Viral Characteristics and Vaccines Flashcards
viruses: most common ____ of humans
infections
viruses: obligate _____
intracellular parasites
virion structure
- nucleic acid (RNA or DNA)
- capsid (structural shell/coat)
- plasma membrane* (stolen from the host)
virus classification
- structure of viral capsule (capsid)
- genetic makeup*
- mode of replication
- specific host cell that virus invades
viral genomes
- DNA virus (ss, ds)
- RNA virus (ss + sense or -sense, ds, retrovirus)
steps of viral infection
1) attachment
2) penetration
3) uncoating
4) replication
5) assembly
6) release
viral entry
- membrane fusion (enveloped virions)
- endocytosis (enveloped or naked virions)
- direct entry (naked virions)
- genetic injection (bacteriophages)
cellular tropism
preferentially infect certain cell types
tissue tropism
preferentially infect certain tissues
host tropism
preferentially infect certain species
cellular effects of viral infection
- inhibition of host cell (DNA, RNA, protein synthesis)
- disruption of lysosomal membranes
- promotion of apoptosis
- carcinogenesis
- promotion of secondary bacterial infections
apoptosis
- derangement of cell metabolism triggers apoptotic pathway (many viruses suppress apoptosis)
- some viruses initiate apoptosis to facilitate infection (virions persist inside apoptotic bodies)
- apoptosis of the cell prior to virion assembly prevents spread of the infection
outcomes of viral infection
- cell death
- latency
- carcinogenesis
- clearance
viral pathogenicity depends on:
- host range
- cell tropism
- mechanism of replication
common manifestations of viral infection
- rashes
- fever
- muscle aches
- respiratory involvement
- swollen lymph nodes
host defenses to viral infection
- antibodies
- cytotoxic T cells
- interferon
cellular effects of interferon
- increases immunoproteasome activity
- upregulates MHC I and II
- destroys RNA
- disrupts protein synthesis
- increases translation of p53 genes
- induces production of antiviral proteins (AVP)
- increases macrophage and NK cell activity
systemic effects of interferon
- fever
- muscle aches
- taste bud function and apoptosis
interferon therapy uses
- viral infections
- cancer (esp. leukemia and lymphomas)
- multiple sclerosis
antiviral countermeasure (how medications can help)
- entry prevention: prevent attachment, prevent endocytosis, prevent uncoating
- viral synthesis inhibition: protease inhibitors, reverse-transcriptase inhibitors, integrase inhibitors, neuraminidase inhibitors
live, attenuated vaccines
- weakened live virus
- elicit the strongest immune response*
- risk for immunocompromised
- require refrigeration
- typically only one dose, occasionally a booster
- ex: MMR, varicella, polio (oral)
inactivated vaccines
- killed virus
- elicit a weaker immune response
- lower risk
- very stable
- often requires multiple doses over several months
- ex: hepatitis A, polio (injected), influenza
subunit vaccines
- very small particles attached to carrier proteins
- lower risk
- very safe
- very stable
- often require multiple doses
- ex: hepatitis B
bacterial vaccines: live, attenuated
TB vaccine
bacterial vaccines: killed bacteria
- pneumococcal pneumonia
- not very immunogenic in children
bacterial vaccines: conjugated
- microbe Ag attached to carrier proteins
- haemophilus influenzae type B
bacterial vaccines: toxoids
- vaccine against bacterial toxins
- DTaP (diphtheria, tetanus, pertussis)
