Characterization of molecules associated to the drug-induced adverse reactions in lymphatic filariasis caused by brugia malayi

Abstract

Standard treatment of lymphatic filariasis with diethylcarbamazine (DEC) is effective at killing microfilariae but shows partial macrofilaricidal activity. Moreover, treatment with DEC is associated with systemic, inflammatory-mediated adverse reactions that are thought to be caused by the rapid release of microfilaria material and Wolbachia endosymbiotic bacteria into the blood. We assessed whether a single dose of doxycycline combination with the standard treatment would reduce the incidence of adverse reactions. A total of 44 individuals from Tak province were recruited to the randomized double-blind clinical trial study: 25 received DEC combination with placebo, and 19 received DEC combination with doxycycline. Incidences of adverse reactions were lower in the doxycycline group (45.5%) than in the placebo group (55.8%). Severe reactions only occurred in the DEC combination with placebo group (3 of 25). IL-6 levels and Wolbachia levels in plasma were significantly lower in the doxycycline group (P < 0.05). These results suggested that Wolbachia was associated with the adverse reactions. To evaluate the ability of surface proteins of Wolbachia to induce inflammatory responses associated with the adverse reactions. Purified human monocytes were exposed with Brugia malayi microfilaria (BmMf) antigens, Wolbachia-depleted BmMf antigens, Wolbachia antigens, Wolbachia surface protein (WSP)-depleted Wolbachia antigens, recombinant WSP (rWSP), and recombinant peptidoglycan-associated lipoprotein (rPAL) for 6 hours. The mRNA expression levels of pro-inflammatory cytokines were examined by quantitative RT-PCR. BmMf antigens significantly increased IL-1, IL-6, and TNF- mRNA expression (P<0.05). However, the mRNA expression levels of these cytokines were decreased to normal levels after Wolbachia depletion (P>0.05). Moreover, the significant increases of these cytokines were found when monocytes were exposed with Wolbachia antigens (P<0.05). rWSP could increase mRNA expressions of these cytokines (P<0.05). Surprisingly, the mRNA expression levels of these cytokines still significantly increased after WSP depletion from Wolbachia antigens (P<0.05). rPAL also significantly increased the mRNA expressions of these cytokines (P<0.05). Interestingly, rPAL could induce significantly higher levels of these cytokines than rWSP did (P<0.05). These results suggested that Wolbachia-derived molecules, rather than microfilaria-derived components, are the inducers of pro-inflammatory cytokines associated with the adverse reactions. Moreover, we found that not only WSP, but other Wolbachia-derived molecules, including PAL, could also induce inflammatory responses in patients.