Week 3: i. Virology Flashcards
History:
Edward Jenner -
pioneer of smallpox vaccine (1796)
History:
Louis Pasteur -
Louis Pasteur - created 1st vaccine for rabies (1885)
History:
Adolf Edward Mayer -
Adolf Edward Mayer - published paper discussing filterable infectious agent that caused dis in plants (1886). Dismissed
History:
Dimitri Ivanofsky -
Dimitri Ivanofsky - demonstrated filterable infectious agent; showed sap of leaves infected w tobacco mosaic disease retained its infectious properties after filtration
History:
Martinis Beijerinck -
Martinis Beijerinck - filterable infectious agent able to multipl in living cells - “contagious living liquid”
True or False,
Viruses infect ALL cellular life forms and are found in soil, air and water
True
Viruses in the human host:
- Non- pathogenic:
Human Virome (viral microbiota) - NB for metabolic homeostasis
Viruses in the human host:
- Pathogenic:
Quiescent (inactive)/ Active: infection/ disease
What is a virus?
What is a virion?
Virion = complete infectious viral particle.
What is a virion composed of? (4)
Composed of:
1. outer coat (envelope); capsid;
2. genome - nucleic acids (allows for replication).
3. Envelope — lipid membrane that encloses the nucleocapsid and has surface proteins - glycoprotein which are antigenic = induce immune response.
4. Capsid — protein shell that protects the genome; present in both enveloped and non-enveloped viruses; in non-enveloped = outer covering; in enveloped = underneath lipid membrane
Types of Virus Structure: (4)
What are the properties of enveloped viruses? (3)
What are the properties of naked viruses? (5)
The Genome:
DNA: (3)
- Single stranded ie Parvovirus
- Double stranded (most) ie HAdV, HPV, polymviruses, herpes viruses, pox viruses
- Reverse transcribing ie Hep B virus
The Genome:
RNA: (5)
- Double stranded ie Rotavirus
- Single stranded ie all other viruses
- Segmented — reassortment/ recombination ie rotavirus, influenza viruses, Bunya viruses, Arenaviruses
- Non-segmented — all other RNA viruses
- Reverse transcribing ie HIV
What is the Baltimore classification system?
Spread of viruses
- Mode of transmission: Respiratory droplet (inhalation)
- Examples:
Spread of viruses
- Mode of transmission: Fecal-oral (ingestion)
- Examples:
Spread of viruses
- Mode of transmission: Blood and blood products/percutaneous/organ transplant
- Examples:
Spread of viruses
- Mode of transmission: Sexual
- Examples:
Spread of viruses
- Mode of transmission: Skin or mucous membrane contact
- Examples:
Spread of viruses
- Mode of transmission: Zoonoses (bite; direct contact)
- Examples:
Spread of viruses
- Mode of transmission: mother-to-child
- Examples:
Previous classifications: (3)
International committee on taxonomy of viruses (ICTV):
Viral Pathogenesis: (2)
- Entry into host
- Primary (localized) replication - permissive cells (@ pt of entry)
- Viremia:
virus goes into transport systems and infects other cells/ invades other system to
- Viremia
= Primary:
lymph and reticular endoplasmic systems
- Viremia
= Secondary:
haematogenous/ neuronal
Viral Pathogenesis
- Systemic replication:
virus goes to target organs ie CNS, CVS, Liver
How does viral replication take place? (5)
- Attachment of virion to a cell - receptors = virus specific
- Entry and unloading into cell - endocytosis/ fusion
- Synthesis of viral genes - transcription of viral genes into mRNA; translation of viral mRNA into proteins and genome replication
- Assembly of viral genome and proteins into virion
- virus release - cell lysis or budding
Outcomes of viral infection:
What is the spectrum of viral infections?
How to diagnose viral infections:
Need correct specimen; correctly collected ; correctly transported and correct test to ensure accurate diagnosis
Viral diagnostics: (2)
- Serology
- Molecular assays/ PCR
What is the method of serology? (2)
- Serology - detection of Ab against spec Ag
- Speciment - blood/ serum: IgM - diagnosis of acute infection; IgG - indicate immunity (from past infection or vaccination)
- Serology
Benefits:
Disadvantage:
- Benefits: cost effective; sensitive; specific; automated testing therefore quick results; doesn’t req viable virus
- Disadvantage: may have false results (due to interfering substances)
What are molecular assays/PCR? (3)
- detection of viral gene
- RNA/ DNA - variety of specimen ie CSF, blood, swaps, urine
- Qualitative ie positive/ negative + Quantitative ie tells viral lode
- Molecular assays/ PCR
Advantage:
Disadvantage:
- Advantage: high sensitive; fast and automated; can culture viable/ unviable specimen
- Disadvantage: can have false positive due to contamination or degradation
Health implications of viral infections:
- Human diseases: (3)
- Minor illness - common cold
- Lethal disease - rabies, VHFs and causes of cancer
- Pandemic diseases - HIV, H1N1-2009
Health implications of viral infections:
Domestic animal disease -
may spill over to humans
Health implications of viral infections:
Research and Diagnostics: (4)
- molecular and cell biology
- dev of vaccine
- treatment (anti-cancer agents, gene vector for treatment of genetic diseases)
- source of enzymes used in molecular biology
