Lecture 3

Question 1

What are the 6 respiratory viruses?

Answer 1

-Influenza
-Parainfluenza
-RSV
-Rhinovirus
-Covid
-Adenovirus

Question 2

What are the properties of influenza viruses?

Answer 2

ssRNA(-) viruses
Pleomorphic envelope (varies in size & shape of envelope)
Helical nucleocapsid capsid
Segmented genome (8 RNA(-) segments)
Genetic structure enhances chance of reassortment of gene segments (Antigenic Shift)
Mutant strains cause epidemic, pandemic
Only influenza A & B important for human disease

Infects upper respiratory tract epithelium
Transcription & replication occurs in the nucleus
Assembly & release at plasma membrane

Question 3

ssRNA(+)

Answer 3

Template for generating copies

Question 4

ssRNA (-)

Answer 4

For packaging of new virus in nucleus

Question 5

Influenza gene products (proteins)

Answer 5

associated with RNA genome

-PB2, PB1, PA – complex of 3 subunits forms the RNA polymerase
-NP – nucleocapsid protein

Question 6

Other components produced in the host cell

Answer 6

HA – hemagglutinin – attachment protein, fusion protein
NA – neuraminidase – cleaves sialic acid in mucus, aids in viral spreading
M2 – membrane protein, channel, facilitates uncoating
M1 – matrix protein, structural
NS1 – IFN antagonist
NS2 – nuclear export protein

Question 7

Influenza A host range

Answer 7

Humans, swine, avian, equines, marine mammals, bats

Question 8

Influenza B host range

Answer 8

Humans, seals

Question 9

Influenza C host range

Answer 9

Humans, swines

Question 10

What are the properties of paramyxovirus

Answer 10

Pleomorphic envelope with specific viral attachment proteins
Helical nucleocapsid
Large, ssRNA(-) viruses
Linear genome
Carries nucleocapsid-associated proteins
3 important genera distinguished by attachment proteins
Cause major diseases including measles, mumps & RSV
Induce syncytia formation
Invade cells by membrane fusion, released by budding
Transmitted by aerosols & establish primary infection in respiratory tract

Question 11

3 important genera of paramyxovirus

Answer 11

Morbillivirus
Measles virus (single serotype)

Paramyxovirus
Mumps virus (single serotype)
Parainfluenza virus 1-4

Pneumovirus
RSV (respiratory syncytial virus)
Metapneumovirus

Question 12

Gene products of paramyxovirus

Answer 12

-Nucleocapsid-associated proteins
NP (nucleoprotein) – binds & protects viral RNA
P (polymerase phosphoprotein) – facilitates RNA replication
L (RNA polymerase)

-Viral-attachment proteins produced in host cell
F protein (membrane protein) – promotes fusion & viral entry
HN (hemagglutinin-neuraminidase)
Paramyxovirus (Parainfluenza virus & Mumps)
H (hemagglutinin) – binds surface receptors, no N
Morbillivirus (Measles)
G (glycoprotein) – for attachment, not a hemagglutinin
Pneumovirus (RSV)
M protein (matrix protein) – assembly of virions

Question 13

Adenovirus Properties

Answer 13

No envelope
Icosadeltahedral capsid
dsDNA virus
linear genome
52 serotypes (1-7 most common)
Replicated & assembled in the nucleus
Lytic in permissive cells
Latent/persistent in non-permissive cells
Transformative only in non-human cells
Extensively studied (introns & RNA splicing)
Useful tools – gene replacement, anti-viral & cancer therapy

Question 14

Adenovirus: Vaps & Receptors

Answer 14

-Fibers at vertices
viral attachment proteins
type-specific antigens provides specificity for serotypes
act as a hemagglutin
toxic to cells, along with pentose base

-Attach via Ig superfamily glycoprotein
Coxsackie adenovirus complex

-Also bind MHC I
Internalized by receptor-mediated endocytosis
Lyse vesicles & enter nucleus

Question 15

Adenovirus gene products

Answer 15

E1A & E1B – inhibit p53 & p105RB
E2 – viral DNA polymerase
E3 – immunosuppressant (blocks apoptosis; decrease MHC I expression)
E4 – prevents apoptosis
Viral-associated RNAs (VA RNAs) – inhibit IFN response
L1 – L5 – structural/capsid proteins

Question 16

Adenovirus Transmission & Disease

Answer 16

-Transmission
inhalation
close contact
oral/fecal
fomites
poorly chlorinated pools
Spread by viremia

Hallmark of infection – inclusion bodies without cellular enlargement

-Clinical Diseases (dependent upon tissue infected and virus type)
Acute febrile pharyngitis and pharyngoconjunctivital fever
Acute respiratory disease
Laryngitis, bronchiolitis, pneumonia
Conjunctivitis (pink eye, swimming pool conjunctivitis)
Gastroenteritis

Question 17

PICORNAVIRUSES: GENERAL PROPERTIES

Answer 17

no envelope
icosahedral capsid
small, ssRNA (+) viruses
linear mRNA genome
replicated & assembled in the cytoplasm
large family of viruses
very resistant to harsh conditions
enteroviruses (tolerate wide pH range)
transmitted by fecal-oral route
Lytic viruses with specific tissue tropisms

Question 18

PICORNAVIRUSES: DIFFERENT GROUPS

Answer 18

-Enteroviruses
Poliovirus
Coxsackie A virus
Coxsackie b virus
Echovirus

-Rhinovirus (common cold)

-Cardiovirus

-Aphthovirus

-Hepatovirus
Hepatitis A virus

Question 19

RHINOVIRUSES: PROPERTIES

Answer 19

number one cause of common cold & upper respiratory tract infections

Use ICAM-1 as rhinoviral receptor

Prefer cooler temperatures

Less resistant than enteroviruses
cannot tolerate environment of GI tract

Acquired by inhalation as aerosols or by fomites
replicates primarily in the nose

Question 20

CORONAVIRUSES: PROPERTIES

Answer 20

enveloped virion
long, flexible, helical genome
ssRNA(+) virus
envelope glycoproteins form club-like projections – “corona”
corona provides resistance to acids of GI tract
Infect upper respiratory tract epithelial cells
Released by exocytosis
Usually remains local due to optimal growth at temperatures less than physiological (33°C to 35°C)
Second most common cause of common cold
SARS – Severe Acute Respiratory Syndrome
MERS – Middle East Respiratory Syndrome
COVID-19 – world-wide pandemic

Question 21

slide 50 review