Virus Intro Flashcards
Virus Outline
Infectious agent in a protein coat. Contain either DNA or RNA (either double/single strands). Strict intracellular parasites (need host cellfor replication) (different from bacteria who reproduce without host cell). Non-living entities
How viruses are classified
Morphology (shape), nucleic acid, replication mechanism, type of host they infect and disease that they cause
Virus Components
Capsid (protein capsomere coat), nucleic acid (DNA/RNA) (joins with capsid to form nucleocapsid) and occasionally envelope (sourced from host cell)
Capsid Overview
Protective shield made up of different capsomer shapes. Contains antigens for interaction with host cell receptors to implement it’s DNA into host cell
Capsid Shapes
cubic/icosahedral, helical and complex
Cubic Capsids Outline
20 equilateral triangle faces. Eg adenovirus
Helical Capsids Outline
protein bound around nucleic acid as helix
Complex Capsid Outline
Neither cubic or helical. Eg poxvirus. Includes bacteriophage which includes separate capsid heads and tails
Capsid Ressistance
Drying, heating, detergents, acids and proteases. This enables it’s survival on surfaces and in the GI tract
Viral Genome
Circular/ linear single/doble stranded DNA/RNA molecules. Codes for host production of viral proteins and replication enzymes
Production of mRNA in human DNA viruses
Can have either single/double strand DNA.single strand DNA becomes double strand DNA. Double strand DNA forms mRNA
Production of mRNA in RNA viruses
Can have either
Viral Envelope Outline
Lipid bilayer that surrounds capsid. Consists of phospholipids and glycoproteins (that acts a s receptors). Derives from host cell’s membrane (via budding)
Distinctive Serological Polypeptides of Envelopes
Surface polypeptides (eg influenza hemagglutinins), antigens and enzymes (eg influenza neuraminidase)
Envelope is sensitive to
Drying, heat, detergents and acids. Thus viruuses with envelope must have moist transitions (droplets), can’t survive GIT, may need cellular and humoral (antibodies, antimicrobials, ect.) to be treated
How viruses are acquired
Vectors (animal/insect bites eg rabies), inhalation (eg influenza), faecal oral (contaminated water eg hepatitis A & E), blood (eg HIV), sexual (eg herpes) and congenital (when born eg rubella)
Virus Cell Tropism
The affinity a virus has for host cells. Determined by cell receptors, physical barriers, temp, pH and oxygen tension enzymes
Virus Replication Outline
virus attachment and entry to cell, virion uncoating, genomic nucleic acid migrates to nucleus, transcription, genome replication, viral mRNA translation, viron aseembly and release of new viruses
How do viruses attach to cell
Viral attachment, Glycoprotein to cell receptor. If compatible virus undergoes endocytosis
Why do viruses need to uncoat
Make genome available pushes viral nucleic acid into cytoplasm
Location of viral nucleic acid synthesis in host cell
cytoplasm and nucleus
Location of viral protein synthesis in host cell
cytoplasm
How viruses leave host cells
enveloped: budding. Non-enveloped: lysis or exocytosis
Viraemia Def
Virus enetring into blood
Cytopathological Activity Def
Impact virus has on host tissue (damage)
Immunopathology Def
What response a pathogen (virus) stimulates (if any eg HIV hiding in body cells)
Virus effects on cells
death, transformation and latent infection
Cell Death Outline
Cytopathogenic effect visible on cell
Cell transformation Outline
Cell becomes malignant or pre-malignant (cancerous) eg pampillivirus
Latent Infection Outline
Viral parts may be only temporarily inactive
What is looked at under electron microiscope
Quick observation of virus
What is looked at under fluorescent microscope
Detection of viral antigens using antibodies (fluroscing antibodies)
What is looked under a light microscope
virus induced masses in cells. can be pathogonomic
Virus Cause of Lymphoma
HIV and Hespatin & Barr virus
Virus Cause Hepatocellular cancer
Hepatitis B and C
Cervical Cancer
papillomavirus
Nasopharyngeal Cancer Virus cause
EBV
Ways viruses spraed
Intracellular (cell to cell intercellular bridges), extracellular ( in hematogenous and lymphatic cells they travel in blood), neural (peripheral nerves to CNS) and nuclear (genome continues in host cell)
Viral infection Outcomes
In most patients viruses are self limiting (can resolve without treatment) but in immunocompromised individuals it can be more severe to fatal. Can be silent (asymptomatic), can reoccur intermittently (can be dormant for a time). Viral effects can be acute (happening now for a limited time) or chronic (permanent changes)
Classifications of antivirals
Deactivating virus (UV, cryotherapy) , Augmentation of host cell (eg intereferons) and viral replication inhibition (eg Aciclovir), vaccinations (eg influenza, HPV)
Lab Infection Diagnosis
Qualitative (detection and ID) and quantitative (amount of virus)
Examples of detection and ID of viruses
Microscopy, viral culture, serology (viral antibody), viral antigen and viral genome
Viral Culture Outline
Animal (host) cells are grown in an artificial culture. Cells are observed for changes specific to particular viral infection. Confirm viral ID by immunofluorescence, neutralisation and haemabsorption inhibition
Viral cell culture disadvantages
Most viruses won’t grow (eg hepatitis B), susptible to bacterial infection, culture can be damaged by viral waste, poor sesitivity and long wait time
How is blood analysed to test for viral antigen
2 samples required: 1 from day of illnes onset and 1 1-2 weeks later. If blood shows a rise in antibodies antigen is present. Tested via ELISA or fluroescent microscopy
Molecular Diagnosis eg PCR Outline
rapid diagnosis, used to guide traement plans and detect antiviral ressistance. Not all viruses can be cultured eg hepatitis C
