NEO-cov virus – Everything you need to know
NeoCov virus (Neocov) is a Class B/Beta-2del inducible virus which is carried by the midge Culex brevis. It was first described in 1929 and has since been characterized in 13 species in 11 different genera. More than 70 discrete virions have been isolated for NeoCov, but only a small number have been obtained for each species and none is easily recognizable as distinct from strains of some other viruses in the family, such as Whisdu, Geovirus, or Rantechvo. Within Culex, there are nine clades containing different strains with limited affinity for L-arginine. Whether the clades are genetically diverse enough to represent different viruses or they represent a single virus type is not known.
Examinations of clades A, B, and C by flow cytometry have found relatively high levels of viral capsid proteins and plasmids in the fluids of infected insects. The viral capsids and membrane proteins were in turn surrounded by a matrix of cellular components. Virus capsid proteins were identified as alpha-antigenic and Beta-hemolytic, and plasmid protein sequences identified as helper strand and chaperone sequences.
The inclusion bodies were positively stained for protein, and viral mRNA was detected within infected cells. The genome was typically found within the viral matrix matrix and was also flanked by an extensive genomic-like (i.e. non-genomic) region that contained genomic elements, but could not be classified as a genomic region, virus-like element, and non-genomic sequence.
However, the laboratory isolation of viral particles and cellular replication have some significant limitations. So far, the process has required the insect or the midge to be anesthetized before the virus enters and infects the cell. The presence of a protein moiety in the virus matrix that interferes with the binding of cell-penetrating antibodies to the matrix may also help the virus into the cell.
Mixed infection of an insect cell may also help the virus to enter the cell. The matrix may also help the virus to escape the cell by rupture. The escape from the insect cell has been shown to involve formation of an intermediate complex between the virus and the cell membrane, resulting in enhanced uptake by the host cell. These data suggest that an insect cell infected with a virus, and which is then killed, may provide a host cell for virus infection and replication.
NeoCov virions may contain a bacterial lipopolysaccharide (LPS) antigen that is attached in an intact, decoy-like structure to a variety of viral or cellular components. The presence of LPS antigen is frequently described as necessary for infection by the midge-endoparasitic helminth Geomyces marinus. Because LPS infection of A. nocturnus and Culex elegans is at least as effective as infection by helminth eggs, this is a possible explanation for the presence of LPS in infected Culex tissue, but not infected midge tissue.
Transmission
NeoCov virus is distributed widely in North and South America but is found only sporadically in Europe and Central Asia.
There is some evidence of midge-rearing by Culex quinquefasciatus (otherwise known as the carpet bug) in China and some animal traps in the Middle East are suspected of harboring NeoCov. We have no evidence of human disease from NeoCov virus.
NeoCov is capable of directly infecting larvae of many biting midges. Studies in Europe suggest that this is an accidental or intentional behavior by the midges; that midge larvae feed on the surface of the larval feeding site, which is contaminated by the injection of the virus. The midge larva can either feed or die and regrow into a second larval stage. The second stage then bites the second time.
In the United States, evidence is accumulating that Culex quinquefasciatus may use many different midge species as intermediate hosts.
Life cycle
The primary infected midge lays a single egg cell into the larval feeding site where it remains infective until hatching. The emerging midge crawls from the feeding site to a water source and drinks water to dehydrate and to escape danger.
At this point, it pokes its head out of the water. The emerging midge then bites another flying insect to urinate on the wound. During this, the emerging midge injects the entire midge midgut, including the pIgM protein, into the midge’s wound. The resulting body fluids cause the midge to become lethargic and dehydrated. Once the midge recovers, it typically bites again, injecting pIgM into the wound. After a subsequent urination, the midge continues to feed. This process repeats until the midge has completed its adult stage.
Individual Neocov particles have an average diameter of 13 micrometers. Of these, a majority of cells have diameter greater than 10 micrometers, but a significant fraction have diameter of less than 3 micrometers.
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