Orthomyxo, Paramyxo, and Picornaviruses Flashcards
Orthomyxovirus
- Morphology
- Unique feature
- Important types
- Transmission
- neg-sense linear ssRNA, helical, 8 segments, enveloped with H and N glycoprotein peplomers (on a separate card), spherical or filamentous, RNA polymerase complexes
- the only RNA virus to replicate in the nucleus (all others in cytoplasm)
- Influenza A, B, C. “A” is for humans, other mammals, birds. B and C are only in humans.
- Respiratory droplets
Orthomyxovirus:
- Important antigens and their pathogenetic relevance
- How does the flu mutate to cause new problems
-Hemagglutinin (HA) 1-15, and Neuraminidase (NA) 1-10 glycoprotein peplomers that are anchored to the lipid membrane by M-proteins
- HA binds to sialic acid receptors present on erythrocytes -> hemagglutination
- HA binds to sialic acid receptors on upper respiratory tract cells -> fusion of host cell membrane -> viral adsorption
- NA cleaves nuraminic acid, disrupting mucin barrier, exposing sialic acid binding sites
- Antigenic drift: point mutations allow for yearly epidemics of mild flu
- Antigenic shift: rare large-scale genetic recombination / reassortment of Influenza A causes pandemics with high mortality. Occurs with bird and pig species.
Orthomyxovirus:
What are some of the historical deadly H-N influenza pandemic types?
(I put asterisks on the most important ones on the answer card)
- -1918: Spanish Flu H1N1. Swine crossover. 50-100 million died.
- -1957: H2N2 Asian Flu, a form of avian flu
- 1968: H3N2 Hong Kong Flu, antigen shift from H2N2.
- 1977: H1N1 Russian Flu.
- -1997: H5N1 Bird Flu, extremely deadly but so-far contained.
- -2009: H1N1 Swine Flu. From Mexico.
Orthomyxovirus:
- Disease/symptoms
- Treatment
- Prevention
- Flu: headache, malaise, fever, chills, anorexia, bronchiolitis. Complicated by pneumonia (e.g. S. aureus)
- Treatment: Tamiflu inhibits neuraminidase, prevents release of virions so it’s only effective if given early. Aspirin contraindicated in children, risk of Reye’s syndrome.
- Prevention: Trivalent vaccine: 2 A + 1 B strain, Quadravelnt: 2 A + 2 B’s. Contains inactivated purified surface antigens of HA and NA. Besides injection, can also be live attenuated nasal spray.
Orthomyxovirus:
Categories of Diagnostic Tests for Influenza:
(not sure if this is important, clinical micro MRS made a big deal about it)
- Virus isolation: culturing for genetic and antigenic analysis. More traditional than practical method for clinics, also done in research.
- Detection of viral proteins: Hemagglutination and Hemagglutination Inhibition. IF, ELISA.
- Detection of viral nucleic acids (RNA): via reverse transciptase + PCR
- Serology: changes in antibodies over 2 weeks. Anti-H antibodies provide immunity, anti-N antibodies inhibit transmission.
What is the mnemonic for all the segmented viruses + how many segments are they?
BOAR: Bunyavirus: 3 Orthomyxovirus: 8 Arenavirus: 2 Reovirus: 11
Paramyxoviruses:
- Morphology
- The viruses to know from the family (will detail them in separate cards)
-neg-sense ssRNA, enveloped, helical nucleocapsid, pleomorphic, spherical or filamentous, replicates in cytoplasm (normal for RNA viruses)
Viruses:
1. Measles / Rubeola
2. Mumps
3. Respiratory Syncytial Virus (RSV)
4. Parainfluenza virus: croup / laryngotracheobronchitis
Paramyxoviruses:
-Measles: features, transmission, disease, diagnosis, prevention, treatment
Measles: caused by morbilli virus serotype.
- Has hemagglutinin and fusion proteins
- Respiratory droplets
- Symptoms: Maculopapular rash, acute rhinitis, conjunctivitis, cough. Koplik spots: vesicles on buccal mucosa.
- Complications: otitis media, bronchitis, bronchopneumonia, deafness from middle ear infection, encephalitis, SSPE (subacute sclerosing panencephalitis).
- Immunocompromised: giant cell pneumonia, encephalitis.
- Diagnosis: clinical signs. Serology: HI, ELISA
- Prevention: MMR vaccine (live attenuated)
- Treatment: Ribavirin is experimental. Vitamin A reduces morbidity/ mortality.
Paramyxoviruses:
-Mumps: features, transmission, disease, diagnosis, prevention
Mumps: parotitis epidemica, mumps virus = rubulavirus genus
- Has hemagglutinin, fusion protein, and neuraminidase. One serotype
- Respiratory droplets
- Enters respiratory tract, spreads to local lymph nodes then distant lymph nodes + spleen. Generalized spread to salivary and other glands. Causes viremia.
- Painful edematous enlargement of parotid / other glands.
- Testis, ovary involvement: orchitis
- Maybe pancreatitis
- Complications: meningitis, encephalitis, thyroiditis, myocarditis
- Diagnosis: virus isolation (saliva, urine, CSF), serology: HI, ELISA-IgM
- Prevention: MMR live attenuated vaccine
Paramyxoviruses:
-RSV: features, transmission, disease, diagnosis, prevention, treatment
Respiratory Syncytial Virus (RSV):
- Attaches to G protein to infect resp epithelial cells. Contains fusion protein.
- Respiratory droplets
- # 1 cause of atypical pneumonia in infants (low fever, tachypnea, tachycardia, expiratory wheezes) + #1 cause of bronchiolitis and necrosis of bronchioles in infants. Epidemic in winter.
- Diagnosis: IFA, ELISA, RT-PCR.
- No vaccine
- Ribavirin, Palivizumab blocks fusion protein
Paramyxoviruses:
-Parainfluenzavirus: features, transmission, disease, diagnosis, prevention
Parainfluenzavirus: cause of croup (severe laryngotracheitis) subglottal swelling with seal-bark cough + pseudomembrane that’s easy to remove compared to diphtheria. Also causes a cold, bronchiolitis, pneumonia.
- Parainfluenza 1,2 -> epidemic croup in first 5 years of age (autumn)
- Parainfluenza 3 -> bronchiolitis, pneumonia in first year (endemic)
- Parainfluenza 4 -> upper respiratory tract infection in children (endemic)
- Diagnosis: ELISA, RIA, IF, isolation
- Prevention: experimental subunit vaccine (F, HN)
Picornaviruses: enterovirus genus (Polio, Coxsackie, Echo and Enterovirus are given in the topic prompt)
- General Morphology/ Features
- Transmission
- General phases of pathogenesis
- linear pos-sense ssRNA (use host RNA polymerase), naked, icosahedral capsid. Replicate in cytoplasm. Cytocidal. 25-30 nm.
- Creates large polyprotein products that need to be cleaved into smaller subunits
- Transmitted fecal-oral, typically in summer and fall. IgA antibodies in the intestine and saliva are protective. Interferon also effective.
-Enteroviruses enter intestinal tract, attach to receptors on intestinal epithelium, replicate in cytoplasm, then move to lymph (lymphatic phase), then bloodstream (viremic phase). Often subclinical. Occasionally a neurological phase occurs afterwards.
Poliovirus:
- Features
- Pathogenesis
- Disease
- Diagnosis
- Prevention
- Picornavirus enterovirus features, naked (+) ssRNA. Acid stable. Poliovirus types 1, 2, and 3.
- After fecal-oral transmission, replicates in MALT like Peyer’s patches over 2-3 weeks. Spreads to anterior horn of spinal cord.
- Disease: Most cases are subclinical. May have paralytic polio (poliomyelitis; Heine-Medin disease): flaccid asymmetric paralysis w/ no sensory loss, respiratory paralysis is major cause of death. Post-polio: after 30-40 years -> neuron destruction, muscle wasting. Polio also causes viral aseptic meningitis.
- Diagnosis: serology (virus absent from CSF)
- Treatment: supportive, assisted breathing (iron lung)
- Prevention: Salk vaccine = killed vaccine, injected. Sabin vaccine = live attenuated, given orally, provides both IgG and mucosal IgA response (risk of spread in feces)
Coxsackievirus: -Features -Pathogenesis -Diagnosis -Prevention (types of coxsackie and diseases on separate card)
- Picornavirus enterovirus features, naked (+) ssRNA.
- Fecal-oral, typically in summer
- Virus enters, binds to adenovirus receptor (CAR) and decay accelerating factor (DAF), internalized and transported to Golgi and ER, virus uncoated, RNA released, translated into proteins, replication, assembly and release.
- Diagnosis: virus isolation from throat, stool, or CSF
- Treatment: supportive
- Prevention: sanitation
Coxsackievirus:
-Types and their diseases
- Coxsackie A (23 serotypes): hand-foot-mouth disease (red vesicular rash, oral and pharyngeal ulceration), aseptic meningitis, herpangina, common cold, lymphoglandular pharyngitis. type 21, 24: common cold + maculopapular rash in children (diff dg meningococcus). type 24: acute hemorrhagic conjunctivitis.
- Coxsackie B (6 serotypes): dilated cardiomyopathy. Bornholm’s disease (pleurodynia): abrupt chest/abdominal pain. Meningitis, mild paresis, muscle weakness, pericarditis, pancreatitis (relation to DM type I?)
