Effects of gamma radiation on Brugia malayi infective larvae and their intracellular Wolbachia bacteria

Abstract

Prior studies have shown that irradiated filarial larvae are developmentally stunted but capable of inducing partial immunity to filariasis in animals. The mechanisms for these effects are poorly understood. Recent studies suggest that intracellular Wolbachia bacteria are necessary for the normal development, reproduction and survival of filarial nematodes. The purpose of this study was to examine the effects of irradiation on Wolbachia in Brugia malayi infective larvae (L3) and on L3 development. The L3 were exposed to 0, 25, 35, 45, 55, 65 or 75 krad of gamma irradiation from a (137) Cesium source and cultured in vitro at 37 degrees C in NCTC/IMDM medium with 10% FCS for 12 days. Irradiation prevented molting of L3 to the L4 stage in a dose-dependent manner. Electron microscopy studies showed that irradiation damaged Wolbachia (25 krad) or cleared them from worm tissues (45 krad). In addition, majority of the irradiated L3s failed to develop the L4 cuticle. Real-time PCR studies showed that irradiation reduced Wolbachia DNA in worm tissues. Parallel in vivo studies confirmed decreased development of irradiated L3 in jirds, with associated effects on Wolbachia. Jirds injected s.c with normal L3 developed antibodies to Wolbachia surface protein (wsp) shortly after the onset of microfilarial patency. In contrast, jirds injected with irradiated L3 did not develop microfilaremia or antibodies to wsp. Additional studies are needed to test the hypothesis that irradiation retards growth and development of filarial L3 by killing Wolbachia.

Cyclic Lipopeptides from Bacillus subtilis ABS–S14 Elicit Defense-Related Gene Expression in Citrus Fruit

“…Linear regression analysis was conducted using the Microsoft Excel program. The PCR efficiency for each primer pair was calculated by the equation E% = (10 1/slope−1 )×100 [18] . The slope was obtained from linear regression of standard curve.…”

Cytokine profiles of filarial granulomas in jirds infected with Brugia pahangi

“…Water was used as a negative control in a PCR. For the detection of Wolbachia 16S rDNA, sequence specific primers were employed and the PCR products were analysed by gel electrophoresis [ 29 ].…”

Wolbachia in filarial parasites: Targets for filarial infection and disease control

“…Interestingly, these processes are particularly susceptible to antibiotic treatment. In addition, molting and embryogenesis have also been shown to be impaired following exposure to gamma radiation, which again, was associated with the depletion of Wolbachia [16,17].…”