Virology revision mindmap
Content by Maryam Imran
On this page you will find bullet point summaries of major topics in virology. These do not give explanations but are very useful to use as checklists of all the detail.
Some sections are more detailed than the main high yield stuff you need to know for exams.
🦠 INFLUENZA
📖 Features
- Haemagglutinin: target for neutralisation (H1-3 in man)
————————————-
- Neuraminidase: destroys neuraminic (sialic) acid,
reduces mucus viscosity, facilitates release of virion, less important for immune response (N1 & N2 in man)
- ssRNA negative (negative strand RNA virus – i.e. genomes are complementary to mRNA)
- 8 segments
- Viral ssRNA-dependent RNA polymerase
The long NA stalk = better transmission for two reasons
1) can transmit via respiratory route, while short stalk cannot
2) short stalk is much more easily inactivated by mucus
- Flu A – pandemics (wild aquatic bird reservoir). Only Flu A shows antigenic shift
- Flu B – milder, epidemics
- Flu C – not pathogenic in man
Viral Entry:
Haemagglutinin on virus binds sialic acid on red cell
surface. The sialic acid sits on protein sialyloligosaccharide
1-3 days incubation
Symptoms: Fever, malaise, headache, myalgia, cough, sore throat
Columnar epithelial cells of respiratory tract are affected
- Rare, acute
- severe dyspnoea (difficulty breathing),
- cyanosis (turning blue) and death
- More common,
- less lethal than viral
- S. aureus / S. pneumoniae
- Post-infection encephalopathy
- Oedema
- Fatty degeneration of liver
- Asthma
- COPD
- Otitis Media
Transmission
- Infectivity period: 3-5 days after onset
- Large droplets and aerosols – inhalation
Fomite
🧐 Diagnosis
- Lateral flow assay on combined nose & throat swab
- Ag detection by nasopharyngeal aspirates
- RT PCR for viral genome
- Ab: acute and convalescent serum
- Viral isolation: strain determination & vaccine development
Seen as haemadsorption on monolayer - Note: swab needs to contain respiratory epithelial cells
💊 Treatment
- Uncoating and penetration
- Amantadine only used for flu A as B doesn’t have the M2+ channel
- Release (neuraminidase removes sialic acid from GP)
Mechanism:
- Release (neuraminidase removes sialic acid from GP)
- Resistance to neuraminidase inhibitors is much
slower than to amantadine
- Grown on chorioallantoic membrane of chick embryo
- Seasonal vaccine contains:
- Influenza A H1N1
- A H3N2
- One or two B strains
- Inactivated for most use
- Inactivated with adjuvant >65 yrs
- Live attenuated for immunisation programs
VIRAL MULTIPLICATION
📖 Cycle
- Binds to receptor – opportunistic
- Enveloped: fusion of membranes +/-
endocytosis
- Non-enveloped: Endocytosis only
Release of genome which remains loosely attached to nucleic acid
Depends on viral mRNA (Baltimore), early genes transcribed before replication and late genes post-replication.
- Self-assembly from genome + capsid +/-
envelope, these were transcribed in
replication and spontaneously come
together.
- Release: enveloped – budding, nonenveloped – lysis of cell
🔬 Investigating: One-step growth curve
Synchronized by using high multiplicity of infection (MOI = 1 – 1 000 000 virions added)
Virus disassembled for replication so is
undetectable
Virus replication reaches its end at beginning
of upward slope on graph – infection is seen
extracellularly
Virions are sampled by plaque assay of both
culture fluid and cells
🧬 Diversity
RNA-dependent RNA polymerases = no proof-reading --
quasispecies
reassortment (whole gene
replacement) – pandemics
Antigenic Drift: point mutations
Recombination: insertion of fragments of genes from other organism such as the host – less important in viruses
BOX 3
📖 Cycle
- Binds to receptor – opportunistic
- Enveloped: fusion of membranes +/-
endocytosis
- Non-enveloped: Endocytosis only
Release of genome which remains loosely attached to nucleic acid
Depends on viral mRNA (Baltimore), early genes transcribed before replication and late genes post-replication.
- Self-assembly from genome + capsid +/-
envelope, these were transcribed in
replication and spontaneously come
together.
- Release: enveloped – budding, nonenveloped – lysis of cell
BOX 4
📖 Cycle
- Binds to receptor – opportunistic
- Enveloped: fusion of membranes +/-
endocytosis
- Non-enveloped: Endocytosis only
Release of genome which remains loosely attached to nucleic acid
Depends on viral mRNA (Baltimore), early genes transcribed before replication and late genes post-replication.
- Self-assembly from genome + capsid +/-
envelope, these were transcribed in
replication and spontaneously come
together.
- Release: enveloped – budding, nonenveloped – lysis of cell
BOX 5
📖 Cycle
- Binds to receptor – opportunistic
- Enveloped: fusion of membranes +/-
endocytosis
- Non-enveloped: Endocytosis only
Release of genome which remains loosely attached to nucleic acid
Depends on viral mRNA (Baltimore), early genes transcribed before replication and late genes post-replication.
- Self-assembly from genome + capsid +/-
envelope, these were transcribed in
replication and spontaneously come
together.
- Release: enveloped – budding, nonenveloped – lysis of cell
BOX 6
📖 Cycle
- Binds to receptor – opportunistic
- Enveloped: fusion of membranes +/-
endocytosis
- Non-enveloped: Endocytosis only
Release of genome which remains loosely attached to nucleic acid
Depends on viral mRNA (Baltimore), early genes transcribed before replication and late genes post-replication.
- Self-assembly from genome + capsid +/-
envelope, these were transcribed in
replication and spontaneously come
together.
- Release: enveloped – budding, nonenveloped – lysis of cell
MMBGold, MMBantomytips, MMB, MMB Gold, Physiology
