Sensitive PCR Test Detects Early Stage Lyme Disease

The successful treatment of Lyme disease (LD) is contingent on accurate diagnosis. However, current laboratory detection assays lack sensitivity in the early stages of the disease. Since delayed diagnosis of LD can result in high healthcare costs and great suffering to the patient, new highly sensitive tests are needed.

In this regard, investigators at the University of Leicester (United Kingdom) developed an internally controlled quantitative PCR test that targeted the multicopy terminase large subunit (terL) gene encoded by prophages that are only found in LD-causing bacteria. A prophage is a bacteriophage genome inserted and integrated into the circular bacterial DNA chromosome or present as an extrachromosomal plasmid. This is a latent form of a phage, in which the viral genes are present in the bacterium without causing disruption of the bacterial cell.

The newly developed Ter-qPCR test was based on the polymerase chain reaction (PCR), which amplifies small amounts of specific genetic material so that it can be detected. To increase the sensitivity of the test for detection of Borrelia burgdorferi, the causative agents of Lyme disease, the investigators adapted it to be specific for the prophage terL gene. The terL protein helps phages package their DNA.

The diagnostic potential of the Ter-qPCR test was evaluated using a set of blood and serum samples collected from healthy volunteers and individuals who were clinically diagnosed with Lyme disease. Results revealed that the detection limit of the Ter-qPCR test was estimated to be 22 copies, the equivalent of one bacterial cell in a bacteria spiked blood sample. Furthermore, significant quantitative differences were observed in terms of the amount of terL detected in healthy individuals and patients with either early or late Lyme disease.

"Early diagnosis of Lyme disease is absolutely vital in reducing suffering, because early Lyme can be treated, but late Lyme is very difficult to treat," said first author Dr. Jinyu Shan, a researcher in the department of respiratory sciences at the University of Leicester. "Current tests cannot typically detect the low numbers of bacteria in early-stage patient blood samples. Our goal was to design a highly sensitive test to help doctors to identify Lyme disease as early as possible. We are currently working with a commercial partner, and investigating regulatory issues and the potential for a clinical trial for this technology."

The Ter-qPCR test was described in the March 15, 2021, online edition of the journal Frontiers in Microbiology.

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