Viral Pathogenesis, Attachment, and Entry (Vocabulary Flashcards)

Vocabulary flashcards covering attachment, penetration, uncoating, receptor usage, entry pathways, and outcomes of viral infection as presented in the lecture.

Tropism

The specificity of a virus for a particular host tissue, largely determined by interactions between viral surface proteins and host cell receptors.

Attachment (adsorption)

Initial binding of a virus to a cell surface receptor or coreceptor; can be highly specific or non-specific and does not guarantee entry.

Receptor

A cell-surface molecule that a virus recognizes and binds to during attachment; can be a protein, carbohydrate, or other molecule.

Coreceptor

A secondary receptor that assists entry after the initial attachment; necessary for some viruses to penetrate and uncoat.

Glycoprotein (spike)

Viral protein embedded in the envelope (enveloped viruses) that mediates attachment and entry by binding receptors.

Capsid protein

Structural protein of nonenveloped viruses that mediates attachment and can serve as a binding site for receptors.

Avidity

Overall strength of the connection between a virus and a cell, influenced by receptor numbers and binding sites per viral protein.

Endocytosis

A cellular uptake process in which the virus is brought into the cell within a vesicle, often following attachment.

Fusion

Merging of the viral envelope with the host cell membrane, allowing entry of the viral genome.

Penetration

Translocation of the virion or parts of it across the cell membrane, often via endocytosis or fusion.

Uncoating

Release of the viral nucleic acid from the capsid (or envelope) to expose the genome for replication.

Early endosome

An intracellular vesicle (pH ~6.5–6.0) formed after endocytosis; a site where some viruses begin uncoating.

Late endosome

A more acidified endosomal compartment (pH ~6.0–5.0) that can drive uncoating for certain viruses.

Lysosome

An organelle with acidic pH containing degradative enzymes; involved in some uncoating pathways.

Three strategies of uncoating

The main routes: (1) at the plasma membrane after fusion, (2) within endosomes following endocytic uptake, (3) at the nuclear membrane near the nucleus.

Plasma membrane uncoating

Uncoating that occurs after viral and cellular membranes fuse at the cell surface, exposing the genome in the cytoplasm.

Endosomal uncoating

Uncoating that occurs inside endosomes as virion components respond to the acidic environment or receptors.

Nuclear membrane uncoating

Uncoating that occurs at the nuclear membrane, delivering the genome into the nucleus.

HIV gp120

Viral envelope glycoprotein that binds CD4 receptor and induces conformational changes to engage coreceptors.

HIV gp41

Viral envelope glycoprotein that mediates fusion between viral and cellular membranes after gp120 binding.

CD4 receptor

Primary host cell receptor for HIV, mainly on immune cells, required for viral entry in combination with a coreceptor.

CCR5/CXCR4 coreceptors

Chemokine receptors that act as HIV coreceptors; usage determines co-receptor dependence and cell tropism.

Sialic acid

Carbohydrate receptor on cell surfaces that influenza HA binds; linkage type (α2,3 or α2,6) influences host range.

Hemagglutinin (HA)

Influenza envelope glycoprotein that binds sialic acid and mediates fusion; cleavage of HA precursor forms HA1/HA2.

Neuraminidase (NA)

Influenza envelope protein that cleaves sialic acid, aiding virus release from cells.

α2,3 vs α2,6 sialic acid linkages

Types of linkages that influenza HA recognizes; α2,6 is common in human respiratory tract, α2,3 in avian species.

Influenza tropism

Breadth of infection determined by HA-sialic acid recognition; broader tropism than HIV due to ubiquity of sialic acid.

Poliovirus receptor (CD155) canyon

Nonenveloped poliovirus binds to CD155 at a canyon-shaped binding site on the capsid.

Adenovirus fiber

Capsid projection that interacts with the CAR receptor to initiate attachment; can require coreceptors for uptake.

CAR (coxsackievirus and adenovirus receptor)

Cell surface receptor used by adenovirus (and some other viruses) to attach prior to entry.

Clathrin-coated endocytosis

A common endocytic route where vesicles form with a clathrin coat to internalize bound viruses.

Endosomal acidification

Lowering pH inside endosomes; triggers conformational changes in viral proteins for uncoating or fusion.

Fusion pore

Opening created during membrane fusion that allows exchange of viral and cellular contents.

Syncytia (multinucleated giant cells)

CPE where infected cells fuse with neighboring cells; common with enveloped viruses expressing fusogenic glycoproteins.

Cowdry Type A intranuclear inclusions

Pathologic inclusion bodies seen in herpesvirus-infected cells, indicating nuclear viral replication.

Negri bodies

Eosinophilic cytoplasmic inclusion bodies seen in neurons infected with rabies virus.

Eclipse period

Phase after initial infection when no infectious virions are observed, though replication is ongoing.

Plaque assay

Quantitative virology method using diluted virus to produce plaques on a cell monolayer, representing infectious units.

Abortive infection

Infection in which a virus enters a cell but cannot complete replication, producing no infectious virus.

Lytic infection

Infection resulting in cell death due to productive viral replication and cytopathic effects.

Persistent infection (flavors)

Infections where virus persists with ongoing production (chronic), latency with no immediate virus production (latent), recurrence (recurrent), or transforming potential.

Chronic persistent infection

Continual production of infectious virus with no visible cytopathology or cell death.

Latent infection

No detectable infectious virus during latency; viral genome persists with little/no viral protein, with potential reactivation.

Transforming infection

Persistent infection that immortalizes the host cell and can lead to oncogenesis.