Infectious agent transmission viruses

Associated with the administration of blood or blood products is the risk of accidental transmission of infectious agents such as hepatitis viruses or HIV. The prevention of accidental pathogen transmission relies upon ... 

To meet the infectivity requirement in the definition of a prion, the abnormal form of the protein must be transmissible to other cells and organisms of the same species. In yeast and filamentous fungi, infectious agents such as viruses and plasmids are naturally transmitted by cytoplasmic mixing during mating or heterokaryon formation (Wickner, 2001). 

Table 9.2. Some of the infectious agents that have been transmitted via administration of infected blood or blood products. Transmission of viruses, particularly hepatitis A and B virus and HIV, are most common...

The abnormal deposits found in the brains of CJD victims consist of an abnormal isoform of PrP. Prion protein is normally found in cells. Detailed structural studies show that normal cellular PrP (PrP ) is a soluble protein whose conformation is rich in a-helices with very little P-sheet. The PrP protein extracted from the brains of CJD victims (i.e., PrP ) is identical in primary amino acid sequence to the normal PrP (PrP ). However, PrP has a much greater content of P-sheet conformation with little a-helical structure. Thus PrP is neurotoxic because of its three-dimensional structure. When the prion protein is predominantly in an a-helical conformation it is nontoxic when the prion protein is predominantly in a P-sheet conformation, it kills neurons. The prion protein is thus made neurotoxic not by its amino acid composition but by its conformation. This concept is both fascinating and terrifying. Prion diseases are transmissible thus prions are infectious agents. However, prions are not like bacteria or viruses, or other infectious microbes—they are simply protein molecules. Prions are not microbes with cell membranes and nucleic acids they are not living things. Indeed, prions are not even infectious molecules, they are infectious molecular shapes. 

Transmission of blood-borne viruses is always a concern when blood and blood-derived products are used. The infection of a large number of hemophiliac patients with hepatitis viruses and HIV during the 1980s prompted the development of virucidal methods to inactivate infectious agents. All currently available plasma-derived factor concentrates come from screened donors and undergo viral... 

The role of the surgical gown is to improve patient safety but also to minimize the spread of infectious agents such as MRSA (MethiciUin-resistant Staphylococcus aureus) and other antibiotic-resistant bacterial strains, and hazards associated with the transmission of blood-borne pathogens (eg, human immunodeficiency virus (HIV), and Hepatitis B and C viruses) and many others, and thereby decrease the risk for staff as well as other patients to be contaminated by these infectious agents. 

The jet plane has made it easy to travel to and from previously inaccessible parts of the world, for business or vacation. Infectious diseases or agents that transmit these diseases can, therefore, be rapidly transferred to countries in which the population has never encountered the diseases, so that the infection rapidly spreads throughout the population. Such transport of pathogens is reminiscent of the transmission of diseases that were previously unknown in North America but were transported from Africa in the slave ships. For example, the mosquito Aedes aegypti, which transmits the virus that causes yellow fever, was probably transported in water barrels on these ships. 

Another microbiological purity issue that has been associated with human blood is the possibility of adventitious contamination with viral pathogens. Likewise, if animal blood is used as the red cell source, a spectrum of viruses have been identified as potential contaminants and possibly as zoonotic agents that may be infectious to humans. " Therefore, in addition to the careful control of the blood used as the Hb source, the process for Hb solution preparation should employ robust virus inactivation and removal steps to reduce the risk of disease transmission. 

An unanswered question does remain regarding the extension of our findings to predict the adsorption characteristics of human hepatitis type A. This virus is the etiologic agent of infectious hepatitis, which is considered to be the most serious problem in the transmission of waterborne virus disease (i). It is similar to other enteroviruses in terms of size (27 nm in diameter), density in CsCl gradients (1.34 g cm ), stability in the presence of chemical and physical agents, and probable nucleic acid type (69). However, electrokinetic properties of this virus have yet to be characterized. This information is required before accurate predictions of electrostatic components of adsorption can be made for this virus. 

---