CRASP: CFP reconstitution across synaptic partners.

Mapping the pattern of connectivity between neurons is widely regarded to be critical for understanding the nervous system. GRASP (GFP reconstitution across synaptic partners) has been used as a promising method for mapping neuronal connectivity, but is currently available in the green color only, limiting its potential applications. Here we demonstrate CRASP (CFP reconstitution across synaptic partners), a cyan-colored version of GRASP. We validated the system in HEK 293T cells, and generated transgenic Drosophila lines to show that the system could reliably detect neuronal contacts in the brain. Furthermore, we showed that the CRASP signal could be selectively amplified using standard immunohistochemistry methods. The CRASP system adds to the toolkit available to researchers for mapping neuronal connectivity, and substantially expands the potential application of GRASP-like strategies.

Structural basis for complement evasion by Lyme disease pathogen Borrelia burgdorferi.

Borrelia burgdorferi spirochetes that cause Lyme borreliosis survive for a long time in human serum because they successfully evade the complement system, an important arm of innate immunity. The outer surface protein E (OspE) of B. burgdorferi is needed for this because it recruits complement regulator factor H (FH) onto the bacterial surface to evade complement-mediated cell lysis. To understand this process at the molecular level, we used a structural approach. First, we solved the solution structure of OspE by NMR, revealing a fold that has not been seen before in proteins involved in complement regulation. Next, we solved the x-ray structure of the complex between OspE and the FH C-terminal domains 19 and 20 (FH19-20) at 2.83 Å resolution. The structure shows that OspE binds FH19-20 in a way similar to, but not identical with, that used by endothelial cells to bind FH via glycosaminoglycans. The observed interaction of OspE with FH19-20 allows the full function of FH in down-regulation of complement activation on the bacteria. This reveals the molecular basis for how B. burgdorferi evades innate immunity and suggests how OspE could be used as a potential vaccine antigen.

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.