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Forty-two antigenic domains were identified across the hepatitis A virus (HAV) polyprotein by using a set of 237 overlapping 20-mer synthetic peptides spanning the entire HAV polyprotein. Nineteen antigenic domains were found within the structural proteins, and 22 were found within the nonstructural proteins, with 1 domain spanning the junction of VP1 and P2A proteins. Five of these domains were considered immunodominant, as judged by both the breadth and the strength of their immunoreactivity. One domain is located within the VP2 protein at position 57-90 aa. A second domain, located at position 767-842 aa, contains the C-terminal part of the VP1 protein and the entire P2A protein. A third domain, located at position 1403-1456 aa, comprises the C-terminal part of the P2C protein and the N-terminal half of the P3A protein. The fourth domain, located at position 1500-1519 aa, includes almost the entire P3B, and the last domain, located at position 1719-1764 aa, contains the C-terminal region of the P3C protein and the N-terminal region of the P3D protein. Four of the five most immunoreactive domains are derived from small HAV proteins and/or encompass protein cleavage sites separating different HAV proteins.

Complement Factor Properdin (CFP) which is a plasma glycoprotein, is a positive regulator of the alternative complement pathway of the innate immune system. CFP binds and stabilizes the C3- and C5-convertase enzyme complexes in a feedback loop that eventually ends with formation of the membrane attack complex and lysis of the target cell. Mutations in CFP lead to 2 forms of properdin deficiency that cause high susceptibility to meningococcal infections.

Transferrin is the iron-transport protein of vertebrate serum and donates iron to cells through interaction with a specific membrane receptor, CD71. Transferrin appears to be indispensable for most cells growing in tissue culture.
It is referred to frequently as a growth factor because, in analogy to other growth factor-receptor interactions, proliferating cells express high numbers of transferrin receptors, and the binding of transferrin to their receptors is needed for cells to initiate and maintain their DNA synthesis. Apart from its role as an iron transport protein transferrin acts as a cytokine and has functions that may not be related to its iron-carrying capacity.

Listeriolysin O (aka LLO) is a hemolysin produced by Listeria monocytogenes bacteria, the pathogen responsible for causing listeriosis. The toxin may be regarded as a virulence factor, since it is crucial for the virulence of L. monocytogenes. LLO is a single polypeptide protein encoded by the hlyA gene and composed of 529 residues. LLO is a thiol-activated cholesterol-dependent pore forming toxin protein; therefore, it is activated by reducing agents and inhibited by oxidizing agents. Still, LLO differs from other thiol-activated toxins, as its cytolytic activity is maximized at a pH of 5.5. Inside the acidic phagosomes (average pH ~ 5.9) of cells that have phagocytosed L. monocytogenes, LLO is selectively activated by maximizing activity at a pH of 5.5. Following the phagosome lysis by LLO, the bacterium breaks out into the cytosol, where it is able to grow intracellularly, and the toxin has reduced activity in the more basic cytosol. Thus, LLO permits L. monocytogenes to break out from the phagosomes into the cytosol without harming the plasma membrane of the infected cell, which allows the bacteria to live intracellularly, where they are sheltered from extracellular immune system factors such as the complement system and antibodies. LLO also brings about dephosphorylation of histone H3 and deacetylation of histone H4 in the early phases of infection, before entry of L. monocytogenes into the host cell. The pore-forming activity is not implicated in causing the histone modifications. The modifications of the histones affect the down regulation of genes encoding proteins involved in the inflammatory response. Therefore, LLO may be significant in subverting the host immune response to L. monocytogenes. At its NH2-terminus it possesses a 25 residues long typical signal sequence excited during the secretion process. Moreover, in its NH2-terminus there is also a 19 amino acids PEST- like sequence that may target this toxin for degradation. The PEST-like sequence found in LLO and is considered crucial for virulence, given that mutants lacking the sequence lysed the host cell. Nevertheless, contrary to PEST's supposed role in protein degradation, evidence implies that the PEST-like sequence may control LLO production in the cytosol rather than increase degradation of LLO.

GST family of enzymescomprises a long list of cytosolic, mitochondrial, and microsomalproteinsthat are 45-55 kDa (dimer form) size and are capable of multiple reactions with a multitude of substrates, both endogenousand xenobiotic. GST catalyses the conjugation of reduced glutathione meaning the sulfhydryl group, to electrophilic centers on a wide variety of substrates. This activity is useful in the detoxification of endogenous compounds such as peroxidised lipids, as well as the metabolism of xenobiotics. GST binds toxins and function as transport protein. Glutathione S-transferase is used to create the so-called 'GST gene fusion system'. The GST is used to purify and detect proteins of interest. In a GST gene fusion system, the GST sequence is incorporated into an expression vector alongside the gene sequence encoding the protein of interest. Induction of protein expression from the vector's multiple cloning sites results in expression of a fusion protein - the protein of interest fused to the GST protein. This GST-fusion protein can then be purified from cells via its high affinity for glutathione. Fusion proteins offer an important biological assay for direct protein-to-protein interactions. The GST tag has the size of 220 amino acids, which, compared to other tags like the myc- or the FLAG-tag, is quite big. It is fused to the N-terminusof a protein. However, many commercially-available sources of GST-tagged plasmids include a thrombindomain for cleavage of the GST tag during protein purification. A GST-tag is often used to separate and purify proteins that contain the GST-fusion. GST-fusion proteins can be produced in Escherichia coli, as recombinant proteins.

Entry of HSV into the host cell involves interactions of several viral glycoproteins with cell surface receptors. The virus particle is covered by an envelope which, when bound to specific receptors on the cell surface, will fuse with the cell membrane and create an opening, or pore, through which the virus enters the host cell. The sequential stages of HSV entry are analagous to those of other viruses. At first, complementary receptors on the virus and cell surface bring the two membranes into proximity. In an intermediate state, the two membranes begin to merge, forming a hemifusion state. Finally, a stable entry pore is formed through which the viral envelope contents are introduced to the host cell.

Alpha crystallins are composed of two gene products ; alpha-A and alpha-B, for acidic and basic, respectively. Alpha crystallins can be induced by heat shock and are members of the small heat shock protein (sHSP also known as the HSP20). They act as molecular chaperones and hold them in in large soluble aggregates. These heterogeneous aggregates consist of 30-40 subunits; the alpha-A and alpha-B subunits have a 3:1 ratio, respectively. Two additional function of a-crystallins are an autokinase activity and participation in the intracellular architecture. Alpha-B is expressed widely in many tissues and organs and occurs in many neurological diseases.

B2 microglobulin is an 11 kDa protein associated with the outer membrane of many cells including lymphocytes. It is the small subunit of the MHC class I molecule. Association with beta 2-microglobulin is generally required for the transport of class I heavy chains from the endoplasmic reticulum to the cell surface. ?2 microglobulin associates with class I-like molecules such as CD1 and Qa as well as with the alpha chain of MHC class I molecules. Very limited amounts of MHC class I molecules can be found on the surface in the absence of ?2 microglobulin. CD8 T cells cannot develop in the absence of MHC class I.
Beta 2-microglobulin is present in small amounts in serum, csf, and urine of normal people, and to a much greater degree in the urine and plasma of patients with tubular proteinaemia, renal failure, or kidney transplants. Human Beta 2 microglobulin levels can rise either because its rate of synthesis has increased (e.g. in AIDS, malignant monoclonal plasma cell dyscrasia, solid tumors and autoimmune disease) or because of impaired renal filtration (e.g. due to renal insufficiency, graft rejection or nephrotoxicity induced by post-transplantation immunosuppressive therapy). Beta-2 microglobulin levels might also be elevated in multiple myeloma and lymphoma cases. Dialysis-related amyloidosis develops after a long-term hemodialysis, it can aggregate into amyloid fibers that deposit in joint spaces.

Killer Cell Lectin-like Receptor Subfamily G, Member 1 (KLRG1) is a member of the killer cell lectin-like receptor (KLR) family, which is a group of transmembrane proteins preferentially expressed in NK cells. Natural killer (NK) cells are lymphocytes which mediate lysis of certain tumor cells and virus-infected cells without previous activation. NK cells can also regulate specific humoral and cell-mediated immunity. The cell surface expression of KLRG1 is up-regulated by MHC class I molecules expression.

ANXA1 is part of the family of Ca(2+)-dependent phospholipid binding proteins which have a Mw between 35kDa-40kDa and are situated on the cytosolic face of the plasma membrane. ANXA1 protein has a Mw of 40kDa, with phospholipase A2 inhibitory activity to bind from two to four calcium ions with high affinity. Since phospholipase A2 is necessary for the biosynthesis of the potent mediators of inflammation, prostaglandins and leukotrienes, ANXA1 might have potential anti-inflammatory activity. ANXA1 promotes membrane fusion and iplays a role in exocytosis. The recognition of ANXA1 protein by immunocytochemical leads a simple, highly sensitive and specific assay for diagnosis of hairy cell leukemia.

Binding immunoglobulin protein (BiP or HSPA5) is a member of the family of ~70kDa heat shock proteins (HSP 70). HSPA5 is a stress response protein which is induced by agents or conditions that adversely affect endoplasmic reticulum (ER) function. HSPA5 is crucial for the proper glycosylation, folding as well as for the maintenance of cell homeostasis and the prevention of apoptosis.

HEPACAM2 is necessary during prometaphase for centrosome maturation. Following poly-ADP-ribosylation (PARsylation) by TNKS, HEPACAM2 translocates from the Golgi apparatus to mitotic centrosomes and takes a significant part in the formation of robust microtubules for quick movement of chromosomes.

HSPB7 is part of the Heat shock protein beta family. The HSPB family is one of the more diverse families within the group of HSP families. Several members have chaperone-like activities and/or participate in cytoskeletal stabilization. Several members also show a dynamic, stress-induced translocation to SC35 splicing speckles. HSPB7 constitutively localized to SC35 splicing speckles, determined by its N-terminus. HSPB7 does not support refolding though HSPB1 and HSPB5 chaperone heat unfolded substrates and keet them folding competent.

TBP-Like 1 (TBPL1) is a member of the TBP family. The TATA box-binding protein (TBP) is an indispensable component of the basal transcriptional machinery. TBPL1 is crucial for spermiogenesis and supposed to be significant in expression of developmentally regulated genes.

TIPIN is a member of the CSM3 family. TIPIN protein is essential for normal advancement of S-phase and vital for cell existence after DNA damage or replication stress. TIPIN is specifically necessary for the ATR - CHEK1 pathway in the replication checkpoint induced by ultraviolet light.

Growth Hormone Binding Protein or GHR, is a protein, part of the cytokine receptor superfamily. GHR binds to 2 receptors, therefore it enhances signal transduction via dimerization of receptors. In elevated levels, growth hormone operates as an antagonist due to high variance in the binding sites affinities. The antagonist operation can be embellished even more when the binding site is reduced its affinity.

PTX3 is part of the pentraxin family sharing the C-terminal domain with short pentraxins and containing a unique N-terminal domain. PTX3 is produced and released at inflammatory sites by various cell types including monocytes/macrophages, endothelial cells, vascular smooth muscle cells, fibroblasts, and adipocytes. PTX3 is involved in the regulation of innate resistance to pathogens, inflammatory reactions, possibly clearance of self-components and female fertility. PTX3 is used as a marker for disease activity of psoriasis. High serum PTX3 levels are associated with the disease severity of systemic sclerosis. Elevated serum PTX3 is associated with pulmonary fungal infections.

Human immunodeficiency virus (HIV) is a retrovirusthat can lead to a condition in which the immune systembegins to fail, leading to opportunistic infections. HIV primarily infects vital cells in the humanimmune systemsuch as helper T cells(specifically CD4+ T cells), macrophagesand dendritic cells. HIV infection leads to low levels of CD4+ T cells through three main mechanisms: firstly, direct viral killing of infected cells; secondly, increased rates of apoptosisin infected cells; and thirdly, killing of infected CD4+ T cells by CD8 cytotoxic lymphocytesthat recognize infected cells. When CD4+ T cell numbers decline below a critical level, cell-mediated immunityis lost, and the body becomes progressively more susceptible to opportunistic infections. HIV was classified as a member of the genus Lentivirus, part of the family of Retroviridae. Lentiviruses have many common morphologies and biological properties. Many species are infected by lentiviruses, which are characteristically responsible for long-duration illnesses with a long incubation period. Lentiviruses are transmitted as single-stranded, positive-sense, enveloped RNA viruses. Upon entry of the target cell, the viral RNA genomeis converted to double-stranded DNAby a virally encoded reverse transcriptasethat is present in the virus particle. This viral DNA is then integrated into the cellular DNA by a virally encoded integraseso that the genome can be transcribed. Once the virus has infected the cell, two pathways are possible: either the virus becomes latentand the infected cell continues to function, or the virus becomes active and replicates, and a large number of virus particles are liberated that can then infect other cells.

Plasma protease C1 inhibitor (SERPING1) is a part of the serpin superfamily of serine protease inhibitors. SERPING1 plays an important role in regulating activation of both the complement and contact systems. That isdue to the fact that SERPING1 regulates the activation of complement factor C1 in addition to the activity of activated C1 by coupling with the active catalytic site at the light chains of C1r and C1s. SERPING1 insufficiency results in hereditary angioedema, which is characterized by recurrent episodes of localized angioedema of the skin, gastrointestinal mucosa or upper respiratory mucosa.

DHH is part of the Hedgehog family which encodes signaling molecules that are involved in regulating morphogenesis. DHH protein is a precursor that is autocatalytically cleaved, the N-terminal portion is soluble and contains the signalling activity while the C-terminal portion is involved in precursor processing. Additionally, the C-terminal product covalently attaches a cholesterol moiety to the N-terminal product, restricting the N-terminal product to the cell surface and preventing it from freely diffusing throughout the organism. Defects in DHH protein have been associated with partial gonadal dysgenesis (PGD) accompanied by minifascicular polyneuropathy. DHH plays a role both male gonadal differentiation and perineurial development.
DHH plays a role in intercellular signaling which is essential for a variety of patterning events during development. DHH functions as a spermatocyte survival factor in the testes & is essential for testes development.

Human HSP40 (heat shock protein with molecular size of 40kDa) is one of the mammalian homologues of bacterial DnaJ heat shock protein and regulates cellular processes by aiding in the folding, transport and assembly. HSP40 protein contains the J-domain which controls interaction with the ATPase domain of DnaK.

Binding immunoglobulin protein (BiP or HSPA5) is a member of the family of ~70kDa heat shock proteins (HSP 70). HSPA5 is a stress response protein which is induced by agents or conditions that adversely affect endoplasmic reticulum (ER) function. HSPA5 is crucial for the proper glycosylation, folding as well as for the maintenance of cell homeostasis and the prevention of apoptosis.

HSPB3 is a muscle-specific small heat shock protein which is expressed specially in heart and skeletal muscle. Mammalian small heat shock proteins (sHSP) are highly expressed proteins with varied roles, including the assembly and impounding of multi-protein complexes, transportation of nascent polypeptide chains thru cellular membranes and regulation of protein folding. HSPB3 perform as an ATP-dependent chaperone protein which takes part in the refolding of denatured proteins and inhibition of actin polymerization.

C11ORF31 (Chromosome 11 Open Reading Frame 31) is a selenoprotein, which contains a selenocysteine (Sec) residue at its active site. The selenocysteine is encoded by the UGA codon which ordinarily signals translation termination. The 3' UTR of selenoprotein genes have a mutual stem-loop structure, the sec insertion sequence (SECIS), which is essential for the recognition of UGA as a Sec codon rather than as a stop signal. The exact function of the C11ORF31 gene is not known, however, selenoproteins are assumed to be responsible for most biomedical effects of dietary selenium. C11ORF31 is involved in a redox-related process.