Relapsing Fever - Vaccine Research

Vaccine Research

There currently is no vaccine against Relapsing fever, but research is on-going. The task to develop a vaccine is very difficult because the spirochetes avoid the immune response of the infected person (or animal)through antigenic variation. Essentially, the pathogen stays one step ahead of antibodies by changing its surface proteins. These surface proteins, called variable major proteins (VMP), are lipoproteins that have only 30-70% sequence in common. This amount of divergence in the amino acid sequence is sufficient to create a new antigenic "identity" for the organism. Antibodies in the blood that are binding to and clearing spirochetes expressing the old VMP do not recognize spirochetes expressing the new VMP. Antigenic variation is a common theme among pathogenic organisms. These include the agents of malaria, gonorrhea, and sleeping sickness. Important questions about antigenic variation are also relevant for such research areas as developing a vaccine against HIV, predicting the next influenza pandemic.