Oncogenic & Pathogenic Viruses Flashcards
Neoplasia
- Uncontrolled cell division in multicellular animal
- Mass of neoplastic cells is tumor
Benign vs. malignant tumors
Benign tumors:
remain in one place and are not generally harmful
Malignant tumors:
also called cancers, metastasis occurs when tumors spread
The Oncogene Theory —Proto-oncogenes and oncogene
promote cell growth and division
• Uncontrolled actvation of oncogenes → cancer, oncogenes transform normal cells into cancerous cells
The oncogene theory— Environmental factor can contribute to the activation of oncogenes
UV
Radiation
Carcinogens (mutagenic chemicals)
Viruses
The oncogene theory—Viruses may cause 20-25% of human cancers
-Carry copies of oncogenes as part of their genomes
-Promote oncogenes already present in host
-Interfere with tumor repression
-Oncogene viruses become integrated into the host cell’s DNA and induce tumors
• Can alter the host cell’s characteristies :
Transformed celled tend to be irregularly shaped, incresed cell motility, lose contact inbition in culture
DNA Oncogenic Viruses examples
Herpesviridae
• Epstein-Barr virus (dsDNA):
- Infect B cells and epithelial cells
- Burkitt’s lymphoma (cancer of the lymphatic system, specifically B cells)
- Vaccines in clinical trials
Hepadnaviridae
• Hepatitis B virus (dsDNA-RT):
- Infect hepatocytes (liver cells), chronic hepatitis B viral infection
- Hepatocellular carcinoma (liver cancer)
- Vaccine available
Papovaviridae
• Human papillomavirus (dsDNA):
- Infects skin and mucosal cells
- Cervical, anal, oropharyngeal (mouth/throat), penile, vaginal and vulvar cancer
- Vaccine available
RNA Oncogenic Viruses
• Some retroviruses contain oncogenes, others contain promoters that turn on oncogenes or other cancer-causing factors
- Viral RNA is transcribed to DNA (using reverse transcriptase), which can integrate into host DNA → provirus
- Human T cell leukemia Viruses (HTLV-1 and HTLV-2) cause adult T cell leukemia and lymphoma
Not all Retroviridae family viruses cause cancer
Viruses to Treat Cancer
Oncolytic viruses: infect and lyse cancer cells
• Clinical trials in humans and mice suggest that oncolytic viral therapy may provide treatment for some cancers
• Viruses are being genetically modified → selectively infect cancer cells
pathogenic viruses-SARS-CoV-2
Structure and symptom
• Severe Acute Respiratory Syndrome Coronavirus 2
• Enveloped, (+)ssRNA virus, ACE-2 receptor on cells required for entry
• Electron microscopy show the spike glycoprotein that gives the virus a shape of a
crown
• In humans, generally cause mild upper respiratory illnesses and cause 10-30% of common cold cases
• Past two decades, 3 highly pathogenic coronaviruses have emerged that can cause severe respiratory illnesses:
- 2002: Severe acute respiratory syndrome coronavirus (SARS-CoV)
- 2011: Middle East respiratory syndrome coronavirus (MERS-CoV)
- 2019: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)
Symptoms of COVID-19
• Begin 1-14 days after exposure to the virus
• Most people have mild symptoms
• Some people develop acute respiratory distress syndrome (ARDS) → cytokine storms, multi-organ failure, septic shock and blood clots
Transmission of SARS-CoV-2
Bats → possible intermediate host (pangolins穿山甲, snake, mammals) → zoonotic transmission to human → human to human (direct and nosocomial)
mRNA vaccines
优缺点
mRNA: encoding antigen of choice encapsulated in lipid nonoparticle
Advantage: simpler and quicker to synthesize, scale-up and purify than proteins or viruses
Disadvantage: difficult to store, less stable
Influenza Virus
• cause Spanish Flu in 1918
• (-)ss, segmented RNA, helical capsid, enveloped with glycoproteins
• The glycoproteins are hemagglutinin (HA) and neuraminidase (NA) each virus has one type of HA and one type of NA
• Infection happened annually because of the plasticity of the genome
- Antigenic drift and Antigenic shift
Antigenic drift vs. Antigenic shift
Antigenic drift
- Minor change in influenza virus antigens due to gene mutation
Antigenic shift
- Major change in influenza virus antigen due to gene reassortment重排
