Viruses: Acellular Pathogens

This flashcard set covers key concepts and terminology related to viruses as discussed in the lecture notes.

What are viruses?

Acellular infectious agents that require a host cell to replicate, containing either DNA or RNA, with no metabolism or independent reproduction.

Definition of virion size range

The size of a virion can range from 20 nm for small viruses up to 900 nm for typical large viruses.

Historical discoverers of viruses

Dmitri Ivanovsky and Martinus Beijerinck discovered the Tobacco mosaic virus; Wendell Stanley crystallized it.

General structure of viruses

Viruses have a nucleic acid core (DNA or RNA), a capsid (protein coat), an optional envelope (lipid membrane), and spikes (glycoproteins for attachment).

Types of viral shapes

Viral shapes include helical (e.g., Tobacco mosaic virus), polyhedral (e.g., Adenovirus), and complex (e.g., Bacteriophage).

Classification of viruses is based on what?

Classification is based on nucleic acid type, capsid structure, envelope presence, and host range.

What is tissue tropism?

It refers to the preference of a virus for certain cell types in specific hosts.

Lytic cycle stages in order

1. Attachment, 2. Penetration, 3. Biosynthesis, 4. Maturation, 5. Release.

What is the lysogenic cycle?

A cycle where viral DNA integrates into the host genome and remains dormant until triggered; can switch to the lytic cycle.

What is transduction in viruses?

It is the process by which a virus transfers bacterial DNA from one host cell to another, occurring in generalized or specialized forms.

Animal virus replication entry methods

Entry can occur through endocytosis or membrane fusion.

Stages of HIV infection

Includes fusion to the host-cell surface, reverse transcription, integration into host DNA, and assembly of new viral particles.

Types of viral infections

Acute (e.g., influenza), Persistent (e.g., HIV), Latent (e.g., herpes), and Oncogenic (e.g., HPV, EBV).

What does viral latency signify?

It indicates that a virus remains dormant in the host and can reactivate under stress.

How are viruses cultivated?

Viruses require living cells for cultivation; methods include using bacteriophages, animal viruses, cell cultures, eggs, or live animals.

Detection methods for viruses

Includes cytopathic effects, hemagglutination assay, PCR/RT-PCR, and ELISA/EIA.

What distinguishes emerging viruses?

Emerging viruses are often zoonotic, transmitted from animals to humans, and can spread via various transmission routes.

Roles of viruses in biotechnology

Viruses are used as vectors for gene therapy, in vaccine development, and in phage therapy.

Best defenses against viral infections

Vaccination and antiviral drugs that inhibit replication, along with hygiene and vector control.

Summary of viruses

Viruses are acellular, host-dependent, and have varied shapes and genomes, reproducing via lytic or lysogenic cycles, potentially causing disease or serving biotechnological purposes.