SCH1111 Fundamental Biomedical Techniques - Viruses

Flashcards about Viruses, including their characteristics, classification, life cycle, pathogenesis, detection methods, and control measures.

What is a Virus?

Too small to be seen with a light microscope; obligate intracellular parasites that infect animals, plants, and bacteria.

Virion

A complete virus particle, composed of nucleic acid (RNA or DNA) surrounded by a capsid (protein coat).

Nucleic Acid Content in Viruses

RNA or DNA; not both. Do not grow by binary fission and lack organelles.

Different Virus Shapes

Helical, Icosahedral, and Complex

Virus Capsid and Envelopes

Capsids are made of subunits called capsomeres. Some viruses have envelopes acquired from host cells.

Hierarchical Virus Classification System

Nature of nucleic acid, symmetry of the capsid, presence/absence of envelope, and dimensions of virion and capsid.

Baltimore Classification

Mechanism of viral genome replication, categorizing viruses into seven groups based on mRNA production.

Requirements for Viral Replication

A living cell, a receptor to enter cell, and a mechanism for leaving the cell.

Viral Replication Steps

Attachment, penetration, uncoating, biosynthesis, maturation, and release by budding or rupture

Acute Viral Infection

Rapid onset, brief symptoms, early virion production, and elimination by the host immune system.

Chronic infection

Infection persists for the life of the host. Can be latent or slow.

Consequences of Viral Infections

Effects on cells, entry into host, course of infection, cell/tissue tropism, damage, immune response, and clearance/persistence.

Cellular Response to Viral Infections

No change, cell death, or transformation.

Primary Replication

Where the virus replicates after initial entry into the host, determining if the infection remains localized or spreads systemically.

Cell Tropism

Viral affinity for specific body tissues, determined by cell receptors, transcription factors, and ability to support replication.

Cell Damage by Viruses

Viruses may replicate without symptoms if they don't cause significant cell damage or death.

Immune Response to Viral Infections

Cellular immunity (T cells) clears the infection, humoral immunity (B cells) protects against reinfection.

Controlling Virus Infections

The route of infection, development of vaccines, and antiviral medications.

After Virus Infection

Remain localized or spread to other tissues.

Virus Identification Methods

Growth in cell culture, nucleic acid testing (PCR), serological tests (antigen/antibody detection), and electron microscopy.

Polymerase Chain Reaction (PCR)

Detects DNA, can be modified for RNA. Samples include serum, urine, and saliva. Problems include no indication of replication competence and potential for false positives.

Breaking the Chain of Infection

Wash hands, use PPE, cook food properly, isolate infected individuals.

Antiviral Medications

Stop nucleic acid replication (e.g., acyclovir) or prevent virus entry into cells (e.g., Relenza). Also Interferon and Gamma globulin.