Bacterial attenuation and vaccines

Abstract

Virulence attenuation, the ‘weakening’ of the pathogenic ability of an organism that prevents it from causing disease while still remaining alive, constitutes one of the most effective approaches in vaccine development against either bacterial or viral diseases. This technique has the advantage of eliciting good immunological memory responses, as compared to vaccines elaborated with dead bacteria, but also has the drawback of potentially being more dangerous, as some organisms can revert in virulence and cause disease. The phenomenon of virulence attenuation was discovered in the 19th century and still remains currently in use; present studies aim to develop new ways of attenuation, with the goal of generating less virulent bacterial strains that closely resemble the original pathogenic organism, hence capable of eliciting good immunity, but innocuous to the people who receive them as vaccines. The present chapter reviews the use of relevant attenuated bacterial vaccines for the prevention of a variety of diseases, caused by either Gram-positive or Gram-negative bacteria