vaccínia

Vaccínia, commonly known as vaccinia virus, is a large, enveloped double-stranded DNA virus of the Orthopoxvirus genus in the family Poxviridae. It is best known for its historical role in smallpox vaccination, where live vaccinia virus is used to elicit protective immunity against variola virus. The precise origin of the vaccine strain is unclear; various strains have circulated since the 19th century, with modern use often favoring safer derivatives for research and vaccination.

Biology: Vaccínia replicates in the cytoplasm of infected cells, carrying its own transcriptional and replication machinery. The genome spans roughly 190 kilobases and encodes about 200 proteins, many of which modulate the host immune response. Two major infectious forms exist: intracellular mature virions and extracellular enveloped virions, enabling spread within tissues and to contacts.

Applications: Historically, vaccination with vaccinia conferred immunity to smallpox. Today, vaccínia is used as a vector for recombinant vaccines and cancer therapies; Modified Vaccinia Ankara (MVA) is a widely used replication-deficient derivative for safe vaccine vectors in humans.

Safety: Vaccination with vaccinia can cause local skin reactions and systemic symptoms; rare but serious adverse events include eczema vaccinatum and progressive vaccinia, particularly in immunocompromised individuals or those with skin conditions. Vaccinia-based vaccines are administered under medical guidance, with monitoring for adverse effects.

Eradication: Smallpox was eradicated globally in 1980, largely due to vaccination programs that used vaccinia-based vaccines. Vaccínia remains primarily a research and biotechnological tool, with restricted use in clinical settings.