Introduction to Virology, Prions, and RNA Viruses of Dental Importance

Flashcards covering general virology principles, prion pathology, RNA virus families, and specific viral diseases relevant to dental practice.

Primary Pathogen

An organism capable of causing disease in an otherwise healthy host, such as Streptococcus mutans in dental caries.

Opportunistic Pathogen

A usually harmless organism that causes disease only in individuals with weakened immune systems or when it gains access to an abnormal body site.

Exogenous Infection

An infectious disease caused by pathogens entering the body from an external source, such as the environment, animals, or another person.

Endogenous Infection

An infection caused by an agent already present in the body (normal flora or dormant) that causes disease when immunity weakens or barriers are breached.

Incubation Period

The time interval between the entry of a pathogen into the host and the onset of symptoms.

Prodrome

The stage of infection marked by mild, non-specific symptoms as the immune system begins its initial response.

Latent Infection

A type of infection where the microorganism remains in the body, characterized by long periods with no overt disease interrupted by symptomatic periods.

PrPC

The normal cellular prion protein which has an alpha helix conformation.

PrPSC

The infective scrapie prion protein which has an abnormal beta-pleated sheet conformation and causes protein misfolding.

Variant CJD (vCJD)

A human prion disease caused by the ingestion of prions from beef cows with bovine spongiform encephalopathy (mad cow disease).

Pulvinar Sign

A diagnostic indicator for vCJD seen in the thalamus during a brain MRI.

Naked Viruses

Viruses lacking an envelope that are stable to temperature, acid, and detergents; they spread easily via fomites and are released by host cell lysis.

Enveloped Viruses

Viruses surrounded by a membrane that are susceptible to acid, heat, and drying, requiring antibody and cell-mediated immune responses for control.

Positive-sense RNA (+ssRNA)

Viral genomes that act directly as mRNA and can be immediately translated into proteins by host ribosomes upon entry.

Negative-sense RNA (-ssRNA)

Viral genomes complementary to mRNA that must carry their own RNA-dependent RNA polymerase to transcribe the genome before translation.

Eclipse Period

The time between viral uncoating and the production of new infectious virions.

Inclusion Bodies

Accumulations of viruses in the nucleus or cytoplasm used for diagnosis, such as Negri bodies in rabies or Owl's eye in cytomegalovirus.

Interferon

A cytokine that serves as the first line of defense against viral infection by degrading viral RNA and preventing protein synthesis in neighboring cells.

Seroconversion

A strong indicator of recent infection defined by a 4-fold or greater rise in antibody titer between acute and convalescent sera.

Rhinovirus

The primary cause of the common cold, which replicates best at $33^{\circ}C$ in the nasal mucosa and is sensitive to acidic pH.

Herpangina

An oral condition caused by Coxsackieviruses or Enterovirus 71 characterized by grey-white papulovesicles on the soft palate, uvula, and tonsils.

Hand, Foot and Mouth Disease (HFMD)

Also called enteroviral stomatitis, an infection causing oral ulcers and skin lesions on the extremities, often caused by Coxsackievirus A16.

Syncytia

Multinucleated giant cells formed by cell-to-cell fusion, common in Paramyxoviridae infections.

Croup

Laryngotracheobronchitis caused by Parainfluenza virus, characterized by subglottal swelling and a "seal bark" cough.

Koplik Spots

Small bluish-white lesions on the buccal mucosa that appear as a prodromal sign of Measles (rubeola).

Antigenic Shift

A major change in Influenzavirus A caused by the gene reassortment of RNA segments from different strains, potentially leading to pandemics.

Hemagglutinin (HA)

An influenza glycoprotein responsible for viral attachment and fusion that elicits neutralizing antibody responses.

ACE2

The host cell receptor recognized by the SARS-CoV-2 spike protein for viral entry.

Negri Bodies

Cytoplasmic aggregates of viral nucleocapsids found in neurons, diagnostic for Rabies virus.

Hepatitis C Virus (HCV)

A blood-borne enveloped RNA virus that becomes a chronic carrier state in approximately $85\%$ of cases and currently lacks a vaccine.

Reverse Transcriptase

An enzyme found in Retroviruses like HIV that allows the synthesis of cDNA from an RNA genome.

gp120

The HIV glycoprotein that binds specifically to the CD4 receptor on T helper cells and macrophages.

AIDS

The clinical stage of HIV infection reached when the CD4 T-cell count falls below $200/\mu l$.