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Hepadnaviridae
''Hepadnaviridae'' is a family of viruses. Humans, apes, and birds serve as natural hosts. The family contains five genera. Its best-known member is hepatitis B virus. Diseases associated with this family include: liver infections, such as hepatitis, hepatocellular carcinomas (chronic infections), and cirrhosis. It is the sole accepted family in the order ''Blubervirales''. Taxonomy The following genera are recognized: * '' Avihepadnavirus'' * '' Orthohepadnavirus'' * '' Herpetohepadnavirus'' * '' Metahepadnavirus'' * '' Parahepadnavirus'' History and discovery Although liver diseases transmissible among human populations were identified early in the history of medicine, the first known hepatitis with a viral etiological agent was Hepatitis A, in the picornaviridae family. Hepatitis B Virus (HBV) was identified as an infection distinct from Hepatitis A through its contamination of yellow fever vaccine. The vaccine contained human serum as a stabilizing agent which was HBV ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hepatitis B Virus
Hepatitis B virus (HBV) is a partially double-stranded DNA virus, a species of the genus '' Orthohepadnavirus'' and a member of the '' Hepadnaviridae'' family of viruses. This virus causes the disease hepatitis B. Classification Hepatitis B virus is classified in the genus '' Orthohepadnavirus'', which contains 11 other species. The genus is classified as part of the '' Hepadnaviridae'' family, which contains four other genera, '' Avihepadnavirus'', '' Herpetohepadnavirus'', '' Metahepadnavirus'' and '' Parahepadnavirus''. This family of viruses is the only member of the viral order ''Blubervirales''. Viruses similar to hepatitis B have been found in all apes (orangutans, gibbons, bonobos, gorillas and chimpanzees), in Old World monkeys, and in New World woolly monkeys (the woolly monkey hepatitis B virus), suggesting an ancient origin for this virus in primates. The virus is divided into four major serotypes (adr, adw, ayr, ayw) based on antigenic epitopes present on it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Avihepadnavirus
''Avihepadnavirus'' is a genus of viruses, in the family ''Hepadnaviridae''. Birds serve as natural hosts. There are five species in this genus. Diseases associated with this genus include: hepatitis, hepatocellular carcinomas (chronic infections), and cirrhosis. Taxonomy The genus contains the following species, listed by scientific name and followed by the exemplar virus of the species: * ''Avihepadnavirus anatigruidae'', Duck hepatitis B virus Duck hepatitis B virus, abbreviated DHBV, is part of the genus '' Avihepadnavirus'' of the ''Hepadnaviridae'', and is the causal agent of duck hepatitis B. DHBV is a small DNA virus with a diameter of 40–45 nm. The viral envelope is ma ... * ''Avihepadnavirus ciconiardeae'', Heron hepatitis B virus * ''Avihepadnavirus psittaunius'', Parrot hepatitis B virus 1 * ''Avihepadnavirus psittaduorum'', Parrot hepatitis B virus 2 * ''Avihepadnavirus bonicursoris'', Elegant-crested tinamou hepatitis B virus Structure Viruses in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orthohepadnavirus
''Orthohepadnavirus'' is a genus of viruses, in the family ''Hepadnaviridae''. Humans and other mammals serve as natural hosts. There are 19 species in this genus. Diseases associated with this genus include: hepatitis, hepatocellular carcinoma (chronic infections), and cirrhosis Cirrhosis, also known as liver cirrhosis or hepatic cirrhosis, chronic liver failure or chronic hepatic failure and end-stage liver disease, is a chronic condition of the liver in which the normal functioning tissue, or parenchyma, is replaced .... Taxonomy The genus contains the following species, listed by scientific name and followed by the exemplar virus of the species: * ''Orthohepadnavirus bassarisci'', Ringtail hepatitis B virus * ''Orthohepadnavirus equidae'', Equid hepatitis B virus * ''Orthohepadnavirus felisdomestici'', Domestic cat hepatitis B virus * ''Orthohepadnavirus hominoidei'', Hepatitis B virus genotype D * ''Orthohepadnavirus lagothricis'', Woolly monkey hepatitis B viru ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Viruses
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are found in almost every ecosystem on Earth and are the most numerous type of biological entity. Since Dmitri Ivanovsky's 1892 article describing a non-bacterial pathogen infecting tobacco plants and the discovery of the tobacco mosaic virus by Martinus Beijerinck in 1898, more than 16,000 of the millions of virus species have been described in detail. The study of viruses is known as virology, a subspeciality of microbiology. When infected, a host cell is often forced to rapidly produce thousands of copies of the original virus. When not inside an infected cell or in the process of infecting a cell, viruses exist in the form of independent viral particles, or ''virions'', consisting of (i) genetic material, i.e., long molecules of DNA or RNA that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transmission Of Hepadnaviruses
The transmission of hepadnaviruses between their natural hosts, humans, non-human primates, and birds, including intra-species host transmission and cross-species transmission, is a topic of study in virology. Hepadnaviruses are a family of viruses that can cause liver infections in humans and animals. They are Group VII viruses that possess double-stranded DNA genomes and replicate using reverse transcriptase. This unique replication strategy, combined with their extremely small genomes and a very narrow host and tissue tropism, has distinguished them enough to be classified in the family Hepadnaviridae. There are two recognized genera: * '' Orthohepadnavirus'', type species: ''hepatitis B virus'' (HBV) * ''Avihepadnavirus'', type species: ''duck hepatitis B virus'' (DHBV) Structure With the example of human HBV: the particular feature of the HBV structure is the presence of three different forms in the plasma of infected patients: * Dane particle (diameter ≈ 42 nm): th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Baltimore Classification
Baltimore classification is a system used to classify viruses based on their manner of messenger RNA (mRNA) synthesis. By organizing viruses based on their manner of mRNA production, it is possible to study viruses that behave similarly as a distinct group. Seven Baltimore groups are described that take into consideration whether the viral genome is made of deoxyribonucleic acid (DNA) or ribonucleic acid (RNA), whether the genome is single- or double-stranded, and whether the sense of a single-stranded RNA genome is positive or negative. Baltimore classification also closely corresponds to the manner of replicating the genome, so Baltimore classification is useful for grouping viruses together for both transcription and replication. Certain subjects pertaining to viruses are associated with multiple, specific Baltimore groups, such as specific forms of translation of mRNA and the host range of different types of viruses. Structural characteristics such as the shape of the viral ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retroviridae
A retrovirus is a type of virus that inserts a DNA copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell. After invading a host cell's cytoplasm, the virus uses its own reverse transcriptase enzyme to produce DNA from its RNA genome, the reverse of the usual pattern, thus ''retro'' (backward). The new DNA is then incorporated into the host cell genome by an integrase enzyme, at which point the retroviral DNA is referred to as a provirus. The host cell then treats the viral DNA as part of its own genome, transcribing and translating the viral genes along with the cell's own genes, producing the proteins required to assemble new copies of the virus. Many retroviruses cause serious diseases in humans, other mammals, and birds. Retroviruses have many subfamilies in three basic groups. * Oncoretroviruses (cancer-causing retroviruses) include human T-lymphotropic virus (HTLV) causing a type of leukemia in humans, and murine le ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hepatitis B Virus DNA Polymerase
Hepatitis B virus DNA polymerase is a hepatitis B viral protein. It is a DNA polymerase that can use either DNA or RNA templates and a ribonuclease H that cuts RNA in the duplex. Both functions are supplied by the reverse transcriptase (RT) domain. Structure The hepadnaviral P protein is organized into four domains: an N-terminal domain called the terminal protein (TP) (), a spacer domain which has no apparent function to the polymerase, a reverse transcriptase (RT) domain related to every other reverse transcriptase domain, and a C-terminal Ribonuclease H (RNase H) domain (). Uniquely, the hepadnavirus terminal protein (TP) domain contains a tyrosine residue that serves as a primer for the synthesis of the (−) DNA strand. Function The Hepatitis B virus (HBV) polymerase is a multifunctional enzyme, with both RNA-dependent and DNA-dependent polymerase functions, as well as an RNase H function. It acts on the HBV pre-genomic RNA (pgRNA) to reverse transcribe it to fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cytoplasm
The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell and contained within the nuclear membrane is termed the nucleoplasm. The main components of the cytoplasm are the cytosol (a gel-like substance), the cell's internal sub-structures, and various cytoplasmic inclusions. In eukaryotes the cytoplasm also includes the nucleus, and other membrane-bound organelles.The cytoplasm is about 80% water and is usually colorless. The submicroscopic ground cell substance, or cytoplasmic matrix, that remains after the exclusion of the cell organelles and particles is groundplasm. It is the hyaloplasm of light microscopy, a highly complex, polyphasic system in which all resolvable cytoplasmic elements are suspended, including the larger organelles such as the ribosomes, mitochondria, plant plasti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reverse Transcriptase
A reverse transcriptase (RT) is an enzyme used to convert RNA genome to DNA, a process termed reverse transcription. Reverse transcriptases are used by viruses such as HIV and hepatitis B to replicate their genomes, by retrotransposon mobile genetic elements to proliferate within the host genome, and by eukaryotic cells to extend the telomeres at the ends of their linear chromosomes. The process does not violate the flows of genetic information as described by the classical central dogma, but rather expands it to include transfers of information from RNA to DNA. Retroviral RT has three sequential biochemical activities: RNA-dependent DNA polymerase activity, ribonuclease H (RNase H), and DNA-dependent DNA polymerase activity. Collectively, these activities enable the enzyme to convert single-stranded RNA into double-stranded cDNA. In retroviruses and retrotransposons, this cDNA can then integrate into the host genome, from which new RNA copies can be made via host-cell ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
