Genetically-modified larvae may reduce animal testing

Using moth larvae to test the efficacy of antibiotics could dramatically cut the number of animals used in laboratory testing, according to British researchers.

BioSystems Technologies Ltd, founded by two University of Exeter scientists, have genome sequenced a colony of Galleria mellonella wax moths, which they sell under the brand name TruLarv to other researchers.

Molecular biologist Dr Olivia Champion, the company's founder and CEO, says the moth larvae offer an inexpensive, ethical, alternative to mammal testing.

Initial tests at Exeter, partnered by contract research organisation Envigo, suggest that moth larvae can successfully be used to test for toxicity of chemicals.

In a separate partnership, with drug discovery company Demuris, the company hopes to see whether larvae could be a fast, cheaper, way to test leads in the urgent hunt for new antibiotic compounds.

Moth larvae have been known to have such potential for some years, but until now, Champion says their genetic variability and the use of antibiotics and hormones by commercial breeders has made accurate testing all but impossible.

She told Reuters: "Beforehand everybody who used the larvae had to buy them as fishing bait. They would have to go online to tackle shops or stop off at their local pet shops and buy 'tubs of grubs' that they used in their labs for research. Obviously, as a scientist, that's introducing into your research an unacceptable level of variability. So the larvae were different ages, they were different weights, they were quite dirty, they were contaminated on the surface. They weren't from a defined genetic breeding colony, so the actual genetic background of the larvae really differed."

Champion says her team's genetic breeding program is unique and is already helping scientists using TruLarv cut their use of mammals by up to 80 percent.

According to Champion, "we breed them from a defined genetic background. We've genome sequenced the breeding colony, and so we know that all the larvae come from the same genetic stock, the larvae are age defined and they're weight defined. They're surface decontaminated, so we know they're not covered in different bacteria and fungi, and also importantly we don't use any antibiotics or hormones or other chemicals in the breeding process."

She says findings from animal tests for the virulence of different bacterial strains correlate to those found in moth larvae testing. Microbes are injected into infection models to determine their relative ability to cause infection. Commonly mammalian animal infection models, such as mice, are used for these tests but TruLarv are now replacing mammals for these studies as the results obtained in larvae reflect the results from mammals.

Individual larva are injected with 10 microlitres of whatever chemical is being tested in the top of their right-hand side pro-leg, a defined injection point that heals once a syringe is withdrawn.

Dr Nicola Senior, BioSystems Technologies Ltd business manager, explained the laboratory process to Reuters, while testing Pseudomonas aeruginosa, an important cause of infection in Cystic fibrosis patients.

She said: "Once we have injected a group of ten larvae for various conditions, then the galleria are put into an incubator at 37 degrees C. We check these at time points of our choosing to see whether there is an effect taking place. With the particular pathogen we're using at the moment we would expect all the galleria to be dead within about 19 hours. So if we come back at that time point and still have live larvae that have been injected with the pathogen and with the extract then we know that the extract is having a protective effect against the action of the pathogen."

The current standard approach in toxicity testing is to use mice, rats or rabbits in the laboratory. By using larvae at early stage tests, promising leads could then be used on mammals, after ineffective or toxic samples are weeded out.

Champion says that in addition to the ethical benefits, using moth larvae offers financial and efficiency savings also.

"It's actually really expensive to work with mice or with other mammals," she said. "If you're a research institution you spend a huge amount of grant income on actually carrying out the experiments in mammals and research larvae - the larvae that we produce - are a fraction of the cost of working with mammals, and so you can actually screen huge panels of potential antibiotics for example and you can screen them at an early stage, and you can identify compounds that may have efficacy, so they actually have activity against a bacterial pathogen, or you can screen compounds for toxicity, and you can't do that scale of an experiment using mammals."

In animal experiments, the attendance of veterinary surgeons is often required, along with technicians dedicated solely to the mammals.

Champion says that experimental data is available within 24 hours of moth larvae experiments. She explained that such testing is not designed to completely replace mammalian testing, but should reduce it dramatically.

Champion set up BioSystems Technologies Ltd with University of Exeter colleague Professor Richard Titball. — Reuters