10. Viruses And Sars Cov Flashcards
– Vero cells
– Vero cells = cells infected with viruses monkey kidney cells that are grown commercially – immortal cells
HeLa cells
– HeLa cells = Henrietta lax, cervical cancer cells, cells are immortal keep growing and don’t die
Viral Structure
- Envelope: Lipid bilayer - membrane acquired as virus buds through the host cell membrane
- Capsid: protein coat for viral genome and proteins
- Can have non envelope viruses only with the capsid and no outer envelope
Proteins on the outside = antigens
Virus genome
- DNA or RNA
- Double stranded
- Single stranded
- Positive or negative sense RNA
- Circular
- Linear
- Most DNA viruses replicate in the nucleus
- Most RNA viruses replicate in the cytoplasm
DNA viruses - 3 examples
Adenoviruses
Hepatitis B virus
Herpes viruses
Adenoviruses
Adenoviruses: ds double stranded DNA, non enveloped
– Respiratory and gastrointestinal infections and conjunctivitis
Hep b
Hepatitis B virus: partially dsDNA, enveloped – circular and slightly double stranded in parts
– Chronic hepatitis, cirrhosis, hepatocellular carcinoma
Herpes viruses: ds DNA enveloped
Herpes viruses: ds DNA enveloped – Herpes simplex (types 1 and 2) – Varicella zoster virus – shingles and chickenpox – Cytomegalovirus – Epstein Barr virus
Hep D
Hepatitis D virus (HDV) is a defective RNA virus which requires the help of hepatitis B virus (HBV) for its replication and assembly of new virions (virus particles). It cannot replicate on its own
RNA viruses
- Influenza virus: ss negative strand RNA , enveloped (RNA dependent RNA polymerase)
- Coronaviruses: ss RNA, enveloped SARS-CoV-2
- Polio: ssRNA, non enveloped
- Hepatitis C: ss positive strand RNA, enveloped
- HIV: ssRNA, enveloped (reverse transcriptase, integrase and viral protease)
Baltimore classification of viruses
—> viruses classifed using this system
• Divide viruses into 7 groups – based on how they use their genetic material to make mRNA
Genetic material —> mRNA —> protein
With RNA you can have two types
• +ve ssRNA
• -ve RNA
• SsRNA has reverse transcriptase to make double strand DNA to make mRNA which makes proteins
Diagnosis of viral infections
- Antigen detection - Hep B detect core antigen, surface antigen, envelope antigen
- PCR – test for SARS-CoV-2 use primers that match a segment of the virus’s genetic material. This allows many copies of that material to be made, which can be used to detect whether or not the virus is present.
- Match segment of genetic material to known virus
- Antibody test – HIV – antibodies to that specific virus
Hepatitis B serology
- Prongs with surface antigen
- Core with geentic material
- Replicate virus in haptocytes
- Release hep E antigen and rise in Hep B surface antigen
- Immune system is exposed in antigen
- Forms anti hep B core antigen antibodies, anti ]bodies to surface and envelop antigens
Viruses and cancer – Human Papillomaviruses
– Some grow in skin, while others grow in mucous membranes such as the mouth, throat, or vagina – spread by contact (touch)
– HPV can cause cervical cancer
– HPV is also implicated in cancers of the penis, anus, vagina, vulva, mouth and throat
Vaccine widely used to prevent HPV infection in young adults
Viruses and cancer – Epstein Barr Virus
- Epstein Barr Virus is responsible for causing infectious mononucleosis (‘kissing disease’)
- Passed from person to person by coughing, sneezing, or by sharing drinking or eating utensils
- Infects and stays B lymphocytes
- Can increase risk of developing nasopharangeal cancer and certain lymphomas, for example, Burkitt lymphoma
Viruses and cancer – HIV
- HIV causes acquired immune deficiency syndrome (AIDS)
- HIV infection increases the risk of cancer, especially some linked to other viruses – Kaposi’s sarcoma - human herpesvirus 8 (HHV8) - human herpes virsu in peopke that are HIV positive cause kaposis sarcoma
Steps in viral replication Viruses undergo similar sequence of events
- Attachment to the appropriate cells
• (eg haemagglutinin of influenza virus or glycoprotein GP 120 of HIV to appropriate cell receptor)- Penetration of virus into cell (endocytosis or fusion of envelope with host cell membrane)
- Uncoating leading to release of their genome and other materials such as enzymes into host cell
- Production of virus specific mRNA resulting in manufacture of virus components
- Assembly of components
Release from target cells and further infection
Death of host cell caused by virus
• Death – the cell is unable to continue functioning normally as the virus takes over for its own multiplication
Transformation of host cell caused by virus
• Transformation – the cell can divide uncontrollably due to activation or introduction of oncogenes
Latent infection of host cell caused by virus
• Latent infection – the virus can remain dormant and does not cause symptoms until it is activated by some factor(s) - eg. Herpes virus becomes latent and cause shingles
chronic infection of host cell caused by virus
• Chronic infection – lasting over a period of time
RNA virus replication
—> RNA viruses normally undergo transcription, translation and replication in the cytoplasm.
Positive sense single stranded RNA
• Positive sense single stranded RNA can function as mRNA and get translated into proteins by the host ribosomes
Negative sense RNA
• Negative sense RNA has to be changed to positive mRNA using the enzyme RNA dependent RNA polymerase to make a positive strand copy which can be read by the ribosomes and result in the manufacture of proteins
