MMR

Question 1

Measles

Answer 1

One of the most contagious diseases, rash covering arms and stomach

Question 2

Measles Virus Characteristics

Answer 2

Paramyxovirus (genus: morbillivirus), negative strand non-segmented RNA virus, enveloped

Question 3

Measles virus characteristics

Answer 3

Lipid envelope studded with viral glycoproteins (H+F)

Question 4

Nucleocapsid

Answer 4

Viral RNA, N(nucleoprotein), P (phosphoprotein), L (large protein).

Question 5

Genome of measles virus

Answer 5

6 Genes encoding 8 proteins, P gene encodes multiple proteins.

Question 6

What proteins does P encode?

Answer 6

P- phosphoprotein required for polymerase activity
V- accessory protein that blocks the innate immune response
C- accessory protein that blocks the innate immune response

Question 7

Measles attachment

Answer 7

H protein binds to CD46 (regulator of complement activation), SLAM (signaling lymphocyte activation molecule), nectin 4 (necently discovered epithelial cell receptor).

Question 8

Measles fusion

Answer 8

F protein mediates fusion between viral envelope and host cell membrane

Question 9

Measles replication and transcription

Answer 9

Catalyzed by viral RNA-dependent RNA polymerase (L and P), takes place in cytoplasm

Question 10

Measles budding

Answer 10

Mediated by M protein, takes place at the plasma membrane.

Question 11

Measles clinical course

Answer 11

Latent period of 10-14 days after spread via respiratory aerosols, 2-3 day prodromal fever, cough, conjunctivitis, rhinitis, followed by characteristic maculopapular rash. Onset of rash coincides with immune response and initation of viral clearance, recovery is accompanied by lifelong immunity.

Question 12

Where does measles enter and where does it replicate/spread?

Answer 12

Virus transmitted through respiratory droplets and enters through the respiratory tract. Initial infection is established in the macrophages and dendritic cells of the respiratory tract. These infected cells transport the virus to local lymphoid tissue where it is amplified leading to viremia. Virus spreads through the blood to a number of organs infecting epithelial cells, endothelial cells, and tissue macrophages. See chart in slides.

Question 13

Syncytium

Answer 13

Virus spread in tissue creates a giant multinucleated cell.

Question 14

Koplik’s spots

Answer 14

Pinpoint gray-white spots (grains of salt-appearance) that appear on mucous membranes, most noticeable on the buccal mucosa.

Question 15

Measles rash

Answer 15

begins on face, spreads to extremities, fever and severe symptoms diminish and the rash progresses

Question 16

Complications from measles

Answer 16

Bacterial superinfection (5-15%): otitis media, mastoiditis, sinusitis, pneumonia. Immune suppression caused by infection can lead to complications, such as TB reactivation. Disease can be very severe in immunocompromised or malnourished patients. Postinfectious or acute disseminiated encephalomyelitis is an autoimmune demyelinating disease that occurs in 1/1000. 20% mortality.

Question 17

How to diagnose measles

Answer 17

Clinical diagnosis: maculopapular rash for 3+days, fever, cough rhinitis conjunctivitis.

Laboratory diagnosis: RT PCR, virus antigen isolation from epithelial cells of nasopharynx.

Question 18

When does appearance of the rash occur?

Answer 18

When immune response occurs and viral clearance begins.

Question 19

How to treat measles?

Answer 19

No specific treatment available.

Question 20

Measles Vaccine

Answer 20

Approved in 1963, edmonston strain attenuated by several passages in chick embryo fibroblasts, administered together with mumps and rubella. 12-15mos, then booster at 4-6 years.

Question 21

Why do we wait until 12-15 months to vaccinate?

Answer 21

because maternal antibody decreases vaccine efficacy.

Question 22

Why are high rates of vaccine coverage necessary to avoid outbreaks?

Answer 22

Because measles is so damn contagious!

Question 23

Mumps

Answer 23

Caused by the mumps virus and presents with swelling of the salivary glands, particularly the parotid gland.

Question 24

Characteristics of the mumps virus

Answer 24

Paramyxovirus family, genus rubulavirus. Negative strand, nonsegmented RNA virus, enveloped. Has HN, F, M, NPL,

Question 25

Mumps Pathogenesis

Answer 25

Enters respiratory tract, virus grows in salivary glands and local lymphoid tissue. Virus spreads to spleen and distant lymphoid tissue (7-10 days). Then viremia occurs, causing diffuse disease.

Question 26

Clinical aspects of mumps

Answer 26

Fever, meningitis, rare encephalitis, approx 30% are subclinical

Question 27

Mumps vaccine

Answer 27

Live attenuated virus, single serotype, administered together with measles and rubella.

Question 28

Rubella

Answer 28

German measles, mild disease w/ red maculopapular rash.

Question 29

Rubella virus characteristics

Answer 29

Togavirus, positive strand RNA virus. Icosahedral nucleocapsid

Question 30

Congenital rubella syndrome

Answer 30

If contracted in early months of pregnancy, rubella is associated with a high rate of birth defects like deafness, cataracts, heart defects.

Question 31

Rubella vaccine

Answer 31

single serotype live attenuated virus vaccine