Question

Bartonella bacilliformis is the causative agent of Carrion's disease, a vector-borne neglected tropical disease endemic to the South American Andes. In the acute phase, known as Oroya fever, the bacteria infect erythrocytes, causing severe hemolytic anemia with a mortality rate of up to 90%. Erythrocyte infection results in hemolysis, contributing to the high mortality rate. Two genes, a porin and a phospholipase, were identified to be essentially involved and represent therefore potential drug targets. It is assumed that prevention of hemolysis might represent a promising anti-virulence strategy to treat Oroya fever patients.

Methods

To prevent hemolysis, we systematically examined a library of 41 known phospholipase inhibitors as well as peptide-based rabbit anti-porin and rabbit anti-phospholipase antibodies in vitro. The hemolytic activity of B. bacilliformis was assessed in a novel in vitro based hemolysis assay using human erythrocytes. Various concentrations of each inhibitor and antibody were tested to determine the optimal hemolysis-inhibitory effect.

Results

Preliminary in vitro results revealed a phospholipase inhibitor reducing hemolysis significantly (68% reduction at a concentration of 10 µM). Furthermore, administration of anti-porin and anti-phospholipase antibodies also reduced hemolysis significantly (porin-antibody: 77%, phospholipase-antibody: 75%).

Conclusions

Our findings indicate that one particular phospholipase inhibitor compound or anti-porin and -phospholipase antibodies may have the potential to prevent hemolysis in vivo. Current efforts are directed to establish an experimental mouse model to verify these findings in vivo. Identification of a hemolysis inhibitor and/or a therapeutic antibody would represent a novel anti-virulence strategy that prevents a key process in the pathogenicity of B. bacilliformis.