Lecture 8: Selected Viruses Flashcards
Characteristics of Human Papilloma Virus
Class
Structure (envelope? Shape? Size? RNA OR DNA SS OR DS?)
Epidemiology (Infects who? transmission mode)
Cause warts on
Baltimore Class 1
No envelope
◦ Icosahedral shape
◦ Diameter of approximately 55 nm
◦ Double stranded DNA virus
◦ Only infects humans
◦ Skin to skin transmission mode (usually during sexual contact)
Hands and feet Genitals Larynx in throat
Cancer causing mechanisms of HPV
- Causes cancer by inserting its DNA into the host DNA
◦ Genes of HPV called E6 and E7 are carcinogenic oncogenes that cause tumours to develop - Inactivates a cancer control mechanism
◦ Human cells have a protein called p53 that regulates cell growth, and promotes cell death in the presence of DNA damage
◦ HPV protein E6 (coded for by gene E6) binds to p53 and inactivates it
Immune response to HPV and laboratory detection
Most people clear the virus, but in some it persists. If it persists, it can lead to warts or cancer, depending on the strain present
Laboratory detection
◦ Polymerase Chain Reaction (PCR) to identify genome of HPV
◦ Sample = wart tissue or skin or cells collected in cervical smear
Disease prevention of HPV
◦ During sexual contact:
◦ Condoms provide some protection
◦ Testing for the virus and/or cervical
screening can detect early lesions
◦ Early treatment of pre-cancerous lesions can prevent HPV developing into cancer
◦ Early treatment of cancerous lesions can prevent metastatic cancer spread
Vaccination: HPV vaccine
HPV treatment
◦ Warts can be physically removed by freezing with liquid nitrogen
◦ Creams such as Imiquimod evoke an immune response and kill HPV infected cells. Specifically the drug encourages cytokine production to produce inflammation and activation of natural killer cells.
◦ Cancerous lesions need to be physically removed “in situ” before cancer spreads
◦ If metastatic spread has occurred, chemotherapy and radiation are used
HIV classification
Structure (envelope? Shape? Types? Size? RNA OR DNA SS OR DS?)
Epidemiology (Infects who? transmission mode)
Class
Causes
HIV-1, HIV-2
Single stranded RNA-RT virus
Baltimore Class VI
Has an envelope
Spherical shape
Diameter of approximately 120 nm
Only infects humans. Virus spreads through sexual, blood-borne and vertical transmission modes
HUMAN IMMUNODEFICIENCY CAUSES ACQUIRED DEFICIENCIES IN THE IMMUNE SYSTEM
Immune response to HIV and Lab detection
T cells are depleted over time, as the virus is destroying them
◦The virus also hides inside these T cells, preventing recognition and access by antibodies and natural killer cells
Lab detection
1. Nucleic acid test ; a viral genome method similar to PCR. Detects viral genome a few days after infection
- Antibody test; Enzyme Linked Immunoassay (EIA) to capture antibodies on antigen targets.
3.Antigen test (p24 antigen); Enzyme Linked Immunoassay (EIA) to capture p24 antigen on p24 antibody targets.
HIV disease prevention
◦ During sexual contact: Condoms
◦ No sharing of needles for IV drug use
◦ Testing for the virus early after unprotected sex does not prevent viral transmission but does allow treatment to start, which prevents AIDS
◦ Testing for the virus in pregnant women allows vertical transmission to be prevented if Mum has treatment
◦ Avoid breast feeding if Mum is HIV positive
◦ Blood Supply:
Antibody and NAT screening of all blood donors at every donation in New Zealand
HIV treatment
*Anti retroviral medications block viral replication
*Drugs include Atazanavir (ATV) and Darunavir (DRV)
By keeping viral load low, T cell count stays in normal range And patient does not become immunocompromised
Characteristics of Hep B
Class
Structure (envelope? Shape? Types? Size? RNA OR DNA SS OR DS?)
Epidemiology (Infects who? transmission mode)
Causes?
◦ 10 types, numbered A - J
◦ Baltimore Class VII
◦ Has an envelope
◦ Spherical shape
◦ Diameter 42 nm
◦ Double stranded DNA-RT virus
◦ Infects humans and other primates
◦ Virus spreads through sexual, blood-borne and vertical transmission modes
Causes liver cancer and liver failure
Cancer causing mechanisms of HBV
◦ HBV DNA becomes part of the human genome in infected individuals. This “insertional mutagenesis” alters gene expression and causes chromosomes to become unstable.
◦ HBV also changes the methylation status of genes, so that normal gene regulation is disrupted
Immune response to HBV and lab detection
Most people clear the virus, but in some it persists
If it persists, it can lead to permanent liver damage/failure and cancer
◦ Antibody detection to check immunity (for example post vaccination)
◦ Antigen detection to check for acute infection (HBsAg)
◦ Polymerase Chain Reaction (PCR) to identify genome of HBV
◦ Sample = blood plasma
Hep B disease prevention
◦ During sexual contact: Condoms
◦ No sharing of needles for IV drug use
◦ Testing for the virus in pregnant women allows vertical transmission to be prevented if baby treated with Hep B immunoglobulin and vaccination soon after birth
◦ Antibody and NAT screening of all blood donors at every donation in New Zealand
Vaccination
Hep B treatment
◦ Hepatitis B immunoglobulin
◦ Anti-viral drugs, for example: ◦ Viread and Epivir
◦ Interferon injections ◦ Liver transplant
Characteristics of SARS-CoV-2 Virus
Structure (envelope? Shape? Size? RNA OR DNA SS OR DS?)
Epidemiology (Infects who? transmission mode)
Class
Baltimore Class IV
Transmission: droplet, fomites, aersols.
◦ Envelope
◦ RNA virus
◦ Diameter 100 nm
◦ Large spike protein
