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Hemopexin (or haemopexin) is a plasma protein that binds heme with the highest affinity of any known protein. Hemopexin is generally expressed in liver, and belongs to acute phase reactants, the synthesis of which is induced after inflammation. Heme is potentially very toxic because of its ability to intercalate into lipid membrane and to generate hydroxyl radicals. Hemopexin’s function of scavenging the heme released or lost by the turnover of heme proteins such as hemoglobin defends the body from the oxidative damage that free heme can cause. Additionally, hemopexin discharges its bound ligand for internalisation upon interacting with a specific receptor located on the surface of liver cells. This hemopexin function is in order to preserve the body's iron. Hemopexin’s levels in the serum are an indication of how much heme is present in the blood. Low Hemopexin levels show that there is a lot of it in the serum. For that reason, low hemopexin levels indicate that there has been consid

Hemopexin (or haemopexin) is a plasma protein that binds heme with the highest affinity of any known protein. Hemopexin is generally expressed in liver, and belongs to acute phase reactants, the synthesis of which is induced after inflammation. Heme is potentially very toxic because of its ability to intercalate into lipid membrane and to generate hydroxyl radicals. Hemopexin’s function of scavenging the heme released or lost by the turnover of heme proteins such as hemoglobin defends the body from the oxidative damage that free heme can cause. Additionally, hemopexin discharges its bound ligand for internalisation upon interacting with a specific receptor located on the surface of liver cells. This hemopexin function is in order to preserve the body's iron. Hemopexin’s levels in the serum are an indication of how much heme is present in the blood. Low Hemopexin levels show that there is a lot of it in the serum. For that reason, low hemopexin levels indicate that there has been consid

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.

Heparanase is an endo ß-D-glucuronidase, which degrades heparan sulfate side chains of heparan sulfate proteoglycans (HSPGs) in the extracellular matrix. Heparanase plays an important role in ECM degradation, facilitating the migration and extravasation of tumor cells and inflammatory leukocytes (1,2,3). Upon degradation, heparanase releases growth factors and cytokines that stimulate cell proliferation and chemotaxis (4,5). Heparanase is a heterodimer comprised of a 50 kDa subunit harboring the active site and a 8 kDa subunit. It is produced as a latent 65 kDa precursor and proteolytically processed to its active form (1,6). Heparanase is highly expressed in myeloid leukocytes (i.e. neutrophils) in platelets and in human placenta. Human heparanase was found to be upregulated in various types of primary tumors, correlating in some cases with increased tumor invasiveness and vascularity and with poor prospective survival (7,8).

Heparanase is an endo-β-D-glucuronidase, which degrades heparan sulfate side chains of heparan sulfate proteoglycans (HSPGs) in the extracellular matrix. Heparanase plays an important role in ECM degradation, facilitating the migration and extravasation of tumor cells and inflammatory leukocytes (1,2,3). Upon degradation, heparanase releases growth factors and cytokines that stimulate cell proliferation and chemotaxis (4,5). Heparanase is a heterodimer comprised of a 50 kDa subunit harboring the active site and a 8 kDa subunit. It is produced as a latent 65 kDa precursor and proteolytically processed to its active form (1,6). Heparanase is highly expressed in myeloid leukocytes (i.e. neutrophils) in platelets and in human placenta. Human heparanase was found to be upregulated in various types of primary tumors, correlating in some cases with increased tumor invasiveness and vascularity and with poor prospective survival (7,8).

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.

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.

HECT and RLD Domain Containing E3 Ubiquitin Protein Ligase 5 (HERC5) is a member of the HERC family of ubiquitin ligases, found in a cluster of HERC family genes on chromosome 4. HERC5 is a protein with a HECT domain and 5 RCC1 repeats. The HERC5 protein localizes to the cytoplasm and perinuclear region and serves as an INF-induced E3 protein ligase that mediates ISGylation of protein targets. HERC5 exhibits antiviral activity towards HIV-1, influenza A virus and human papillomavirus. HERC5 is a major E3 ligase for ISG15 conjugation. HERC5 also serves as a positive regulator of innate antiviral response in cells induced by INF. Pro-inflammatory cytokines upregulate HERC5 in endothelial cells. HERC5 is physically connected with polyribosomes, broadly modifies recently synthesized proteins in a cotranslational fashion.

HERPUD1 is a multi-pass membrane protein which is a part of the endoplasmic reticulum quality control system. HERPUD1 owns 1 N-terminal ubiquitin-like domain and is expressed highly in the brain. HERPUD1 is also known as ER-associated degradation (ERAD) which takes part in ubiquitin-dependent degradation of misfolded endoplasmic reticulum proteins.

HERVK is related with several tumors such as passenger virus, and anti-Retroviral therapy against amyotrophic lateral sclerosis/ALS has exhibited to decrease the symptoms of amyotrophic lateral sclerosis/ALS. High counts of viral sequences exist in the human genome but stay silent. Though, in pathological conditions, these viruses are produced. Human Endogenous Retrovirus-K, is produced in neurons of a subpopulation of patients with amyotrophic lateral sclerosis/ALS, a progressive neurodegenerative disease. The envelope protein of this HERV results in degeneration of neurons, and transgenic animals producing this protein advance an ALS-like syndrome triggered by nucleolar dysfunction in motor neurons. Reactivation of the HERVK is controlled by the transcription factor TDP-43. Therefore, therapeutic tactics against this virus alter the course of the disease.

Hairy and enhancer of split 2 (HES2) belongs to the HES family and comprised of one basic helix-loop-helix (bHLH) domain and one orange domain. The HES family members form a complex with TLE, the mammalian homologue of Groucho, and this interaction is mediated by the carboxy terminal WRPW motif of the HES proteins. Activation of Notch signaling pathway initiates activation of HES family genes throughout the interaction between Notch intracellular domain and RBPSUH (CSL). HES2 is expressed in placenta, pancreatic cancer, colon cancer with RER, cervical cancer, and in head and neck tumors.

HES7 belongs to the Hairy and enhancer of split family of bHLH transcription factors. The mouse ortholog of the HES7 is set by Notch signaling. The protein serves as a transcriptional repressor, and is involved in correct patterning of the axial skeleton. A mutation in HES7 has been shown to result in spondylocostal dysostosis. Multiple transcript variants encoding different isoforms have been discovered for HES7.

Hepatitis E virus (HEV), the major etiologic agent of enterically transmitted non-A, non-B hepatitis worldwide, is a spherical, non-enveloped, single stranded RNA virus that is approximately 32 to 34 nm in diameter. HEV belongs to a genus of HEV-like viruses (unassigned genus). HEV has a single-stranded polyadenylated RNA genome of approximately 8 kb. Based on its physicochemical properties it is presumed to be a calici-like virus.

Hepatitis E virus (HEV), the major etiologic agent of enterically transmitted non-A, non-B hepatitis worldwide, is a spherical, non-enveloped, single stranded RNA virus that is approximately 32 to 34 nm in diameter. HEV belongs to a genus of HEV-like viruses (unassigned genus). HEV has a single-stranded polyadenylated RNA genome of approximately 8 kb. Based on its physicochemical properties it is presumed to be a calici-like virus.

Hepatitis E virus (HEV), the major etiologic agent of enterically transmitted non-A, non-B hepatitis worldwide, is a spherical, non-enveloped, single stranded RNA virus that is approximately 32 to 34 nm in diameter. HEV belongs to a genus of HEV-like viruses (unassigned genus). HEV has a single-stranded polyadenylated RNA genome of approximately 8 kb. Based on its physicochemical properties it is presumed to be a calici-like virus.

Hepatitis E virus (HEV), the major etiologic agent of enterically transmitted non-A, non-B hepatitis worldwide, is a spherical, non-enveloped, single stranded RNA virus that is approximately 32 to 34 nm in diameter. HEV belongs to a genus of HEV-like viruses (unassigned genus). HEV has a single-stranded polyadenylated RNA genome of approximately 8 kb. Based on its physicochemical properties it is presumed to be a calici-like virus.

Hepatitis E virus (HEV), the major etiologic agent of enterically transmitted non-A, non-B hepatitis worldwide, is a spherical, non-enveloped, single stranded RNA virus that is approximately 32 to 34 nm in diameter. HEV belongs to a genus of HEV-like viruses (unassigned genus). HEV has a single-stranded polyadenylated RNA genome of approximately 8 kb. Based on its physicochemical properties it is presumed to be a calici-like virus.

HEXA is the alpha subunit of the lysosomal enzyme beta-hexosaminidase which, combined with the cofactor GM2 activator protein, catalyzes the degradation of the ganglioside GM2, and other molecules having N-acetyl hexosamines terminus. The two subunits composing Beta-hexosaminidase, alpha and beta, belong to the glycosyl hydrolases family and are encoded by distinct genes. Alpha subunit gene mutations can cause Tay-Sachs disease (GM2-gangliosidosis type I).

HEXA is the alpha subunit of the lysosomal enzyme beta-hexosaminidase which, combined with the cofactor GM2 activator protein, catalyzes the degradation of the ganglioside GM2, and other molecules having N-acetyl hexosamines terminus. The two subunits composing Beta-hexosaminidase, alpha and beta, belong to the glycosyl hydrolases family and are encoded by distinct genes. Alpha subunit gene mutations can cause Tay-Sachs disease (GM2-gangliosidosis type I).

HEXA is the alpha subunit of the lysosomal enzyme beta-hexosaminidase which, combined with the cofactor GM2 activator protein, catalyzes the degradation of the ganglioside GM2, and other molecules having N-acetyl hexosamines terminus. The two subunits composing Beta-hexosaminidase, alpha and beta, belong to the glycosyl hydrolases family and are encoded by distinct genes. Alpha subunit gene mutations can cause Tay-Sachs disease (GM2-gangliosidosis type I).

Hexarelin stimulates GH secretion. Hexarelin is more resistant to proteolytic degradation than GHRP-6.

HEXIM1 expression is induced by hexamethylene-bis-acetamide in vascular smooth muscle cells. HEXIM1 is a transcriptional regulator which acts as a universal RNA polymerase II transcription inhibitor. In cooperation with 7SK snRNA sequesters P-TEFb in a large inactive 7SK snRNP complex inhibits RNA polymerase II phosphorylation following transcriptional elongation. HEXIM1 regulates NF-kappa-B, ESR1, NR3C1 and CIITA-dependent transcriptional activity.

Hemochromatosis (HFE) is a member of the MHC class I family. The Hemochromatosis protein contains 1 Ig-like C1-type (immunoglobulin-like) domain. HFE is a membrane protein, which is similar to MHC class I-type proteins and associates with beta-2 microglobulin (beta2M). It is assumed that the HFE protein acts to regulate iron absorption by regulating the interaction of the transferrin receptor (TFR) with transferrin. HFE binds to transferrin receptor (TFR) and reduces its affinity for iron-loaded transferrin.

Hepatocyte Growth Factor (HGF) is a multifunctional growth factor which regulates both cell growth and cell motility. It exerts a strong mitogenic effect on hepatocytes and primary epithelial cells. HGF synergizes with Interleukin-3 and GM-CSF to stimulate colony formation of hematopoietic progenitor cells in vitro and may, therefore, also modulate hematopoiesis.

Hepatocyte Growth Factor (HGF) is a multifunctional growth factor which regulates both cell growth and cell motility. It exerts a strong mitogenic effect on hepatocytes and primary epithelial cells. HGF synergizes with Interleukin-3 and GM-CSF to stimulate colony formation of hematopoietic progenitor cells in vitro and may, therefore, also modulate hematopoiesis. HGF is secreted as a single inactive polypeptide which is cleaved by serine proteases into a 69kDa Alpha chain and 34kDa Beta chain. A disulfide bond linking the alpha and beta chains produces the active heterodimeric molecule.

Hepatocyte Growth Factor (HGF) is a multifunctional growth factor which regulates both cell growth and cell motility. It exerts a strong mitogenic effect on hepatocytes and primary epithelial cells. HGF synergizes with Interleukin-3 and GM-CSF to stimulate colony formation of hematopoietic progenitor cells in vitro and may, therefore, also modulate hematopoiesis.

Hepatocyte Growth Factor (HGF) is a multifunctional growth factor which regulates both cell growth and cell motility. It exerts a strong mitogenic effect on hepatocytes and primary epithelial cells. HGF synergizes with Interleukin-3 and GM-CSF to stimulate colony formation of hematopoietic progenitor cells in vitro and may, therefore, also modulate hematopoiesis.

Hepatocyte Growth Factor (HGF) is a multifunctional growth factor which regulates both cell growth and cell motility. It exerts a strong mitogenic effect on hepatocytes and primary epithelial cells. HGF synergizes with Interleukin-3 and GM-CSF to stimulate colony formation of hematopoietic progenitor cells in vitro and may, therefore, also modulate hematopoiesis.

HGF, also known as scatter factor (SF) and Hepatocyte growth factor, is secreted from mesenchymal cells, targets and acts mainly on epithelial and endothelial cells. The protein is a paracrine cellular growth, motility and morphogenic factor. HGF can also be part of haemopoietic progenitor cells and T cells. HGF has a crucial role in embryonic organ development, mainly in myogenesis. In adults HGF takes part in organ regeneration and wound healing.

GH is a member of the somatotropin/prolactin family of hormones which play an important role in growth control. The gene, along with four other related genes, is located at the growth hormone locus on chromosome 17 where they are interspersed in the same transcriptional orientation; an arrangement which is thought to have evolved by a series of gene duplications. The five genes share a remarkably high degree of sequence identity. Alternative splicing generates additional isoforms of each of the five growth hormones, leading to further diversity and potential for specialization. This particular family member is expressed in the pituitary but not in placental tissue as is the case for the other four genes in the growth hormone locus. Mutations in or deletions of the gene lead to growth hormone deficiency and short stature.

The homeobox protein family of transcription factors has many members that take part in developmental processes such as HHEX. HHEX is known to interact with Promyelocytic leukemia protein and expression in specific hematopoietic lines indicates that this protein is involved in hematopoietic differentiation.

HIBCH enzyme is in charge of hydrolysis of both HIBYL-CoA and beta-hydroxypropionyl-CoA. Damages in the HIBCH gene linked to 3-hyroxyisobutyryl-CoA hydrolase deficiency. Multiple transcript variants exist as a result of alternative splicing.

Hypoxia-inducible factor-1 (HIF-1), identified as one of the transcription factors, has been found to play an essential role in cellular and systemic oxygen homeostasis. HIF-1 is a heterodimer composed of HIF-1b subunit and one of three subunits (Hif-1a, Hif-2 (or Hif-3)). The activation of Hif-1 (is closely associated with a variety of tumors and oncogenic pathways. Hif-1 (consists of DNA binding domain (DBD domain), Dimerization domain and C-terminal regulatory domains, including two transactivation domains (TAD), an oxygen-dependent degradation (ODD) domain, and inhibitory domains. Under hypoxic conditions HIF1A activates the transcription of more than 40 genes, including, erythropoietin, glucose transporters, glycolytic enzymes, VEGF, and other genes whose protein products increase oxygen delivery or facilitate metabolic adaptation to hypoxia. HIF-1A also plays a crucial role in embryonic vascularization, tumor angiogenesis and pathophysiology of ischemic disease. It binds to core DNA sequence 5'-[AG]CGTG-3' within the hypoxia response element (HRE) of target gene promoters. Activation involves recruitment of transcriptional coactivators such as CREBPB and EP300. Its activity is improved by interaction with both, NCOA1 or NCOA2. Interaction with redox regulatory protein APEX appears to activate CTAD and potentiates activation by NCOA1 and CREBBP. The induction is under reduced oxygen tension. HIF1A is also induced by a variety of receptor-mediated factors such as growth factors, cytokines, and circulatory factors for example PDGF, EGF, FGF-2, IGF-2, TGF-1 beta, HGF, TNF alpha, IL-1 beta, angiotensin-2 and thrombin. Nevertheless, this induction is less intense than that stimulated by hypoxia.

HIF1A has a role as a master transcriptional monitor of the adaptive response to hypoxia. Under hypoxic conditions HIF1A activates the transcription of over 40 genes, including, erythropoietin, glucose transporters, glycolytic enzymes, vascular endothelial growth factor, and genes whose protein products increase oxygen release or facilitate metabolic adaptation to hypoxia. HIF1A functions as an essential role in embryonic vascularization, tumor angiogenesis and pathophysiology of ischemic disease.

HIF1A has a role as a master transcriptional monitor of the adaptive response to hypoxia. Under hypoxic conditions HIF1A activates the transcription of over 40 genes, including, erythropoietin, glucose transporters, glycolytic enzymes, vascular endothelial growth factor, and genes whose protein products increase oxygen release or facilitate metabolic adaptation to hypoxia. HIF1A functions as an essential role in embryonic vascularization, tumor angiogenesis and pathophysiology of ischemic disease.

Overexpression of the HIF1AN is linked with tumor aggressiveness in pancreatic endocrine tumors. HIF1AN hydroxylates Notch ICD at two residues that are crucial for the function of Notch ICD as a transactivator within cells and during neurogenesis and myogenesis. HIF1AN is commonly expressed in invasive breast carcinoma. The hypoxic response and survival recommends that tumour regulation of HIF1AN is an additional important mechanism for HIF pathway activation. HIF1AN is an asparaginyl hydroxylase enzyme that controls the transcriptional activity of hypoxia-inducible factor. FIH1 is a part of the Fe2+ and 2-oxoglutarate-dependent dioxygenase superfamily, FIH1 is protein that hydoxylates a specific asparagine residue (Asn-803) within the HIF1A C-terminal transactivation domain. In normoxia, the HIF1AN-mediated hydroxylation of the HIF1? transactivation domain which results in blockage of the HIF1A-p300/CBP interaction and represses transcriptional activity of HIF1A targeted genes.

HINT1, also known as Histidine triad nucleotide-binding protein 1 is part of the superfamily named for a near C-terminal HXHXHXX motif (H:Histidine, X:a hydrophobic amino acid) positioned at the ?-phosphate of nucleotide substrates. HINT1 hydrolyzes adenosine 5'-monophosphoramidate substrates such as AMP-morpholidate, AMP-N-alanine methyl ester, AMP-alpha-acetyl lysine methyl ester and AMP-NH2. Though it was initially considered to be a protein kinase C inhibitor and act as a haplod-insufficient tumor suppressor including spontaneous tumor formation in Hint+/- and Hint-/- , its actual physiologic function is not known.

Histidine triad nucleotide-binding protein 2 (HINT2) belongs to the triad proteins, which are nucleotide hydrolases and transferases that act on the alpha-phosphate of ribonucleotides. Hydrolase is most likely involved in steroid biosynthesis, furthermore it might play a role in apoptosis. HINT2 shows high expression in liver and pancreas. Expression is significantly down-regulated in hepatocellular carcinoma (HCC) patients.

Histidine triad nucleotide-binding protein 2 (HINT2) belongs to the triad proteins, which are nucleotide hydrolases and transferases that act on the alpha-phosphate of ribonucleotides. Hydrolase is most likely involved in steroid biosynthesis, furthermore it might play a role in apoptosis. HINT2 shows high expression in liver and pancreas. Expression is significantly down-regulated in hepatocellular carcinoma (HCC) patients.

Recombinant Hirudin is a potent thrombin inhibitor originally derived from the medicinal leech. Hirudin acts directly on thrombin rather than through other clotting factors. The mechanism of Hirudin-thrombin appears to be unique. The conversion of fibrinogen into fibrin by the serine protease enzyme thrombin is a major event in the final stages of blood coagulation. In the final stages of coagulation prothrombinase converts prothrombin into thrombin. Fibrin is subsequently cross linked by factor XIII to form a blood clot. The primary inhibitor of thrombin in normal blood circulation is antithrombin III. The anticoagulatant activity of hirudin is derived from its ability to inhibit the pro-coagulant activity of thrombin (similar to antithrombin III activity). Hirudin is the strongest natural inhibitor of thrombin. Hirudin binds to and inhibits only the activity of thrombin forms with a specific activity on fibrinogen contrasting to antithrombin III activity. Therefore, hirudin has a thrombolytic activity since it prevents or dissolves the formation of clots and thrombi. Hirudin also has therapeutic significance in blood coagulation disorders, in the treatment of skin hematomas and of superficial varicose veins. Hirudin does not hinder with the biological activity of other serum proteins and can also act on complexed thrombin, thus having an advantage over more common anticoagulants and thrombolytics. It is complicated to extract large quantities of hirudin from natural sources; therefore a method for producing and purifying hirudin using recombinant biotechnology has been developed.

His tag peptide also called polyhistidine-tag is chain of amino acids that are attached to proteins and consist of at least six histidine (6xHis, Hexa Histidine) residues, often at the N- or C-terminus of the protein. Polyhistidine-tags are used for affinity purification of genetically engineered proteins.

Histone is vastly alkaline protein exists in eukaryotic cell nuclei which set and direct the DNA into structural units named nucleosomes. 5 key families of histones are: H1/H5, H2A, H2B, H3, including H4. The core histones are H2A, H2B, H3 and H4, whereas histones H1/H5 are identified as the linker histones. Moreover the dynamics of chromatin structure depend on posttranslational modification of histones in addition to the appearance of different histone variants. Histone H3 as well as H4 are modified covalently at several residues. The histone code is constitute by these and the H2A/H2B modifications.

Histrelin is a hormone similar to one normally released from the hypothalamus gland in the brain. Histrelin works by decreasing the amount of estrogen and testosterone in the blood. Suppressing estrogen can cause thinning of the bones or slowing of their growth. Histrelin acetate is a potent LHRH agonist which stimulates LH and FSH release and inhibits the actions of sex steroids on the male and female reproductive tracts. After a transient increase, continuous administration results in down regulation of LH and FSH levels followed by a suppression of ovarian and testicular steroid biosynthesis. Histrelin potency in vivo and in vitro is similar to that of the D-Trp6-containing analog. Especially because of its high water solubility and greater lipophilic character, it appears promising for clinical application.

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.

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.

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.

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.

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.