Abstract
Cuba is an HBsAg low-prevalence country with a high coverage of anti-hepatitis B vaccine. Its population is essentially the result of the population mix of Spanish descendants and former African slaves. Information about genetic characteristics of hepatitis B virus (HBV) strains circulating in the country is scarce. The HBV genotypes/subgenotypes, serotypes, mixed infections, and S gene mutations of 172 Cuban HBsAg and HBV-DNA positive patients were determined by direct sequencing and phylogenetic analysis. Phylogenetic analysis of HBV S gene sequences showed a predominance of genotype A (92.4%), subgenotype A2 (84.9%) and A1 (7.6%). Genotype D (7.0%) and subgenotype C1 (0.6%) were also detected but typical (sub)genotypes of contemporary West-Africa (E, A3) were conspicuously absent. All genotype A, D, and C strains exhibited sequence characteristics of the adw2, ayw2, and adrq serotypes, respectively. Thirty-three (19.1%) patients showed single, double, or multiple point mutations inside the Major Hydrophilic domain associated with vaccine escape; eighteen (10.5%) patients had mutations in the T-cell epitope (amino acids 28-51), and there were another 111 point mutations downstream of the S gene. One patient had an HBV A1/A2 mixed infection. This first genetic study of Cuban HBV viruses revealed only strains that were interspersed with strains from particularly Europe, America, and Asia. The absence of genotype E supports previous hypotheses about an only recent introduction of this genotype into the general population in Africa. The presence of well-known vaccine escape (3.5%) and viral resistance mutants (2.9%) warrants strain surveillance to guide vaccination and treatment strategies.
Highlights
Despite advances in the prevention, diagnosis and treatment of hepatitis B, this viral infection continues to be a major public health concern in many countries
Genotype E is highly prevalent throughout West-Africa but essentially restricted to the sub-Saharan genotype E crescent expanding from Senegal to the Central African Republic and to Namibia in the South [8]
This has led to speculations that this genotype E has only been recently introduced in the general African population [9]
Summary
Despite advances in the prevention, diagnosis and treatment of hepatitis B, this viral infection continues to be a major public health concern in many countries. Additional genotypes I and J have been proposed [3, 4]. Genotype D is divided into several subgenotypes and is the most prevalent and the most widely distributed HBV genotype in Western populations and in other parts of the world including Northern Africa [5, 7]. The high prevalence and the extensive spread within Africa are in sharp contradiction with the very low genetic diversity of genotype E strains. This has led to speculations that this genotype E has only been recently introduced in the general African population [9]
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