Sverdlovsk incident (2 April 1979)
Despite signing the 1972 agreement to end bioweapon production, the government of the Soviet Union had an active bioweapons program that included the production of hundreds of tons of anthrax after this period. On 2 April 1979, some of the over one million people living in Sverdlovsk (now called Ekaterinburg, Russia), about 1,370 kilometres (850 mi) east of Moscow, were exposed to an accidental release of anthrax from a biological weapons complex located near there. At least 94 people were infected, of whom at least 68 died. One victim died four days after the release, 10 over an eight-day period at the peak of the deaths, and the last six weeks later. Extensive cleanup, vaccinations, and medical interventions managed to save about 30 of the victims. Extensive cover-ups and destruction of records by the KGB continued from 1979 until Russian President Boris Yeltsin admitted this anthrax accident in 1992. Jeanne Guillemin reported in 1999 that a combined Russian and United States team investigated the accident in 1992.Nearly all of the night-shift workers of a ceramics plant directly across the street from the biological facility (compound 19) became infected, and most died. Since most were men, some NATO governments suspected the Soviet Union had developed a sex-specific weapon. The government blamed the outbreak on the consumption of anthrax-tainted meat, and ordered the confiscation of all uninspected meat that entered the city. They also ordered all stray dogs to be shot and people not have contact with sick animals.
Anthrax components: protective antigen (PA), edema factor (EF), and lethal factor (LF). PA plus LF produces lethal toxin, and PA plus EF produces edema toxin. These toxins cause death and tissue swelling (edema), respectively. To enter the cells, the edema and lethal factors use another protein produced by B. anthracis called protective antigen, which binds to two surface receptors on the host cell. A cell protease then cleaves PA into two fragments: PA20 and PA63. PA20 dissociates into the extracellular medium, playing no further role in the toxic cycle. PA63 then oligomerizes with six other PA63 fragments forming a heptameric ring-shaped structure named a prepore. Once in this shape, the complex can competitively bind up to three EFs or LFs, forming a resistant complex. Receptor-mediated endocytosis occurs next, providing the newly formed toxic complex access to the interior of the host cell. The acidified environment within the endosome triggers the heptamer to release the LF and/or EF into the cytosol. It is unknown how exactly the complex results in the death of the cell. Edema factor is a calmodulin-dependent adenylate cyclase. Adenylate cyclase catalyzes the conversion of ATP into cyclic AMP (cAMP) and pyrophosphate. The complexation of adenylate cyclase with calmodulin removes calmodulin from stimulating calcium-triggered signaling, thus inhibiting the immune response. To be specific, LF inactivates neutrophils (a type of phagocytic cell) by the process just described so they cannot phagocytose bacteria. Throughout history, lethal factor was presumed to cause macrophages to make TNF-alpha and interleukin 1, beta (IL1B).