotype D. Two distinct types of variants were identified in the basic core promoter: substitution only (N = 14) and major deletion (N = 9). The commonest substitutions were located at nucleotide positions 1753, 1762, and 1764; 10/14 (71.4%) were associated with the precore 1896A substitution resulting in the premature stop of the precore reading frame and 6/14 (42.9%) had viral loads above 400 copies/ml. Two forms of deletion variants were found: 8 bp deletion (1763–1770) (N = 2) and a novel 12 (1746–1757) + 8 bp (1763–1770) deletion (N = 7). The deletion sequences were never associated with the precore 1896A substitution and all had viral load below 400 copies/ml with negative HBeAg phenotype. The polymorphism 1773C was found in 9/14 (64.3%) substitution sequences whereas all deletion sequences had 1773T. Two donors had mixed sequences of basic core promoter substitution and major deletions (both 8 bp and 12 + 8 bp). While the deletion variants in these two donors were similar to others found in isolation, the substitutions were of a different pattern. Further studies are required to understand the selection process behind these variants. J. Med. Virol. 68:328–334, 2002. © 2002 Wiley-Liss, Inc.

Two distinct types of hepatitis B virus core promoter variants in Yemeni blood donors.

Pediatric diagnosis of human immunodeficiency virus type 1 infection: the problem of false negative DNA polymerase chain reaction results.

Susceptibility to hepatitis B virus (HBV) infection among 987 young adult male blood donors in 2 major Yemeni cities was investigated. Hepatitis B surface antigen (HBsAg) was detected in 10.8% (107/987) of donors and 284 (28.8%) had evidence of ongoing or past HBV infection. Hepatitis B surface antibody (anti-HBs) only was detected in 34 (3.4%) donors. Thus, 67.8% (669/987) of donors had no detectable HBV-markers indicating susceptibility to infection. The proportion of HBV-susceptible donors decreased from 70.9% (249/351) in donors aged 34 years (P = 0.002). The high proportion of susceptible young adults in a community with a high HBsAg carrier rate could be the result of changing epidemiology of hepatitis B in Yemen. Consideration should therefore be given to immunizing young adults as an adjunct to the current expanded infant immunization programme.

C.Y. William Tong

Papers

The significance of 'anti-HBc only' in the clinical virology laboratory.

African links and hepatitis B virus genotypes in the Republic of Yemen

Two distinct types of hepatitis B virus core promoter variants in Yemeni blood donors.

Pediatric diagnosis of human immunodeficiency virus type 1 infection: the problem of false negative DNA polymerase chain reaction results.

Increase in susceptibility of young adults to hepatitis B infection in the Republic of Yemen.