Influenza & Viral pneumonia Flashcards
What is pneumonia?
an inflammation of the lungs caused by infection with a virus or bacteria + immune response of body
mainly parenchyma, alveoli are affected
Which populations are most likely to experience viral pneumonia?
young children or older adults b/c of their weakened immune systems
also those with cardiac or pulmonary disease
What are typical symptoms of pneumonia?
cough
fever
chills
SOB
What are common causes of viral pneumonia?
Influenza Virus A & B
RSV
Human parainfluenza virus
Why is is RSV called respiratory syncytial virus?
b/c it forms a syncitia as cells fuse together. eventually, one cell has hundreds of nuclei.
What are some less common causes of viral pneumonia?
Adenoviruses
Rhinoviruses
Metapneumoviruses
SARS
What are disease causing viruses that can secondarily cause pneumonia?
Herpes simplex virus Varicella-zoster virus Measles Rubella Cytomegalovirus
What does human parainfluenza virus cause?
croup
Which of the viruses that we have talked about belong to the paramyxovirus family?
RSV
human parainfluenza virus
What are some pulmonary defense mechanisms that keep junk from getting into the lower airway?
cough reflex
epiglottis
Describe the defense mechanisms in the lower airway.
goblet cells are in the airway along w/ ciliated columnar respiratory epithelium.
goblet cells secrete mucus & the cilia beat it upwards to the mouth.
What is a defensive antibody in the airway?
IgA–mucosal immunity
Which category of viruses cause influenza?
Family of Orthomyxo, includes paramyxo.
These are enveloped neg strand RNA viruses.
How is the influenza virus transmitted? What are the different types? Which type is responsible for the most pandemics?
transmitted via resp droplets
Types A,B,C
Pandemics caused by A, B–>but mostly A.
What are 2 important things on the surface of the influenza A virus? How many subtypes of each?
Hemagluttinin HA: 16
(need for leaving the cell) NA: 9
What are the 2 ways that the influenza virus can change & therefore cause pandemics?
antigenic shift: reassortment of genome RNA when 2 different viruses infect the same cell.
antigenic drift: small mutations in genome RNA
What does HA do on the influenza virus?
agglutinates RBCs
sometimes a viral attachment protein.
What is the incubation period of the flu? After this period, which symptoms pop up?
24-48 hours fever myalgia headache sore throat cough
When do the symptoms of the flue subside?
in 4-7 days
but can be longer if pneumonia results.
For the flu….
what determines immunity? Treatment? Prevention?
Immunity-IgA that targets HA
Treatment-Tamiflu & Relenza
Prevention–vaccines for Influenza A & B
Which receptor does the influenza virus bind to in the lungs?
sialic acid receptor–found everywhere in the lungs
then receptor mediated endocytosis
What is the season for influenza?
fall & early spring
Describe the entire replication cycle for the influenza virus.
Receptor mediated endocytosis (sialic acid receptor)
Segmented ribonucleoproteins released into the cytoplasm
Genome transported to the nucleus
Replication and transcription
Viral mRNAs transported to the cytoplasm for translation
Early viral replication proteins transported back to the nucleus
Assembly and budding occurs at the plasma membrane
If a negative sense RNA strand is transacted into a lung epithelial cell what will happen?
It won’t infect unless it has with it an RNA-dependent RNA polymerase to make a positive sense strand. Then it can use the cell machinery to make the necessary proteins for infection.
The early proteins that are made in a host cell from an influenza virus are usu ________. the late proteins usu______.
early–>replication proteins
late–>builds capsid, structural function.
Where does the transcription & replication of the RNA virus occur in host cells? For influenza…
in the cell nucleus, unusual for an RNA virus.
T/F WIth influenza, the lung cells die.
True.
How do the ribonucleoproteins get into the cytosol of the host cell?
the low pH of the endosome facilitates membrane fusion & release of them into the cytosol.
What makes up the RNA polymerase?
3 viral proteins (P proteins) are responsible for transcription
What do matrix proteins do?
form a shell below the viral membrane
interact w/ viral glycoprotein
T/F only 1 RNA virus can infect a host cell at a time.
False. 2 can infect it at once & that is how we get reassortment.
T/F Different NA/ HA are what determine the type of influenza virus i.e. A, B, C
False. The types of nucleocapsid & matrix proteins (internal) are what determine A, B, C. They don’t drift as much.
What determines the subtypes of influenza A?
HA & NA
What are the rules for classification of an influenza virus? Ex: A/Hong Kong/03/68(H3N2)
Type A, host origin, location, date, HA & NA classification
When it is pulled out of a human, leave blank.
What is the function of HA & NA? Which are targeted when?
HA: binds viruses to host cells. Targeted by IgA & other body antibodies.
NA: facilitates release of virus particles from infected cells during the budding process. Targeted by vaccines.
Which is more dramatic & consequential–shift or drift?
SHIFT. THis is what causes pandemics.
Drift–is more point mutations.
What are ways that you can tell that someone has been infected by the influenza virus?
interferon is seen in resp secretions 1 day post infection
antibody & cell mediated immunity–can be seen 1-2 weeks later.
What does IFN do?
activated by double stranded RNA, viral glycoproteins, bacterial LPS etc
it signals for macrophages & NK cells. Stops viral replication. Warns neighboring cells that there is a virus around. Upregulates the amount of MHC everywhere.
Which form of immunity is a little late to the party when it comes to fighting influenza viral infections?
cell mediated immunity. comes around in 1-2 weeks b/c viral infections usu only last about 7 days.
What is a fomite?
a virus that is still infectious on a contaminated surface.
What is a bad thing that can happen when someone gets the flu?
if there are susceptible
can get a secondary bacterial infection b/c a lot of their ciliary respiratory epithelium has been compromised.
WHat are the recommendations for flu vaccines?
anyone greater than 6 months every year
What are the 3 types of flu that are circulating lately?
A H1N1, A H3N2, B
What does RSV cause? Which age group? Transmission?
causes pneumonia & bronchiolitis in neonates, premature infants, & those w/ cardiopulmonary disease
resp droplets transmit it.
What symptoms do you see with RSV infection in infants?
cough & expiratory wheezing
What does RSV do to adults? Elderly?
Adults: common cold & bronchitis
Elderly: pneumonia
How can you detect an RSV infection? What are the treatment options?
Rapid antigen test to detect virus
Ribavirin & passive immunization w/ antibody is possibility for treatment, but more with severely ill patients.
What does ribavirin do?
Ribavirin is a guanosine (ribonucleic) analog used to stop viral RNA synthesis and viral mRNA capping; simply put, it is a nucleoside inhibitor.
What is bronchiolitis? Remember–can be caused by RSV
Bronchiolitis is inflammation of the bronchioles, the smallest air passages of the lungs. It presents with coughing, wheezing and shortness of breath which can cause some children difficulty feeding.
What type of virus is RSV?
paramyxovirus
Most children get RSV before they are age ___. 20% of those will have signs of ______. 1-2% of those will need _________.
age 5
pneumonia
need to be hospitalized
What are the surface spikes on RSV called?
fusion proteins–causes cells to fuse & gives multinucleated giant cells
NOT HA or NA
What is the party season for RSV?
winter season
What do parainfluenza viruses cause? Transmission?
croup, laryngitis, bronchiolitis, and pneumonia in children
resp droplets
What do parainfluenza viruses cause in adults?
something that looks like the common cold
PIV1 & 2 often cause what?
croup–infection of upper airway characterized by barking cough & hoarseness
PIV3 causes what?
lower respiratory infections
PIV4 causes what?
nothing more than the common cold
What are the different things that parainfluenza viruses cause?
croup, common cold, pharyngitis, laryngitis, otitis media, bronchitis, and pneumonia
Describe the surface spikes for the parainfluenza virus?
F proteins & HA/NA proteins (share the same spike)
also form multinucleated cells w/ the F protein
What generally speaking do parainfluenza viruses cause?
upper & lower resp infections w/o viremia
I have immunity to the F protein on the parainfluenza virus. Will I get infected?
Nope. If you had immunity to the HA one you wouldn’t get infected either.
