Transcript Papilloma viruses & Polyoma viruses

Papilloma viruses
&
Polyoma viruses
Human Papilloma viruses (HPV)
DNA virus, double strand, circular, Icosahedral
nucleocapsid, small size (45-55nm). No envelope
Human Papilloma virus (HPV)
70 different types (HPV-1 to HPV-70).
It replicates only in the nucleus of epithelial cells.
Infection occurs in skin and mucosal surfaces.
HPV are species-specific.
HPV
Wart
(Condylomata accuminata by HPV-2, -3, -10)
Common wart:
HPV-2, -3 and -10
(on knees and fingers)
plantar wart
HPV-1
HPV-4
Genital warts
HPV-6, -11, -16, -18 and- 32
on penis, vulva and perianal regions.
Can blossom into cauliflower-like protuberances.
Transmission through sex contacts is increasing.
HPV & Cervical Cancer
The agents: HPV16 & HPV18 responsible for 70%
of all cervical carcinoma.
Starts with a flat area of dysplasia (visible as a white
plaque).
Cervical and anal-cervical carcinoma is associated
with persistent HPV infections.
HPV Pathogenesis (1)
It infects cells in the basal
layers of the skin or mucosa.
Common period: 1-6 months
Viral antigen and infectious
virus is produced when the cells
begin to become squamifed
and keratinized.
Several months later, the wart
may regress.
HPV Pathogenesis (2)
Cell mediated immunity
(CMI) responses are more
important in recovery.
In immunocompromised
patients (e.g. post
transplant), there may be
warts as a result of
reactivation.
Diagnosis
Diagnosis is clinical
HPV cannot be cultivated in the laboratory
Serological tests are neither useful nor available
Treatment
Using keratolytic agents:
Salicylic acid (to soften and cause desquamation
of epithelium or horny layer of skin).
Removing warts by surgery.
Destruction of wart tissue by freezing with dry ice
(solid CO2) or with liquid nitrogen.
Using Podophyllin
Polyoma viruses
JC and BK viruses
Clinical findings
Parvoviruses
Parvoviruses
Unusual requirements for replication: either a
helper virus (a helper adenovirus) or rapidly dividing
cells.
The virus replicates when cell growth cycle is in “S”
stage (when host DNA replication produces two
identical sets of chromosomes.)
Virus replication is in nucleus of the cell.
B19
A parvovirus replicating in erythroid precursor cells,
so the main place for virus replication is: fetal bone
marrow and liver.
Favorite receptor on erythrocytes: p Ag (Globoside).
It can transmit from mother to embryo.
B19 can be found in blood and respiratory
secretions.
A human virus which cannot pass to animals.
The virus interrupts the production of
erythrocytes in embryo causing sever anemia
and abortion.
Erythema infectiosum, (fifth disease), is the
commonest clinical manifestation of B19
virus infection.
In children (age 5-15) and sometimes adults
(up to 30). 40-60% infections are
asymptomatic.
Fifth disease
(Erythema infectiosum)
First stage:
7-8 days after infection, a prodromal influenza-like
illness, characterized by headache, malaise, chills.
Second stage:
17 to 18 days after infection, the development of a
mild feverish illness and a maculopapular rash. It
starts with erythema of the cheeks (Slapped cheek)
followed by a rash (resembling the rash of rubella)
on the trunk and limbs. These symptoms
disappeared 1-3 weeks.
Anemia & aplastic crisis
The virus infects erythroid precursor cells in the bone
marrow and leads to anemia. Sever anemia in blood
disorders (e.g. in Sickel cell anemia, Leukemia or
hemolytic anemia)
It leads to erythroid aplasia (Aplastic crisis) in
patients with hemolytic anemia or immune
deficiency, such as people with transplantation event.
Anemia and aplastic crisis is self-limiting.
Diagnosis
Detecting viral DNA in serum (PCR)
A rise in parvovirus-specific IgM or IgG.
Bone marrow examination shows an absence of
erythroid precursors.
Transmission
B19 is anywhere, all through the year, different ages,
sporadic or epidemic.
Spread through respiratory secretions, vertical
transmission from mother
Many cases are subclinical.
Control and treatment
There is no antiviral therapy or vaccine
Most infections are asymptomatic
The anemia is self-limiting, but blood transfusion
support is required until the bone marrow recovers.
Antiserum decreases symptoms.
Sanitation