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Introduction. The vertical route of hepatitis B virus (HBV) transmission is a significant problem in African countries, which is characterized by late diagnosis of the disease and high mortality. The high prevalence of hepatocellular carcinoma (HCC) in Africa may be due to variability in the HBV preCore/Core region, mutations in which contribute to disease progression. Molecular genetic characterization of strains circulating among pregnant women may reflect the overall mutational profile of the pathogen in the population. The objective of this study was to analyze the variability of the HBV preCore/Core region circulating among pregnant women in the Republic of Guinea. Materials and methods. The study material included 480 plasma samples obtained from HBV-positive pregnant women from the Republic of Guinea. For all samples, the nucleotide sequences of the preCore/Core region of the HBV genome were sequenced and analyzed. Results. Amino acid variability in the preCore region was determined in 211 (43.96%), and in the Core region in 473 (98.54%) patients. 12 polymorphic sites of the preCore region were identified in which amino acid substitutions occurred, including 8, 2 and 5 positions identified for genotypes E, A and D, respectively. In the Core region, 67 substitution positions were identified, including 46 in samples of genotype E, 23 in HBV genotype A and 26 in genotype D. It was shown that the distribution of substitutions in the preCore and Core regions in HBV genotypes E, A and D differs significantly with a predominance in mutations among HBV genotype E — p 0.0001. Individual characteristic mutations have been identified for each genotype. The most common clinically significant mutations in the preCore/Core region in the study group were identified, including pc-H5D (27,08%), pc-W28* (35,21%), c-E64D (33,54%), c-L116I/V/G (91,46 %), c-T146N (73,13%). The double mutation A1762T/G1764A in the basal core promoter was shown in 74 samples of HBV genotype E, which accounted for 15.42% of the total group and 16.59% of patients with HBV genotype E. Conclusion. The frequency of clinically significant preCore/Core mutations among pregnant women in the Republic of Guinea was determined. The data obtained reflect their prevalence in the general population and can be used to predict the progression of chronic HBV among the region's population.

The aim of this study was to assess the prevalence of occult hepatitis B infection among blood donors in St. Petersburg, as well as to characterize the identified virus isolates. The study material was represented by 2800 blood plasma samples collected in 2019 from blood donors living in St. Petersburg. The ELISA study for HBV marker rate consisted of HBsAg, anti-HBs IgG, anti-HBcore IgG. HBV DNA was analyzed by nested PCR with real-time hybridization-fluorescence detection on three targets allowing to determine virus DNA at low viral load, including HBsAg-negative chronic hepatitis B. Hepatitis B serological markers were detected in 69.43% of those surveyed, HBsAg was found in 0.43% of individuals, and all of which donated blood first time. A significant excess of the anti-HBcore IgG antibodies occurrence among primary donors (15.1%) compared with repeated/regular donors (7.48%) was shown. The prevalence of virus DNA in the group was 3.14%, including 2.71% of cases in HBsAg-negative CHB. Based on phylogenetic analysis of 88 isolates, HBV subgenotypes were determined in the following order: D1 and D2, 40.91% each, D3 and A2, 9.09% each. While determining the serological subtype in detected isolates, the serotype ayw3 (52.27%) vs ayw2 (46.59%) and adw2 (10.23%) prevailed. Drug resistance mutations, including compensatory ones, were detected in six examined patients (6.82%). In all genotype D isolates, multiple amino acid substitutions were identified in the RT, SHB, MHB, LHB, and Core regions; mutations in the preCore region were detected in 21.59% samples. In the MHR of the HBV genotype D genome, twenty-six positions were identified in which amino acid substitutions occurred, and all isolates showed modifications at positions 113, 114, 131, 134, 159, 161, 168, in 76 — at position 122, in 68 — at position 127, in 36 — at position 118, in 24 — at position 128. In HBV A2 isolates, mutations T113S, S143T, Y161F were identified. Nine isolates in the preCore region showed a polymorphism including a stop codon W28*W; in five isolates the W28S substitution was shown in the same position, and the W28*S variant was found in one more sample. The high incidence of HBsAg-negative CHB cases among blood donors, as well as the predominance of HBV isolates that simultaneously carry mutations resulting in diagnostic failure of HBsAg tests and prophylactic failure of immunoglobulin or vaccines and virus reactivation, mutations that contribute to disease progression obviously pose a threat to health and require to be further examined.

Introduction. The World Health Organization estimates that as of 2019, more than 296 million people were living with chronic hepatitis B virus (HBV) infection. The prevalence of HBsAg-negative, occult form of the disease in blood donors varies depending on the region of the world and the sensitivity of the methods of analysis used. Considering that the genetic diversity of viruses demonstrates space and time variations and taking into account that the genetic profile of isolates in key groups, which may turn into a source of the pathogen spread, is important for forecasting of the epidemiological situation, the attention should be given to identification of HBV genotypes currently circulating among regular blood donors in regions of the Russian Federation. The aim of this work was molecular and genetic characterization of HBV genomes identified in HBsAg-negative blood donors in the Ural Federal District. Materials and methods. The study material was 1400 plasma samples obtained from HBsAg-negative blood donors in Ural Federal District. The study included the testing for HBsAg, anti-HBs IgG and anti-HBcore IgG antibodies, HBV DNA. For all identified HBV DNA containing samples, sequencing and analysis of the nucleotide sequences of the complete HBV genomes were performed. Results. The prevalence of HBV DNA was 4.93%, including 4 (0.28%) cases of false occult hepatitis B. Among anti-HBcore IgG-positive samples, HBV DNA was found in 18.08% of cases, while in persons with detected HBV DNA the anti-HBcore IgG positivity rate was 46.38%. In 8.69% of the isolates, anti-HBs IgG antibodies and viral DNA were detected simultaneously in the absence of anti-HBcore IgG. Based on phylogenetic analysis, HBV subgenotypes distribution in HBsAg-negative blood donors was as follows: D3 53.62%, D2 21.74%, D1 18.84%, C2 5.8%. The high variability in the S, C, P regions of the virus genome in the examined group was shown. In all cases of HBsAg-negative chronic HBV infection identified in blood donors, viral sequences contained at least one amino acid substitution in positions, mutations in which are associated with immune escape. In 3 (4.35%) cases mutations in reverse transcriptase region of P gene that are associated with resistance to the following drugs were identified: lamivudine, telbivudine, entecavir. Mutations in the preCore/Core regions that contribute to the progression of liver disease were also identified. Conclusion. Occult HBsAg-negative chronic HBV infection poses a threat of HBV transmission through transfusion of blood and its components due to the extremely low viral load, which does not allow the virus to be detected using routinely used diagnostic kits. The situation can be exacerbated by the abundance and diversity of virus amino acid substitutions that we have identified, including immune escape mutations, drug resistance mutations, and mutations that contribute to the progression of the disease.

Hepatitis B, despite of being a controlled infection today, is one of the most common form of hepatitis in the world. According to the experts' evaluation there are about 3 million patients with chronic hepatitis B in our country. The global strategy of the World Health Organization includes the elimination of viral hepatitis by 2030.The program used in the North-West Federal District to eliminate acute hepatitis B has reduced the incidence rate due to the widespread vaccination coverage of children and the annual increase in adult immunization coverage.However, the relevance of HBV-infection in children still remains high which is associated with a high infection by hepatitis B virus in women of childbearing age and the possibility of the transmission of the infection from mother to her child. In case of perinatal infection the formation of chronic hepatitis B in children reaches up to 90%. The natural course of chronic hepatitis B is characterized by a change in pathogenetically determined phases, and HBsAg-negative infection, which is a latent (occult) form of hepatitis, was added to them in 2009. Occult hepatitis B is an epidemiological danger, for the child as well, if the mother suffers from this form of chronic hepatitis B. Monitoring of pregnant women is often limited to identifying only HBsAg, which is not enough to detect occult hepatitis B. Lately diagnosed occult HBV-infection can become a source of the infection for the baby, especially in cases when due to some reasons there are disorders in hepatitis B vaccination schedule after birth. The article presents an interesting clinical case of family hepatitis B.

Aim. Evaluate significance of covalently closed circular DNA of hepatitis В virus as a marker for detection of occult viral hepatitis В in Uzbekistan population with hepatitis of various genesis. Materials and methods. Blood plasma and liver biopsy from 39 patients with different severity levels of liver fibrosis and cirrhosis served as study material. HBV covalently closed circular DNA detection was carried out according to Pollicino T. et al. (2004). Results. Covalently closed circular DNA of hepatitis В virus was detected in 82% of samples, including in 54.5% of patients with chronic viral hepatitis C (CVHC) and in 100% of patients with hepatitis of unknown etiology. Quantitative evaluation of content of covalently closed circular DNA of hepatitis В virus in liver tissue in patients with CVHB has shown an average of 2.5 copies of HBV genome as ccc DNA per cell, in patients with CVHB + D an average of 0.7 copies/cell, in patients with co-infection by HCV and HBV - 0.5 copies/cell, in patients with CVHC an average of 0.12 copies/cell, and in patients with cryptogenic hepatitis - 0.2 copies/cell. Conclusion. Detection of HBV DNA is a complex problem for effective laboratory diagnostics of hepatitis. Detection of H BV ccc DNA as a marker of occult hepatitis В in patients with CVHC and patients with hepatitis of unclear etiology is an important factor for diagnostics, selection of adequate therapy, prognosis of disease outcome and prevention of development of severe liver diseases.

The article presents the data on the rates of blood-borne viral infections (BBVI) in potential organ donors and blood donors at the N.V.Sklifosovsky Research Institute for Emergency Medicine in the period from 2008 to 2014. Differences in BBVI rates and multidirectional trends in the proportion of infected individuals were seen in different age groups of blood donors and potential organ donors. We analyzed the established algorithm for laboratory testing of potential organ donors for BBVI in the Russian Federation and major risks for BBVI transmission in organ and tissue transplantation. We have shown that the current algorithm of screening for BBVI in organ donors does not detect these infections duringa "window period", nor their occult forms. We studied the causes of occult BBVI forms and their significance for clinical transplantation.

The concept of occult infection caused by hepatitis B virus (HBV) is determined as the presence of HBV DNA in blood sera or liver with the absence of detectable HBsAg. The actuality of this problem is associated with the fact, that occult hepatitis B (OHB) can be transmitted during hemotransfusions, cause reactivation of chronic hepatitis B in immune compromised individuals, facilitate development of liver cirrhosis and hepatocellular carcinoma. Several different hypotheses of OHB immunopatho-genesis have been proposed, including a low number of copies of HBV DNA, altered immune response of the macroorganism, genetic variability of the S gene, integration of viral DNA into host genome, infection of mononuclear cells of peripheral blood, presence of immune complexes that hide HBsAg, and interference by other viruses such as HCV and HIV Molecular mechanisms of HBVvirus in HBsAg-negative individuals are not fully understood, however, viral mutations seem a very significant factor. Approaches of OHB prophylaxis including use of a polyvalent vaccine, that allows vaccination against wild and mutant HBV viruses, are examined.

In this report we present current data on prevalence, clinical significance and methods of diagnostics of occult hepatitis B. Mechanisms of occult hepatitis B formation are reviewed, among which the most important is co-infection with other hepatotropic viruses. Diagnostic significance of anti-HBcAg antibodies is shown. An algorithm of occult hepatitis B detection developed by the authors involves two stages: detection of viral markers in serum and liver tissue. Attention is drawn to the role of morphologic methods including histochemistry, immunohistochemistry and electron microscopy in verification of HBVinfection and direct visualization of virions in cytoplasm of hepatocytes.

To analyze the method for detecting HBV DNA in peripheral blood at low viral load and evaluate its significance in identifying HBsAg-negative viral hepatitis B. In this work, samples of blood and liver tissue biopsy material were used from 128 patients living in the Russian Federation and the Republic of Uzbekistan without CHB and with CHB confirmed detection of circle covalently closed HBV DNA in hepatocytes. Plasma viral load was measured using the «AmpliSens® HBV-Monitor-FL» kit. HBV at low viral load was detected by nested PCR. Analytical sensitivity was checked by step dilution. According to our method, at the first stage, an asymmetric PCR is carried out using extended oligonucleotide primers with different melting points, complementary to the hepatitis B different genotypes genomes greatest similarity region. To increase the sensitivity, a second PCR is performed using the first reaction amplification product and internal primers. The sensitivity of the method for DNA extraction from 100 μl of plasma was 5 IU / ml, specificity 100%. Since, in spite of the HBV genotypes characteristic geographical distribution, the detection of "alien" genovariants for certain territories is becoming more frequent, we tested the method in geographically remote but active international relations with the Russian Federation regions with a high frequency of hepatotropic viruses. The developed method for detecting HBV DNA in blood plasma at low viral load based on PCR technology allows the various HBV gene variants identification and genotyping, both characteristic and rare in the Russian Federation, circulating in other world regions. The method can be used to detect HBV in risk groups, in a population, as well as when screening blood donors in order to ensure the blood transfusions safety., Competing Interests: The authors declare no conflict of interest.

To analyze the method HBV covalent-closed circular DNA quantitative determination in liver puncture biopsies and evaluate its significance in identifying HBsAg-negative viral hepatitis B. In this work, samples of liver tissue biopsy material were used from 128 patients living in St. Petersburg, in various regions of the Russian Federation, as well as in the Republic of Uzbekistan. For quantitative analysis of HBV covalently closed circular DNA in a biopsy material a method was developed based on real-time PCR using TaqMan probes for the target fragment and for the endogenous reference gene, based on the detecting ccc HBV DNA method of Pollicino T. et al. When quantifying ccc DNA HBV in liver tissue of 18 moderately HBV activity with HBV DNA PCR positive results patients and 16 inactive HBsAg carriers, the ccc DNA HBV content was significantly different between groups (p<0.034) and in terms 1 copy of the β-globin gene among moderate activity HBV patients amounted to 1.71±1.32 copies/cell, and for inactive HBsAg carriers 0.15±0.14 copies/cell. In the group of patients with severe liver fibrosis and cirrhosis, the amount of ccc DNA HBV in liver tissue in patients with HBV averaged 2.5±0.4 copies/cell, in patients with HBV + D on average 0.7±0.25 copies/cell, in patients with HCV + HBV co-infection 0.45±0.07 copies/cell, in patients with a preliminary diagnosis of chronic hepatitis C hepatitis, on average 0.12±0.04 copies/cell, in patients with cryptogenic hepatitis 0.2± 0.05 copies/cell. A significant difference was shown between the group of patients with chronic hepatitis B with marked fibrosis and cirrhosis of the liver with other patients groups, except for the group of 18 moderate activity chronic hepatitis B patients. The values of Student's t-test when compared with other groups were respectively: for patients with a HCV preliminary diagnosis t=5,92 p<0,05 f = 19, patients with cryptogenic hepatitis t=5,71 p<0,05 f = 18, with «inactive HBsAg carriage» t=5,55 p<0,05 f = 29, with HCV + HBV co-infection t=5,05 p<0,05 f = 15 and HBV + D co-infection t=3,82 p<0,05 f = 17. The covalently closed circular DNA HBV quantitative assessment method in liver puncture biopsies allows identifying HBsAgnegative chronic viral hepatitis B forms and also reflects the virus replication activity, which, in turn, makes it possible to assume further disease progression and evaluate the antiviral therapy effectiveness., Competing Interests: The authors declare no conflict of interest.

Occult hepatitis B (ОHB) characterized by the absence of blood HBsAg attracts the attention of specialists of different profiles; however, its clinical morphological aspects have not been practically studied., Aim: to estimate the proportion of OHB in the structure of fatal outcomes in chronic viral hepatitis (CVH) and to characterize its clinical course and structural changes on autopsy materials., Material and Methods: A total of 455 autopsy cases of CVH were examined for its etiology in the S.P. Botkin Clinical Hospital of Infectious Diseases in 2014-2016. An in-depth prospective clinical analysis was made to investigate 28 cases of OHB in the stage of decompensated liver cirrhosis, which had subsequently culminated in death. The criteria of inclusion were history data and clinical symptoms of CVH in the detection of markers for hepatitis A, C, and D and HIV in serum HBcAb in the absence of HBsAg. HBsAbs were also determined. Along with the traditional morphological examination, immunohistochemistry (IHC) for HBsAg and HBcAg was carried out., Results: There were 108 CVHB cases (23.7% of the total cases of CVH), including 77 OHB cases (71.3% of those of CVHB) while HBsAg was not determined. HBsAb-negative patients were more often observed to have clinical signs of jaundice (p<0.05) and skin itching (p<0.05). Dyspepsia and hemorrhagic manifestations prevailed in patients with HBsAb (more than 10 IU/l) (p<0.05). All the cases were found to have characteristic morphological signs of CVH, including intranuclear inclusions and nuclear polymorphism in 10.7% of deaths. There was an IHC-positive reaction to VHB antigens in 28.6% of the patients and a doubtful reaction in 25.0%., Conclusion: Serum НВсAb may serve as a diagnostic marker for HBV infection. Clinical and morphological correlations enabled the authors to state that CVHB was present in all cases in the absence of serum HBsAg in the patients.