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
Some cause warts and some others
are associated with cancer.
They are transmitted by contacts
(both direct and indirect).
Wart
(Condylomata accuminata by HPV-2, -3, -10)
Resembling a cauliflower or a solid blister by
producing excess cells.
Mucocutaneous lesions: Hands, feet, genital area
and even other locations.
A small, rough benign tumor
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 (a resinous powder obtained by precipitating
an alcoholic tincture of the rhizome of American Mayapple)
Polyoma viruses
Structure:
DNA virus, double strand, circular, Icosahedral
nucleocapsid, small size (45-55nm). No envelope
Well-known Human polyoma viruses: JC and BK
(all around the world)
JC and BK viruses
They can be remained in kidney &
lymphoid tissues after a primary infection.
They can be reactivated after kidney
transplantation or pregnancy or oldness.
Clinical findings
Polyomavirus (BK) nephropathy usually happens in
5% of kidny recipients and causing rejection in 50%
of them.
BK hemeoragic cystitis in patients with bone morrow
transplantation.
JC is the agent of PML (progressive multiphocal
locoencephalopaty) in immune deficiency involving
5% of AIDS cases.
Parvoviruses
Structure:
- Nonenveloped, icosahedral particle, Single
and Positive DNA strand.
- Very small viruses (18-26 nm) and ubiquitous.
- Infect many species of animals.
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).
• B19 can be found in blood and respiratory
secretions.
• It can transmit from mother to embryo.
B19
• 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