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Caenorhabditis elegans is a free-living nematode that resides in soil and typically feeds on bacteria. We postulate that haematophagic C. elegans could provide a model to evaluate vaccine responses to intestinal proteins from hematophagous nematode parasites, such as Necator americanus. Human erythrocytes, fluorescently labelled with tetramethylrhodamine succinimidyl ester, demonstrated a stable bright emission and facilitated visualization of feeding events with fluorescent microscopy. C. elegans were observed feeding on erythrocytes and were shown to rupture red blood cells upon capture to release and ingest their contents. In addition, C. elegans survived equally on a diet of erythrocytes. There was no statistically significant difference in survival when compared with a diet of Escherichia coli OP50. The enzymes responsible for the digestion and detoxification of haem and haemoglobin, which are key components of the hookworm vaccine, were found in the C. elegans intestine. These findings support our postulate that free-living nematodes could provide a model for the assessment of neutralizing antibodies to current and future hematophagous parasite vaccine candidates.

Alimentary products of medicinal Lucilia sericata larvae are studied to determine their mechanisms of action, particularly in the contexts of wound debridement and disinfection. Furthermore, the larvae can be applied to patients in contained devices, such as the BioBag (BioMonde). Here, we tested the materials and larval content of the most commonly used BioBag (the “BB-50”) to explore the possibility that endotoxins may be contributing to the bio-activity of the product, given that endotoxins are potent stimulants of cellular activation. Using standardised protocols to collect larval alimentary products (LAP), we proceeded to determine residual endotoxin levels in LAP derived from the BioBag, before and after the neutralisation of interfering enzymatic activity. The BB-50 device and its associated larval content was not a significant source of LPS activity. However, it is clear from these experiments that a failure to remove the confounding serine proteinase activity would have resulted in spuriously high and erroneous results. The residual LPS levels detected are unlikely to be active in wound healing assays, following cross-referencing to publications where LPS at much higher levels has been shown to have positive and negative effects on processes associated with wound repair and tissue regeneration.

Lucilia sericata Meigen (Diptera: Calliphoridae) larvae are manufactured worldwide for the treatment of chronic wounds. Published research has confirmed that the primary clinical effect of the product, debridement (the degradation of non-viable wound tissue), is accomplished by a range of enzymes released by the larvae during feeding. The quality assessment of larval activity is currently achieved during production using meat-based assays, which monitor insect growth and/or the reduction in substrate mass. To support this, we have developed a complementary radial-diffusion enzymatic assay (RDEA) to produce a visual and measureable indication of the activity of larval alimentary products (LAP) collected under standardised conditions, against a gelatin substrate. Using basic laboratory equipment and reagents, the assay is rapid and suited to high-throughput. Assay reproducibility is high (SD 0.06 - 0.27, CV 0.75 - 4.31%) and the LAP collection procedure does not adversely affect larval survival (mortality < 2%). As a cost- and time-effective method, it is suited to academic or industrial use, supporting good manufacturing (or laboratory) practice (GMP and GLP) as a quality control (QC) assay.