Viral Replication - Vocabulary Flashcards

Vocabulary flashcards covering steps of viral replication, genome types, replication strategies, release mechanisms, mutation consequences, and antiviral therapies.

Attachment

First step of viral entry: virion binds to specific receptors on the host cell; naked viruses attach via direct capsid contact; enveloped viruses use surface glycoproteins (spike) to attach.

Penetration

Entry of the virus into the host cell; can occur by endocytosis, fusion at the plasma membrane, or direct penetration depending on the virus.

Uncoating

Removal of the viral genome from the capsid after entry; can occur at the cell membrane, within endosomes, or in the cytosol.

Transcription

Synthesis of viral mRNA from the viral genome using viral and/or host polymerases.

Translation

Synthesis of viral proteins from viral mRNA by host ribosomes.

Replication

Synthesis of new viral genomes using viral and/or host polymerases; strategies depend on genome type (RNA or DNA).

Assembly

Packaging of the viral genome into a capsid to form the nucleocapsid; genomes have packaging signals that initiate packaging.

Release

Exit of virions from the host cell; mechanisms include lysis (naked and some enveloped), budding (enveloped), and exocytosis.

dsDNA viruses

Viruses with double-stranded DNA genomes; often replicate in the nucleus and may use viral or host polymerases.

ssDNA viruses

Viruses with single-stranded DNA genomes.

ssRNA(+): Positive-sense RNA

Genome acts as mRNA and can be directly translated by host ribosomes.

ssRNA(-): Negative-sense RNA

Genome is complementary to mRNA and must be transcribed to positive-sense RNA before translation; requires viral RNA-dependent RNA polymerase.

dsRNA viruses

Genomes composed of double-stranded RNA; replication uses viral RNA-dependent RNA polymerase.

Reverse transcription

Process by which retroviruses convert RNA genome into DNA using reverse transcriptase.

Retroviruses

RNA viruses that reverse transcribe their genome into DNA and integrate it into the host genome; replication involves transcription by host enzymes.

RNA-dependent RNA polymerase

Viral enzyme that copies RNA genomes from RNA templates; not present in host cells.

RNA-dependent DNA polymerase (Reverse Transcriptase)

Enzyme used by retroviruses to convert RNA to DNA, enabling integration into the host genome.

Positive-sense RNA

ssRNA that functions as mRNA and is immediately translated by ribosomes.

Negative-sense RNA

ssRNA that must be transcribed to positive-sense RNA before translation.

Nucleocapsid

Complex of genome and capsid proteins; genome packaging occurs with signals guiding encapsidation.

Packaging signals

Genome sequence signals that initiate and direct packaging of the genome into the capsid.

Lysis

Destructive release of virions by rupturing the host cell, common for naked viruses.

Budding

Release of enveloped virions through budding from membranes, acquiring a host-derived envelope with glycoproteins.

Exocytosis

Release of virions via secretory vesicles; can involve naked or enveloped viruses.

Tropism

The range of cell or tissue types that a virus can infect, influenced by receptor usage and intracellular factors.

Antigenic drift

Minor antigenic changes in influenza H and N proteins due to point mutations; can cause epidemics without changing subtype.

Antigenic shift

Major antigenic change from reassortment of genome segments; can lead to pandemics and a new subtype.

Mutation consequences

Mutations can alter tropism, antigenicity, drug resistance, and virulence of viruses.

Latency

Persistent, dormant infection in host cells (e.g., herpesvirus in ganglia) with potential reactivation.

Retrograde transport

Movement of a virus from peripheral sites to sensory nervous system ganglia along nerves.

Monoclonal antibodies (mAbs)

Therapies that target viruses to neutralize them, used in HIV, CMV, RSV among others.

Entry inhibitors

Drugs that block attachment or fusion of viruses (e.g., HIV, HSV) to prevent entry.

Uncoating inhibitors

Drugs that prevent viral uncoating, thereby blocking genome release (e.g., for Flu A and picornaviruses).

Viral DNA polymerase inhibitors

Drugs that inhibit DNA synthesis by viral polymerases (e.g., some herpesviruses).

Viral RNA polymerase inhibitors

Drugs that inhibit RNA synthesis by viral polymerases.

Reverse transcriptase inhibitors (RT inhibitors)

Drugs that block reverse transcription in retroviruses (e.g., HIV, HBV).

Protease inhibitors

Drugs that block viral protease activity, preventing maturation of viral proteins.

Integrase inhibitors

Drugs that prevent integration of viral DNA into the host genome (e.g., HIV).

Neuraminidase inhibitors

Drugs that block release of influenza virions by inhibiting neuraminidase.