Is new always better than old? The development of human vaccines for anthrax

TLDR: Recombinant Protective Antigen (rPA), the nontoxic cell-binding component of anthrax lethal toxin, is the principal immunogen of the vaccines currently undergoing human clinical trials and investigators are seeking to identify additional vaccine targets with which to extend the spectrum of protection conferred by rPA.

Abstract: Anthrax is caused by a Gram-positive aerobic spore-forming bacillus called Bacillus anthracis. Although primarily a disease of animals, it can also infect man, sometimes with fatal consequences. As a result of concerns over the illicit use of this organism, considerable effort is focused on the development of therapies capable of conferring protection against anthrax. while effective concerns over the toxicity of the current vaccines have driven the development of second-generation products. Recombinant Protective Antigen (rPA), the nontoxic cell-binding component of anthrax lethal toxin, is the principal immunogen of the vaccines currently undergoing human clinical trials. While these new vaccines are likely to show reduced side effects they will still require multiple needle based dosing and the inclusion of the adjuvant alum which will make them expensive to administer and stockpile. To address these issues, researchers are seeking to develop vaccine formulations capable of stimulating rapid protection following needle-free injection which are stable at room temperature to facilitate stockpiling and mass vaccination programs. Recent concerns over the potential use of molecular biology to engineer vaccine resistant strains has prompted investigators to identify additional vaccine targets with which to extend the spectrum of protection conferred by rPA. While the injection of research dollars has seen a dramatic expansion of the anthrax vaccine field it is sobering to remember that work to develop the current second generation vaccines began around the time of the first gulf war. Almost two decades and millions of dollars later we still do not have a replacement vaccine and even when we do some argue that the spectrum of protection that it confers will not be as broad as the vaccine it replaces. If we are to respond effectively to emerging biological threats we need to develop processes that generate protective vaccines in a meaningful time frame and yield products in months not decades!