SMALLPOX: CAN WE STILL LEARN FROM THE JOURNEY TO ERADICATION?

Sunday, 9th of March 2014

[source]The Indian Journal of Medical Research[|source]

Almost two hundred years after Edward Jenner s landmark publication showing the efficacy of prophylactic immunization for smallpox, a worldwide campaign successfully eradicated this dreaded disease that produced 30 per cent mortality after infection and resulted in 10 per cent of the world s blind. In the decade long drive to small pox eradication (1967-1977), the science of immunology was still in its infancy. It was a time before the revolution of molecular immunology was ushered in

 

In this report, the authors articulate that Smallpox virus was eradicated from the globe because of its unique virological and immunological characteristics. The report documents the lessons from small pox eradication that can be used to inform future eradication drives. More details are accessible at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3734679/

 

 

Abstract

One of the most celebrated achievements of immunology and modern medicine is the eradication of the dreaded plague smallpox. From the introduction of smallpox vaccination by Edward Jenner, to its popularization by Louis Pasteur, to the eradication effort led by Donald Henderson, this story has many lessons for us today, including the characteristics of the disease and vaccine that permitted its eradication, and the obviousness of the vaccine as a vector for other intractable Infectious diseases. The disease itself, interpreted in the light of modern molecular immunology, is an obvious immunopathological disease, which occurs after a latent interval of 1-2 weeks, and manifests as a systemic cell-mediated delayed type hypersensitivity (DTH) syndrome. The vaccine that slayed this dragon was given the name vaccinia, and was thought to have evolved from cowpox virus, but is now known to be most closely related to a poxvirus isolated from a horse. Of interest is the fact that of the various isolates of orthopox viruses, only variola, vaccinia and monkeypox viruses can infect humans. In contrast to the systemic disease of variola, vaccinia only replicates locally at the site of inoculation, and causes a localized DTH response that usually peaks after 7-10 days. This difference in the pathogenicity of variola vs. vaccinia is thought to be due to the capacity of variola to circumvent innate immunity, which allows it to disseminate widely before the adaptive immune response occurs. Thus, the fact that vaccinia virus is attenuated compared to variola, but is still replication competent, makes for its remarkable efficacy as a vaccine, as the localized infection activates all of the cells and molecules of both innate and adaptive immunity. Accordingly vaccinia itself, and not modified replication incompetent vaccina, is the hope for use as a vector in the eradication of additional pathogenic microbes from the globe.