Lecture 4: Viruses Flashcards
How big is a virus
20-300nm
What shapes can a virus be
Icosahedral or helical
What are some features of viruses
Capsid
- protein coat that encloses genome and core proteins
Some have an envelope
- lipid bilayer that surrounds the capsid
- has glycoproteins that form projections
Can contain either DNA or RNA
- positive or negative polarity
- single molecule or fragmented
Ways of transmitting viral infections
Horizontal - airborne - fecal-oral - sexual - vector borne - blood Vertical - in utero through placenta during pregnancy - intra partum at childbirth
sizes of droplets and aerosols
droplets are >2μm
aerosols are <2μm
viruses that do airborne transmission
- common cold (rhinovirus)
- influenza (orthomyxoviridae)
- measles and mumps (paramyxoviridae)
- rubella (logaviridae)
- chickenpox (herpesviridae)
virus that travels through fecal-oral route
hepatitis A and E
which family of viruses travel through vector-borne transmission
arboviruses
viruses that travel through blood contamination
HIV, hepatitis B and C
viruses that travel through vertical transmission
- HIV, hepatitis B and C
- citomegalovirus, zika virus, rubella
outline viral replication
1) interaction between viral glycoproteins and cell receptors
2) penetration of the virus into the host cell
3) enzymatic removal of the protein coat and liberation of the viral nucleic acid and core proteins into cytoplasm of the host cell
4) production of viral mRNA and host cell ribosomes synthesise the viral proteins
5) morphogenesis and maturation of the new viruses
6) release of virus, either through lysing or budding
how is the viral mRNA synthesised
DNA viruses
- uses host’s DNA dependent RNA polymerase
negatively charged RNA viruses
- need viral RNA-dependent RNA polymerase
positively charged RNA viruses
- used directly as RNA template
cytopathic effects of viral replication
- inhibits cell transcription and translation
- changes membrane permeability
- alters cytoskeleton or trafficking pathways
- cell to cell fusion
- induces apoptosis
how can viruses spread from their initial site of replication
- haematogenous
- lymphatic
- neural
what is a tropism and what does it depend on
the ability of different viruses to infect different cell types
depends on:
- specific receptors on the host cell
- specific host enzymes for viral maturation
- temperature and pH
example of disease caused by direct cytopathic effect
West Nile virus affects neurons, induces apoptosis, causes encephalitis and movement disorders
example of disease caused by antibody-mediated immunity
dengue fever causes a massive release of cytokines after reinfection from a different serotype (strain). Causes vascular leakage and hemorrhage
example of disease caused by virus-induced tumorigenesis
- HPV causes cervical cancer
- hepatitis B and C cause hepatocellular carcinoma of the liver
ways to diagnose a viral infection
- microscopy
- particle agglutination test (virus coated with viral antibodies)
- immunofluorescence technique (IFT)
- serology (use of antibodies to detect viral antigen)
- quantitative PCR (qPCR) and reverse transcription PCR (RT-PCR)
- ELISA
- haemagglutination test
- complement fixation test
what is latency
- period when the productive replication cycle is silent, but can reinitiate
- common with herpesviridae viruses
antiviral treatment for SAR-CoV-2
remdesivir which inhibits RNA dependent RNA polymerase
how can antiretrovirals work
- attachment inhibitors
- fusion inhibitors
- integrase inhibitors
- protease inhibitors
- nucleoside and non-nucleoside reverse transcriptase inhibitors
prevention of HIV
- pre-exposure prophylaxis (PrEP)
- post exposure prophylaxis after sexual exposure (PEPSE)
- condoms and male circumcision
