Respiratory Viruses Flashcards
rhinovirus type of virus
- ss RNA
importance of rhinovirus infection when young
- may sensitive an individual to early onset asthma
do we have antivirals for RSV
- not specific ones
do we have vaccines for RSV
- no
do we have antivirals for measles
- no
do we have vaccines for measles
- yes
do you normally have a fever during a cold
what about during the flu?
- rare
- yes
how fast does a cold come on?
- over a few days
how fast does the flu come on?
- sudden
which people are most susceptible to the flu
- the very old and very young
influenza infection often coincides with bacterial superinfection from
- MRSA
- staph aureus
- strep pneumo
- Group A Strep
how long does it take after exposure to flu to develop protective serum antibody?
- about a month
viral infection of respiratory epithelium
- destroys epithelial cells
- damages mucous membrane
- membranes are colonized with bacteria
type A influenza virus affects which group
- humans and other animals
- all age groups
severity of illness for type A influenza
- moderate to severe illness
type B influenza virus affects which group
- humans only
- primarily children
importance of type C influenza virus
- no neuraminidase activity
- HA contains esterase activity instead
role of hemagglutinin
- binds the virus to cells with sialic acid on the membrane
role of neuraminidase
- cleaves sialic acid
which type of influenza virus is zoonotic
- type A
what is the process that involves gradual adaptation of zoonotic viruses that allow human infection and transmission
- antigenic drift
what is the process that involves reassortment of the SEGMENTED GENOME that potentially allows swapping of genes between different virus types
- antigenic shift
how does antigenic drift work
- accumulation of point mutations results in amino acid substitutions
- differences in antigenic sites where host antibody binds to HA and NA glycoproteins
- prevent binding of antibodies induced by previous infection
how does an antigenic shift work
- HA/NA switch to new chimeric status
antigenic shift only occurs for which type of influenza virus
- type A
MOA of amantidine and rimantadine
- M2 ion channel inhibitors that block endosomal release of disassembling virus
which type of influenza virus possesses M2 channels
- type A only
MOA of zanamivir, oseltamivir, and permavir
- neuraminidase inhibitors
how neuraminidase inhibitors work
- interfere with ability of neuraminidase to cleave sialic acid
- stops virus from budding
how influenza virus uses cap snatching
- flu virus makes its own mRNA
- steals 5’ cap from host
- propagates own life cycle and inhibits host mRNA
role of Xoflusa
- inhibits flu cap snatching
the most variable antigen on the influenza virus is what?
- HA
what is a good target for a universal influenza vaccine
- the stem of HA
structure of paramyxovirus
- enveloped, nonsegmented, negative sense RNA
what is the life of immunity to RSV
- only 2-3 months
who is at the greatest risk of hospitalization as a result of RSV infection
- young infants < 1 month
pathogenesis of RSV
- mucus congests small airways of bronchioles
- clogged also by inflammatory cells (macrophages and neutrophils)
structure of flu
- enveloped virus with negative sense segmented genome
antiviral treatment for RSV
- ribavirin (nonspecific)
can the measles virus be transmitted from the host prior to the onset of rash
- yes
measles pathogenesis
- inhaled
- gets into lung
- disseminates out of lung and into lymph and becomes systemic
characteristic symptom of measles even before rash comes on
- Koplik’s spots - white on mucosa of the oral cavity
main target of measles
- alveolar macrophages and dendritic cells
THEN - T and B cells
complications of measles
- pneumonia
- immunosuppression with increased susceptibility to other infections
- complications from CNS infection
Coronavirus structure
enveloped
+ ssRNA (non-segmented)
RNA packaged in coiled structure composed of nucleocapsid (N) proteins
receptor for SARS-CoV-2
ACE2
ACE2 receptor expressed where
by epithelial cells in the oral cavity and lung (intestine, kidneys and blood vessels)
Comorbidities among patients at risk for serious Covid-19
HTN and diabetes
both conditions treated with ACE inhibitors; leads to increased ACE2 expression –> may promote viral infection
Differences between SARS-CoV-2 and Influenza A
SARS-CoV-2: occasional mutations (better proofreading RdRP) lead to sporadic epidemics
w/o segment, no potential for shift mediated by reassortment
Influenza: continuous drift (small-scale mutations due to error-prone RdRp)
shift (large changes in viral HA and NA due to reassortment of viral RNA segments)
viruses that infect the HUMAN respiratory tract
Influenza A/B
RSV
SARS-CoV-2
Which virus can lead to SSPE (subacute sclerosing panencephalitis)
Measles Virus
For RSV, Influenza and SARS-CoV-2 name the:
time of year of infection
antivirals
vaccines
reservoir
RSV: annual/seasonal, no specific antivirals, no licensed vaccines, humans only
Influenza: annual/seasonal, specific antivirals, vaccines available, zoonotic
SARS-CoV-2: current pandemic, no specific antivirals, vaccines available, zoonotic
RSV is in the same family as which virus?
Measles
RSV infection in what demographic?
most frequent cause of lower airway disease in infants
increasingly associated wth disease in elderly and immunocompromised
RSV and children
nearly 100% children infected by 2-3 years of age
symptomatic
leads to bronchiolitis!!
RSV bronchiolitis
mucus and inflammatory material occlude small airways in infants and young children
Treatment for RSV
non-specific antiviral (ribavirin)
anti-RSV antibody
RSV structure for attachment and entry
viral factors: glycoprotein G, fusion protein F
host receptors: TLR4, ciliated cell receptors
most common causes of bacterial superinfection
staph. aureus and strep. pneumo
Pulmonary and Non-pulmonary complications w/ Influenza
Pulmonary → primary influenza viral pneumonia, secondary bacterial pneumonia, Croup, exacerbates lung disease
Non-pulmonary → Toxic shock syndrome (S. aureus superinfection), Guillain-Barré syndrome
Influenza type C
uncommon, no epidemic potential
prevents binding of antibodies
antigenic drift
differences in key antigenic sites in HA and NA glycoproteins
antigenic drift
accumulation of point mutations results in amino acid substitutions
antigenic drift
reassortment of viral segments in Type A viruses
antigenic shift
may occur in animals or humans
antigenic shift
may result in new H/NN combinations
antigenic shift
Responsible for pandemics every 10-40 years
antigenic shift