Transcript TORTORA • FUNKE • CASE Microbiology AN INTRODUCTION EIGHTH EDITION B.E Pruitt & Jane J.

TORTORA • FUNKE
• CASE
Microbiology
AN INTRODUCTION
EIGHTH EDITION
B.E Pruitt & Jane J. Stein
Chapter 19, part B
Disorders Associated with the
Immune System
Acquired Immunodeficiency
Syndrome (AIDS)
• 1981In U.S., cluster of Pneumocystis and
Kaposi's sarcoma in young
homosexual men discovered. The
showed loss of immune
• 1983Discovery of virus causing loss of
immune function.
men
function.
Acquired Immunodeficiency Syndrome (AIDS)
Figure 19.12a
The Origin of AIDS
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Crossed the species barrier into humans in Africa in the 1930s
Patient who died in 1959 in Congo is the oldest known case
Spread in Africa as a result of urbanization
Spread in world through modern transportation and unsafe sexual
practices
• Norwegian sailor who died in 1976 is the first known case in Western
world
HIV Infection
Figure 19.12b
HIV Infection
Capsid
Reverse
transcriptase
DNA
Virus
Two identical + stands of RNA
1 Retrovirus penetrates
host cell.
Host
cell
DNA of one of the host
cell’s chromosomes
5 Mature
retrovirus
leaves host
cell, acquiring
an envelope as
it buds out.
Reverse
transcriptase
Viral RNA
Identical
strands of
RNA
2 Virion penetrates
cell and its DNA is
uncoated
4 Transcription of the
Viral proteins
RNA
provirus may also occur,
producing RNA for new
retrovirus genomes and
RNA that codes for the
retrovirus capsid and
envelope proteins.
Provirus
3 The new viral DNA is
tranported into the host cell’s
nucleus and integrated as a
provirus. The provirus may
divide indefinitely with the
host cell DNA.
Figure 13.19
HIV Infection
Figure 19.13
HIV Infection
Figure 19.14
The Stages of HIV Infection
• Category A Asymptomatic or persistent
lymphadenopathy
• Category B Persistent Candida albicans infections
• Category C Clinical AIDS. CMV, TB,
Pneumocystis, toxoplasmosis,
Kaposi's sarcoma
The Stages of HIV Infection
Figure 19.15
Some Common Diseases Associated with AIDS
Table 19.5
Diagnostic Methods
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Seroconversion takes up to 3 months
HIV antibodies detected by ELISA
HIV antigens detected by Western blotting
Plasma viral load is determined by PCR or nucleic acid
hybridization
HIV Transmission
• HIV survives 6 hours outside a cell
• HIV survives >1.5 days inside a cell
• Infected body fluids transmit HIV via:
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Sexual contact
Breast milk
Transplacental infection of fetus
Blood-contaminated needles
Organ transplants
Artificial insemination
Blood transfusion
Modes of HIV Transmission
Figure 19.17
AIDS Worldwide
• U.S., Canada, western Europe, Australia, northern Africa, South
America
– Injecting drug use, male-to-male sexual contact
• Sub-Saharan Africa
– Heterosexual contact
• Eastern Europe, Middles East, Asia
– Injecting drug use, heterosexual contact
AIDS Worldwide
Figure 19.16
Clades
• HIV-1 is the most common. It has 11 clades:
– 90% of U.S. infections caused by clade B
– Clade C predominates in sub-Saharan African
– Clades B, C, & E are in south and southeast Asia
• HIV-2 is seen in western Africa
Prevention of AIDS
• Use of condoms and sterile needles
• Health-case workers use universal precautions
– Wear gloves, gowns, masks, goggles
– Do not recap needles
– Risk of infection from infected needlestick injury is 0.3%
Vaccines in Clinical
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Whole-cell Salmonella with gp120 gene
Subunit vaccine using gp120 expressed in Saccharomyces
Canarypox virus with HIV capsid protein genes
Naked DNA consisting of tat (transcription factor) or gag (capsid
protein) genes
Chemotherapy
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Nucleotide Reverse Transcriptase Inhibitors
Non- Nucleoside Reverse Transcriptase Inhibitors
Protease Inhibitors
Virus decoys
Highly Active Antiretroviral Therapy (HAART):
• Combinations of nucleoside reverse transcriptase inhibitors +
– Non-nucleoside reverse transcriptase inhibitor or
– Protease inhibitor