Biomedical Engineering Reference
In-Depth Information
21.3.2.3 Biacore 2000 Analyzer, (Biacore Inc.) ..........................................587
21.4 Future Commercially Available Immunosensors ....................................................588
21.5 Conclusions ....................................................................................................................589
References ..................................................................................................................................590
21.1
Introduction
According to epidemiologic studies, viral diseases are the primary cause of serious disor-
ders that do not require hospitalization among people who reside in developed countries.
Among infants and children, they exact a heavy toll in mortality and permanent disabil-
ity. Emerging viral diseases, such as those brought about by HIV, Ebola virus, and
Hantavirus, appear regularly. In addition, while antibiotics effectively combat most bacte-
rial-based infections, viral infections are not so readily controlled; by comparison, they
pose a greater threat to people's health. Additionally, according to some data, the broad
range of established viral diseases known today appears to be expanding into other seri-
ous human ailments including tumors, juvenile diabetes, rheumatoid arthritis, and a vari-
ety of neurological and immunological disorders [1].
Virus may even have had a role in the natural selection of animal species because like
other microorganisms they have the ability to infect all forms of life including bacteria,
plants, protozoa, fungi, insects, fish, reptiles, birds, and mammals. In a manner similar to
the selective role smallpox virus played in humans, the natural selection of rabbits that
were resistant to virulent myxoma virus occurred, and was documented during several
epidemics deliberately induced to control the Australian rabbit population.
Another unproven but possible way in which virus may affect evolution [2] is through
the introduction of viral genetic material into animal cells by mechanisms similar to those
that govern gene transfer by bacteriophages. For instance, when genes from a virulent
retrovirus are integrated into genomes of chickens or mice, they produce resistance to rein-
fection by related, virulent retroviruses. Reports of human leukemia-causing retroviruses
indicate that the same relationship may exist for human retroviruses.
As small, subcellular agents, virus are unable to multiply outside a host cell (intracellu-
lar, obligate parasitism). Only one type of nucleic acid (RNA or DNA) is present in the
assembled virus (virion), in addition to a protective protein coat in simple virus. The
nucleic acid carries the genetic data needed to program the synthetic machinery of the host
cell for viral replication while the protein coat serves two functions: it protects the nucleic
acid from extracellular environmental insults such as nucleases, and permits attachment of
the virion to the membrane of the host cell, which otherwise exhibits a negative charge that
repels a naked nucleic acid. Once the host cell is infected through viral genome penetration,
virus replication becomes dependent on that host cell for its energy and synthetic needs.
The basic structure of virus [3,4] seems to permit them to be simultaneously adaptable
and selective, since the various virion components are synthesized separately within the
cell, after which they are assembled to form progeny particles. Distinguishing them from
all other small, obligate, intracellular parasites, this assembly type of replication is unique
to the virus. Under experimental conditions, viral genomes are so adaptable that once they
have penetrated the cell membrane, viral replication can occur in almost any cell.
Alternatively, intact virus are so selective that most of them are able to infect only a lim-
ited range of cell types, which selectivity exists largely because penetration of the nucleic
acid usually requires a specific reaction that enables the coat to attach to specific intracel-
lular components and the host cell membrane.
