Frequency of HBsAg variants in occult hepatitis B virus infected patients and detection by ARCHITECT HBsAg quantitative

Objective

To analyze the amino acid substitution caused by mutations in the major hydrophilic region (MHR) of the S-region genes in the serum samples of occult hepatitis B virus infection (OBI), and to explore the reasons for the missed detection of HBsAg.

Method

The full-length gene of the S-region in hepatitis B virus(HBV) in the chronic hepatitis B virus(CHB)(10 samples) and OBI groups(42 samples) was amplified using a lab-developed, two-round PCR amplification technology. The PCR amplification products were sequenced/clone sequenced, and the nucleotide sequences of the S-region gene in HBV were compared to the respective genotype consensus sequence.

Results

Only 20 of the 42 samples in the OBI group had the S-region genes successfully amplified, with the lowest HBV DNA load of 20.1IU/ml. As S-region genes in HBV, 68 cloned strains were sequenced. In the OBI and CHB groups MHR region, with a mutation rate of 3.21% (155/4828) and 0.70% (5/710). The genetic mutation rate was significantly higher in the OBI group than in the CHB group (P<0.05). The common mutation types in the MHR region were: I126T, L162R, K122E, C124R, and C147Y.Mutations at s122, s126, and s162 were associated with subgenotypes, most of which being C genotypes. The high-frequency mutation sites L162R and K122E found in this study have not been reported in previous literature.

Conclusion

The results of this study confirmed that MHR mutations can cause the missed detection of HBsAg, giving rise to OBI.

Systematic Optimization of Universal Real-Time Hypersensitive Fast Detection Method for HBsAg in Serum Based on SERS

Hepatitis B virus (HBV) is a major cause of liver cirrhosis and hepatocellular carcinoma, with HBV surface antigen (HBsAg) being a crucial marker in the clinical detection of HBV. Due to the significant harm and ease of transmission associated with HBV, HBsAg testing has become an essential part of preoperative assessments, particularly for emergency surgeries where healthcare professionals face exposure risks. Therefore, a timely and accurate detection method for HBsAg is urgently needed. In this study, a surface-enhanced Raman scattering (SERS) sensor with a sandwich structure was developed for HBsAg detection. Leveraging the ultrasensitive and rapid detection capabilities of SERS, this sensor enables quick detection results, significantly reducing waiting times. By systematically optimizing critical factors in the detection process, such as the composition and concentration of the incubation solution as well as the modification conditions and amount of probe particles, the sensitivity of the SERS immune assay system was improved. Ultimately, the sensor achieved a sensitivity of 0.00576 IU/mL within 12 min, surpassing the clinical requirement of 0.05 IU/mL by an order of magnitude. In clinical serum assay validation, the issue of false positives was effectively addressed by adding a blocker. The final sensor demonstrated 100% specificity and sensitivity at the threshold of 0.05 IU/mL. Therefore, this study not only designed an ultrasensitive SERS sensor for detecting HBsAg in actual clinical serum samples but also provided theoretical support for similar systems, filling the knowledge gap in existing literature.

Comparison of S gene mutations in patients with occult and chronic hepatitis B virus infection

BACKGROUND AND AIM

This study aimed to detect mutations in the HBV S gene and evaluate their relationship to occult hepatitis B virus (HBV) infection (OBI).

METHODS

The study included 32 patients with negative serum HBsAg and HBV DNA who underwent liver biopsy due to different clinical indications defined as the OBI group and 32 patients who underwent liver biopsy due to chronic hepatitis B (CHB) as the comparison group. The HBV S gene region was amplified by Nested PCR, and Sanger sequencing was performed.

RESULTS

At least one amino acid (aa) mutation was detected in the major hydrophilic region (MHR) of the HBV S gene in 14/32 (43.75%) of the patients with OBI and 8/32 (25.0%) with CHB. The genotype of all patients with OBI and CHB was HBV/D. Although 9 (28.1%) of the cases with OBI had sub-genotype HBV/D3, none of the patients with CHB had sub-genotype HBV/D3. Unlike patients with CHB, L15*, D33N, Q51P, V63F, L91I, P108S, T115I, P120L, T125M, Q129H, T189I, L216F, P217L mutations were detected in the HBV S gene in OBI cases. Also, P127T aa polymorphism was frequently detected. Mutation frequency in the HBV S gene in the major hydrophilic region (MHR) was higher in patients with OBI with sub-genotypes HBV/D3 and D2 than those with HBV/D1 and those with serotype HBV/ayw3 compared to those with HBV/ayw2 (p < 0.05).

CONCLUSIONS

Sub-genotypic-specific mutation patterns were seen in the "a" determinant region and T helper cell epitopes of HBsAg, especially in the C-terminus domain; this may be associated with OBI.

Occult Hepatitis B Infection among Hemodialysis in Tabriz, Northwest of Iran: Prevalence and Mutations within the S Region

Regardless of the extensive screening for the detection of hepatitis B surface antigen (HBsAg), hemodialysis (HD) patients are still severely at the risk of occult hepatitis B virus infection (OBI), especially in developing countries. OBI is defined as the presence of HBV DNA with undetectable HBsAg in the liver and/or Serum. This study aims to determine the prevalence of OBI in HD patients in Tabriz Province, northwest of Iran, and inquire about the mutations in the detected HBsAg. In this cross-sectional descriptive study, ELISA method assessed serum and plasma samples of 118 HBsAg-negative patients undergoing HD treatment for HBV serological markers (HBsAg and Anti-HBc). Specific primers by nested polymerase chain reaction have been utilized to examine HBV DNA; also, direct sequencing of surface genes was carried out to characterize the viral genotypes and S gene mutations. Finally, followed by real-time PCR, the quantity of viral load in OBI-positive patients was determined. A total of 118 HD patients were included (63.6% were male and 36.4% female), with an overall mean age of 60.8 ± 12.8 years old. The prevalence of antihepatitis B core antibody (Anti-HBc) in the study population was 26.3% (31/118). Five patients (4.2%) were positive for HBV DNA and labeled OBI-positive; their plasma HBV-DNA load was less than 100 IU/ml. Following the phylogenetic analysis, the samples with OBI roughly belonged to genotype D, subtype ayw2 and only two had mutations within the S ’gene’s major hydrophilic region (MHR), including T123I, C124F, and P127T. This study reports the prevalence of OBI in the HBsAg-negative HD patients being at a rate of 4.2%, which can be a clinically vital consideration in this region. HBV serologic screening approaches need to be renewed to cover nucleic acid testing in the setting of hemodialysis and all the other high-risk groups associated with it (i.e., blood and organ donors).

Research Progress on the Mechanism of Persistent Low-Level HBsAg Expression in the Serum of Patients with Chronic HBV Infection

Among HBV-infected persons, there is a group of people with hepatitis B surface antigen (HBsAg) showing persistently low levels of expression. The production of low-level HBsAg does not mean a good outcome of chronic HBV infection. Patients still have virus replication and sustained liver damage, and they have the potential to transmit the infection. This risk poses a challenge to clinical diagnosis and blood transfusion safety and is a major concern of experts. However, the mechanism behind persistent low-level HBsAg expression in serum is not completely clear, and complete virus clearance by the host is vital. In this review, we summarize the research progress on the mechanism behind low-level expression of HBsAg in patients with chronic HBV infection in recent years.

Occult hepatitis B virus infection in patients with chronic liver disease of different etiology in a Brazilian referral center: comparison of two different hepatitis B virus deoxyribonucleic acid amplification protocols: a cross-sectional study

BACKGROUND

Occult hepatitis B virus infection (OBI) is defined as the presence of hepatitis B virus (HBV) deoxyribonucleic acid (DNA) in the liver of individuals with undetectable hepatitis B virus surface antigen (HBsAg) in the serum. The actual prevalence of OBI and its clinical relevance are not yet fully understood.

OBJECTIVE

To evaluate the prevalence of HBV DNA in liver biopsies of HBsAg-negative patients with chronic liver disease of different etiologies in a referral center in Brazil and compare two different HBV DNA amplification protocols to detect HBV.

DESIGN AND SETTING

This cross-sectional observational study was conducted at the Liver Outpatient Clinic, Hospital das Clínicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil, between January 2016 and December 2019.

METHODS

HBV DNA was investigated in 104 liver biopsy samples from individuals with chronic liver disease of different etiologies, in whom HBsAg was undetectable in serum by nested-polymerase chain reaction (nested-PCR), using two different protocols.

RESULTS

OBI, diagnosed by detecting HBV DNA using both protocols, was detected in 6.7% of the 104 individuals investigated. Both protocols showed a good reliability.

CONCLUSION

In addition to the differences in the prevalence of HBV infection in different regions, variations in the polymerase chain reaction technique used for HBV DNA amplification may be responsible for the large variations in the prevalence of OBI identified in different studies. There is a need for better standardization of the diagnostic methods used to diagnose this entity.

Comparative assessment of immunochromatography and ELISA diagnostic tests for HBsAg detection in PCR-confirmed HBV infection

INTRODUCTION AND AIMS

Viral hepatitis, which appears most frequently at birth or during childhood, is a disease whose transmission routes include tears, bile, sexual fluids, sweat, milk, urine, feces, and saliva. The aim of the present study was to analyze the specificity of the immunochromatographic and ELISA diagnostic tests for hepatitis B surface antigen and compare them with PCR testing.

MATERIALS AND METHODS

The study sample was made up of 140 men and 60 women referred to the Urmia Medical University hospital to undergo PCR testing for HBV diagnosis. The ELISA test was performed using the Pioneer Medicine Company kit (Tehran, Iran).

RESULTS

The results of the HBs-Ag rapid test and the ELISA test were compared with the PCR test. The HBs-Ag rapid test had 97% sensitivity and 91% specificity, whereas the ELISA test had 78% sensitivity and 76% specificity.

DISCUSSION AND CONCLUSION

According to our results, the immunochromatographic test was accurate for diagnosing HBs-Ag in blood and the ELISA test had acceptable sensitivity and specificity, compared with PCR testing.

Occult HCV and occult HBV coinfection in Iranian human immunodeficiency virus-infected individuals

The presence of hepatitis C virus (HCV) genome in liver biopsy or peripheral blood mononuclear cell (PBMC) specimens in the absence of detectable HCV-RNA in plasma of the people with or without anti-HCV antibodies has defined as occult HCV infection (OCI), whereas occult hepatitis B virus infection (OBI) is detection of hepatitis B virus (HBV) genome in the absence of traceable hepatitis B surface antigen in the plasma samples of patients. The purpose of this study is to determine the presence of OBI and OCI in human immunodeficiency virus (HIV)-infected individuals. In this cross-sectional research, 190 Iranian HIV-infected individuals were enrolled from September 2015 to February 2019. All participants were tested regarding various serological markers for HCV and HBV infections. Viral RNA and DNA were extracted from plasma and PBMC specimens, and the presence of HCV-RNA in plasma and PBMC samples was tested using reverse transcriptase-nested polymerase chain reaction (PCR), HBV viral load was determined in plasma samples using COBAS TaqMan 48 Kit, and also the presence of the HBV-DNA in PBMC samples was tested by real-time PCR. In this study, the prevalence of OBI and OCI in HIV-infected individuals was 3.1% and 11.4%, respectively. The genotypes of HCV in the patients with OCI were as follows: 57.1% were infected with subtype 3a, 35.7% were infected with subtype 1a, and 7.1% was infected with subtype 1b. It is noteworthy that in this study, two patients (1.1%) had OCI/OBI coinfections. The present study revealed that 1.1% of Iranian HIV-infected individuals had OBI and OCI at the same time. Therefore, it seems that designing prospective surveys to determine the presence of this coinfection in HIV-infected individuals is informative.

Association of HBsAg mutation patterns with hepatitis B infection outcome: Asymptomatic carriers versus HCC/cirrhotic patients

INTRODUCTION AND OBJECTIVES

The hepatitis B virus (HBV) surface antigen (HBsAg) variations suggested having some effects on infection outcome. Due to some controversial issues, the aim of this study was to compare the pattern of HBsAg variation between asymptomatic carriers and HCC/cirrhosis patients.

MATERIALS AND METHODS

In this cross-sectional study, 19 HCC/cirrhotic and 26 asymptomatic patients were enrolled. After viral DNA extraction, HBs gene was amplified using an in-house nested-PCR. Then, PCR products were introduced into bi-directional Sanger sequencing. The retrieved sequences were compared with references, to investigate the variation of immunologic sites, major hydrophilic region (MHR) of HBsAg as well as reverse transcriptase (RT), and also to determine genotype/subtype.

RESULTS

The analysis of MHR and epitopes on HBsAg showed dozens of substitution, which occurred more prevalently in I110, P120, Y134, G159, S193, Y206, S207, I208, L213 and P214 positions. However, Y134N/F/L (P=0.04) and P120T/S (P=0.009) were significantly detected in MHR and B-cell epitope of HCC/Cirrhotic group. A number of truncation-related mutations were higher in HCC/Cirrhotic group (P>0.001), albeit only C69* stop codon was statistically significant (P=0.003). In RT, some potentially resistant substitutions such as Q215S, V191I and V214A, were revealed. Phylogenetic analysis showed that all of isolates belonged to genotype D, and the major serotype was ayw1.

CONCLUSION

The higher frequency of substitutions in MHR and immune epitopes at positions such as Y134 and P120 as well as stop codons such as C69* in HCC/cirrhotic group might candidate them as predictive factors for infection outcome.

Conformational analysis of hepatitis B virus surface antigen mutations among HIV-positive patients diagnosed with occult hepatitis B virus

Aim: We analyzed the role of mutations on the conformational structure of hepatitis B surface antigen (HBsAg) among HIV-1 positive patients who were infected with occult hepatitis B. Methods: The effects of the potential impact of amino-acid substitutions on the 3D structures of the HBsAg and molecular ducking were investigated using bioinformatics software. Results: Mutations classified in seven groups in accordance with their positions in occult hepatitis B virus infection patients. Some substitutions of residues could linearize the ‘a’ determinant loops. The affinity of binding in mutant HBsAg structures to MAb 12 was lower compared with the wild ones. T123I and P127L substitutions were undergone decrease in HBsAg antigenicity. Conclusion: These findings could be beneficial for a better understanding of hepatitis B virus antigen/antibody interactions.

The modulation of HBsAg level by sI126T is affected by additional amino acid substitutions in the S region of HBV

The hepatitis B surface antigen (HBsAg) is a vital serum marker for hepatitis B virus (HBV) infection. Amino acid (AA) substitutions in small hepatitis B surface protein (SHBs) are known to affect HBsAg level. However, how the genetic backbones of SHBs sequences would affect the roles of a specific AA substitution on HBsAg level remains unclear. In this study, we found that sI126 had a very high substitution detection rate of 17.54% (40/228) in untreated chronic hepatitis B cohort with subgenotype C2 HBV infection. Among different substitution types at sI126, the sI126T (N = 28) was found to be associated with significantly lower serum HBsAg level. Clone sequencing revealed that sI126T-harboring SHBs sequences had varied genetic backbones with zero to nine additional AA substitutions. Thus, we constructed 24 HBsAg expression plasmids harboring sI126T without (plasmid 1, P1) or with (P2-P24) additional AA substitution(s) and studied them in the HepG2 cells. The HBsAg levels were determined by both ELISA and Western blot. In vitro experiments showed that P1 significantly reduced HBsAg level and its secretion (p < .05), however, P2-P24 showed various extracellular and intracellular HBsAg levels. No significant differences were detected among the HBsAg mRNA levels of nine representative mutant plasmids. Our findings suggest that the modulation of HBsAg level by sI126T is affected by additional AA substitution(s) in the S region of HBV. The effects of AA combination substitutions in SHBs sequences on HBsAg levels are worthwhile for more attentions in terms of HBV biology and its clinical application.

Roles of Hepatitis B Virus Mutations in the Viral Reactivation after Immunosuppression Therapies

Reactivation of hepatitis B virus (HBV) is a major problem in patients receiving chemotherapy for malignant diseases or immunosuppression therapies. It has been thought that a reduction in the immune responses might result in the reactivation of HBV replication from covalently closed circular DNA (cccDNA) residing in hepatocytes. However, not only the host’s immune status, but also viral mutations have been reported to be associated with reactivation. Especially, several case reports about amino acid mutations in hepatitis B surface antigen (HBsAg) that escape from immune reactions have been reported, and recent reports showed that the frequencies of such mutations are higher than previously expected. In this review, we summarize the characteristics of viral mutations, including immune escape mutations in HBV-reactivated patients, and discuss their significance.

Molecular and serological characterization of occult hepatitis B virus infection among patients with hemophilia

BACKGROUND

The occult hepatitis B virus infection (OBI) is a health concern among high-risk groups and immunosuppressed individuals. There is still a paucity of data regarding the occult hepatitis B virus infection among hemophilic patients. With this in mind, we aimed to evaluate the molecular prevalence of OBI among clients with hemophilia.

METHODS

Totally, 87 hemophilic patients were selected to be studied. To detect OBI, nested polymerase chain reaction test was used to amplify HBV-S, X, and Core regions. Viral load was determined using an in-house real-time PCR assay. Finally, sequence of S gene was used for genotyping and analysis of mutations.

RESULTS

The mean age of patients was 28.4 ± 5.3 years old, with 90.7% of whom were men. HBV-DNA was detected in eight subjects (9.3%). The rate of OBI was much higher in anti-HBs seronegative subjects than that in other patients (P = 0.019). All OBI cases had HBV genotype D, subgenotype D1. In addition, five out of eight cases (62.5%) showed detectable viral loads (a mean viral load of 4.5 × 10 ² copies/mL). sR73H, sI110L, sP120A, sP127T, sQ129H, sG130R, and sC137S were shown to be the most determinant escape mutation and OBI-relevant mutants.

CONCLUSION

The rate of OBI among the studied population of hemophilia seems to be remarkable. Therefore, screening for OBI must be a routine practice in patients with hemophilia and also patients undergoing immunosuppressive treatments. Amino acid substitutions were observed in the major hydrophilic region. However further investigations are needed for analysis of exact function.

Epidemiology, risk factors, and molecular characterization of occult hepatitis B infection among anti-hepatitis B core antigen alone subjects

OBJECTIVES

Features of occult hepatitis B virus (HBV) infection among the anti-hepatitis B core antigen (anti-HBc) positives have yet to be described in more details. This study aimed to determine the molecular prevalence of occult HBV infection (OBI), and association to risk factors among seropositives for anti-HBc.

METHODS

This was part of a community-based screening project that included 5234 cases. All participants completed a questionnaire on demographic and socio-epidemiological information. Then, the blood samples were collected and tested for anti-HBc and HBsAg using ELISA method. To identify OBI, nested-polymerase chain reaction (PCR) assays were performed for HBV-S and X genes, and viral load was determined using an in-house real-time PCR. Sequencing and phylogenetic analysis have been implemented for genotyping.

RESULTS

Overall, 596 cases, positive only for anti-HBc were included in the study. OBI was detected among 61 cases (10.2%). The genotype and subgenotype of HBV among all of them was D1, except one that was D4. Most of them had low viral loads ranged from 1.2 × 10² to 1.34 × 10 ³  copies/mL; 19.6% had undetectable viral loads. Important mutations in surface protein and reverse transcriptase were sI92T, sQ129H, rtL80I, rtS85F, rtL91I. The prevalence of OBI was related to some risk factors, such as tattooing (P = 0.02), sexual activities (P = 0.009), and diabetes (P = 0.031).

CONCLUSION

Our study suggests that OBI should be considered among anti-HBc seropositive subjects. This form of HBV infection was accompanied with some mutations, risk factors, and diseases. However, further investigations are needed to determine virological importance of documented mutations.

Detection of HBV genome in the plasma and peripheral blood mononuclear cells of Iranian HBsAg negative patients with HIV infection: occult HBV infection

The presence of hepatitis B virus (HBV) DNA in the absence of traceable hepatitis B surface antigen (HBsAg) in the plasma specimen of patients is defined as occult HBV infection (OBI). This study aimed to detect HBV-DNA in the plasma and peripheral blood mononuclear cells (PBMCs) of Iranian HBsAg negative patients with human immunodeficiency virus (HIV) infection. This cross-sectional study was conducted on 172 patients with HIV infection from September 2015 to August 2017. The patients were tested for serological parameters (HBsAg, HBcAb, HBeAg and HBeAb) against HBV infection. Moreover, they were tested for HBV viral load (using COBAS TaqMan 48 Kit, Roche, USA) in plasma and the presence of the HBV genome in PBMC specimens using real-time PCR. The mean age of the patients was 35.4 ± 13.4 years. Of the 172 studied patients, 109 (63.4%) were male. In this study, 151 (87.8%) patients were negative for HBsAg, 111 (64.5%) patients were negative for all HBV infection serological markers, 9 (5.2%) patients were only positive for HBsAg and 29 (16.9%) patients were only positive for HBcAb. Moreover, five (3.3%) patients with HBsAg negative had OBI (in the plasma sample of four patients and PBMC specimens of all five patients, HBV-DNA was detected). The present study revealed that 3.3% of the patients with HIV infection had occult HBV infection. Presumably, designing prospective studies to identify this infection in patients with HIV infection is informative and valuable.

Diagnostic accuracy of tests to detect hepatitis B surface antigen: a systematic review of the literature and meta-analysis

BACKGROUND

Chronic Hepatitis B Virus (HBV) infection is characterised by the persistence of hepatitis B surface antigen (HBsAg). Expanding HBV diagnosis and treatment programmes into low resource settings will require high quality but inexpensive rapid diagnostic tests (RDTs) in addition to laboratory-based enzyme immunoassays (EIAs) to detect HBsAg. The purpose of this review is to assess the clinical accuracy of available diagnostic tests to detect HBsAg to inform recommendations on testing strategies in 2017 WHO hepatitis testing guidelines.

METHODS

The systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines using 9 databases. Two reviewers independently extracted data according to a pre-specified plan and evaluated study quality. Meta-analysis was performed. HBsAg diagnostic accuracy of rapid diagnostic tests (RDTs) was compared to enzyme immunoassay (EIA) and nucleic-acid test (NAT) reference standards. Subanalyses were performed to determine accuracy among brands, HIV-status and specimen type.

RESULTS

Of the 40 studies that met the inclusion criteria, 33 compared RDTs and/or EIAs against EIAs and 7 against NATs as reference standards. Thirty studies assessed diagnostic accuracy of 33 brands of RDTs in 23,716 individuals from 23 countries using EIA as the reference standard. The pooled sensitivity and specificity were 90.0% (95% CI: 89.1, 90.8) and 99.5% (95% CI: 99.4, 99.5) respectively, but accuracy varied widely among brands. Accuracy did not differ significantly whether serum, plasma, venous or capillary whole blood was used. Pooled sensitivity of RDTs in 5 studies of HIV-positive persons was lower at 72.3% (95% CI: 67.9, 76.4) compared to that in HIV-negative persons, but specificity remained high. Five studies evaluated 8 EIAs against a chemiluminescence immunoassay reference standard with a pooled sensitivity and specificity of 88.9% (95% CI: 87.0, 90.6) and 98.4% (95% CI: 97.8, 98.8), respectively. Accuracy of both RDTs and EIAs using a NAT reference were generally lower, especially amongst HIV-positive cohorts.

CONCLUSIONS

HBsAg RDTs have good sensitivity and excellent specificity compared to laboratory immunoassays as a reference standard. Sensitivity of HBsAg RDTs may be lower in HIV infected individuals.

Impact of "a" determinant mutations on detection of hepatitis B surface antigen (HBsAg) in HBV strains from Chinese patients with occult hepatitis B

This study was designed to detect mutations that occur within the "a" determinant in the S gene of the hepatitis B virus (HBV) in patients with occult hepatitis B (OHB), and to analyze the influence of these mutations on expression and reactivity of the hepatitis B surface antigen (HBsAg). Twenty-three certified OHB samples were compared to 32 HBsAg positive samples from patients with chronic hepatitis B. The median HBV DNA levels in the OHB group were significantly lower than those in the control group (P < 0.0001). Mutations within the "a" determinant were analyzed by gene amplification and sequencing. This revealed mixed infections in which clones within a sample displayed either different mutations or mutations in association with clones that exhibited wild type amino acid patterns. Sequencing analysis also showed a significant difference between the proportions of amino acid mutations observed in the OHB and control groups. Seven recombinant S (rS) proteins with corresponding OHB mutations and three wild type alleles were expressed and purified in the Pichia pastoris expression system to preserve conformational attributes, and their reactivity analyzed using six commercial HBsAg assays. The OHB sera were HBsAg nonreactive while the rS proteins with corresponding OHB mutations were universally reactive. Thus, we postulate that the reduced binding affinity between mutated HBsAg and its antibody may not be as important in defining OHB as is the effect of specific mutations in the preS/S region of the genome that affect the synthesis and secretion of the S protein and/or the virion.