3.6.2. Viral Upper Respiratory Infections

Question 1

Describe the structure of Rhinovirus.

Answer 1

1. Structure: non enveloped

Question 2

Describe the characteristics of Rhinovirus

Answer 2

Characteristics: +ssRNA genome (is infectious), >100 serotypes, ICAM-1 is primary cellular receptor; temperature sensitive (88-90 F; prefers the temperatures of the nose and lung

Question 3

What are the target cells of the Rhinovirus?

Answer 3

1. Target Cells: respiratory epithelial cells

Question 4

Describe the life cycle of the rhinovirus.

Answer 4

Life Cycle: after entry to cell, viral mRNA directly binds to ribosomes to make polyproteins [encodes its own RNA polymerase]; these proteins are cleaved by viral proteases to generate structural proteins and replicate +ssRNA; proteins insert into genome and viral release achieved via cytolysis

Question 5

Describe the structuve of respiratory syncytial virus

Answer 5

Structure: enveloped; two major envelope proteins - F (fusion) and G (attachment) proteins

Question 6

Describe the characteristics of the respiratory syncytial virus.

Answer 6

Characteristics: -ssRNA genome, helical capsid, encodes its own RNA-dependent-RNA polymerase

Question 7

What are the target cells of respiratory syncytial virus?

Answer 7

Target Cells: nasopharyngeal epithelium

Question 8

Describe the life cycle of the respiratory syncytial virus.

Answer 8

Life Cycle: is absorbed/fused and inserts -ssRNA; undergoes transcription to produce viral mRNA and replicate RNA genome; forms surface glyco-proteins on epithelium cells and exocytoses genome with glycoproteins to develop syncytia

Question 9

What is the structure of adenovirus?

Answer 9

Structure: largest, non-enveloped virus; at least 51 serotypes; icosahedral

Question 10

Describe the characteristics of adenovirus?

Answer 10

Characteristics: ds linear DNA genome; replicates in the nucleus

Question 11

What are the target cells of the adenovirus?

Answer 11

Target Cells: mucoepithelial cells in resp/GI tract and conjunctiva or cornea

Question 12

Describe the life cycle of the adenovirus.

Answer 12

Life Cycle: replication is temporal, it encodes its own DNA polymerase; the virus will persist in lymphoid tissues; two outcomes following infection: lytic in mucoepithelial cells; latent in adenoid cells

Question 13

What is the structure of the Epstein-Barr Virus (EBV)?

Answer 13

Structure: “gamma” herpesvirus; enveloped

Question 14

What are the characteristics of EBV?

Answer 14

Characteristics: restricted host range; large genome; linear dsDNA; encodes its own DNA-dependent-DNA polymerase

Question 15

What are the target cells of EBV?

Answer 15

Target Cells: epithelial cells and lymphocytes (may be latent in endothelial cells and lymphocytes)

Question 16

What is the life cycle of EBV?

Answer 16

Life Cycle: attachment and penetration by fusion, immediate early protein synthesis, early protein synthesis and replication of genome inside the nucleus, late protein synthesis (structural) and exocytosis and release, eventual lysis and release

Question 17

How is rhinovirus transmitted?

Answer 17

Rhinovirus - transmitted via aerosol droplets and direct contact with contaminated surfaces

Question 18

What is the pathogensis, symptoms, and complications associated with rhinovirus?

Answer 18

1. pathogenesis: short incubation, self-limiting
2. symptoms: nasal discharge, congestion, sneezing, sore throat, myalgias, fatigue, edema of nasal mucosa, headache
   complications: in rare cases, may cause bronchopneumonia in young children

Question 19

What are the pathogensis, symptoms, and complications associated with respiratory syncytial virus?

Answer 19

1. pathogenesis: entry via epithelia of nose and eyes (aerosoles, fomites); self limiting [7-10 days]
2. symptoms: runny nose, fever, rapid breathing, wheezing/breathlessness, cough, lips turn blue; infection produces protective immunity that is NOT long lasting, resulting in repeated infection
   complications: repeat infection; brochiolitis in infants

Question 20

What are the pathogenesis, symptoms, and complications associated with adenovirus?

Answer 20

1. pathogenesis: transmission by direct contact: fecal-oral, contaminated water, objects, aerosol; endemic for acute respiratory disease in military recruits - Ad4, 7
2. symptoms: varies with the age and immune status of the host
3. complications: acute respiratory disease, pharyngoconjunctival fever, pertussis-like syndrome (infants/young children), pneumonia

Question 21

What are the pathogenesis, symptoms, and complications of EBV?

Answer 21

1. pathogenesis: ubiquitous, >95% of adults are thought to be infected; “kissing disease”; glandular fever; transmission is primarily through the oral route; incubation lasts 6-8 weeks with symptoms for 2-3 weeks
2. symptoms: soreness and reddening of the throat and tonsils, white patches may be seen on the tonsils; cervical lymphadenopathy; pharyngitis, sore throat, atypical lymphocytosis are the most prevalent symptoms
   complications: Burkitts, Non-hodgkins, and Hodgkins lymphomas; nasopharyngeal carcinoma and oral hairy leukoplakia are all seen with latent EBV; usually due to decreased immunogenicity

Question 22

Describe the diagnosis of rhinovirus, respiratory syncytium virus, adenovirus, and EBV.

Answer 22

1. Rhinovirus
   
   1. Diagnosis: based on symptoms; virus culture, PCR of nasal samples
2. Respiratory Syncytial Virus
   1. Diagnosis: nasal washings or swab samples for antigen detection; ELISA or DFA; viral cultures; molecular assays
3. Adenovirus
   1. Diagnosis: detection of antigen from nasopharyngeal aspirates and throat washings; isolation of virus from aspirates, throat swabs, and feces; retrospective serology; PCR assays
4. Epstein-Barr Virus
   
   1. Diagnosis: atypical lymphocytes (CD8 CTL); agglutination test for heterophile antibodies; EBV antibody ELISA; PCR for EBV

Question 23

Describe the preventive measures of rhinovirus, respiratory syncytium virus, adenovirus, and EBV.

Answer 23

Rhinovirus: Preventative measures: sanitation and hygiene to prevent the spread

Respiratory Syncytium Virus: None listed

Adenovirus: Preventative measures: sanitation and hygiene

EBV: None listed

Question 24

Describe the vaccination of rhinovirus, respiratory syncytium virus, adenovirus, and EBV.

Answer 24

Rhinovirus: Vaccination: none available due to >100 serotypes; mucosal IgA is protective, type I interferons control viral spread but causes pathogenesis

Respiratory Syncytial Virus: Vaccination: no licensed vaccine currently available

Adenovirus: Vaccination: neutralizing antibodies are protective against same serotype; by age 10, most have antibodies against the endemic serotypes; difficult to vaccinate, because it encodes proteins that play a role in immune evasion (E3 protein) which down regulates MHC class I and inhibits TNF mediated lysis

EBV: Vaccination: none

Question 25

Describe the treatment of rhinovirus, respiratory syncytium virus, adenovirus, and EBV.

Answer 25

Rhinovirus: Treatment: treat the symptoms

Respiratory Syncytium Virus: Treatment: ribavirin has had limited success; O2 treatment and hospitalization for infants with severe brochiolitis; RespiGam (polyclonal antibody) and Synagis (anti-F protein monoclonal antibody) for passive immunotherapy

Adenovirus: Treatment: treatment of symptoms; disease resolves in 7-10 days; vaccine no longer produced; live vaccine tablets being tested in military commands

EBV: Treatment: symptomatic; is self-limiting and rapidly controlled by the immune response

Question 26

What does a nice summary slide of all of this look like?