HSS 1100 Lecture Notes - Lecture 8: Human Respiratory Syncytial Virus, Respiratory Tract, Respiratory Tract Infection
29 Nov 2016
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Lecture 8. Viruses
• Viruses require living cells for growth and replication
o Cell cultures, embryonated eggs, living animals and plants
o do’t kill a irus, you ould iatiate it or kill the ells it harors i
• Can have DNA or RNA, but never both
• Size varies from 10-300nm
• Separate synthesis of genome and proteins, then combine to form new virus particles
o Use host machinery to do so
• Viral components
o Nucleic acids are the infectious genetic material
▪ Naked viral nucleic acid
▪ Positive sense RNA virus
o Protein coat (capsid) for protection of genome
o Surface antigens can be protein or carbohydrate
▪ Highly variable
▪ Can be spikes on the capsid or a protein in the lipid membrane
▪ What the body recognizes as non-self
o Can have a lipid bilayer
• Replication
o Adsorption
▪ Determines which cells can be infected based on surface antigens
o Penetration and uncoating
o Nucleic acid and protein synthesis
o Assembly
o Release
• Viral diagnosis
o Can detect a virus itself, or detect the immune response with antibodies
o Detection in clinical specimens
▪ Visualize with electron microscope
▪ Cell culture to determine cytopathic effects, hemagglutination,
immunofluorescence
▪ Certain techniques used based on the properties of the suspected virus
o Detetio of a patiet’s iue respose
▪ ELISA can detect antibody (immunity test)
▪ Rise in antibody titre or high antibody titre (diagnostic test)
• Respiratory viruses
o Cause respiratory disease
o Not grouped based on viral anatomy, instead grouped on tropism
Influenza Viruses
• Influenza A causes major epidemics
• Influenza B causes a milder disease
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• Produce hemagglutinin (good for diagnosis)
o A surface antigen
• Have neurominidase
o Combination of H and N for classification
• Frequent recombination
o High antigenic variability
o Pandemics
o Due to 8 part genome randomly packaged
o RNA based genome
• Clinical findings
o Fever, variable respiratory symptoms (whole body infection)
▪ Respiratory symptoms not always present
o Infants and elderly more susceptible
• Diagnosis
o Throat washing, naso-pharyngeal aspirate inoculated into cell culture
• Serum
o Paired sera (acute and convalescent stages)
• Prevention
o Annual vaccination especially for high risk groups
• Disease severity?
o Greatest burden in people 60 years +
▪ Unusual flu season when young adults are highly infected
o Certain groups can have risk of complications
▪ Pregnant women, asthma, diabetes, immune suppression, heart disease,
kidney disease
▪ Same as a usual flu season
• H1N1
o Influenza has 8 RNA segments
o 3 from classical swine, 2 from Asian swine, 2 from avian, 1 from human
o vaccination was major effort to fight pandemic
o Canada has a dedicated vaccine manufacturer
o Adjuvant vs unadjuvanted vaccine?
▪ Adjuvant allows reduction of amount of vaccine protein per dose
▪ New adjuvant was a possibility but not fully studied yet
Parainfluenza Viruses
• Infants and young children
o Get infected once and then gain lifelong immunity
o Virus is quite stable over time
• Also a segmented vaccine but not as many outbreaks
• Respiratory infection that could have serious complications
• Croup (barking cough, high pitch sound on inhalation)
• Bronchiolitis, bronchopneumonia
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• No vaccine
Respiratory syncytial virus
• Major pathogen for children less than 2
o Will quarantine people with this
• Pneumonia and bronchiolitis
o Occasionally fatal
• Epidemics
• No vaccine but ribavizine is an antiviral
Rhinovirus
• Common colds (upper respiratory tract)
• Over 100 serotypes so no cross immunity
o repeated infections
Adenovirus
• pharyngitis and conjunctivitis; pneumonia in young children
• children are most commonly infected
• asymptomatic infection is common
• vaccines used in army
Enteric virus
• infect intestinal and lymphoid cells
• poliovirus, coxsackievirus, echovirus
• multiply in GI tract but cause systemic infection
o rarely cause gastroenteritis
o 95% inapparent infection, 5% minor illness, 1% serious illness
• excretion in feces
• primary viremia is a systemic infection whereas secondary viremia is infection of a
target tissue
o secondary viremia is when symptoms tend to present
• usually no capsule and quite resilient
Poliovirus
• humans are the only natural host
• cause poliomyelitis
o highly infectious, invades the host nervous system and can cause total paralysis
in as little as a few hours
• global polio eradication initiative
o launched in 1988
o large number of case decreases but areas of conflict and antivaccination
campaign decrease the effectiveness of this goal
• diagnosis
find more resources at oneclass.com
find more resources at oneclass.com
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