Enteroviruses

Question 1

Do different enteroviruses only affect different tissues?

Answer 1

No, different enteroviruses have varying affinities for tissues but there is always a probability of infecting other tissues that have lower affinity

Question 2

What are picornaviruses?

Answer 2

A family of RNA viruses including enterovirus, parechovirus and hepatovirus genera

Meningitis, encephalitis
URTI
HFMD
Hepatitis
Myocarditis

Question 3

What are enteroviruses?

Answer 3

Small viruses with +ve ss RNA, no envelope but resistant to harsh environmental conditions

Cytolytic

Includes poliovirus, coxsackie A, rhinovirus etc

Question 4

Pathogenesis of enterovirus infection?

Answer 4

Replicate in oropharynx, go to target tissues to exert direct effects
Can cause secondary viremia, infection of other organs that come into contact with infected blood

Asymptomatic infection and prolonged excretion of virus in stool is common, particularly in immunocompromised patients and neonates

Question 5

How are enteroviruses transmitted?

Answer 5

Faecal-oral, respiratory routes

Question 6

What are the symptoms of poliovirus?

Answer 6

Can cause paralysis

Viremia, virus in stools, fever, malaise, headache, nausea, meningitis, stiffness of neck/back

Question 7

Poliovirus vaccines?

Answer 7

Salk vaccine (IPV, inactivated virus thats injected) and sabin vaccine (OPV, live virus thats taken orally)

Oral vaccine might be able to induce IgA, easy to administer, not invasive and effective for controlling a big outbreak, but can cause vaccine derived poliovirus! Only use during an outbreak

Use injected inactivated vaccine when not in an outbreak

Question 8

Attenuated vs inactivated vaccines?

Answer 8

Attenuated viruses lose their virulence, but have a chance of reverting back to virulence, better for outbreak control

Inactivated viruses are killed, viruses cannot replicate but still have antigens present to produce immunoglobulins

Question 9

What are parechoviruses

Answer 9

A, B, C, D

A causes infections with diseases similar to those caused by enteroviruses

Majority of infections appear to occur within 1st year of life

Question 10

What is HPV?

Answer 10

Non enveloped dsDNA virus infecting humans, monkeys, cattle, rabbits and dogs

Infects surface epithelia to produce warts at site of multiplication

Question 11

What do HPVs cause?

Answer 11

Several benign tumours like cutaneous and genital warts

Respiratory papillomas

Cancers of the cervix and oropharynx, esp tonsillar cancer

Question 12

What HPVs cause cervical cancer?

Answer 12

HPV 16 and HPV 18 are responsible for the majority of cervical cancer

Question 13

Are HPVs site specific?

Answer 13

Yes, cutaneous HPV are rarely found in the mucosa and vice versa

Question 14

How do host factors affect HPV symptoms?

Answer 14

Warts tend to increase in size and lesion in conditions associated with immune impairment

Most warts regress within 2 years in immunocompetent patients

Question 15

How is HPV transmitted?

Answer 15

Skin abrasions (skin warts)
Sexual intercourse (genital warts)
Through the birth canal (juvenile onset laryngeal papilloma)
Oral sex (papillomas of the oral cavity)

Question 16

Pathogenesis of HPV

Answer 16

HPV infects cells of the basal layer of the epithelium, undergoing proliferation to form a wart (with all layers of epithelium represented)

Lesions vary widely in morphology, site of occurence and oncogenic potential

Question 17

How do cutaneous HPVs present?

Answer 17

Cutaneous warts on hands, characteristically domed shaped

Deep plantar warts occur singly with thickened corneal layer

Flat warts occur in groups on the face, arms and knees

Children and young adults

Skin cancers?

Question 18

How do mucosal HPVs present?

Answer 18

Genital tract infection on penis, around anus, perineum, cervix
Most regress with time but may increase in size during pregnancy
Can cause local irritation and itching to become infected

A large proportion are asymptomatic with no cytological abnormality

Oral cavity warts

Question 19

What HPVs cause oral cavity warts?

Answer 19

HPV 6 and HPV 11

Question 20

Can HPV cause neoplasia?

Answer 20

Yes, with a progressive spectrum of abnormalities ranging from low grade neoplasia –> high grade neoplasia –> invasive cancer

Question 21

What are risk factors for HPV associated head and neck cancers?

Answer 21

A history of multiple sexual partners and oral sex (as opposed to alcohol and tobacco use)

HPV 16 accounts for more than 90%

Question 22

What are the current HPV vaccines?

Answer 22

Bivalent - 16 and 18
Quadrivalent - 6, 11, 16 and 18
Nanovalent - lots of different types but always includes 16 and 18

Immunity against 16 and 18 also has cross-immunity for 6 and 11

HPV vaccines are primary prevention against cervical cancer