Complement Evasion in Borrelia spirochetes: Mechanisms and Opportunities for Intervention

Lyme disease (LD) is an increasingly prevalent, climate change-accelerated, vector-borne infectious disease with significant morbidity and cost in a proportion of patients who experience ongoing symptoms after antibiotic treatment, a condition known as post-treatment Lyme disease syndrome (PTLDS). Spirochetal bacteria of Borrelia species are the causative agents of LD. These obligate parasites have evolved sophisticated immune evasion mechanisms, including the ability to defeat the innate immune system's complement cascade. Research on complement function and Borrelia evasion mechanisms, focusing on human disease, is reviewed, highlighting opportunities to build on existing knowledge. Implications for the development of new antibiotic therapies having the potential to prevent or cure PTLDS are discussed. It is noted that a therapy enabling the complement system to effectively counter Borrelia might have lower cost and fewer side-effects and risks than broad-spectrum antibiotic use and could avert the need to develop and administer a vaccine.