A research team led by Professor Peter Kraiczy at Universitätsmedizin Frankfurt and Goethe University announced on June 10 the identification of five closely related proteins crucial for the survival of Borrelia recurrentis, the bacterium responsible for louse-borne relapsing fever. The disease is transmitted by body lice and can be fatal in up to 20 percent of untreated cases, especially in areas lacking comprehensive medical care.
Louse-borne relapsing fever, first described by Hippocrates, presents with recurring episodes of high fever. It is classified as a poverty-related neglected disease. While major outbreaks occurred in Europe during the last century, current sporadic outbreaks are reported around the Horn of Africa, including Eritrea, Ethiopia, Somalia, and South Sudan. Infected body lice have not been found in Europe according to individual studies; however, increased diagnoses among refugees brought attention to the disease in European countries in 2015.
The identified Chi proteins are considered homologous and appear to have evolved from a common ancestor. These proteins bind specifically to blood proteins and prevent activation of the human complement system—a key part of innate immunity—thus protecting Borrelia recurrentis from being marked and destroyed by immune cells. Additionally, Chi proteins can bind plasminogen and convert it into active plasmin.
Kraiczy said, "We know from other pathogens that they use the body's own plasmin to invade tissues. Together with the ability of the Chi proteins to block the complement system, this gives Borrelia recurrentis significant advantages in surviving and spreading after entering the human body." Based on these findings, diagnostic tests have already been developed by Kraiczy's team for faster identification of infections.
Kraiczy said, "Fever of unknown origin occurs in many infectious diseases, so pathogen-specific tests make it possible to quickly initiate the appropriate antibiotic treatment against the causative agent. We have already made considerable progress in this area and are currently conducting studies in Kenya and Nigeria using serological tests developed in our laboratory." He also said vaccines targeting these proteins could help prepare for future epidemics: "Although European body lice do not currently carry the pathogen, we must assume that future unrest and crises may once again lead to infected individuals arriving in Europe and introducing infected body lice... which could then trigger disease outbreaks here."
The research was funded by Hesse’s LOEWE Center DRUID (Novel Drug Targets against Poverty-related and Neglected Tropical Infectious Diseases) between 2018 and 2024 with a goal to advance research at Hessian universities against neglected tropical diseases.
