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TwistDx offers RPA as versatile alternative for veterinary diagnostics

UK firm TwistDx believes its technology can provide a robust alternative to diagnostics developed using polymerase chain reaction (PCR). Animal Pharm editor Joseph Harvey spoke to the company about its burgeoning technology.

Throughout many product categories, animal health is following closely in the footsteps of innovations in human health.

The field of veterinary diagnostics is no different, with both sectors requiring more rapid, easy-to-perform testing in a point-of-care or near-patient environment.

"What has happened in human health is happening in animal health," explained Tony Hill, commercial director at TwistDx. "We're seeing this dynamic in human healthcare where there's been continual growth in point-of-care testing and its driven by the economics of having rapid and accessible diagnostic capability that allows one to make a decision on treatment more rapidly than if you were to send the test away to a lab."

TwistDx – a name signifying the twisted strands of DNA – was founded in 2002 on the basis of its technology – recombinase polymerase amplification (RPA), which it believes is a viable isothermal alternative to PCR.

Mr Hill said: "RPA offers a very versatile alternative to PCR. It can be used in pretty much any application one uses PCR for today. That differentiates RPA from any other isothermal technology that is available. Anywhere you're using PCR, you could be using RPA.

"RPA uses an enzymatic process – a series of proteins that combine with DNA and initiate the replication process, which is all done typically at body temperature. Whereas, with PCR, you require thermocycling.

"RPA is readily deployable in a near-patient setting because the testing does not require any extensive equipment, it's extremely rapid and it's not cold chain-dependent. So it is ideally suited to developing tests in that point-of-need setting."

While PCR cannot be easily performed on a point-of-care basis, another advantage of RPA is its rapid time-to-results (10 minutes compared to traditional PCR's average of one hour). RPA can also be used by operators with little training, said Mr Hill.

Although there are currently around 10 isothermal methods being developed among the diagnostics sector as PCR alternatives, Mr Hill believes "RPA differs because it offers the best combination of low temperature, rapid testing and versatility".

Technique

Typical incubation temperature

Incubation time (mins)

Application versatility

Multiplexing?

RPA

20-45ºc

<10

Real-time fluorescence, lateral flow, next-generation sequencing, single nucleotide polymorphisms, microarray, nesting, e-chem, solid-phase, microfluidics and naked eye

Yes, including unbalanced titer targets

PCR

Thermocycling

20-180

Real-time fluorescence, lateral flow, next-generation sequencing, single nucleotide polymorphisms, microarray, nesting, e-chem, solid-phase, microfluidics and naked eye

Yes

Loop-mediated isothermal amplification (LAMP)

60-65ºc

<60

Real-time fluorescence, lateral flow, gel, turbidity, microfluidics and naked eye

High complexity (multiple primers per assay)

Source: TwistDx

Commercial strategy

In 2010, TwistDx was acquired by US point-of-care diagnostics specialist Alere. At the end of last year, Alere was itself purchased by US healthcare firm Abbott (who sold its animal health assets to Zoetis in 2014).

Cambridge-based TwistDx acts as an R&D arm for Abbott and Alere – it develops human in vitro diagnostics for its parent companies. However, where TwistDx operates independently is in areas outside human in vitro diagnostics.

The firm provide kits on a research-only use label to clients who are developing assays across a very broad variety of fields. TwistDx currently has around 650 customers in 56 different countries. Its target sectors include biodefence and water hygiene.

However, alongside the food and beverage space, TwistDx is heavily focused on clients in the veterinary diagnostics market. In fact, these two markets are where it has the highest amount of scientific publications covering the RPA technology. The firm is aware of over 250 peer-reviewed publications on assays developed with RPA. Around 58 of these detail work on veterinary assays.

While TwistDx licences its technology on an R&D basis, the company has an emerging strategy to partner on a commercial basis.

Mr Hill said: "If somebody wishes to go further with their assay and use it in a commercial function, then they need to have a discussion with us about access to the technology.

"We need to find partners and work with them to use RPA as a core technology to develop a broad range of tests to take out into the veterinary market. That would be a company active in veterinary diagnostics, or a company looking to get into veterinary diagnostics, who already has that access into the marketplace."

Case study of bTB

Mr Hill highlighted one published study that provides a case study of how RPA can be used to help quickly inform veterinary decisions on a point-of-care basis.

Previously, researchers at the UK's University of Nottingham used RPA-based bacteriophage amplification technology to diagnose early bovine tuberculosis (bTB) infection in the peripheral blood of cattle. This acted as an alternative to the current bTB test being used in the UK – a country that is looking for next-generation solutions to slow the spread of bTB.

"Bacteriophage amplification technology is an alternative approach, which exploits bacteriophages that infect and replicate in mycobacterial cells as a surrogate for growth of the bacterium itself," explained TwistDx.

"The species-specific bacteriophages infect only viable mycobacterial cells in a sample, replicate in them and then lyse the bacterial cells, releasing virus and bacterial DNA, target sequences of which can be amplified, traditionally using PCR, and detected."

The scientists said the technology could be adapted for the rapid detection of mycobacterial infections in other species such as goats, pigs and llamas.

The video below gives an overview of the university's work using the RPA technology for bTB diagnosis.

More examples

Among the 250 peer-reviewed publications on RPA are papers covering rapid detection of peste des petits ruminants, porcine epidemic diarrhea virus, carp edema virus, bovine ephemeral fever virus, canine parvovirus 2, African swine fever, Q fever, rabies and a host of other viruses. A database of publications can be searched here.

Mr Hill also highlighted these other RPA case studies:

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