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CASE FILES: BIOCHEMISTRY
A N SW E R S TO C A SE 5: H U M A N IM M U N O D E F IC IE N C Y
V IR U S
Summary:
A 32-year-old male with history of IV drug use has numerous
upper-respiratory symptoms and adenopathy, and he presents now with sore
throat with numerous white plaques. He also has a low CD4 count. The
pathogen has a ribonucleic acid (RNA) genome.
Most likely diagnosis:
Candida esophagitis secondary to human
immunodeficiency virus (HIV).
Biochemical mechanism of disease:
The HIV genome is composed of
single-stranded RNA. Reverse transcription of the viral RNA is required
to infect the host cells. HIV causes immunosuppression because it has a
propensity for attaching to helper T cells (CD4 cells), the cells that
support cell mediated immunity.
Enzyme necessary:
Reverse transcriptase.
C L IN IC A L C O R R E L A T IO N
This 32-year-old male likely acquired HIV infection by sharing needles with an
infected individual. Initially, an HIV infection may cause systemic flu-like
symptoms, adenopathy, and fatigue. During this phase, the patient experiences
a viremia. The next phase is largely asymptomatic as the virus slowly causes
attrition of the CD4 helper T cells. When the levels of these important cells drop
to low levels, the patient will not be able to fend off organisms that are com-
monly colonizing the skin, gastrointestinal tract, or in the air. Treatment for
HIV infection includes agents that attack the unique aspects of the virus such
as nucleoside analogue reverse transcriptase inhibitors and protease inhibitors.
A PPR O A C H TO H IV
O bjectives
1.
Understand normal transcription/translation.
2.
Be familiar with reverse transcriptase and mechanism by which HIV
works.
3.
Know the mechanism of action of HIV medications.
D efinitions
Deoxyribonucleic acid (DNA) replication:
The process by which DNA is
duplicated in the cell. This process takes place during the S-phase of the
cell cycle. DNA is duplicated in a semiconservative manner; that is, each
new DNA double-strand contains one of the original strands (parent
strands) and one of the newly synthesized strands (daughter strands).
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