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

Effects of Gamma and Electron Radiation on the Structural Integrity of Organic Molecules and Macromolecular Biomarkers Measured by Microarray Immunoassays and Their Astrobiological Implications

High-energy ionizing radiation in the form of solar energetic particles and galactic cosmic rays is pervasive on the surface of planetary bodies with thin atmospheres or in space facilities for humans, and it may seriously affect the chemistry and the structure of organic and biological material. We used fluorescent microarray immunoassays to assess how different doses of electron and gamma radiations affect the stability of target compounds such as biological polymers and small molecules (haptens) conjugated to large proteins. The radiation effect was monitored by measuring the loss in the immunoidentification of the target due to an impaired ability of the antibodies for binding their corresponding irradiated and damaged epitopes (the part of the target molecule to which antibodies bind). Exposure to electron radiation alone was more damaging at low doses (1 kGy) than exposure to gamma radiation alone, but this effect was reversed at the highest radiation dose (500 kGy). Differences in the dose-effect immunoidentification patterns suggested that the amount (dose) and not the type of radiation was the main factor for the cumulative damage on the majority of the assayed molecules. Molecules irradiated with both types of radiation showed a response similar to that of the individual treatments at increasing radiation doses, although the pattern obtained with electrons only was the most similar. The calculated radiolysis constant did not show a unique pattern; it rather suggested a different behavior perhaps associated with the unique structure of each molecule. Although not strictly comparable with extraterrestrial conditions because the irradiations were performed under air and at room temperature, our results may contribute to understanding the effects of ionizing radiation on complex molecules and the search for biomarkers through bioaffinity-based systems in planetary exploration.

Cyclic LIPopeptides from Bacillus subtilis ABS-S14 elicit defense-related gene expression in citrus fruit

Effects of cyclic lipopeptides (CLPs) obtained from Bacillus subtilis ABS-S14 on eliciting defense-related gene transcription and activity of defense-related enzymes; glucanase (GLU), chitinase (CHI), peroxidase (POX) and lipoxygenase (LOX) in Citrus sinensis cv. Valencia fruit were determined. The maximum level of GLU transcripts induced in fruit treated with fengycin was significantly greatest among treatments at 48 h. Surfactin enhanced the LOX and POX transcripts. In parallel, corresponding enzyme activities were correlated with changes in gene expression observed in fruit inoculated with Penicillium digitatum following treatment with individual CLPs. Synergistic effects of fengycin and iturin A, fengycin and surfactin were shown in gene transcript of GLU and CHI, respectively, and surfactin induced POX and LOX gene expression of citrus flavedo without pathogen infection. These results suggest that fengycin and surfactin act as elicitors of defense-related gene expression in “Valencia” fruit following infection.

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

Lymphatic filariasis and onchocerciasis are debilitating diseases caused by parasitic filarial nematodes. These nematodes have evolved a mutualistic symbiosis with intracellular bacteria of the genus Wolbachia, which are required for nematode embryogenesis and survival. The essential role of these bacteria in the biology of the nematode and their demonstrated involvement in the pathogenesis of filariasis make Wolbachia a promising novel chemotherapeutic target for the control of filarial infection and disease. This article reviews the recent findings, which highlight potential processes that form the basis of the symbiosis, the role of Wolbachia in filarial pathogenesis, and the efficacy of Wolbachia-targeted antibiotic chemotherapy in human trials. Future prospects for the development of an anti-Wolbachia treatment regimen suitable for integration into mass drug administration programs are also discussed.

Brugia malayi: Effects of nitazoxanide and tizoxanide on adult worms and microfilariae of filarial nematodes

There is an urgent need for safe and effective antifilarials. Prior studies have shown that the nitazoxanide (NTZ) exhibits broad activity against anaerobic bacteria, protozoa, and certain intestinal helminths. We examined the effects of NTZ and tizoxanide (TZ) on Brugia malayi nematodes in vitro and in vivo. In vitro, NTZ and TZ reduced worm motility and viability in a dose-dependent manner. Worm viability was reduced by 50% with both compounds at 2.5 and 20 microg/ml killed adult worms. NTZ or TZ (5 microg/ml) significantly reduced microfilaria release. These compounds blocked worm's embryogenesis, and decreased microfilarial motility and viability. Treated worms had damaged cuticles and abnormal mitochondria. Wolbachia were not cleared by NTZ or TZ treatment. Neither NTZ nor TZ cleared adult worms or microfilariae in infected gerbils. These results show that NTZ and TZ have potent effects on B. malayi nematodes in vitro. However, they were not effective in vivo.

Effects of radiation (Cobalt-60) on the elimination of Brevipalpus phoenicis (Acari: Tenuipalpidae) Cardinium endosymbiont

Brevipalpus phoenicis (Geijskes) (Acari: Tenuipalpidae) is a polyphagous mite with worldwide distribution and it is also a vector of several plant viruses. In citrus, B. phoenicis transmits Citrus leprosis virus (CiLV), the causal agent of leprosis, a disease that costs millions of dollars per year for its prevention and control. Brevipalpus phoenicis mites reproduce through thelytokous parthenogenesis, producing haploid females. This characteristic is attributable to the presence of an endosymbiont bacterium of the genus Cardinium; however, very little is known about the biological and ecological implications of the presence of this endosymbiont in Brevipalpus mites. In order to investigate the role of Cardinium in the transmission of CiLV to citrus plants, our goal was to eliminate the bacterium from the mite. We assessed the effectiveness of different doses of radiation from a Cobalt-60 source to cure B. phoenicis populations from Cardinium sp. The efficiency of irradiation on the elimination of the endosymbiont was determined by counting the number of females and males obtained in the F(1) generation after irradiation and confirming the presence of the endosymbiont by PCR. Both radiation treatments influenced the oviposition period and the number of eggs laid by irradiated females. Also, irradiation eliminated the Cardinium endosymbiont and increased the number of males in progeny of the exposed populations. Although macroscopic morphological abnormalities were not observed among the treated mites, the mortality was higher compared to the non-irradiated control group.

Cytokine profiles of filarial granulomas in jirds infected with Brugia pahangi

Background

A granulomatous inflammatory response develops in jirds infected subcutaneously or intraperitoneally with filarial nematodes namely Brugia pahangi and B. malayi. Previous studies by light and electron microscopy have shown cellular inflammatory responses in and around these granulomas. Furthermore, the cellular inflammatory responses of granulomas found in the lymphatics and peritoneal cavity appear to be similar. The purpose of this study was to determine the cytokine profiles of granulomas in the peritoneal cavity of B. pahangi-infected jirds and to determine whether the granulomas release any proinflammatory cytokines ex vivo.

Methods

A semiautomated quantitative polymerase chain reaction (Q-PCR) was performed on cDNA prepared from the granulomas of infected jirds to study the species-specific mRNA expression of IL-2, IL-4, IFN-γ, IL-5, and IL-10. Genomic DNA was extracted from the granulomas, and parasite DNA was detected by Q-PCR by amplifying the HhaI repeat sequence. The levels of the inflammation-causing cytokines IL-6 and TNFα that were secreted by the granulomas were measured by cell-based assays.

Results

Florid granulomas showed higher levels of IFN-γ than other cytokines, linking this Th1 cytokine to the granulomatous inflammation that develops in jirds and humans. IL-4 expression was much lower than that of IFN-γ but higher than that of IL-10. A low level of IL-5 mRNA expression was detectable in all granulomas as was the level of IL-2 expression. The levels of the inflammatory cytokines IL-6 and TNFα, secreted by intact granulomas, spontaneously increased by 48 h after culture. Parasite antigen stimulation and subsequent release of IL-6 and TNFα by the granulomas indicated a moderate increase in the levels of these two cytokines. The amplification of the Brugia HhaI repeat DNA and Wolbachia 16S rDNA indicated worm components and bacterial components in the granulomatous tissue.

Conclusion

Granuloma development in filarial infections is a complex process involving cellular reactions responding to parasite/bacteria and their components. The interactions between worm-derived granulomas and their hosts are dynamic and multifaceted. The data collected thus far suggest that the expression profiles of many of the measured cytokines in the lymphoid tissues of Brugia-infected jirds are different from those of the cytokines in granulomas. Moreover, granulomas have the ability to secrete the inflammatory cytokines IL-6 and TNFα.