The history and constitute of adenoviral particle

Adenovirus is a non-encapsulated particle with a diameter of 70-90 nm. It consists of 252 shells arranged in a squamous plane. Each shell has a diameter of 7 to 9 nm. The capsid is a linear double-stranded DNA molecule containing approximately 4.7 kb and an inverted repeat of approximately 100 bp in length. Since the 5' end of each DNA strand is covalently bound to a protein molecule having a relative molecular mass of 55X103Da, a cyclic structure of double-stranded DNA can occur.

Brief history of research

There are 52 known human adenoviruses, named adl~ad52, respectively. The most detailed study is ad2. The adenoviral genome is transcribed to produce mRNA, and there are at least five known transcription units: the EI region is located on the left side of the viral genome and can be subdivided into EIA and EIB.The EII region encodes a DNA-binding protein that is involved in viral replication; the EIII region encodes a glycoprotein that appears on the surface of the host cell; the EIV region is located at the right end of the ad2 genome and is regulated by the DNA-binding protein encoded by the EII region; The transcription unit synthesizes ad2 protein IV in the mid-virus infection.

Adenoviruses are carcinogenic to rodents or can transform rodent cells cultured in vitro. Transforming cells requires only a portion of the adenoviral genome, which is located at the left end of the genome, accounting for approximately 7% to 10% of the entire genome. Although adenovirus is widely distributed, it does not cause carcinogenicity to the human body. Human cells are a type of permissive cell, that is, such cells allow infection-invading viruses to replicate and proliferate in cells, and finally cell lysis dies to release a large number of progeny viruses. Adenoviral particles were not detected in various human tumor cells cultured in vitro, but there is an integration site of adl2 on human chromosome 1, which means that human cells may also be non-permissive cells for adenovirus, ie this type After the virus is infected, the virus cannot replicate in the cell, but it can be integrated into the genome of the infected cell. These cells are transformed by the virus, the phenotype is altered, and passage can be cultured indefinitely in vitro.

Constitute

The adenovirus is a non-encapsulated spherical structure, and its virions are often arranged in a lattice in the infected nucleus. Each virus particle contains a 36 kb line.

The double-stranded DNA has a 100-600 bp inverted terminal re-peat (ITR) at both ends, and the inside of the ITR is a viral packaging signal, which is a cis-acting element required for viral packaging.The genome contains an early expressed E1~E4 gene associated with adenoviral replication and a lately expressed L1~L5 gene associated with adenoviral particle assembly. The linear double-stranded DNA and the core protein form a core of 60-65 nm in diameter and are wrapped in the capsid.The capsid is icosahedral and consists of 252 shells with a diameter of 8~10 nm. The shells are arranged on the surface of the triangle, 6 on each side, 240 of which are hexon (non-apical shell), and Twelve are pentad bases (vertex shells).Each hexon is a homotrimer of a hexon protein, the hexon molecule of the trimer has a triangular apex and a pentahedral base, and the tower region consists of four rings, namely loop1, loop2, loop3 , loop4, the base contains two areas P1, P2 ,Epitopes on hexon are the criteria for diagnosing different serotypes, including the antigenic component of the mammalian adenovirus genus, which is the most sensitive site for virion selection. Each of the five adjacent bases is bound with one (mammalian adenovirus) or two (avian adenovirus) long 9~77. 5 nm fiber protrusions, which are protruded from the shell surface by the penton protein. The tip of the fiber forms the cephalic region, which is serum specific and contains a species-specific epitope responsible for hemagglutination in vitro.