Pox, Parvo, Adeno and PaPoVa Viruses

Y2S2 – Infection module2010/11 batch

Champa RatnathungeDepartment of Microbiology

Learning outomes

• General properties and classification• Viral replication and methods of identification • Mechanisms by which viruses cause disease• Host defenses against viruses• Main clinical features• Principles of treatment and prevention

Poxviruses• Large , enveloped, DNA virus.• Family Poxviridae• The virion is large, brick shaped• Four genera of poxviruses may infect humans: 1. orthopox 2. parapox 3. yatapox 4. molluscipox

1.Orthopox: smallpox virus(variola), vaccinia virus, cowpox virus, monkeypox virus

2. Parapox: orf virus, pseudocowpox, bovine papular stomatitis virus

3. Yatapox: tanapox virus, yaba monkey tumor virus

4. Molluscipox: molluscum contagiosum virus (MCV)[1]

• Smallpox and molluscum contagiosum are specific to humans. • The other viruses cause rare zoonotic infections in humans. • Vaccinia virus can also infect humans – used in vaccination.

Viral replication

• Virion attaches to a cell surface receptor• Inside cell – virus uncoats – genome core

released• Proteins necessary for genome replication

produced• Viral particle assembled in Cytoplasm of host

cell• Time from cell infection to cell death – 12hours

Smallpox virus© Robert Alain, SME, INRS-Institut Armand-Frappier

Disease: SmallpoxDate of eradication: Declared eradicated in 1978 by WHO. (virus conserved in certain laboratories)

Smallpox (Variola virus)

Historical importance

• Earliest recorded case – EGYPT 2000BC• Spread to INDIA – 1ST century BC.• From Asia to Europe – 800AD.• Americas - early 16th century. Defeat of the Aztecs (South

America) was due to a smallpox epidemic. (in two years over 3.2 million Aztecs died. )Defeat of the Native Americans (Red Indians) -?? Bio terrorism

• Earliest attempt at IMMUNIZATION – Variolization• Edward Jenner – 1796 – Vaccination with Cow pox virus• Eradication of small pox – 1978 – due to successful global

vaccination

Vaccinia virus

• Common ancestral virus for – Variola, Vaccinia and Cow pox viruses

• Vaccinia virus :used as a vaccine, replicates at the site of inoculation, forming local erythematous maculopapules. These maculopapules then vesiculate (ie, jennerian vesicles), scar, and heal over 10-14 days

• Associated with tenderness and fever • Cannot cause “Small pox”, but can cause fatal Vaccinia

infection rarely• Present day –used to vaccinate military and health care

workers at risk in USA

Vaccination with Vaccinia – Skin

lesion.Following vaccination for smallpox, patient with leukemia developed vaccinia gangrenosum.

Parapox viruses: Orf virus• Zoonosis from sheep.• It causes a purulent-

appearing papule locally and generally no systemic symptoms. Infected locations can include the finger, hand, arm, face.

• Usually self limiting.• Can cause sever disease in

immunocompromised and severe damage in eye disease

• Diagnosis - clinical

Molluscipox :Molluscum Contagiosum

• Common, benign viral infection of the skin and mucous membranes

• Caused by the molluscum contagiosum virus.

• Typically affects children (1 -10Yrs)

• can be transmitted sexually in adults.

• Lesion - umbilicated papule.

• Spread – Direct skin-to-skin contact, Sharing clothes etc.

• Incubation period – 2 -7 weeks

• If untreated can last upto 6 months

Parvo virus

• Parvoviridae family

• Small , uncapsulated, DNA viruses

• Human infection – Parvovirus B19

Parvovirus B19 is associated with:

** Affects rapidly dividing tissue – Haematopoitic cells, foetal cells, GIT epithelial cells.

1. Erythema infectiosum / 5th disease/ Slapped cheek syndrome

2. Aplastic crisis in patients with chronic haemolytic anaemias.

3. Fetal loss in pregnancy4. Persistent infection in immunocompromised

patients

1.Spread by saliva or mucus2. Usually mild disease3. usually affects children

First disease: measles (rubeola)Second disease: scarlet feverThird disease: German measles (rubella)Fourth disease: "Filatov-Dukes' disease" (doubt exists over the existence of this as a disease entity)Fifth disease: erythema infectiosum (slapped cheek syndrome)Sixth disease: roseola infantum (herpesvirus 6 infection; "exanthem subitum")

Intrauterine fetal death at the 25th week of gestation, showing hydrops fetalis (the mother suffered from erythema infectiosum at the 10th week of gestation)

Adeno viruses

• Family Adenoviridae• Medium-sized , nonenveloped, icosahedral

DNA viruses

• In humans, there are 56 accepted human adenovirus types. Different types/serotypes are associated with different conditions

• transmitted via direct inoculation to the conjunctiva, a fecal-oral route, aerosolized droplets, or exposure to infected tissue or blood.

• Capable of infecting multiple organ systems; most infections are asymptomatic.

• Adenovirus is often cultured from the pharynx and stool of asymptomatic children, and most adults have measurable titers of anti-adenovirus antibodies, implying prior infection

• Respiratory disease – 5-10% of URTI in children (Tonsitilis, common cold, ear infections). Can cause pneumonia, bronchitis and bronchiolitis in infants.

• Conjunctivitis • Gastroenteritis • Rarely – Meningitis/ Encephalitis• Combinations of the above

Diagnosis - antigen detection, antibody detectionculture, PCR

No specific treatment. Best is PREVENTION by good hygiene – HAND WASHING.

Virus survives for long periods in the environment.

PAPOVA viruses

• PA – Papilloma viruses• PO – Polyoma viruses(VA – Vacuolating viruses)

• Family Papovaviridae is no longer used in taxonomy. It is split into Papillomaviridae and the Polyomaviridae.

• Non-enveloped, icasohedral, DNA viruses

Papilloma viruses/ Papillomaviridae

 Highly adapted to replication in a single animal species

Human Papilloma Virus (HPV)

• Infect keratinocytes exclusively• Viral particles released by desquamation of

cells. • Keratinocyte stem cells in the epithelial

basement layer can maintain papillomavirus genomes for decades

• The viral oncogenes E6 and E7 promote cell growth by inactivating the tumor suppressor proteins p53 and pRb.

Over 100 types of HPV have been identified.

• Clinical manifestations involve the epidermal surfaces – – common warts (verrucae vulgaris), – palmo-plantar warts, – flat warts (verrucae plana), – oral warts, – genital warts (condyloma acuminata),– papillomas of the mucosal surfaces– intraepithelial neoplasias.

• Genital human papillomavirus (HPV) infection is a common Sexully transmitted Disease (STD). -

• Strong evidence indicates that certain papillomaviruses are involved in cervical and genital cancers – Cervical Intra-epithelial Neoplasia (CIN) when infection persists for a long period.

• Vaccines for some HPV types are available – READ!!

Cervical intraepithelial neoplasia

• The major cause of CIN is chronic infection of the cervix with the sexually transmitted HPV, especially the high-risk HPV types 16 or 18.

• May regress, or progress to cancer.• CIN is found by a screening test,

the Papanicolaou or "Pap" smear – histology• Grades – 1,2,3• Treatment – depends in grade

Polyomavirus / Polyomaviridae • polyoma refers to the viruses' ability to produce multiple (poly-)

tumors (-oma).• Merkel cell virus– Associated with Merkel cell carcinoma• JC virus can infect the respiratory system, kidneys

or brain ,sometimes causing the fatal Progressive Multifocal Leukoencephalopathy (PML)

• BK virus produces a mild respiratory infection and can affect the kidneys of immunosuppressed transplant patients.

SUMMARY

• DNA viruses.• Poxvirus – Variola (Small pox), vaccinia, Orf,

MCV• Parvovirus – Parvovirus B19 – 5th disease• Adenovirus – common cause of respiratory

disease. Can get multisystem infection• PAPOVA – Papilloma viruses – Epithelial and

mucosa associated warts. Associated with cancer (CIN). Vaccine available

MCQ:

1. True / False1. Cowpox virus causes disease only in humans2. Vaccinia virus infection can be severe in some cases.3. Adenoviruses are a common cause of the common cold.4. Parvovirus B19 causes 5th disease in children.5. Papillomaviruses cause warts.

Thank you..