The HIV contains a unique enzyme that enables the viruses to make DNA copies of its
6.
RNA. This enzyme, commonly referred to as reverse transcriptase, is an
RNA-dependent DNA polymerase that catalyzes the reverse flow of genetic
information from RNA to DNA. Once the DNA is made, these viruses use other
enzymes to insert, or integrate, the DNA copies of their genes into the
chromosomal DNA of the host cell. Insertion having been accomplished, the
proviral DNA genes become a part of the genes of the host cell. Once present in
the cellular DNA, retrovirus "proviral" genes may be: (1) nonfunctional or silent, (2)
partially transcribed with subsequent expression of individual viral proteins within
the cell or on its surface, or (3) fully transcribed to produce new viral RNA genes
that are encapsulated in viral structural proteins to form new virus particles. These
new virons may then infect any cell they contact.
(para 7-6)
Human Immunodeficiency Virus is cytopathic for many of the lymphocytes in which the
7.
virus actively replicates. The primary targets for HIV are the T4 helper lymphocytes. However,
other cells may become infected; these other cells include the monocytes,
macrophages, B lymphocytes, dendritic reticular cells, and some glial and
endothelial cells in the brain may become infected.
(para 7-7)
8.
The HIV virus destroys many of the body's T4 helper cells. The infected T4 cells
that are not destroyed are functionally defective. The infected monocytes appear
to be nonfunctional. The virus appears to stimulate all B cells into producing
antibodies, thereby, leaving no unstimulated B cells available to respond to new
infections.
(para 7-8)
ELISA or EIA procedures are the most widely used screening tests for HIV. These
9.
procedures test for antibodies formed against various proteins or glycoproteins
from HIV. There are new procedures available now to test directly for HIV
antigens. This allows for earlier and more definitive detection of the disease. The
procedure, which is presently used for confirmation of positive screening tests
(ELISA, EIA), is the Western blot.
(para 7-9)
10.
Viral hepatitis has been recognized by the medical community for almost two
centuries and remains a disease of major significance in the world today. It is an
infection which results in inflammation of the liver caused by one of at least 4
distinct viral agents. The diagnosis of acute viral hepatitis sometimes can be
made on the basis of clinical features and history that suggest a particular
causative agent. In most cases and due to recent immunological advances,
specific tests exist which accurately detect, diagnose, and monitor the progression
of hepatitis.
(para 7-10)
MD0838
7-22