Characterization of hepatitis B virus in Turkish blood donors, and the prevalence of the SP1 splice variant

Genomic Variability of Hepatitis B Virus Circulating in Brazilian Western Amazon

The emergence of clinically relevant mutations in the hepatitis B virus (HBV) genome has been a matter of great debate because of the possibility of escape from the host’s immune system, the potential to cause more severe progression of liver diseases and the emergence of treatment-resistant variants. Here we characterized the circulating variants of HBV in Rondônia State, in the north of Brazil. Serum samples of 62 chronic HBV carriers were subjected to PCR assays and clinical data were collected. Mutations and genotypes were characterized through direct sequencing. The findings show the presence of subgenotypes A1 (54.83%, 34/62), D3 (16.13%, 10/62), F2 (16.13%, 10/62), A2 (4.84%, 3/62), D2 (3.23%, 2/62), D1 (1.61%, 1/62), D4 (1.61%, 1/62) and F4 (1.61%, 1/62). Deletions in the pre-S2 region were found in 13.79% (8/58) of the samples, mutations in the S gene in 59.68% (37/62) and RT mutations in 48.39% (30/62). We found a variable genotypic distribution in different locations and important mutations related to immune escape and drug resistance in Western Amazonia, which contributed to genetic surveillance and provided important information to help control the disease.

Alternative splicing of viral transcripts: the dark side of HBV

Regulation of alternative splicing is one of the most efficient mechanisms to enlarge the proteomic diversity in eukaryotic organisms. Many viruses hijack the splicing machinery following infection to accomplish their replication cycle. Regarding the HBV, numerous reports have described alternative splicing events of the long viral transcript (pregenomic RNA), which also acts as a template for viral genome replication. Alternative splicing of HBV pregenomic RNAs allows the synthesis of at least 20 spliced variants. In addition, almost all these spliced forms give rise to defective particles, detected in the blood of infected patients. HBV-spliced RNAs have long been unconsidered, probably due to their uneasy detection in comparison to unspliced forms as well as for their dispensable role during viral replication. However, recent data highlighted the relevance of these HBV-spliced variants through (1) the trans-regulation of the alternative splicing of viral transcripts along the course of liver disease; (2) the ability to generate defective particle formation, putative biomarker of the liver disease progression; (3) modulation of viral replication; and (4) their intrinsic propensity to encode for novel viral proteins involved in liver pathogenesis and immune response. Altogether, tricky regulation of HBV alternative splicing may contribute to modulate multiple viral and cellular processes all along the course of HBV-related liver disease.

Hepatitis B virus burden in developing countries

Hepatitis B virus (HBV) infection has shown an intermediate or high endemicity level in low-income countries over the last five decades. In recent years, however, the incidence of acute hepatitis B and the prevalence of hepatitis B surface antigen chronic carriers have decreased in several countries because of the HBV universal vaccination programs started in the nineties. Some countries, however, are still unable to implement these programs, particularly in their hyperendemic rural areas. The diffusion of HBV infection is still wide in several low-income countries where the prevention, management and treatment of HBV infection are a heavy burden for the governments and healthcare authorities. Of note, the information on the HBV epidemiology is scanty in numerous eastern European and Latin-American countries. The studies on molecular epidemiology performed in some countries provide an important contribution for a more comprehensive knowledge of HBV epidemiology, and phylogenetic studies provide information on the impact of recent and older migratory flows.

Hepatitis B virus genotype and subgenotype prevalence and distribution in Montenegro

The Mediterranean area and the Balkans in particular show the highest level of genetic heterogeneity of HBV in Europe. Data about the circulation of HBV genotypes in Montenegro are lacking. It was studied the prevalence and distribution of HBV genot/subgenotypes in a total of 150 HBV infected patients living in Montenegro. Phylogenetic analysis of 136 successfully amplified P sequences showed a high degree of genetic heterogeneity of HBV in Montenegro. Subgenotype D2 (36.8%) and D3 (32.3%) were the most prevalent, followed by genotype A (subgenotype A2 in all of the cases-19.8%). Eight patients were infected with recombinant strains. HBV-D1 which is the most spread HBV subgenotype in the south-eastern Mediterranean countries, seems to be relatively rare in Montenegro, suggesting a penetration of HBV more probably from North-East or West than from Eastern Mediterranean countries. The relatively different prevalence of D3 and A2 among subjects infected through sexual route, seems to confirm the association of these subgenotypes with different route of transmissions (mainly parenteral for D3 and mainly sexual for A2) even in Montenegro. The low prevalence of D2 among children and its absence in perinatal transmission, suggests that this subgenotype circulated prevalently in the past. If this is due to changes in the most prevalent way of transmission and in the recent different contacts of Montenegro with other European countries, it remains to be established by other larger studies.

Epidemiology of HBV subgenotypes D

The natural history of hepatitis B virus infection is not uniform and affected from several factors including, HBV genotype. Genotype D is a widely distributed genotype. Among genotype D, several subgenotypes differentiate epidemiologically and probably clinically. D1 is predominant in Middle East and North Africa, and characterized by early HBeAg seroconversion and low viral load. D2 is seen in Albania, Turkey, Brazil, western India, Lebanon, and Serbia. D3 was reported from Serbia, western India, and Indonesia. It is a predominant subgenotype in injection drug use-related acute HBV infections in Europe and Canada. D4 is relatively rare and reported from Haiti, Russia and Baltic region, Brazil, Kenya, Morocco and Rwanda. Subgenotype D5 seems to be common in Eastern India. D6 has been reported as a rare subgenotype from Indonesia, Kenya, Russia and Baltic region. D7 is the main genotype in Morocco and Tunisia. D8 and D9 are recently described subgenotypes and reported from Niger and India, respectively. Subgenotypes of genotype D may have clinical and/or viral differences. More subgenotype studies are required to conclude on subgenotype and its clinical/viral characteristics.

Subgenotypes and mutations in the s and polymerase genes of hepatitis B virus carriers in the West Bank, palestine

The mutation rate and genetic variability of hepatitis B virus (HBV) are crucial factors for efficient treatment and successful vaccination against HBV. Until today, genetic properties of this virus among the Palestinian population remain unknown. Therefore, we performed genetic analysis of the overlapping S and polymerase genes of HBV, isolated from 40 Palestinian patients' sera. All patients were HBsAg positive and presented with a viral load above 105 HBV genome copies/ml. The genotyping results of the S gene demonstrated that HBV D1 was detected in 90% of the samples representing the most prominent subgenotype among Palestinians carrying HBV. Various mutations existed within the S gene; in five patients four known escape mutations including the common G145R and D144E were found. Furthermore, a ratio of 4.25 of non-synonymous to synonymous mutations in the S gene indicated a strong selection pressure on the HBs antigen loops of HBV strains circulating in those Palestinian patients. Although all patients were treatment-naïve, with the exception of one, several mutations were found in the HBV polymerase gene, but none pointed to drug resistance. The study presented here is the first report to address subgenotypes and mutation analyses of HBV S and polymerase genes in Palestine.

Dating the origin and dispersal of hepatitis B virus infection in humans and primates

The origin of hepatitis B virus (HBV) infection in humans and other primates remains largely unresolved. Understanding the origin of HBV is crucial because it provides a framework for studying the burden, and subsequently the evolution, of HBV pathogenicity with respect to changes in human population size and life expectancy. To investigate this controversy we examined the relationship between HBV phylogeny and genetic diversity of modern humans, investigated the timescale of global HBV dispersal, and tested the hypothesis of HBV-human co-divergence. We find that the global distribution of HBV genotypes and subgenotypes are consistent with the major prehistoric modern human migrations. We calibrate the HBV molecular clock using the divergence times of different indigenous human populations based on archaeological and genetic evidence and show that HBV jumped into humans around 33,600 years ago; 95% higher posterior density (HPD): 22,000-47,100 years ago (estimated substitution rate: 2.2 × 10(-6) ; 95% HPD: 1.5-3.0 × 10(-6) substitutions/site/year). This coincides with the origin of modern non-African humans. Crucially, the most pronounced increase in the HBV pandemic correlates with the global population increase over the last 5,000 years. We also show that the non-human HBV clades in orangutans and gibbons resulted from cross-species transmission events from humans that occurred no earlier than 6,100 years ago.

CONCLUSION

Our study provides, for the first time, an estimated timescale for the HBV epidemic that closely coincides with dates of human dispersals, supporting the hypothesis that HBV has been co-expanding and co-migrating with human populations for the last 40,000 years. (HEPATOLOGY 2013).

Hepatitis B virus DNA splicing in Lebanese blood donors and genotype A to E strains: implications for hepatitis B virus DNA quantification and infectivity

Hepatitis B virus (HBV) is one of the major viruses transmissible by blood that causes chronic infection in immunocompromised individuals. The study of 61 HBV carrier blood donors from Lebanon revealed multiple patterns of spliced HBV DNA. HBV DNA splicing was examined and quantified in samples of five genotypes and in seroconversion panels. The Lebanese sample median viral load was 1.5 ×10(2) IU/ml. All strains were genotype D, serotype ayw; 35 clustered as subgenotype D1 and 7 clustered as subgenotype D2. Three splice variants (SP1, SP1A, and Pol/S) were observed in 12 high-viral-load samples. Twenty samples of each genotype, A to E, were tested for the presence of HBV spliced DNA and SP1-specific splice variant. An unspliced HBV genome was dominant, but 100% of strains with a viral load of ≥10(5) copies/ml contained various proportions of spliced DNA. SP1 was detected in 56/100 (56%) samples in levels that correlated with the overall viral load. HBV DNA quantification with S (unspliced) and X (total DNA) regions provided different levels of viral load, with the difference corresponding to spliced DNA. During the highly infectious window period, the SP1 variant became detectable shortly after the hepatitis B surface antigen (HBsAg), suggesting a correlation between the initiation of splicing and the production of detectable levels of HBsAg. The quantification of HBV DNA with primers located outside and inside the spliced region might provide different estimations of viral load and differentiate between infectious and defective viral genomes. The role of splicing neoproteins in HBV replication and interaction with the host remains to be determined.

Production of hepatitis B defective particles is dependent on liver status

Defective hepatitis B virus (dHBV) generated from spliced RNA is detected in the sera of HBV-chronic carriers. Our study was designed to determine whether the proportion of dHBV changed during the course of infection, and to investigate whether dHBV might interfere with HBV replication. To achieve this, HBV wild-type and dHBV levels were determined by Q-PCR in sera from 56 untreated chronic patients and 23 acute patients, in sequential samples from 4 treated-patients and from liver-humanized mice after HBV infection. The proportion of dHBV was higher in patients with severe compared to null/moderate liver disease or with acute infection. Follow-up showed that the proportion of dHBV increased during disease progression. By contrast, a low and stable proportion of dHBV was observed in the humanized-mouse model of HBV infection. Our results highlight a regulation of the proportion of dHBV during liver disease progression that is independent of interference with viral replication.

Spatial and temporal dynamics of hepatitis B virus D genotype in Europe and the Mediterranean Basin

Hepatitis B virus genotype D can be found in many parts of the world and is the most prevalent strain in south-eastern Europe, the Mediterranean Basin, the Middle East, and the Indian sub-continent. The epidemiological history of the D genotype and its subgenotypes is still obscure because of the scarcity of appropriate studies. We retrieved from public databases a total of 312 gene P sequences of HBV genotype D isolated in various countries throughout the world, and reconstructed the spatio-temporal evolutionary dynamics of the HBV-D epidemic using a bayesian framework.The phylogeographical analysis showed that India had the highest posterior probability of being the location of the tree root, whereas central Asia was the most probable location of the common ancestor of subgenotypes D1-D3. HBV-D5 (identified in native Indian populations) diverged from the tree root earlier than D1-D3. The time of the most recent common ancestor (tMRCA) of the tree root was 128 years ago, which suggests that the common ancestor of the currently circulating subgenotypes existed in the second half of the XIX century. The mean tMRCA of subgenotypes D1-D3 was between the 1940s and the 1950-60s. On the basis of our phylogeographic reconstruction, it seems that HBV-D reached the Mediterranean area in the middle of the XX century by means of at least two routes: the first pathway (mainly due to the spread of subgenotype D1) crossing the Middle East and reaching north Africa and the eastern Mediterranean, and the second pathway (closely associated with D2) that crossed the former Soviet Union and reached eastern Europe and the Mediterranean through Albania. We hypothesise that the main route of dispersion of genotype D was the unsafe use of injections and drug addiction.

Hepatitis B virus in transfusion medicine: still a problem?

Hepatitis B virus (HBV) has probably evolved with humans for nearly 35,000 years. HBV diversified into 9 genotypes (A-I) presenting specific features directing epidemiology, clinical expression and testing. Genotypes E and C are more infectious and carry higher risk of chronicity and cancer. HBsAg blood screening implemented 40 years ago enormously decreased the risk of transfusion transmission but the remaining risk requires extremely sensitive nucleic acid testing (NAT) to be removed. Limitations of the host immune system, the impact of immunodeficiency and the mechanisms utilised for viral persistence were recently identified. HBV replication produces excess HBsAg and infectious and defective viral particles but screening assays for HBsAg or viral particles alone do not allow fully efficient detection, making necessary screening for both. The host immune system fails to completely control the virus that escapes and persists unrecognized at very low levels or as immuno-selected variants. Variants may not be identified by assays, explaining false negative results. Specific mutations may affect post-transcriptional mechanisms including HBV RNA splicing. Asymptomatic HBV infected blood donors are at risk of long-term complications through mechanisms to be understood for appropriate counselling. Infectivity of occult HBV infection (OBI) by transfusion appears low, anti-HBc (anti-core antigen) only being more infectious than anti-HBs (anti-S protein) positive units.