Hepatitis B Virus Surface Antigen Mutants

Creative Diagnostics has established a global-leading Hepatitis B Virus Surface Antigen Mutants manufacture platform using Yeast expression system. With years of exploration, different highly purified HBsAg/their mutants were obtained. Our products are the best choice for multiple purposes.

*Catalog No.*	*Mutated Amino Acid*	*Product Description*
DAG-T1048	Asparagine	HBsAg (Subtype adw2, Mutation D-144-A)
DAG3933	Glycine	HBsAg (Subtype adw, Mutation G-145-R)
DAG1468	Glycine	HBsAg (Subtype ayw, Mutation G-145-R)
DAG3935	Methionine	HBsAg (Subtype adw, Mutation M-133-H)
DAG-T1047		HBsAg (Subtype adw2, Mutation M-133-H)
DAG3936		HBsAg (Subtype adw, Mutation M-133-L)
DAG-T1046		HBsAg (Subtype adw2, Mutation M-133-L)
DAG3940	Threonine	HBsAg (Subtype adw, Mutation T-126-N)
DAG-T1042		HBsAg (Subtype adw2, Mutation T-126-N)
DAG-T1041		HBsAg (Subtype adw2, Mutation T-126-S)
DAG3941		HBsAg (Subtype adw, Mutation T-143-K)
DAG-T1043		HBsAg (Subtype adw2, Mutation T-143-K)
DAG3937	Proline	HBsAg (Subtype adw, Mutation P-142-S)
DAG-T1044	Proline	HBsAg (Subtype adw2, Mutation P-142-S)
DAG3938	Glutamine	HBsAg (Subtype adw, Mutation Q-129-H)
DAG-T1039		HBsAg (Subtype adw2, Mutation Q-129-H)
DAG4720		HBsAg (Subtype adw, Mutation Q-129-L)
DAG-T1040		HBsAg (Subtype adw2, Mutation Q-129-L)
DAG-T1038		HBsAg (Subtype adw2, Mutation Q-129-R)
DAG3934	Lysine	HBsAg (Subtype adw, Mutation K-141-E)

HBV Surface Antigen and Mutants

Hepatitis B virus (HBV) is a partially double-stranded DNA virus and enveloped virus, belonging to the Hepadnaviridae family. This virus will lead to hepatitis B. The structure is shown in Figure 1 below.

Figure 1. the Structure of HBV

Although Hepatitis B virus belongs to a sort of DNA virus, the polymerase within does not possess proofreading activity which confers a high mutation rate. HBV surface antigen (HBsAg) is the main component of HBV to be recognized by immune system. It is composed of 226 amino acids with high heterogeneity, but there are some conserved regions in the protein that define the genotype.

The HBsAg mutant with substitution of a single amino acid in the major hydrophilic region or antigenic region of HBsAg, known as "a" determinant, is related to immune evade, failure of HBV detection and HBsAg vaccination.

Up to now, creative diagnostics has developed large variety of subtypes of HBsAg mutants with certain point mutation, such as Mutant K-141-E implies the Lysine is replaced by Glutamic acid at the position of 141, Mutant M-133-H implies the Methionine is replaced by Histidine at the position of 133, Mutant M-133-L implies the Methionine is replaced by Leucine at the position of 133, Mutant P-142-S, implies the Proline is replaced by Serine at the position of 142, Mutant Q-129-H, implies the Glutamine is replaced by Histidine at the position of 129, Mutation T-126-N, implies the Threonine is replaced by Asparagine at the position of 126, Mutation T-143-K. implies the Threonine is replaced by Lysine at the position of 143, Mutation Q-129-L, implies the Glutamine is replaced by Leucine at the position of 129, Mutant G-145-R implies the Glycine is replaced by Arginine at the position of 145.

Among those, Mutant G-145-R is the most commonly described vaccine-evade mutant, which is horizontally transmissible and stable over time. Nearly all of the detection assays for HBsAg depends on the antibodies against the "a" determinant, the substitution of amino acid within this region may result in the failure of detection. Consequently, HBsAg mutants related to detection failure of HBsAg were also noted in acute Hepatitis B patients. Therefore, it is highly required to produce antibodies specific to the subdominant regions within "a" determinant of HBsAg, which is the focus of many recent studies. HBsAg mutants can also be identified by nucleic acid detection of HBV in serum. At present, a variety of molecular analysis essays are developed to detect HBsAg mutants, which includes sequencing, real-time PCR, gap ligase chain reaction (gLCR) and limiting dilution cloning PCR (LDC PCR).

Application of HBsAg and Its Mutants

HBsAg and its mutant is a biomarker of HBV infection, which has been qualitatively utilized in the diagnosis of HBV, and the quantitative analysis of HBsAg is helpful to figure out the phase of chronic Hepatitis B. The level of HBsAg or its mutant in patients can reflect the prognosis status of Hepatitis B, the decline of HBsAg level as well as HBV DNA implies a critical milestone to desired prognosis. Virologically, compared to the information of HBV DNA level, a complementary information regarding the replication activity of the virus provided by HBsAg or its mutant level can confer a more comprehensive understanding of the patient's infection. HBsAg and its mutant can be regarded as a biomarker for therapeutic response in chronic Hepatitis B, both in peginterferon treatment and nucleos(t)ide analogue (NA) therapy.

Clinical Significance of HBsAg Mutants

Some HBsAg mutants are related to immune escape, HBsAg detection failure, HCC development and other major biological or clinical events.

HBsAg mutants associated with immune escape

The "a" determinant region exposed to the outer surface of virus renders its immunogenicity. The antibody produced after HBV vaccination and the antibody used for the diagnostic assays of detecting serum HBsAg are both targeted at this region. Mutants with single amino acid mutation may appear on loops of the "a" determinant and may lead to immune escape, which means the mutants could evade the immune response of patients to maximize their ability of being transmitted to a fresh host or to proceed to grow.

HBsAg mutants associated with failed HBsAg detection

It is revealed that commonly used commercial assays cannot detect serum HBsAg in patients since the HBsAg mutants take the place of HBsAg. HBsAg reactivity was detected only in very little portion of the assays in the presence of the aa substitution mutants, such as G145R, T131I, K141E and so on.

HBsAg mutants associated with HCC development

Its revealed that the patients with hepatocellular carcinoma (HCC) got higher chances of carrying HBsAg mutant than those without. The growing evidences on the positive correlation between HBsAg mutants with mutations in pre-S1or pre-S2 regions and the development of HCC were given in the last decade. Besides, some researches also showed that among the HBsAg-positive patients, the prevalence of HBsAg W4P/R mutants was higher in patients with cirrhosis or HCC than in those with a less severe liver illness.

In conclusion, some HBsAg-negative subjects may be infected with HBV because the presence of HBsAg mutant with amino acid substitutes which cannot be detected by commercially available assays, clinicians and healthcare staff working in laboratories and blood banks should take this case into account. And the mutant with mutation in some region or point may imply a higher chance to develop HCC.

Detection Methods for HBsAg and Mutants from Creative Diagnostics

The current commonly used detection methods for HBsAg and HBsAb are elucidated here.

*Catalog No.*	*Principle*	*Product Name*	*Application*	*Analyte*
DEIA060	ELISA	Antibody to HBsAg ELISA Kit	Quantitative	Antibody
DEIA001		HBs Antigen ELISA Kit	Qualitative	Antigen
DEIA002		HumanHBsAb ELISA Kit	Qualitative	Antibody