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HBsAg is the surface antigen of the Hepatitis-B-Virus (HBV). The capsid of a virus has different surface proteins from the rest of the virus. The antigen is a protein that binds specifically on one of these surface proteins. It is commonly referred to as the Australian Antigen.

Human norovirus is classified into two groups, group 1& group 2. Norwalk virus is the species which belongs to group 1 and was discovered in 1968 at Ohio. Norovirus is a familiar virus which causes human gastroenteritis with the following symptoms vomiting, diarrhea and sickness. CDC report revealed that there are 19-21 million Americans infected by Nororvirus annually with 800 deaths, 1 in 15 people with infection. Around the world, this virus affects about 267 million people and causes over 200,000 deaths each year; these losses are mostly in less developed countries and in the very young, elderly and immuno-suppressed population, though, most cases are self-limited with a full recovery within just a few days. Norovirus is extremely contagious and can spread from human to human through infected food, water or contaminated surfaces. The outbreaks usually occur from November-April, while the peak is in January. Norovirus is a positive sense RNA virus with 7.5 kb nucleotides, encoding a major structural protein VP1 with 50-55kDa. The full length of VP1 capsid comprises the internal N-terminal, Hinge, shell (S) and protruding (P) domains. P domain from 225 to 520 forms P1- P2-P1 structure. Moreover, P domain has a receptor binding region which recognizes human histo-blood group antigens (HBGAs). P domain expressed in bacteria can spontaneously form a P dime as well as a P particle aggregated by 12 P dimmers. P particle displays an increased binding activity to HBGAs higher than virus-like particle (VLP) formed by the full-length capsid. For norovirus vaccine development, we consider P domain as a good candidate.

Helicobacter pylori is a Gram negative bacteria which colonizes in the human stomach and stimulates gastric mucosal inflammations leading to acute gastritis-associated diseases among them are atrophic gastritis, peptic ulcer and gastric cancer.

H. pylori is found in half of the world’s population and is defined as a group I carcinogens. .

An important virulence factor of H. pylori is Cytotoxin-associated gene A (CagA) which is located at the end of an approximately 40-kb cluster of genes called cag pathoge¬nicity island (PAI).

Cag PAI encodes a type-IV secretion system and transfers CagA protein into the intracellular region of gastric epithelial cell.

This relocation induces cellular hyper proliferation, apoptosis and leading to failure of gastric epithelial cell in maintaining its normal cytoskeletal structure. Furthermore it increases the secretion of cytokines such as tumor necrosis factor (TNF) and interleukin (IL) 1, 6 and 8 by the epithelial cells.

The IL-8 leads to extreme inflammatory responses and also stimulates the production of oxygen free radicals that could cause DNA damage to adjacent cells and lead to genetic modifications of gastric epithelial cells which are carcinogenic.

FADD is an adaptor protein that cooperates with a variety of cell surface receptors and mediates cell apoptotic signals. Using its C-terminal death domain, FADD is recruited by TNFRSF6/Fas-receptor, tumor necrosis factor receptor, TNFRSF25, and TNFSF10/TRAIL-receptor, and consequently it take parts in the death signaling initiated by these receptors. FADD interaction with the receptors reviels the N-terminal effector domain of, which allows it to recruit caspase-8, and thus initiate the cysteine protease cascade. Knockout studies in mice furthermore propose the significance of FADD in premature T cell development. FADD plays a role in survival/proliferation and cell cycle development. FADD also takes part in cellular sublocalization, protein phosphorylation, and inhibitory molecules.

Brain Abundant Membrane Attached Signal Protein 1 (BASP1) is a membrane bound protein with numerous transient phosphorylation positions and PEST motifs. Preservation of proteins with PEST sequences amongst diverse species supports their functional significance. PEST sequences take place in proteins with high turnover rates. Immunological attributes of this protein are species specific. BASP1 undergoes N-terminal myristoylation.

Mitochondrial antiviral signaling protein (MAVS) is vital for innate immune defense against viruses. MAVS is an intermediary protein essential in the virus-triggered IFN-beta signaling pathways. MAVS is involved in activation of transcription factors that regulate expression of IFN-beta and contributes to antiviral immunity.

HIV-1 Nef is a 27kDa protein highly produced after a very short time after virus infection. HIV-1 Nef is an essential factor for efficient viral replication and phatogenesis.
HIV-1 Nef facilitates virus replication and improves virions infectivity. HIV-1 Nef exerts pleiotropic effect. HIV-1 Nef down-modulates surface MHC-I molecules, decreases cell surface CD4 antigen by interacting with the Src family kinase LCK thereby inducing LCK-CD4 dissociation and by increasing clathrindependent endocytosis of this antigen to target it to lysosomial degradation. HIV-1 Nef guards the infected cell from apoptosis in order to keep it alive until the next virus generation is ready to strike. HIV-1 Nef protein bypasses host Tcell signaling by inducing a transcriptional program nearly identical to that of anti-CD3 cell activation.

Serpin Peptidase Inhibitor, Clade C Member 1 (SERPINC1), which is a part of the serpin superfamily, is a plasma protease inhibitor. SERPINC1 inhibits thrombin and other activated serine proteases of the coagulation system, and regulates the blood coagulation cascade. SERPINC1 also inhibits Thrombin and Factors IXa, Xa and XIa. Deficiencies in SERPINC1 can cause ATIII deficiency, an autosomal dominant disease which might lead to a hereditary thrombophilia.

IL2-Ra is one of the three constituent subunits of the IL2 receptor. IL-2Ra is released into the serum after increased cellular expression such as increased activation of B and T cells. Clinical manifestations of IL2-Ra elevation include autoimmune conditions and some leukemias and lymphomas.

CD8 is a cell surface glycoprotein found on most cytotoxic T lymphocytes that mediates efficient cell-cell interactions within the immune system. CD8 acts as a co-receptor, and the T-cell receptor on the T lymphocyte recognize antigen displayed by an antigen presenting cell (APC) in the context of class I MHC molecules. The functional CD8 is either a homodimer composed of two alpha chains, or a heterodimer composed of one alpha and one beta chain. Both alpha and beta chains share significant homology to immunoglobulin variable light chains.
CD8 identifies cytotoxic/suppressor t-cells that interact with MHC class I bearing targets. CD8 is thought to play a role in the process of t-cell mediated killing. CD8 alpha chains bind to class-I MHC molecules alpha-3 domains.

IFIH1 is a DEAD box protein which is upregulated in response to treatment with beta-interferon and a protein kinase C-activating compound, mezerein. Irreversible reprogramming of melanomas can be attained by therapy with both these agents; treatment with either agent alone only achieves reversible differentiation. DEAD box proteins are implicated in several cellular processes involving alteration of RNA secondary structure such as translation initiation, nuclear and mitochondrial splicing, and ribosome and spliceosome assembly.

Darbepoetin is a mutant recombinant human EPO-Alpha protein re-engineered, containing 5 amino acid changes at N30, T32, V87, N88, T90. Darbepoetin exhibits longer half-life stimulating red blood cell production than Erythropoietin. Darbepoetin maintains hemoglobin more effectively compared to EPO-Alpha.

Hepatitis B is one of a few known non-retroviralviruses which employ reverse transcriptionas a part of its replication process. (HIV, a completely unrelated virus, also uses reverse transcription, but it is a retrovirus.) HBV invades the cell by binding to surface receptor and become internalized. The viral core particles then migrate to the hepatocyte nucleus and the partially double-stranded, relaxed circular genomes (RC-DNA) are repaired to form a covalently closed circular DNA (cccDNA), which is the template for viral genomic and sub-genomic RNAs by cellular RNA polymerase II. Of these, the pregenomic RNA (pgRNA is selectively packaged into progeny capsids and is then reverse-transcribed into new RC-DNA. The core can either bud into the endoplasmic reticulum to be enveloped or exported from the cell or recycled back into the genome for conversion to cccDNA.

B220 (CD45R) is a member of the protein tyrosine phosphatase (PTP) family. PTPs are known to be signaling molecules that regulate a variety of cellular processes including cell growth, differentiation, mitotic cycle, and oncogenic transformation. This PTP contains an extracellular domain, a single transmembrane segment and two tandem intracytoplasmic catalytic domains, and thus belongs to receptor type PTP. This gene is specifically expressed in hematopoietic cells. This PTP has been shown to be an essential regulator of T- and B-cell antigen receptor signaling. It functions through either direct interaction with components of the antigen receptor complexes, or by activating various Src family kinases required for the antigen receptor signaling. This PTP also suppresses JAK kinases, and thus functions as a regulator of cytokine receptor signaling. Four alternatively spliced transcripts variants of this gene, which encode distinct isoforms, have been reported.
B220 (CD45R) is required for t-cell activation through the antigen receptor. The first ptpase domain has enzymatic activity, while the second one seems to affect the substrate specificity of the first one.

Factor IX is a glycoprotein, which is synthesized in the liver. The domain structure of factor IX is similar to that of the other vitamin K dependent coagulation factors. The NH2-terminal region contains 12 g-carboxyglutamic acid (gla) residues, which facilitate the calcium dependent binding of factor IX to negatively charged phospholipid surfaces. Two domains which are homologous to epidermal growth factor (EGF) span the region between the NH2-terminal gla domain and the activation peptide (Ala-146 to Arg-180). Factor IX is activated by either factor XIa or the factor VIIa/tissue factor/phospholipid complex. Cleavage at site A yields the intermediate IXa, which is subsequently converted to the fully active form IXab by cleavage at site B. The NH2-terminal light chain (GLA and EGF domains) remains covalently attached to the COOH-terminal heavy chain by a disulfide bond. The serine protease catalytic triad (Ser-365, His 221, Asp-269) is located in the heavy chain. Factor IXab is the catalytic component of the “intrinsic factor Xase complex” (factor VIIIa/IXa/Ca2+/phospholipid) which proteolytically activates factor X to factor Xa.

A fusion tag called FLAG consists of eight amino acids (AspTyrLysAspAspAspAspLys) including an enterokinase-cleavage site. FLAG is specifically designed for immunoaffinity chromatography. It allows elution under non-denaturing conditions. Several antibodies against this peptide have been developed. One antibody. denoted as M1. binds the peptide in the presence of bivalent metal cations. preferably Ca(+). Elution is effected by chelating agents. Another strategy is competitive elution with excess of free Flag Peptide.
The FLAG peptide purifies and detects recombinant fusion proteins. FLAG peptide is useful in Western blotting, immunocytochemistry, immunoprecipitation, flow cytometry, protein purification, and in the study of protein-protein interactions, cell ultrastructure, and protein localization. Flag peptide is a hydrophilic tag which significantly improves the detection and purification of recombinant fusion proteins.

CD44 is a cell-surface glycoprotein that plays a role in cell-cell interactions, cell adhesion and migration. CD44 is a receptor for hyaluronic acid and also interacts with other ligands, such as osteopontin, collagens, and matrix metalloproteinases. CD44 participates in a wide variety of cellular functions such as lymphocyte activation, recirculation and homing, hematopoiesis, and tumor metastasis.
CD44 and CD49d are putative activity markers and CD44 a potential novel therapeutic target in multiple sclerosis. Increased CD44 antigen is associated with relapses in non-small cell lung cancers.

α-Synuclein (amino acids 1-140), an acidic neuronal protein of 140 amino acids, is extremely heat-resistant and is natively unfolded with an extended structure primarily composed of random coils. α-synuclein has been suggested to be implicated in the pathogenesis of Parkinson’s disease and related neurodegenerative disorders, and more recently, to be an important regulatory component of vesicular transport in neuronal cells. Moreover, recent studies have shown that α-synuclein has chaperone activity and that this activity is lost upon removing its C-terminal acidic tail (amino acids 96-140).

EPCAM is a carcinoma-associated antigen and belongs to a family which includes at least 2 type I membrane proteins. The EPCAM protein has a role in embryonic stem cells proliferation and differentiation. EPCAM is used as a target for immunotherapy treatment of human carcinomas. EPCAM is expressed on most normal epithelial cells and gastrointestinal carcinomas and acts as a homotypic calcium-independent cell adhesion molecule. Epithelial cell adhesion molecules (EPCAM) can act as a physical homophilic interaction molecule between intestinal epithelial cells (IECs) and intraepithelial lymphocytes (IELs) at the mucosal epithelium for supplying immunological barrier as a first line of defense against mucosal infection. EPCAM gene mutations result in congenital tufting enteropathy.

CCL23 (MIP-3) is a ligand for the CCR1chemokine receptor. CCL23 is one of several cytokine genes clustered on the q-arm of chromosome 17, in a locus containing several other CC chemokines. MIP-3 chemoattracts monocytes, resting T-lymphocytes and neutrophils, but not activated lymphocytes. Furthermore, it was shown that MIP-3 inhibits colony formation of bone marrow myeloid immature progenitors. MIP-3 is mainly expressed in lung and liver tissue, but can be also found in bone marrow and placenta, as well as in some cell lines of myeloid origin.
Alternative splicing of the CCL23 gene produces 2 mRNAs which encode a short (CK?8) and a long (CK?81) isoform of the MIP-3. CK?8 cDNA encodes a 120 amino acid residue precursor protein with a putative 21 a.a. residue signal peptide which is cleaved to generate a 99 a.a. residue mature CK?8 (a.a. 22-120). Further N-terminal processing of the 99 a.a. residue variant can produce a 75 a.a. residue CK?8 (a.a. 46-120) which is considerably more active than the 99 a.a. residue variant.
MIP-3 may be involved in the malignant progression of certain human cancer cells which overexpress ErbB2 through the transactivation of ErbB2 tyrosine kinase. MIP-3 may also be involved in angiogenesis via upregulation of matrix metalloproteinase MMP-2 expression.

NCF1 is a cytosolic subunit protein of neutrophil NADPH oxidase which a
Multi-component enzyme that is activates production of superoxide anion. NCF1, along with NCF2 and a membrane bound cytochrome b558, is necessary for activation of the latent NADPH oxidase necessary for superoxide production. Mutations in this NCF1 have been related with chronic granulomatous disease.

AMRC10 is a protein which contains an armadillo repeat and transmembrane domain. Upregulation of the AMRC10 gene has a role in hepatocellular carcinoma. AMRC10 decreases the transcriptional activity of the tumor suppressor protein p53 through direct interaction with the DNA-binding domain of p53, moreover it might play a role in cell growth and survival.