Page 385 - Review of Medical Microbiology and Immunology ( PDFDrive )

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PART IV Clinical Virology
374
infection is widespread. Disease occurs when latent JC
virus is activated in an immunocompromised patient. The
for more information.
virus persists in the kidney and is excreted in the urine. The
diagnosis is typically made by polymerase chain reaction
SLOW DISEASES CAUSED BY
assay of a brain biopsy specimen or spinal fluid. There is no
effective antiviral treatment, but cidofovir may be
beneficial.
There are five human TSEs caused by prions: kuru, CJD,
variant CJD, Gerstmann-Sträussler-Scheinker (GSS) syn-
Subacute Sclerosing Panencephalitis PRIONS
drome, and fatal familial insomnia. Table 44–2 describes
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Subacute sclerosing panencephalitis (SSPE) is a slowly pro-
some important features of slow viral diseases in humans
gressive disease characterized by inflammatory lesions in
caused by prions.
many areas of the brain. It is a rare disease of children who
were infected by measles virus several years earlier. Unlike
PML, immunosuppression is not a predisposing factor.
This fatal disease is characterized by progressive tremors
SSPE begins with mild changes in personality and ends
and ataxia but not dementia. It occurs only among the Fore
with dementia and death.
tribes in New Guinea. It was transmitted during a ritual in
SSPE is a persistent infection by a variant of measles
which the skulls of the dead were opened and the brains
virus that cannot complete its replication. The evidence for
this is as follows:
acquired: either by eating the brains or via cuts in the skin
(1) Inclusion bodies containing helical nucleocapsids,
that occurred during the preparation of the brains at which
which react with antibody to measles virus, are seen in the eaten. There are two ways the disease could have been
time brain tissue was introduced into the body. Since the
affected neurons.
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practice was stopped, kuru has almost disappeared. The
(2) A virus very similar to measles virus can be induced
agents of kuru and CJD (see next) have been transmitted
from these cells by cocultivation with permissive cells in
serially in primates.
culture. The induced virus has a different matrix protein;
this protein is important in viral assembly.
(3) Patients have high titers of measles antibody in the
blood and spinal fluid.
Pathologic examination of the brains of patients with CJD
(4) SSPE has virtually disappeared in the United States
and kuru reveals a spongiform (sponge or Swiss cheese)
since the onset of widespread immunization with measles
appearance similar to that associated with scrapie in sheep
vaccine.
(see later). The spongiform changes are the result of neuro-
nal vacuolation and neuronal loss rather than demyelin-
A progressive panencephalitis can also occur in patients
ation. No inflammatory cells are seen in the brains. Prions
with congenital rubella.
cause scrapie and have been found in the brains of CJD
Acquired Immunodeficiency Syndrome
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In contrast to kuru, CJD is found sporadically world-
AIDS is caused by human immunodeficiency virus (HIV),
wide and affects both sexes. The incidence of CJD is
a member of the lentivirus group of retroviruses. AIDS is a
approximately 1 case per 1 million population, and there is
disease with a long latent period and a progressive course
no increased risk associated with dietary habits, occupation,
TABLE 44–2 Important Features of Slow Viral Diseases Caused by Prions
Pathogenesis
Important Feature
Disease
Caused by ingesting or handling brain tissue; occurred in New
Kuru
Transmissible/infectious
Guinea tribes people
Iatrogenic transmission by corneal transplant, brain electrodes,
Creutzfeldt-Jakob disease
1. Transmissible/infectious
and growth hormone
Mutation in germ cells
2. Hereditary/genetic

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3. Sporadic
No relationship to any known cause; possible new mutation in
somatic cells; most common form
Transmissible/infectious
Variant Creutzfeldt-Jakob disease
with mad cow disease
Mutation in germ cells
Hereditary/genetic
Gerstmann-Sträussler-Scheinker syndrome
Hereditary/genetic
Mutation in germ cells
Fatal familial insomnia
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