Antigenic variation of Borrelia hermsii

Area of Science:

• Microbiology
• Immunology
• Genetics

Background:

• Borrelia hermsii is a bacterial species known to cause relapsing fever.
• Antigenic variation is a key mechanism for immune evasion in many pathogens.
• Understanding the serotype diversity and switching mechanisms of Borrelia hermsii is crucial for disease control.

Purpose of the Study:

• To investigate the serotype diversity of Borrelia hermsii originating from a single organism.
• To determine the rate and conditions of serotype conversion in Borrelia hermsii.
• To assess the spontaneous conversion rate of Borrelia hermsii serotypes.

Main Methods:

• Identification of Borrelia hermsii serotypes using fluoresceinated antisera against cloned organisms.
• Monitoring spirochetemia and serotype changes in infected mice.
• Culturing Borrelia hermsii in vitro to observe spontaneous serotype conversion.

Main Results:

• At least 24 distinct serotypes were identified from a single Borrelia hermsii organism.
• Each serotype demonstrated the ability to convert into seven or more other serotypes.
• Persistent spirochetemia with frequent relapses and constant serotype conversions were observed in mice; spontaneous conversion occurred in vitro at a rate of approximately 10(-4)-10(-3) per cell per generation.

Conclusions:

• Borrelia hermsii possesses a remarkable capacity for antigenic variation, generating extensive serotype diversity from a single progenitor.
• Serotype conversion in Borrelia hermsii is a continuous process, independent of host immune responses or relapsing fever episodes.
• The high rate of spontaneous serotype switching suggests a significant role for this mechanism in the persistence and evolution of Borrelia hermsii.