MICR 454L Emerging and ReEmerging Infectious Diseases Case Study

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MICR 454L Emerging and Re-Emerging Infectious
DiseasesCase Study 10

• David Song
• Jonathan Chen
• Reina Deogracias

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Overview of symptoms

• Initial onset
• Became acutely ill and began vomiting
• Developed high Fever (40C)
• Led to coughing, rhinorrhea, conjunctivitis (itch
  in both eyes) and dried and cracked lips
• Greatly reduced urinary output
• Physical examination
• Fever (38.5C)
• Controlled by Tylenol
• High pulse and respiratory rate
• 100 O2 saturation in room air
• Edema in feet
• Shotty Lymphadenopathy

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Diagnosis

• Influenza Virus

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Key Information Pointing to Diagnosis

• General Symptoms
• Bilateral Conjunctivitis
• May accompany viral infections of the upper
  respiratory
• Causes eye redness, itchiness of eyes, light
  sensitivity, and eye pain
• Dehydration
• Caused by fever, diarrhea, and vomiting
• Causes decreased urinary output and dry lips
• Swelling of lymph nodes
• No history of rashes
• Presence of rashes could indicate possible
  measles infection
• Multiple sick contacts
• Easily spread from person to person via aerosol
  droplets

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Classification of Influenza Virus

• Family Orthomyxoviridae
• 3 types A, B, C
• Type C mild respiratory illness
• Not a threat to cause epidemic
• Type A and B is what causes the seasonal epidemic
• US winters
• Each Type is further subdivided based on surface
  antigens
• Hemagglutinins
• Neuraminidase

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Structure of Influenza Virus

• Hemagglutinin (HA)
• Neuraminidase (NA)
• (-)ssRNA
• Segmented genome
• 8 segments
• Coding for 11 proteins

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Pathogenesis of Influenza

• Infection of Upper Respiratory epithelial
• Loss of ciliate epithelial cells
• Secondary infections
• Viral replication induces cytokine release
• Inflammatory response (edematous feet)

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Diagnostic Tests

• Can be confirmed by culturing virus from
  nasopharyngeal swabs, washes or aspirates
• Antigen testing
• Direct assay
• Hemagglutination Assay
• Indirect assay
• Hemagglutination-Inhibition Assay
• Immunoflurescence
• Enzyme immunoassay (EIA)
• Optical Immunoassay

http//www.cdc.gov/flu/professionals/diagnosis/lab
procedures.htm
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Treatments for Influenza

• Typical
• Rest
• Fluids
• Acetaminophen
• to reduce fever
• Avoid aspirin
• Reyes syndrome - brain and liver damage
  resulting in death
• Recovery within 1 week
• Antiviral Drugs
• M2 inhibitors - prevents uncoating
• Amantidine
• Rimantidine
• NA inhibitors - prevents release of virus
• Zanamivar (Relenza)
• Oseltamivir (Tamiflu)

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Prevention of Influenza

• Population at Risk
• Elderly and children
• Individuals with chronic medical conditions
• Pregnant women
• Healthcare workers and caregivers
• Household contacts
• Vaccines
• Inactivated virus vaccine
• Live vaccine
• Live, attenuated cold adapted virus (LAIV or
  FluMist)
• Benefits
• Avoiding infection
• Relieve economic burden

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Epidemiology and Threats

• Generation of genetic variations
• Antigenic Shift
• Infection with at least 2 different strains
• Get mixtures of surface antigens
• Different gene segments
• Antigenic Drift
• Viral RNA polymerase
• Error Prone
• Some errors allows for selective advantage (new
  host)
• Genetic variants
• Become more pathogenic
• Jump the species barrier

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Primary ArticleKerry P, Willsher N, Fodor E. A
cluster of conserved basic amino acids near the
C-terminus of the PB1 subunit of the influenza
virus RNA Polymerase is involved in the
regulation of viral transcription. 2008.
Virology.373202-210.

• Introduction
• PB1 is part of viral vRNA polymerase complex
• Cleaves host capped pre-mRNA into fragments that
  can initiate viral mRNA synthesis
• Mutation of AA K669, R670, and R672 inhibits
  primer-dependent viral mRNA synthesis.
• mutations inhibited the polymerase by causing a
  decrease in its ability to bind to the vRNA
  promoter and capped RNA.
• Methods
• - The levels of vRNA, cRNA and mRNA were assayed
  by primer extension
• Polymerase complexes were purified using the TAP
  method from 293T cells temporarily expressing the
  polymerase proteins.
• A TAP-tagged PB2 subunit was analyzed by SDS-PAGE
  and stained with silver.
• The transcription activity of these complexes
  were assayed using a model RNA template and a
  rabbit globin mRNA (cap donor).

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• Results
• Expression of the K669A/R670A double mutant
  resulted in a significant decrease in mRNA levels
  (10 of wild type)
• In contrast, a significant increase in cRNA
  levels was observed (196 of wild type) when the
  K669A and R670A mutations were incorporated into
  recombinant viruses
• Both mutant viruses showed decreased levels of
  mRNA compared to the replication intermediate
  cRNA which is fully consistent with a defect in
  viral mRNA transcription.
• These results in the context of viral infection
  indicate RNA replication is independent of viral
  mRNA transcription.
• Conclusion
• The C-terminal half of the PB1 subunit of the
  influenza RNA polymerase has been proposed to be
  involved in
• promoter binding
• endonuclease cleavage of host mRNA
• binding to the PB2 subunit (which itself binds
  the cap structures of host mRNAs).
• This study shows this regions importance in the
  regulation of viral mRNA synthesis.

• .

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Take Home Message

• Influenza is caused by a SS (-) RNA virus.
• Typical symptoms include Fever (3-4 days),
  coughing, sneezing, fatigue, nasal congestion,
  and headache.
• Diagnostics include testing nasopharyngeal
  samples for the influenza virus via
  hemagglutination assays, hemagglutination-inhibiti
  on assays, immunoflurescence, enzyme immunoassay
  (EIA), and optical Immunoassay
• Therapy is based on treatment of symptoms and, if
  necessary, antiviral drugs neuraminidase
  inhibitors and M2 inhibitors.
• Prognosis in healthy individuals is usually
  recovery within a week.
• Prevention involves vaccination during each
  years winter flu season.
• Transmission is spread person to person via
  aerosol droplets.
• It is a constant threat to individuals with
  weakened immune systems and there is always the
  possibility of an antigenic shift resulting in a
  deadly and highly infectious strain of influenza.

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References

• Kerry P, Willsher N, Fodor E. A cluster of
  conserved basic amino acids near the C-terminus
  of the PB1 subunit of the influenza virus RNA
  Polymerase is involved in the regulation of viral
  transcription. 2008. Virology.373202-210.
• Centers for Disease Control and Prevention.
  Influenza The Disease. http//www.cdc.gov/flu/abo
  ut/disease/index.htm
• E. Porter and N. McQueen. Lecture 10 Influenza
  Viruses. Microbiology 454L. Cal State Los
  Angeles. Spring 2008.