Respiratory Viruses

Question 1

Three types of RNA viruses

Answer 1

Positive stranded, negative stranded, retroviruses. If positive, similar to RNA, if negative, transcription must occur first.

Question 2

Retroviruses

Answer 2

RNA is first transcribed to DNA. Transcription, translation, and replication often occur in the cytoplasm.

Question 3

Paramyxovirus structure

Answer 3

Negative sense, single stranded, nonsegmented RNA. Helical nucleocapsid with three proteins NP, polymerase phosphoprotein, large protein. Matrix protein lines lipid bilayer inside the viron envelope. Lipid bilayer studded with glycoproteins, fusion protein, attachment proteins

Question 4

NP, P, L, M, F, HN, H, G

Answer 4

Nucleoprotein, polymerase phosphoprotein, large protein, matrix protein, fusion protein, attachment proteins.

Question 5

How does the paramyxovirus replicate?

Answer 5

Attachment proteins bind to sialic acid on host cell surface, genome transcribed into individual mRNAs and full length positive sense RNA template. Nucleocapsid associates with matrix and plasma membranes and leaves the cell by budding.

Question 6

Parainfluenza virus

Answer 6

Primarily affects young children, causing upper and lower respiratory tract infections like croup, common cold, bronchiolitis, pneumonia

Question 7

HPIV1

Answer 7

Causes croup along with HPIV2, both occur in fall

Question 8

HPIV 3

Answer 8

primarily causes pneumonia and bronchiolitis. Throughout the year, but peak in spring.

Question 9

Pathogenesis of HPIV

Answer 9

Infects the nasal and pharyngeal mucosal epithelia then spreads locally along the respiratory epithelium to the larynx and trachea.

Question 10

Anatomic hallmark of croup?

Answer 10

Steeple sign = narrowing of the trachea in the subglottic region.

Question 11

Transmission of parainfluenza virus

Answer 11

Spread via respiratory droplets or direct person to person contact with infected secretions.

Question 12

Diagnosis of parainfluenza virus

Answer 12

Antigen detection (direct fluorescent Ab, ELISA), cell culture, PCR

Question 13

Treatment of HPIV

Answer 13

Self-limited infection, treatment is primarily supportive (dexamethasone, epinephrine)

Question 14

RSV Virus Clinical Syndromes

Answer 14

Bronchiolitis or pneumonia, most patients have upper respiratory disease, more serious manifestation involving the lower respiratory tract in older children/adults

Question 15

Who is at increased risk for RSV infection?

Answer 15

Preterm birth, cyanotic or complicated congenital heart disease (esp. pulm hypertension), immunodeficiency, old age

Question 16

Pathogenesis of RSV

Answer 16

Replicates in nasopharynx, then infects the bronchiolar epithelium. Extends to the alveolar pneumocytes by cell to cell spread, aspiration of secretions and formation of syncytia. Necrosis of bronchi and bronchioles results in mucus plugs, fibrin, and necrotic material. Immune response to RSV seems to play a role in the pathogenesis and severity of bronchiolitis.

Question 17

Treatment for RSV

Answer 17

Supportive, ribavirin

Question 18

Ribavirin

Answer 18

Nucleoside analog that inhibits nucleic acid synthesis

Question 19

Palivizumab

Answer 19

Monoclonal antibody against F protein, used for high risk infants

Question 20

Human metapneumovirus

Answer 20

2nd leading cause of bronchiolitis in infants, causes 15% of common colds in children, also can cause pneumonia, croup, upper respiratory tract infections

Question 21

Who is at risk for contracting hMPV?

Answer 21

Immunocompromised, preterm birth, transplant, cardiopulmonary disease.

Question 22

Transmission of hMPV?

Answer 22

Direct or close contact with contaminated secretions. Nosocomial infections have been reported.

Question 23

When does hMPV infection peak?

Answer 23

Late winter/early spring in temperate climates.

Question 24

Can hMPV be grown in culture?

Answer 24

Yes, but it has a very long incubation period and is difficult to grow.

Question 25

Coronavirus structure

Answer 25

Enveloped, single stranded positive sense RNA, glycoproteins form halo-like projections around surrounding envelope. RNa genome plus N protein form helical nucleocapsid.

Question 26

Replication of coronavirus

Answer 26

Virus fuses w/ cell and genome is released in cytoplasm. Translation of the genome occurs in two phases: early phase produces RNA polymerase, late phase negative sense RNA yields structural and nonstructural proteins.

Question 27

Where does the coronavirus assemble within a cell?

Answer 27

At the rough ER, and is released via exocytosis.

Question 28

Coronavirus clinical syndromes

Answer 28

Common cold and other respiratory infections, gastroenteritis, SARS

Question 29

Reservoir of coronavirus

Answer 29

Common in many animal species, generally cause infections in winter and spring.

Question 30

Coronavirus transmission

Answer 30

Respiratory tract secretions through person-person contact or fomites.

Question 31

Coronavirus diagnosis

Answer 31

PCR of respiratory secretions/stool, antibody assays, electron microscopy

Question 32

Where does transcription/replication for DNA viruses occur?

Answer 32

In the nucleus, usually more genetically complex then RNA viruses.

Question 33

Adenovirus Structure

Answer 33

Linear double stranded DNA virus, non encapsulated icosadeltahedron, capsid is made of 240 capsomeres consisting of hexons and pentons. 12 pentons each have a base and a fiber which contains viral attachment protein

Question 34

How does adenovirus replicate?

Answer 34

Viral fibers attach to a glycoprotein member of the immunoglobulin superfamily. Penton base interacts with an integrin on host cell which results in endocytosis. DNA genome delivered to the nucleus, transcription of mRNA occurs in two phases.

Question 35

Where are adenovirus capsid proteins produced?

Answer 35

Cytoplas, and then transported to the nucleus for viral assembly. Virus remains in the cell and is released when the cell degenerates or lyses.

Question 36

Adenovirus clinical syndromes

Answer 36

URI/LRI, pharyngo-conjuctivitis, gastroenteritis, hemorrhagic cystitis

Question 37

Where does adenovirus persist?

Answer 37

In lymphoid tissue, can lead to viremia

Question 38

Cidofovir

Answer 38

Cytosine analog that serves as a substrate and inhibits viral DNA synthesis. Nephotoxic, requires IV administration.

Question 39

Rhinovirus

Answer 39

Causes common cold, pharyngitis, otitis media

Question 40

How is rhinovirus transmitted?

Answer 40

Aerosols and fomites, hands are major factors