Diagnostic Peptide Epitope for Lyme Disease Identified with ProArray Ultra®

Outer Surface Protein C Peptide Derived from Borrelia burgdorferi Sensu Stricto as a Target for Serodiagnosis of Early Lyme Disease.

Arnaboldi PM, et al. (2013). Outer Surface Protein C Peptide Derived from Borrelia burgdorferi Sensu Stricto as a Target for Serodiagnosis of Early Lyme Disease. Clin Vaccine Immunol. 20(4):474-81. [PubMedID: 23365204]

Dr. Paul Arnaboldi and his colleagues at New York Medical College have used ProImmune’s ProArray Ultra® assay service to identify the bacterial peptide epitope OspC1, which could form the basis of a new and more accurate assay for diagnosing early-stage Lyme disease.

Lyme disease is endemic in many regions of North America and Europe, spread by ticks of the genus Ixodes which carry Borrelia bacteria . If untreated it can lead to permanent neurological and musculoskeletal damage, but early-stage infection can be resolved with a course of antibiotics. Early identification and treatment is therefore critical to patient outcome, but clinical diagnosis is limited by Lyme’s varying and non-specific symptoms. Diagnosis instead relies on detecting antibodies against the bacterium or bacterial proteins in serological assays, as the presence of the Borreliabacterium itself cannot be detected by classic microbiologic methods.

The current two-tier assay used for Lyme diagnosis, an ELISA followed by a western blot, is unreliable at detecting early infection. The target proteins lack in both sensitivity and specificity, with significant sequence variation and a high level of cross-reactivity with antigens from other bacteria. The assay combination fails to identify the presence of early Lyme in up to 50% of cases. Arnaboldi’s team hope to identify at least five peptide epitopes which are both highly specific to Borrelia and highly conserved, and thereby develop a sensitive multi-peptide diagnostic assay which will detect the presence of human-generated antibodies against Lyme.

Image description: An Ixodes genus tick being removed with forceps from a glass vial

The team focused on the Borrelia surface protein OspC as a potential source of epitopes. OspC was chosen as it is required for bacterial transmission from ticks to humans, and therefore is always present in Lyme infection. However, there is a high degree of variation within the sequence of the protein as a whole. Arnaboldi chose to use the ProArray Ultra® assay service to investigate whether the OspC protein contained any epitopes which were highly conserved in Borrelia and provoked an antibody response from sera of Lyme-infected patients.

ProArray Ultra® rapidly identified potential epitopes

ProImmune synthesised a library of 37 overlapping 15-mer peptides from the OspC sequence and performed linear epitope mapping using ProArray Ultra®. This flexible peptide microarray has more than 30,000 features per slide, and is capable of detecting thousands of ligand interactions simultaneously. The peptides were screened against sera samples from eight patients which were known to contain antibodies against Borrelia, and positive antibody binding was detected using fluorochrome-labelled secondary antibodies. From the data generated from ProArray Ultra®, Arnaboldi and colleagues were able to identify three peptides which bound to over 50% of the Lyme samples, with the entire process taking place over just five weeks.

Subsequent ELISAs confirmed that one of these epitopes, OspC1, positively detects Lyme in over 75% of early Lyme patients and is highly conserved. It is therefore a good candidate to form part of an assay to reliably detect early-stage Lyme and ensure timely treatment of the disease. Arnaboldi hopes to identify several more of these highly specific, conserved Borrelia epitopes, for an assay with high diagnostic specificity which could significantly improve the ability to diagnose Lyme disease, and increase positive patient outcomes.