Information on AAV Infection Cycle

Information on AAV Infection Cycle

AAV infection cycle according to the experts come in several steps, namely from cell infection to production of new infectious particles. Some are as follows:            

Receptor mediated endocytosis Attachment to cell membrane Escape from late lysosome or endosome Endosomal trafficking Uncoating Translocation to nucleus Creation of AAV genome in Double standard DNA replicative form Rep genes expression Release from infected cell Complete virions assembly Cap genes expression, progeny ssDNA particle synthesis Genome replication

Useful information for AAV Infection Cycle

Few steps mentioned above might appear different especially in the different cell types, which, in part, is likely to contribute towards the well defined and limited native AAV tropism. Virus replication is also likely to differ among one particular cell type, which again depends upon the existing cell cycle phase of the cell.

Features of AAV Infection Cycle Adenovirus vector system’s characteristic feature is replication deficiency. Thereby, it is not in a position to multiple in the unaffected cells. Rather, AAV is known to spread across simply by co-infecting the cell using a helper virus. The initial helper virus had been described as offering new AAV particles with successful generation and has been termed as the adenovirus. It is from here that the name AAV had originated first. Then, it was shown that it is possible to facilitate Adenovirus transduction replication by deriving selected cells from adenovirus genome through other viruses like the vaccinia, HSV or genotoxic agents like the hydroxyurea or UV irradiation. AAV lifecycle tends to follow either lysogenic or lytic pathway, depending upon absence or presence of the helper virus. The gene expression of AAV is found to get activated if there is present a helper virus, thereby allowing replication of this virus by using polymerase in the host cell. As the host cell is destroyed by the helper virus, new AAV virions get released during the process. In case, there is not present any helper virus, then lysogenic behavior is clearly exhibited by the AAV system. As the cell alone gets infected by the AAV, the gene expression does get repressed, which means, there is no further Adenovirus production noticed.

This way, its genome gets incorporated within the host genome (which is within the human

chromosome 19). However, lysis may occur even without the helper virus in some rare cases.

Usually, the AAV will not be in a position to replicate and destroy the cell by itself.

The minimum adenoviral genes set necessary for ensuring efficient progeny AAV particle generation has been discovered by Matsushita. It is this discovery that had allowed recombinant AAV to be produced by using new techniques, where adenoviral co-infection of AAV producing cells will not be essential. But if genotoxic factors or helper virus is not present, then AAV DNA may either persist in some episomal form or perhaps integrated within host genome. Integration in latter case is said to be mediated by Rep68 and Rep78 which does need ITR presence that flanks the integrated region.

You can get more details at https://www.genemedi.net/i/adenovirus-packaging!