Immunology
Smallpox virions have a repertoire of mechanisms by which they initiate and maintain infection. Extracellular secreted proteins bind cytokines, interferon, and chemokines, and intracellular secreted proteins prevent apoptosis of infected cells.[29]
Recovery from naturally occurring or vari-olation-induced smallpox was accompanied by lifelong immunity to reinfection. On the other hand, the duration of immunity conferred by vaccination is not really known. There is definite evidence that immunity wanes with time and that periodic revaccination resulted in improved survival during past smallpox epidemics.
Vaccination utilizes vaccinia virus to confer cross-reactive immunity against variola. It induces a strong vaccinia virus-specific CD8(+) CTL and interferon--producing T-cell response.[30] This specific T-cell immunity persists for up to 50 years after childhood vaccination.[31] The humoral response to vaccination includes neutralizing and complement-fixing antibodies. In a study of antibody responses to revaccination, titers decreased significantly during the first 3 years after revaccination but remained stable for at least 30 years thereafter.[32]
Skinmed. 2004;3(4) © 2004 Le Jacq Communications, Inc.
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