Neutrophil accumulation around Onchocerca worms and chemotaxis of neutrophils are dependent on Wolbachia endobacteria

Unlike in many other helminth infections, neutrophilic granulocytes are maj or cellular components in the host's immune response against filarial worms . The pathways that drive the immune response involving neutrophils are unc lear. This study shows that Wolbachia endobacteria (detectable by polyclona l antibodies against endobacterial heat shock protein 60 and catalase and b y polymerase chain reaction being sensitive to doxycycline treatment) are d irect and indirect sources of signals accounting for neutrophil accumulatio n around adult Onchocerca volvulus filariae. Worm nodules from untreated on chocerciasis patients displayed a strong neutrophil infiltrate adjacent to the live adult worms. In contrast, in patients treated with doxycycline to eliminate the endobacteria from O. volvulus and to render the worms sterile , the neutrophil accumulation around live adult filariae was drastically re duced. Neutrophils were absent in worm nodules from the deer filaria Onchoc era flexuosa, a species which does not contain endobacteria. Extracts of O. volvulus extirpated from untreated patients showed neutrophil chemotactic activity and in addition, induced strong TNF-alpha and IL-8 production in h uman monocytes, in contrast to filarial extracts obtained after doxycycline treatment. Thus, neutrophil chemotaxis and activation are induced directly by endobacterial products and also indirectly via chemokine induction by m onocytes. These results show that the neutrophil response is a characterist ic of endobacteria-containing filariae. (C) 2001 Editions scientifiques et medicales Elsevier SAS.