L2 Flashcards
Respiratory Syncytial Virus
croup, bronchitis, respiratory tract infections
Varicella Zoster Virus
chickenpox
Rotavirus →
gastroenteritis
Poliovirus →
gastroenteritis
Measles Virus Biology
Paramyxovirus
Measles virus genome
: (-)ssRNA
Measles virus Virion:
enveloped
Measles virus protein
Proteins: L – polymerase P (C&V) – phosphoprotein H – hemagglutinin F – fusion M – matrix N – nucleocapsid
Measles virus Replication in the
cell
Measles virus
Fusion protein causes
syncytia formation
Measles infection
Infection – Inhalation of aerosolized droplets
Measles incubation
Incubation period (10-14 days)
Primary infection in respiratory epithelial tissues →
measles
primary viremia
Measles Symptom onset
Coincides with second round of virus replication. Occurs in LN, tonsils, lungs, GI tract, and spleen → secondary viremia
Measles Recovery,
approximately 20 days after infection
Measles is the most
Most deadly of the childhoodrash/fever illnesses (CDC)
Measles Characteristic rash
Virus & immune response damage to epithelial and endothelial cells
Koplik spots
Measles Immune suppression
Interference with CD46 & signaling lymphocyte activation molecule (SLAM) receptors
Measles Opportunistic infections
Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae
Measles blindness in
Blindness in vitamin A deficient children
Measles Acute disseminated encphalomyelitis (ADEM) –
rare 1:1000 children, demyelinating disease
Measles Subacute sclerosing panencephalitis (SSPE) –
very rare 1:1,000,000 children, 7 to 10 years after infection, progressive neurological deterioration
Measles symptoms
2-3 days fever + cough, coryza, & conjunctivitis
Rash: Koplik spots “small, bright red spots with bluish centers on buccal mucosa…pathognomonic for measles”
Measles in the lab
Virus isolation in culture (difficult)
Serology
ELISA, RT-PCR
Measles Prevention
One of the most contagious diseases known
Number of cases from one illness (R0) in a naïve population is 15 to 20
Measles - people are infectious
People are infectious 2-3 days prior to rash
Measles host
human only
Measles vaccine
Primary option Life long immunity Live attenuated vaccine Safe Autism & colitis correlation retracted
Measles Providing
vitamin A can reduce severity
No antivirals
Measles prevelence
Measles was declared eliminated from the US in 2000, but remains common in other countries
Measles continues to be introduced to the US through international travel
222 cases in 2011
Outbreaks continued in 2013
Brooklyn, NY – 17 yr old visited London, 58 cases total, none were previously vaccinated
NC – individual visited India, 22 cases resulting, most were not vaccine, 3 had been
Respiratory Syncytial Virus Biology
Paramyxovirus
Respiratory Syncytial Virus Biology - Genome:
(-)ssRNA
Respiratory Syncytial Virus Biology - Virion:
enveloped
Respiratory Syncytial Virus Biology proteins
Proteins: L – polymerase G – glycoprotein F – fusion M – matrix P – phosphoprotein N – nucleocapsid NS1&NS2 – replication & immune response
Respiratory syncytial virus biology Replication in the
cell – similar steps as for measles virus
RSVB Infects
ciliated cells in the respiratory tract epithelium
RSVB Fusion protein creates
syncytia
RSVB Virus buds from
cellular surface
Respiratory Syncytial Virus Disease
the most important viral agent of serious pediatric respiratory tract infections
RSVB infection
Infection by inhalation of aerosol, fomites
RSVB virus replication limited to
Virus replication limited to respiratory tract
RSVB Incubation period
4-5 days
RSVB Lower respiratory tract symptoms
1 to 3 days after upper respiratory tract symptoms
RSVB Recovery
7 to 12 days after symptom onset
RSVB Virus that infects humans
does not infect other animals – no animal reservoir
RSVB Infection does not yield
life long immunity
RSVB Infants have an immature immune system
Infection limited to
respiratory tract epithelial cells where IgA response is short lived
RSVB Low cytotoxicity thought to result in
slower immune response
RSVB Risk factors for infection
Attending day care
School age siblings
RSVB Risk for more severe disease
Premature birth, male, second hand exposure to tobacco smoke, lack of breast feeding
Respiratory Syncytial Virus Prevention may use
ribavirin administered by inhalation
RSVB No vaccine
Vaccines in development
Formalin inactivated vaccine not successful
Challenge to immunize infants who are at the greatest risk
RSVB Passive immunoprophylaxis
Palivizumab – humanized monoclonal antibody
Targets F protein
Given IM once a month
Varicella Zoster Virus Biology
Alphaherpesvirus
Varicella Zoster Virus Biology genome
dsDNA, large
VZV Virion:
enveloped, hundreds of proteins
Replication : Varicella Zoster Virus Biology (Cont.)
Replication in the Cell
Active cell for replication
Resting cell (e.g. neuron) → latent infection (circular genome)
Infects neighboring cells first
Chickenpox (VZV) the DiseaseL: Infection –
Inhalation of aerosolized droplets
VZV Incubation period
(10 to 21 days)
VZV Symptoms
Fever, malaise, headache,
Rash 1-2 days after symptom onset
Rash progresses for 3-6 days
Rash on scalp, face, trunk primarily
VZV Recovery usually by
2 weeks post symptom onset
cell mediated immunity most important
VZV Usually establishes
latent infections that can be reactivated – shingles
Not to be confused with smallpox
Chickenpox Prevention vaccination
Vaccination
Primary option
Life long immunity
Live attenuated vaccine
Antivirals VZV
Acyclovir: Interferes with genome replication Cannot eliminate latent virus Does not prevent infection of cells Drug resistance is being observed
Poliovirus Biology
Picornavirus
Poliovirus genome
(+)ssRNA
Poliovirus Virion:
Non-enveloped
Poliovirus protein
Proteins
Capsid - VP1,VP2, VP3, VP4
Non-structural - proteases, polymerase, others
Poliovirus replcation
Replication in cell
Poliovirus Virus particle creates
pore in cell membrane
Poliovirus Genome serves as
mRNA
Poliovirus prevelent in
endemic areas such that infections are most common in naïve children
Poliovirus infection
Infection by ingestion of material containing virus
As few as 100 TCID50
Poliovirus Primary replication in
Peyer’s patches of small intestine - Minor viremia
Poliovirus Secondary replication
Major viremia
Poliovirus
Mild disease
Fecal shedding of virus for 6 weeks
Poliovirus
CNS involvement in 1:200 of infections
Risk factors: physical exertion, trauma, tonsillectomy
Poliovirus Virus replicates in
gray matter of brain and spinal cord
Limb paralysis from anterior horn cell damage
Respiratory paralysis from damage to medulla oblongata
Poliovirus vaccines
Two effective vaccines available
Salk – killed
Sabin – live attenuated
Poliovirus is human
only
Rotavirus
Reoviridae
Rotavirus Genome:
dsRNA, 11 segments
Rotavirus Virion:
non-enveloped
Rotavirus proteins
Proteins: VP1 – polymerase VP2 – RNA binding VP3 – transferase VP4 – attachment & fusion Other structural and non-structural proteins
Rotavirus replication in
cell - Membrane disruption
Genome never exposed
Rotavirus Infection by
ingestion of material containing the virus
Rotavirus Incubation of
2 days – Vomiting & fever
Rotavirus Diarrhea -
2 to 3 days after vomiting, 3 to 8 days in duration
Rotavirus Virus shedding for
weeks before symptom onset and days after recovery
Rotavirus Severe disease most common
in 6 to 24 month old children
Rotavirus diagnoses
Diagnose by antigens in stool
Rotavirus infant
vaccine available
Rotavirus treatment
No antivirals Hygiene Hand washing Treatment Oral rehydration
**Exceptions to virus replications:
RNA virus: influenza virus replicates in nucleus
DNA virus: poxvirus replicate in cytoplasm