Avian viruses

After obtaining pure total RNA from eukaryotic cells, the RNA needs to be rewritten into cDNA to serve as a template in PCR, as RNA cannot be amplified by PCR. The task of rewriting is accomplished with reverse transcriptase (RT), a viral enzyme used by retroviruses (whose name stems from harboring this enzyme and the ability to rewrite RNA into cDNA). The group of retroviruses has such members as the AIDS virus, Avian myeloblastosis virus, Murine leukemia virus (Frohmann, 1988 Kawasaki, 1988), and Adenovirus. Commonly employed reverse transcriptases stem from either the avian virus (AMV-RT) or the murine leukemia virus (MMLV, used in the Clontech RT-kit). 

Fig. 4. A diagrammatic comparison of the structures of the human c-fms protein, the human PDGF receptor and the v-kit oncogene of the avian virus HZ4. Solid dots represent the position of cysteine residues in the extracellular domains of the proteins.

Interferon Alfa-n3 (injection). Interferon alfa-n3 (Alferon N) is a polyclonal mixture of up to 14 natural a-interferon subtypes and contains 166 amino acid residues. Its commercial production involves induction of pooled units of human leukocytes with an avian virus (Sendai virus). The purification prtK css involves immunoaffinity and nitration chromatography. It is indicated primarily by intralcsional injection for the treatment of genital wans. The solution should be stored at a temperature of. 36 to 46°H and should not be shaken. 

Embryonated hens eggs are still the most convenient hosts for growth of the viruses that are needed for influenza and yellow fever vaccines. Influenza viruses accumulate in high titre in the allantoic fluid of the eggs and yellow fever virus accumulates in the nervous system of the embryos. It is important to use eggs from disease-free flocks and emphasis is placed on screening the latter for various avian viruses. The allantoic fluid or embryos must be har-... 

There are animal viruses, plant viruses, and bacterial viruses called bacteriophages. Animal viruses include mammalian viruses, both human and otherwise, avian viruses, and no doubt reptilian viruses. Additionally, there are insect viruses, from which, oddly enough, plant viruses may have evolved. (Some insects may carry an enormous load of viruses, but remain unaffected, although this is not necessarily the case for humans. Bee stings, for instance, have been correlated with melanoma occurrences, but whether these are attributable to viruses or to the toxins is apparently not known.) There are also fungal viruses and protozoan viruses (affording a potential mode of treatment or cure for malaria). The virus families are referred to as the... 

I nfluenza virus is responsible for 36 000 deaths/yr in the U,S. The virus is clas> sified into types A, B, and C, and subtypes C rains ) according to differences in virai proteins. One particular strain of avian virus ( bird flu ) is of particular concern because it has the potentiai to cause widespread human disease. The World Health Organization identifies flu strains so that vaccines can be prepared. Conventional typing methods are expensive and require days or weeks. An RNA array has the potential to reduce cost and time. 

The results obtained in these studies suggest that paucity of receptors for avian viruses in the upper respiratoiy tract in humans is one of the factors preventing efficient human-to-human transmission. This concept is supported by recent studies showing that H5N1 mutants binding to a2-6 linked sialic acid are transmitted between ferrets through the air [37, 38]. 

Recent data, however, contradict Rabat s hypothesis. DNA complementary to y-globin mRNA was synthesized with the aid of an avian virus reverse transcriptase. Hybridization of this DNA with DNA of differentiating erythroblast cells of humans showed that the DNA of these cells has y-globin genes (Mitchelfand Williamson, 1977). The presence of genes for and y-globins was found in sheep... 

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