Herpesviridae Viruses & influenza Flashcards
Herpesvirus family
Epstein-Barr Virus (EBV)
Cytomegalovirus (CMV)
varicella Zoster Virus
Innate defense to viruses
Viral DNA is detected by toll-like receptors
infected cells stimulate interferons (IFN) & inflammatory cytokines
CD8+ kill virally infected cells
Virus Escaping Immune Defenses
- frequent genetic mutations - poor fidelity polymerase
- recombine their genome with other related viruses
- evade interferons & phagocytic cells etc
- latent virus / provirus
Laboratory testing for viral infections
viral antigens
serology
molecular tests
Epstein Barr Virus
large, dsDNA, w/ capsid & envelop
capable of establishing a latent infection
Infectious Mononucleosis!
lymphoproliferative disease
EBV infection
mainly infects B lymphocytes
infected EBV cells cause release of large amounts of cytokines
~95% of world’s population exposed to virus
EBV transmission
most are exposed to virus before 5 years old (asymptomatic)
second wave occurs during late adolescence
via saliva
Infectious Mononucleosis
^^ WBC -flipped diff
+ for heterophile antibodies
Mono-spot test - collodial gold immunoassay w/ cow RBC extracts
Cytomegalovirus General Characteristics
member of the herpes family
most people are asymptomatic
50-80% of adults are infected
spread via saliva, urine etc
CMV risk in babies
pregnant mothers become infected (most common virus transmitted to the fetus)
80% born with congenital CMV are asymptomatic
10% are symptomatic
10% are asympomatic at birth but develop issues later
CMV symptoms
most are asymptomatic
will only re-emerge if immune system is shot
characteristic dot rash
CMV in transplants
CMV infects most cell types
could cause an infection / death in a transplant patient
Preventing CMV transmission via transplants
- use CMV seronegative blood
- use leukoreduced RBCs ( has resulted in transmission of CMV through blood products in transplant recipients to around 0.1%)
CMV testing
IgM antibodies to CMV - current or recurrent infection
IgG antibodies to CMV- past infection
PCR amplification of CMV DNA
Varicella - Zoster Virus General Characteristics
causes 2 diseases:
varicella - Chickenpox
Herpes zoster - Shingles
highly contagious - aerosols
Vericella Primary Infection Characteristics
Chickenpox - mild & self-limiting
blistering rash w/ lesions
mostly on head & trunk
Varicella Secondary Infection Characteristics
Shingles- illness caused by reactivation
most often in individuals over 50
painful blisters
Varicella Zoster Vaccine
2005 vaccine that combines varicella vaccine w/ measles, mumps, & rubella
Influenza Viral Structure
surface contains:
Hemagglutinin (H) - binds to surface sialic acid
Neuraminidase (N)- cleaves sialic acid for virus exit from the cell
ssRNA in 8 segments
Influenza Grouping
3 groups: based on internal nucleoprotein
Influenza A: most widespread ‘pandemics’
Influenza B: less widespread
Influenza C: mild, not widespread
Influenza Subtypes
3 types of hemagglutinin bind to human cells : H1, H2, H3
2 different neuraminidase N1 & N2
Influenza A Characteristics
human pandemics massive antigenic variation highly contagious - aerosol antigenic drift & antigenic shift makes people susceptible to re-infection ~90% of deaths occur over age 65
Influenza A diagnosis & Testing
rapid influenza tests - colloidal gold immunoassays (nasal swab)
reverse-transcriptase PCR is the gold standard
Antigenic Drift
minor DNA changes (point mutations)
missense mutation leads to evasion of antibodies
Antigenic shift
reassortment in doubly infected cell in which a viron is packed with a segment of RNA from a different virus creating a new virus
only influenza A can infect animal cells for this to occur
