Hepatitis B virus

Epidemiology : endemic worldwide, the areas of highest endemicity being China and Southeast Asia, sub-Saharan Africa, most Pacific islands, and tropical regions of the Amazon river basin. The > 350 million HBsAg carriers in the world constitute the main reservoir of HBV. However, a prevalence of up to 5 to 20% has been found in the Far East and in some tropical countries; in persons with Down's syndrome, lepromatous leprosy, leukemia, Hodgkin's disease, polyarteritis nodosa; in patients with chronic renal disease on hemodialysis; and in injection drug users. In hyperendemic areas, such as Korea and China, infection rate with HBV exceed 50% by the age of 30. Other groups with high rates of HBV infection include spouses of acutely infected persons, sexually promiscuous persons (especially promiscuous men who have sex with men), health care workers exposed to blood, persons who require repeated transfusions especially with pooled blood product concentrates (e.g., hemophiliacs), residents and staff of custodial institutions for the developmentally handicapped, prisoners, and, to a lesser extent, family members of chronically infected patients. In volunteer blood donors, the prevalence of anti-HBs, a reflection of previous HBV infection, ranges from 5-10%, but the prevalence is higher in lower socioeconomic strata, older age groups, and persons—including those mentioned above—exposed to blood products. Prevalence of infection, modes of transmission, and human behavior conspire to mold geographically different epidemiologic patterns of HBV infection.

in the Far East and Africa, hepatitis B, a disease of the newborn and young children, is perpetuated by a cycle of maternal-neonatal spread.

Taiwan : there are presently 3 million people infected with HBV
Albania : one or more serological markers of HBV infection are found in 75% of Albanians, confirming the endemic nature of this virus in the Albanian community. The overall prevalence of HBsAg ranges from 10^ref-13.6^ref-19-22.2% (the highest carrier rate for HBsAg was found in the age group 21-25 years. A relevant finding was a prevalence of HBsAg of 8.1% in children 10 years and under^ref; 13.4% in pregnant women^ref), and the carrier rate is higher in males than in females. The high HBsAg prevalence among children suggests that HBV infection is usually acquired in early childhood^ref. Prevalence of total anti-HBcAg antibody is 62.1^ref-70.6% (70.8% in pregnant women : anti-HBc IgM 0.4%^ref), prevalence of anti-HBsAg antibody is 40.5-47.6%^ref (53% in pregnant women^ref), prevalence of HBeAg is 21.1% (7.7% among HBsAg carriers^ref; 1.2% in pregnant women; 7.5% of HBsAg carrier pregnant women^ref), prevalence of anti-HBeAg antibody is 46.2% (58.6% in pregnant women^ref). Prevalence of hepatitis B markers, as determined by HBsAg and/or anti-HBs and/or total anti-HBc was significantly higher in pregnant women with a history of previous hospitalization in Albania and those with previous history of hepatitis. The high prevalence of hepatitis B markers in pregnant Albanian refugees proves that HBV infection is highly endemic in Albania and the possibility of perinatal transmission to the offsprings urges for HBV vaccination programmes. On the other hand improvements in the socioeconomic conditions and the sanitation system in Albania is anticipated to reduce the incidence of HAV and HBV infections^ref. Here is the situation for the other viral hepatitides :

prevalence of anti-HAV is 96-98.2% (96.2% in pregnant women^ref); it was very high in children 0-10 years, suggesting that HAV infection is largely acquired during childhood and that poor ambiental conditions influence the spreading of this viral infection.
prevalence of anti-HCV antibodies is 1.75% (0.3 in HBsAg carriers^ref; 0.6% in pregnant women^ref)
prevalence of anti-HDV antibodies ranges from 1.1^ref-12.7%^ref (0.4% in pregnant women^ref). Of the 62 patients, 75.8% had HBeAg-negative chronic hepatitis B. Genotype D was found in all 39 patients with detectable HBV viremia, for whom the heterogeneity of the region modulating HBeAg expression was assessed. Basic core promoter (BCP) mutations (1762/1764) were observed more often in anti-HBe-positive and older patients. In > 90% of the HBeAg-negative chronic hepatitis B patients with detectable viremia, HBV that carries the G to A pre-core mutation at nucleotide 1896 was found. Patients with HBeAg-positive chronic hepatitis B were younger than HBeAg-negative chronic hepatitis B patients, and for symptomatic and asymptomatic liver-disease patients, the age of peak prevalence was >10 years lower for HBeAg-positive chronic hepatitis B patients. In conclusion, the virological and clinical pattern of chronic hepatitis B in Albania is similar to that observed in other Mediterranean countries; it seems to be independent of the HBV endemicity level^ref.
prevalence of anti-HEV antibodies is 2% in pregnant women^ref

^ref

in North America and western Europe, hepatitis B is primarily a disease of adolescence and early adulthood, the time of life when intimate sexual contact as well as recreational and occupational percutaneous exposures tend to occur.

Italy : 1.800.000 people HBsAg⁺
USA : about 1.25 million Americans are infected and another 100,000 are infected annually

Genomics : it integrates near RARb / HBV-activated protein

. HBV has been classified into 8 genotypes (A, B (further divided into Ba ("a" stands for Asia) and Bj ("j" for Japan)), C, D, E, F, G, H) based on genome sequence divergence. Genotypes of HBV have distinct geographical distributions, and two genotypes account for most HBV worldwide. Hepatitis B e antigen expression lasts longer and liver disease is more severe with graver outcomes in carriers of genotype C than B in Asia. Accumulating lines of evidence indicate a better response to interferon and lamivudine in patients with chronic hepatitis B who are infected with genotype B rather than C. The therapeutic response may differ, however, in patients infected with HBV of the same genotype. For example, the response to lamivudine is poorer in patients infected with subtype Ba, which contains a recombination with genotype C, than in those with subtype Bj without such a recombination. Influence of genotypes on therapeutic response needs to be examined in patients infected with the other genotypes, particularly in those with genotype A or D infection. A restriction site for EarI in genotype B was absent in spite of its presence in all the other genotypes and genotype C has no restriction site for AlwI. Only genotype E is digested with NciI, while only genotype F has a restriction site for HphI. Genotype A can be distinguished by a single restriction enzyme site for NlaIV, while genotype D digestion with this enzyme results in 2 products that migrates at 265 and 186 bp^ref.
Proteomics :

HBsAg on pericapsid (previously called Australia Ag, then discovered on Dane particles (virion aggregates) : HBsAg secreted largely in excess (to act as a decoy for Abs) by HBV-infected hepatocytes and present in the plasma of infected individuals is a complex macromolecule composed of proteins and lipids. The 22-nm coreless HBsAg lipoprotein particles contain 3 natural variants of HBsAg designated large (LS), middle (MS), and small (S) surface proteins. The major HBsAg species is the small, secreted S protein present as nonglycosylated p24 and glycosylated gp27. The MS protein contains an additonal N-terminal preS2 domain and is expressed as nonglycosylated p33 and glycosylated gp36. The intracellular LS protein with additional preS1 and preS2 domains N-terminal to the S region is expressed as nonglycosylated p39 and glycosylated gp42. All 3 HBsAg species form particulate structures when expressed individually. The MS and S Ags are efficiently secreted from transfected cells, whereas the LS Ag is excluseively found intracellularly. Each strain has strain-specific epitopes (d, y, w or r), but all 3 natural HBsAg variants in all strains contain the conformational a determinant in the S_120-147 region that is recognized by most human and murine Abs. The a determinant of S protein forms a loop between 2 transmembrane domains, is glycosylated, and is present in envelope proteins of almost all known HBV isolates, even if some strains have point mutations. The preS region of the large envelope protein L binds IL-6 and IL-6R facilitates virus entry into cells. HBV pre-s2 binding protein 1
HBcAg on capsid (core (C) protein). Its expression is negatively modulated by NR2C2 / TR4 . It is phosphorylated by SRPK1 and SRPK2, a prerequisite for pregenomic RNA encapsidation into viral capsids
HBeAg in capsid (a proteolytic fragment of C protein) : please note some pre-core mutants prevents production of HBeAg, an immunodominant epitpope for CMI.
HBxAg = pX, a v-oncogene that inhibits p53 and p110^RB1. and is negatively regulated by HBV-X associated protein / aryl hydrocarbon receptor interacting protein (AIP). Further it interacts with HBV pX associated protein-8 and C6 subunits of 26S proteasome

NR5A2

binds specifically to the B1 region (AACGACCGACCTTGAG) within the major functional unit (B unit) of Enhancer II (ENII), activating one of the essential cis-elements for the transcriptional regulation of HBV gene expression. SON DNA binding protein binds to a specific DNA sequence upstream of the upstream regulatory sequence of the core promoter and ENII : through this binding, it represses HBV core promoter activity, transcription of HBV genes, and production of HBV virions.
The highly conserved encapsidation signal (e) of HBV pregenomic RNA has been reported as an essential component for encapsidation and protein priming of HBV polymerase : it is bound by interleukin enhancer binding factor 3, 90kDa (ILF3) / NF90/interleukin enhancer binding factor 2, 45kDa (ILF2) / NF45 and heat-shock protein gp96 / adenotin / tumor rejection antigen-1 (TRA-1)
Transmission : it resists for about 4 hours at 60°C and years at -20°C

parenteral route (blood transfusion or by sharing of needles among drug users) : risk of infection after single exposure = 2-40% according to HBsAg positivity; in approximately 66% of patients with acute type B hepatitis, there is no history of an identifiable percutaneous exposure; many cases of hepatitis B result from less obvious modes of nonpercutaneous or covert percutaneous transmission.
HBsAg has been identified in almost every body fluid from infected persons, and at least some of these body fluids are infectious, albeit less so than serum, when administered percutaneously or nonpercutaneously to experimental animals.

the 2 nonpercutaneous routes considered to have the greatest impact are

intimate (especially sexual) contact
perinatal transmission via transplacental route (35-50% of carriers). In sub-Saharan Africa, intimate contact among toddlers is considered instrumental in contributing to the maintenance of the high frequency of hepatitis B in the population. Perinatal transmission occurs primarily in infants born to HBsAg carrier mothers or mothers with acute hepatitis B during the third trimester of pregnancy or during the early postpartum period. Perinatal transmission is uncommon in North America and western Europe but occurs with great frequency and is the most important mode of HBV perpetuation in the Far East and developing countries. Although the precise mode of perinatal transmission is unknown, and although approximately 10% of infections may be acquired in utero, epidemiologic evidence suggests that most infections occur approximately at the time of delivery and are not related to breast feeding. The likelihood of perinatal transmission of HBV correlates with the presence of HBeAg; 90% of HBeAg-positive mothers but only 10 to 15% of anti-HBe-positive mothers transmit HBV infection to their offspring. In most cases, acute infection in the neonate is clinically asymptomatic, but the child is very likely to become an HBsAg carrier. Perinatal transmission of and infection with HBV in early childhood are observed in a small proportion of the offspring of HBsAg⁺ mothers who are vaccinated against HBV immediately after giving birth. The children may be infected by wild-type HBV or by variants with amino acid substitutions in the "a" determinant of HBsAg, particularly at position 145 and, rarely, at positions 120, 126, 129, 131, 141, and 144. When 446 newborn infants of HBsAg-positive mothers in the northeastern part of the Czech Republic received combined active and passive immunisation against HBV, only 1 child became an HBsAg carrier. This followed a mild, acute HBV illness in the beginning of the second year of his life : HBV DNA encoding the "a" determinant and surrounding region of HBsAg was sequenced after amplification from the plasma of the child and his mother. The child was infected with variants of HBsAg with substitutions at residues 137 and 139. The virus of the mother had changes at residues 120 and 121. HBV from both child and mother had an unusual substitution at residue 118 and seemed to be of the ayw subdeterminant^ref.

inefficient nonpercutaneous routes

semen : both spermatozoa and mononuclear cells contain HBV-DNA. Moreover, free HBV-DNA was identified in the semen of patients without markers of viral replication in serum indicating that sexual transmission could still occur^ref.
urine : the likely source for HBV-DNA are peripheral blood leucocytes^ref
saliva : the likely source for HBV-DNA are peripheral blood leucocytes^ref. Oral ingestion has been documented as a potential but inefficient route of exposure because antireceptor is inactivated by carboxypeptidase A in gut : anyway some strains lack protease for HBeAg production and are transmitted mainly from oro-faecal route (once called hepatitis F virus (HFV)). After intensive source and contact tracing 20% of acute HBV infections remain unexplained. Saliva may be an unexpected vehicle of HBV DNA transmission. Median HBV DNA levels in serum are 2.10 x 10⁵ genome equivalents per ml (geq/ml) and ranged from 373 geq/ml to 4.13 x 10⁹) geq/ml; median HBV DNA levels in saliva were 2.27 x 10⁴ geq/ml and ranged from 373 geq/ml to 9.25 x 10⁶ geq/ml. A clear correlation was shown between HBV DNA in serum and saliva; log HBV DNA in saliva=1.01 + 0.56 x (log HBV DNA in serum)^ref. Saliva testing is feasible for HBV screening among children in low prevalence populations (specificity and sensitivity of anti-HBc tests on saliva was 100%), but any anti-HBc reactivity should be confirmed by plasma analysis^ref. The frequency of HBsAg detection by Enzyme Immune Assay (EIA) in saliva of patients in acute period was found to correlate with the frequency of its detection in serum. In early convalescence the frequency of detection of that antigen in serum (59.5% of patients) was significantly higher than in saliva (23.8%) (P < 0.001).The frequencies of HBeAg detection by EIA in saliva samples was significantly higher than that in serum samples in both acute phase (84.3% and 28.1% of patients, respectively) and in early convalescence (56.2% and 3.1% of patients, respectively). The study of frequencies of detection of these antigens in the dynamics of the disease up to the total recovery of patients (observations were carried out for the period of 60 days and longer) showed that in most patients there was a faster disappearance HBsAg from saliva than from serum. By the end of second month this antigen was detected in saliva of only 8.3% of patients whereas in serum in the same period HBsAg was detected in 33.3% of patients. HBeAg became undetectable in blood whereas HBs-antigenemia was still pronounced, and a month after the beginning of the disease it was not found in serum specimens. In saliva, HBeAg was detected in 95.8% of patients observed directly after admission. A month after the beginning of the disease it was detected in saliva of 66.7% of patients and, by the end of observation period, in 12.5% of patients recovered from viral hepatitis. HBV DNA revealed by PCR in saliva and serum of HBV-infected patients was detected in acute period not only in serum (84.6% of cases) but also in saliva (46.2% of cases)^ref. A report found a non-invasive saliva testing method to be a possible alternative approach for determining chronic HBV carrier status in pregnant women if the sensitivity of the test can be improved^ref.

Susceptibility : HLA-B8 and HLA-DR7, codon 54 of exon 1 mutation in MBL

.
Resistance (=> persistance) : HLA-DRB1*1302.
Pathogenesis : damage is mainly immune mediated (MHC class I-associated HBcAg and HBeAg presentation). Increase in SGPT up to 4,000 U/L at 37°C : HBV reduces steady-state levels of apoAI

and apoCIII

mRNAs. Chromosome 20 open reading frame 18s is an HBV associated factor. Infection increases expression of PCNA and GST-pi. Soluble TRAIL

may participate in the liver damage
Incubation : 30÷180 days.
=> acute hepatitis

B (AHB) / (homologous) serum hepatitis / inoculation hepatitis / long-incubation hepatitis / MS-2 hepatitis in immunocompetent indivuals. If immune system is hyperergic => fulminant hepatitis

Laboratory examinations :

ground glass hepatocytes (GGHs) are the historic hallmarks for the hepatocytes in the late and nonreplicative stages of HBV infection

type I GGHs contain HBsAg mutants with deletions over the pre-S1 region
type II GGHs contain HBsAg mutants with deletions over the pre-S2 region, often appear in hepatic nodules in the late phases of HBV infection and proliferate in clusters, suggesting that these mutant pre-S1/S2 HBsAg may be involved in HBV-related hepatocarcinogenesis, associated with ER stress

^ref

serum markers (no longer required in Italy at admission in hospital) ...

... of infection : high [HBsAg]_pl (< 10 mIU/mL => negative)
... of viral replication :

high [HBV-DNA]_pl measured by the Digene Hybrid Capture II microplate assay (Digene Diagnostics), the HBV Monitor assay (Roche Diagnostics) as well as an in-house developed HBV DNA TaqMan assay.
high [HBeAg (only when produced !!!)]_pl (< 10 mIU/mL => negative)

... of acute hepatitis B : high [anti-HBcAg IgM]_pl

< 0.2 index => negative
0.201-0.8 index
0.801-1.2 => borderline
> 1.20 => acute hepatitis

... of recovery (i.e. end of acute hepatitis B) :

high [anti-HBsAg IgM]_pl (while [HBsAg]_pl disappears)
high [anti-HBeAg IgM]_pl (while [HBeAg]_pl disappears)

_pl

=> persistent hepatitis B in individuals with TNF-a

-308 polymorphism. Most patients recover completely and become HBsAg-negative in 3 to 4 months, but some remain chronic carriers for > 6 months and 10-20% develop chronic hepatitis

B, expecially in young males (80% before age 6 !), chronic alcoholists, CMID

and Oriental races : no development of anti-HBsAg IgM, persistent HBsAg and anti-HBcAg IgG.
HBV carriers who develop the "pre-S" protein on their livers have a 56% chance (twice that for normal HBV carriers) for getting hepatocellular carcinoma (HCC)

in 10 years. According to computer estimations, the chances of developing liver cancer would increase to 65% in 15 years^ref. Elevated serum HBV DNA level (> 10,000 copies/mL) is a strong risk predictor of hepatocellular carcinoma independent of HBeAg, serum alanine aminotransferase level, and liver cirrhosis^ref.
Complications :

acute glomerulonephritis
polyarteritis nodosa
type III hypersensitivity 2 weeks before jaundice onset in acute hepatitis : maculopapular exanthema on trunk and limbs, arthralgias, and urticaria
essential mixed cryoglobulinemia
carotid atherosclerosis ^ref
Gianotti-Crosti syndrome (GCS) / papular acrodermatitis of childhood (PAC)
no association with Hodgkin's lymphoma (HBV infection was 0,5%^ref in Hungarian blood donors and 0,9% in HD patients^ref)

Virus is found in blood, saliva and sperm (but nor in urine) of infected individuals.
Prevention :

Hepatitis B vaccine and immunoglobulin, solely or in combination, reduce hepatitis B occurrence in newborn infants of mothers seropositive for hepatitis B surface antigen (HBsAg) : there is no significant differences between low dose and high dose vaccine nor recombinant and plasma derived vaccine, but vaccine + immunoglobulin was superior to vaccine alone^ref
Therapy :

entecavir : among patients with HBeAg-negative chronic hepatitis B who had not previously been treated with a nucleoside analogue, the rates of histologic improvement, virologic response, and normalization of ALT levels were significantly higher at 48 weeks with entecavir than with lamivudine^ref. Among patients with HBeAg-positive chronic hepatitis B, the rates of histologic, virologic, and biochemical improvement are significantly higher with entecavir than with lamivudine^ref. The safety profile of the 2 agents was similar, and there was no evidence of viral resistance to entecavir
lamivudine
N-nonyl deoxynojirimycin (NN-DNJ)
adefovir dipivoxil

Reactivation of HBV is a well-recognized complication of chemo/immunosuppressive therapy in individuals who are HBsAg⁺ inactive carriers and in individuals with chronic HBV infection. Although it is well established that chemo/immunosuppressive therapy enhances HBV replication with a resultant increase in the viral load and disease activation, the role of prophylactic lamivudine therapy to prevent chemo/immunosuppressive therapy-induced HBV activation in HBV⁺ individuals who are to receive chemo/immunosuppressive therapy remains controversial. The aims of the present article are: (i) to determine the effect of lamivudine prophylaxis in HBV carriers with haemato-oncological malignancies who require chemotherapy; (ii) to define the duration and safety of lamivudine in such individuals; and (iii) to identify the effect of lamivudine prophylaxis on the outcome of chemotherapy administered for the primary disease. The data currently available suggest that lamivudine prophylaxis prevents chemotherapy-induced HBV reactivation in HBV carriers with haemato-oncological malignancies who receive chemotherapy. Lamivudine is safe and tolerable in such individuals. The duration of lamivudine prophylaxis is not yet known; however, it would appear prudent to begin lamivudine at the time of the initiation of the chemotherapy and to continue it throughout the period of chemotherapy administration and for > 1 and possibly 2 years following the discontinuation of the chemotherapy. Finally, the prophylactic use of lamivudine in inactive HBV carriers with haemato-oncological malignancy prevents interruptions in their treatment for primary disease as a result of HBV reactivation^ref.