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| Vaccine description | |
|---|---|
| Target | Anthrax |
Anthrax vaccines arevaccines to prevent the livestock and human diseaseanthrax, caused by thebacteriumBacillus anthracis.[1]
They have had a prominent place in the history of medicine, from Pasteur's pioneering 19th-century work with cattle (the first effectivebacterialvaccine and the second effective vaccine ever) to the controversial late 20th century use of a modern product to protect American troops against the use ofanthrax inbiological warfare. Human anthrax vaccines were developed by theSoviet Union in the late 1930s and in the US and UK in the 1950s. The current vaccine approved by the U.S.Food and Drug Administration (FDA) was formulated in the 1960s.
Currently administered human anthrax vaccines include acellular (USA, UK) and live spore (Russia) varieties. All currently used anthrax vaccines show considerable local and generalreactogenicity (erythema,induration,soreness,fever) and serious adverse reactions occur in about 1% of recipients.[2] New third-generation vaccines being researched include recombinant live vaccines and recombinant sub-unit vaccines.
In the 1870s, the French chemistLouis Pasteur (1822–1895) applied his previous method of immunising chickens againstchicken cholera toanthrax, which affectedcattle, and thereby aroused widespread interest in combating other diseases with the same approach. In May 1881, Pasteur performed a famous public experiment at Pouilly-le-Fort to demonstrate his concept of vaccination. He prepared two groups of 25 sheep, one goat and several cows. The animals of one group were twice injected, with an interval of 15 days, with an anthrax vaccine prepared by Pasteur; acontrol group was left unvaccinated. Thirty days after the first injection, both groups were injected with a culture of live anthrax bacteria. All the animals in the non-vaccinated group died, while all of the animals in the vaccinated group survived.[3] The public reception was sensational.
Pasteur publicly claimed he had made the anthrax vaccine by exposing the bacilli to oxygen. His laboratory notebooks, now in theBibliothèque Nationale in Paris, in fact show Pasteur used the method of rivalJean-Joseph-Henri Toussaint (1847–1890), aToulouseveterinary surgeon, to create the anthrax vaccine.[4][5] This method used the oxidizing agentpotassium dichromate. Pasteur's oxygen method did eventually produce a vaccine but only after he had been awarded apatent on the production of an anthrax vaccine.
The notion of a weak form of a disease causing immunity to the virulent version was not new; this had been known for a long time forsmallpox. Inoculation with smallpox (variolation) was known to result in far less scarring, and greatly reduced mortality, in comparison with the naturally acquired disease. The English physicianEdward Jenner (1749–1823) had also discovered (1796) the process ofvaccination by usingcowpox to give cross-immunity tosmallpox and by Pasteur's time this had generally replaced the use of actual smallpox material in inoculation. The difference between smallpox vaccination andanthrax orchicken cholera vaccination was that the weakened form of the latter two disease organisms had been "generated artificially", so a naturally weak form of the disease organism did not need to be found. This discovery revolutionized work in infectious diseases and Pasteur gave these artificially weakened diseases the generic name "vaccines", in honor of Jenner's groundbreaking discovery. In 1885, Pasteur produced his celebrated first vaccine forrabies by growing the virus in rabbits and then weakening it by drying the affected nerve tissue.
In 1995, the centennial of Pasteur's death,The New York Times ran an article titled "Pasteur's Deception". After having thoroughly read Pasteur's lab notes, the science historianGerald L. Geison declared Pasteur had given a misleading account of the preparation of the anthrax vaccine used in the experiment at Pouilly-le-Fort.[6][7][8] The same year,Max Perutz published a vigorous defense of Pasteur inThe New York Review of Books.[9][10][11]
The Austrian-South African immunologist Max Sterne (1905–1997) developed an attenuated live animal vaccine in 1935 that is still employed and derivatives of his strain account for almost all veterinary anthrax vaccines used in the world today.[12] Beginning in 1934 at the Onderstepoort Veterinary Research Institute, north ofPretoria, he prepared an attenuated anthrax vaccine, using the method developed by Pasteur. A persistent problem with Pasteur's vaccine was achieving the correct balance between virulence and immunogenicity during preparation. This notoriously difficult procedure regularly produced casualties among vaccinated animals. With little help from colleagues, Sterne performed small-scale experiments which isolated the "Sterne strain" (34F2) of anthrax which became, and remains today, the basis of most of the improved livestock anthrax vaccines throughout the world.[13]As Sterne's vaccine is a live vaccine, vaccination during use of antibiotics produces much reduced results and should be avoided. There is a withholding period after vaccination when animals cannot be slaughtered. No such period is defined for milk and there are no reports of humans being infected by products from vaccinated animals. There have been a few cases when humans accidentally self-inject the vaccine when trying to administer to a struggling animal. One case developed fever and meningitis, but it is unclear whether the illness was caused by the vaccine. Livestock anthrax vaccines are made in many countries around the world, most of which use 34F2 with saponin adjuvant.[14]
Anthrax vaccines were developed in the Soviet Union in the 1930s and available for use in humans by 1940.[15][16] A live attenuated, unencapsulated spore vaccine became widely used for humans. It was given either by scarification or subcutaneous injection (only in emergency)[14] and its developers claimed that it was reasonably well tolerated and showed some degree of protective efficacy against cutaneous anthrax in clinical field trials.[16] The efficacy of the live Russian vaccine was reported to have been greater than that of either of the killed British or US anthrax vaccines (AVP and AVA, respectively)[17][18][19][20] during the 1970s and '80s. The STI-1 vaccine, consisting only of freeze-dried spores,[14] is given in a two-dose schedule, but serious side-effects restricted its use to healthy adults.[21] It was reportedly manufactured at theGeorge Eliava Institute of Bacteriophage, Microbiology and Virology inTbilisi, Georgia, until 1991.[22] As of 2008, the STI-1 vaccine remains available, and is the only human anthrax vaccine "nominally available outside national borders".[14]
China uses a different live attenuated strain for their human vaccines, designated "A16R". The A16R vaccine is given as a suspention in 50% glycerol and distilled water. A single dose is given by scarification, followed by a booster in 6 or 12 months, then annual boosters.[14]
British biochemistHarry Smith (1921–2011), working for the UK bio-weapons program atPorton Down, discovered the threeanthrax toxins in 1948. This discovery was the basis of the next generation of antigenic anthrax vaccines and for modernantitoxins to anthrax.[23] The widely used British anthrax vaccine—sometimes called Anthrax Vaccine Precipitated (AVP) to distinguish it from the similar AVA (see below)—became available for human use in 1954. This was a cell-free vaccine in distinction to the live-cell Pasteur-style vaccine previously used for veterinary purposes.[24] It is now manufactured by Porton Biopharma Ltd, a Company owned by the UK Department of Health.
AVP is administered at primovaccination in three doses with a booster dose after six months. The active ingredient is a sterile filtrate of analum-precipitated anthrax antigen from the Sterne strain in a solution for injection. The other ingredients arealuminium potassium sulphate,sodium chloride and purified water. The preservative isthiomersal (0.005%). The vaccine is given by intramuscular injection and the primary course of four single injections (3 injections 3 weeks apart, followed by a 6-month dose) is followed by a single booster dose given once a year. During theGulf War (1990–1991), UK military personnel were given AVP concomitantly with thepertussis vaccine as an adjuvant to improve overall immune response and efficacy.
TheUnited States undertook basic research directed at producing a new anthrax vaccine during the 1950s and '60s. Research under the auspices of the US Army at Fort Detrick in Frederick, MD was led by George G. Wright and Milton Puziss.[25] The Wright/Puziss vaccine, known asAnthrax Vaccine Adsorbed (AVA)—trade nameBioThrax—was licensed in 1970 by the U.S.National Institutes of Health (NIH) and in 1972 theFood and Drug Administration (FDA) took over responsibility for vaccine licensure and oversight. AVA is produced from culture filtrates of an avirulent, nonencapsulated mutant of theB. anthracis Vollum strain known as V770-NP1-R.[26] No living organisms are present in the vaccine which results in protective immunity after 3 to 6 doses.[26] AVA remains the only FDA-licensed human anthrax vaccine in theUnited States and is produced byEmergent BioSolutions, formerly known asBioPort Corporation inLansing, Michigan. The principal purchasers of the vaccine in the United States are theDepartment of Defense andDepartment of Health and Human Services. Ten million doses of AVA have been purchased for the U.S.Strategic National Stockpile for use in the event of a massbioterrorist anthrax attack.
In 1997, the Clinton administration initiated theAnthrax Vaccine Immunization Program (AVIP), under which active U.S. service personnel were to be immunized with the vaccine. Controversy ensued since vaccination was mandatory andGAO published reports that questioned the safety and efficacy of AVA, causing sometimes serious side effects.[27] A Congressional report also questioned the safety and efficacy of the vaccine and challenged the legality of mandatory inoculations.[28] Mandatory vaccinations were halted in 2004 by a formal legal injunction which made numerous substantive challenges regarding the vaccine and its safety.[29] After reviewing extensive scientific evidence, the FDA determined in 2005 that AVA is safe and effective as licensed for the prevention of anthrax, regardless of the route of exposure. In 2006, the Defense Department announced the reinstatement of mandatory anthrax vaccinations for more than 200,000 troops and defense contractors. The vaccinations are required for most U.S. military units and civilian contractors assigned to homelandbioterrorism defense or deployed inIraq,Afghanistan orSouth Korea.[30]
A number of experimental anthrax vaccines are undergoing pre-clinical testing, notably theBacillus anthracis protective antigen—known as PA (seeAnthrax toxin—combined with variousadjuvants such asaluminum hydroxide (Alhydrogel),saponinQS-21, and monophosphoryl lipid A (MPL) insqualene/lecithin/Tween 80 emulsion (SLT). One dose of each formulation has provided significant protection (> 90%) against inhalational anthrax inrhesus macaques.
Fortunately, Pasteur's colleagues Chamberlain [sic] and Roux followed up the results of a research physician Jean-Joseph-Henri Toussaint, who had reported a year earlier that carbolic-acid/heated anthrax serum would immunize against anthrax. These results were difficult to reproduce and discarded although, as it turned out, Toussaint had been on the right track. This led Pasteur and his assistants to substitute an anthrax vaccine prepared by a method similar to that of Toussaint and different from what Pasteur had announced.
