PID Virology Flashcards
The single biggest threat to man’s continued dominance on the planet is?
Viruses
characteristics of a virus are?
Viruses are non-living entities.
- Viruses contain nucleic acid genome (DNA or RNA) surrounded by a protein coat and, in some cases, other layers of material, such as a lipid envelope.
- Viruses do not possess standard cellular organelles such as mitochondria, chloroplasts, Golgi, and endoplasmic reticulum with associated ribosomes.
- Viruses cannot make energy or proteins by themselves and have to rely on a host cell.
- All Viruses are obligate intracellular parasites. Outside the living cell, viruses are inert or dormant particles, whereas, inside the cell, the virus hijacks and utilizes the host cell machinery to produce its proteins and nucleic acid for the next generation of virus.
- Viruses do not have the genetic capability to multiply by division. The process of Virus reproduction resembles an assembly line in which various parts of the virus come together from different parts of the host cell to form new virus particles.
the smallest virus is
the parvo virus (18-28nm)
Virion vs Virus
- Virion: A complete virus particle that consists of an RNA or DNA core with a protein coat sometimes with external envelopes and that is the extracellular infective form of a virus.
- Virus: is a broad general terminology used to describe any aspect of the infectious agent and includes: the infectious (Virion) or inactivated virus particle, or viral nucleic acid and protein in the infected cell.
what is a viroid
Viroid: An infectious particle smaller than any of the known viruses, an agent of certain plant diseases. The particle consists only of an extremely small circular RNA (ribonucleic acid) molecule, lacking the protein coat of a virus.
Edward Jenner did what?
he inoculated some “cowpox matter” (probably infected pus) repeatedly into arms of a healthy 8 year boy who became immune and did not succumb to small pox. Vaccination –derived from the Latin word ‘vacca” meaning “cow” – had been invented.
Louis Pasteur did what?
injected dried, potassium hydroxide treated, infected rabbit brain material in two boys bitten by rabid dogs and both of them recovered.
what is the strx and composition?
A capsid is the protein shell of a Virus. Capsid is usually symmetrical
A capsomer is the basic subunit protein in the capsid of a virus.
Capsid + Virus Nucleic acid (DNA or RNA)/Genome = Nucleocapsid
Some Viruses may have an envelope, which is usually a lipid bilayer with embedded proteins. The envelope facilitates virus entry into host cells and may also help the virus to evade the host immune system.
Glycoproteins on the surface of the envelope serve to identify and bind to host cell surface (cell membrane) and are also significant to host immunity.
6 shapes of viruses
Tadpole-shaped Bullet-shaped Filament-shaped Rod-shaped Brick-shaped Spherical
Pleomorphism is
the ability of some Virus to alter their shape or size
Some Virions also contain Enzymes critical to Infection what are they?
Lysins: Hydrolytic enzymes produced by bacteriophages to cleave the host’s cell wall.
Retroviral integrase (IN): Enzyme produced by a retrovirus (such as HIV) that enables its genetic material to be integrated into the DNA of the infected cell.
Reverse transcriptase (RT): Enzyme used to generate complementary DNA (cDNA) from a RNA template.
Nucleic acid polymerases: Viral Genome Replication.
Neuraminidases: Enzymes that cleave glycosidic bonds. Allows release of viruses from host cell
what are the steps of viral replication?
- Attachment
- Penetration
- Uncoating
- Synthesis of Viral Nucleic acid and Protein
- Assembly and Maturation
- Release in Large Numbers
one-step viral growth curve
- viral adsorption and entry
- viral uncoating and replication (eclipse period)
- viral maturation
- viral release (Burst)
(2 & 3 = latent period)
the hight of the growth curve represents what?
the # of virions released after maturation
the fastest replicating virus is?
the slowest replication virus is?
(measured by the # of particles / host cell / hr)
fastest is Picornavirus
slowest is retrovirus
viral Attachment to Host Cell Surface is mediated by?
Mediated by interactions between the Virus and Complimentary Receptor on Host Cell surface. Cell that lack the appropriate receptor escape being infected by viruses.
- In some cases, binding to a cellular receptor is not sufficient for infection: an additional cell surface molecule, or co-receptor, is required for entry.
viruses have evolved to use Host Cell Surface receptors, what are these receptors made of?
Receptors may be proteins, carbohydrates, glycoproteins, lipids, lipoproteins, or even complexes
viral uncoating is?
- Release of Viral Genome in Host Cell. Virion can no longer be detected; known as the “eclipse period”
- Some animal viruses begin to uncoat after binding to the external receptor, but are not completely uncoated until inside the cell (Poliovirus).
- Uncoating in some animal viruses requires a complex series of steps involving both host and viral gene products (Poxvirus).
- In some other viruses, such as retroviruses and reoviruses, the first stages of the viral replication cycle (transcription, replication) actually occur inside the capsid.
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Virus Nucleic Acid and Protein Synthesis
DNA VIRUS REPLICATION
DNA Viruses:
Replication of Viral DNA primarily occurs in host cell nucleus.
Capsid and other proteins are synthesized in host cell cytoplasm using host cell machinery.
Newly formed Viral proteins localize in the nucleus to combine with newly synthesized Viral DNA to form new Viral particles.
Pox Viruses are an exception, as they have been found to replicate in the cytoplasm of infected cells.
- Viruses with Small, Single-Stranded DNA Genomes (Parvovirus): Single-Stranded DNA genome double-stranded DNA mRNA Replication occurs in the nucleus
- Viruses with Large Double-Stranded DNA Genome (Herpesviridae) Complex Replication process. Encode additional proteins. These proteins can either be structural (capsid proteins, matrix proteins, envelope proteins, etc) or regulatory (transcription factors, polymerases, enzymes involved in nucleotide metabolism, etc)
Virus Nucleic Acid and Protein Synthesis
RNA VIRUS REPLICATION
RNA Viruses: Most replicate entirely in the cytoplasm of infected cells. Exceptions are orthomyxoviruses and retroviruses, where host cell nucleus is involved. (+) Strand Viruses: Synthesis of viral proteins (including replicase) from viral genomic RNA. (-) Strand Viruses: Synthesis of + strands using the virion associated polymerase. These + strands can either be full length or subgenomic mRNAs. Viruses with Double-Stranded RNA Genomes: Early transcription occurs in partially uncoated virions using Viral enzyme in host cell cytoplasm mRNA translated into protein final stages of viral replication and gene expression occur in newly formed Viral particles in host cell. Retroviruses: (+) sense Viral RNA cDNA integrated into host cell chromosome Reverse Transcriptase The host cell then treats the viral DNA as part of its own genome, translating and transcribing the viral genes.
VIRUS REPLICATION:
Assembly is:
Assembly of Virus Genome and Proteins into New Virions follow a Specific Order. May take place in Nucleus, Cytoplasm, or in Plasma Membrane (Most Enveloped Viruses).
possible impact on the host cell by a virus?
- Cell Death: Lysis
Alteration Cell Membrane
Apoptosis (Cell Suicide) - Transformation of Cell to Malignant one
- Fusion of Cells, Multinucleated (hybrids)
- No apparent changes to the infected cell. Latent, Persistent or Chronic infection
Virus Epidemiology and its Surveillance is?
.
- The study of the determinants, dynamics, and distribution of vital diseases in populations. Public Health
- The systematic collection, analysis, interpretation, and dissemination of data on Viral Diseases on an ongoing basis, to gain knowledge of the pattern of disease occurrence and potential in a community, in order to control and prevent disease in the community
Porcine Epidemic Diarrhea Virus (PEDV) what did/can it
cause economically?
causes severe Diarrhea and Vomiting in Pigs. First identified in the United States in May 2013. By the end of January of 2014, spread quickly across many US states, causing severe economic losses.
what is Molecular Epidemiology of Viruses
The use of molecular biological data as the basis of epidemiological investigation of Viral Diseases
