The Culex approximation

I woke to a high pitch whine in my ear.

Springing immediately from the bed, I set to work. Every mosquito in that room was going to die! It was the early hours of the morning in a hotel at Ma’ale HaHamisha, just outside Jerusalem. I wasn’t at all sure if I was in West Nile Virus territory or not. I was however quite sure that there would be no sleep if action was not swift and spiteful.

Frozen still and primed for action, I waited for the whispered scream of mosquito taking flight. One of them made a dive – I thrashed at it with a bath towel…CRACK!

The blood spatter against the wall screamed success, but was disappointing on a personal level. Sure enough, I could see several inflamed bites across my torso. Teeth clenched, resolve strengthened – the hunt resumed. Another lunged in my direction. I flailed and gyrated, knuckles bleached white with intent.

A lunatic engaged in a fist fight with a fly – I caught a glimpse of myself in the mirror.

It wasn’t pretty, nor was it effective. Several minutes passed as I stalked the perimeter of the room. I could hear at least one, probably several more, but couldn’t put eyes on them. It seemed likely that others had successfully scrounged a meal from me, and were perhaps looking for a mate. Amazingly, the males and females of many mosquito species have very different flying tones. They actually identify each other through the combined harmonic note created by their own distinctive sounds blending together (Arthur et al., 2014). Genuinely fascinating, but-there-was-no-time-for-that-CRAAAAACK!

That was end of the line for another she-devil. More blood.

Six mosquitoes paid the ultimate price that night, only one of which had not fed on me – probably a male (they don’t bite). I spent a few minutes studying their crumpled bodies, legs fractured and askew. I tried to identify the species. Conceding eventually that I knew absolutely nothing about such things, I reverted to web images, and was satisfied with a fairly convincing Culex approximation.

I rifled through my personal effects, and scrawled a mostly serious note in my diary for two weeks hence – “check for neurological disease”. Satisfied that I had done everything that could be done, I got back into bed.

At breakfast that morning, I could see that my fellow conference-goers had not fared well at all. Angry red bites ruptured from arms and legs. We shared stories about late night blood-feeding raids and talked about the scourge of mosquito-borne diseases in general. Eventually we discussed genetic approaches to insect control, and Oxitec…

Oxitec – breaking the PR mould

pr brazil
Shopping mall pop-ups engage the public in Brazil (Oxitec Ltd)

“Let him come into your house
He’s the solution
Aedes transgenic mosquito
It’s not a ‘muriçoca’, no.

He fights dengue
And doesn’t sting anyone
Protects your health
This is a mosquito of good.

Hello mummy, hello daddy,
Clever family stops and thinks.
Aedes transgenic project,
This one makes the difference

Aedes transgenic project,
This one makes the difference

Yes, it’s like that my people, to fight dengue.
Aedes transgenic project makes the difference!

Aedes transgenic project,
This one makes the difference”

(Moscamed / Oxitec song – played during OX513A friendly mosquito release)

Oxitec have broken the mould when it comes to public engagement in biotech.

Vans play happy-go-lucky jingles, market stalls trade in sci-comm, and the CEO operates a never-say-no interview policy…

Complete transparency. It could never have worked any other way.

When you’ve developed a genetically engineered, fluorescent, living insecticide that you need to release into open air – you move slowly, deliberately, visibly.

Oxitec colour marker and wild mosquito no marker
The lower two Aedes aegypti larvae are genetically engineered OX513A. The fluorescent marker allows scientists to track movement of the mosquitoes in real time (Oxitec Ltd)

Although the technology employed by Oxitec (originally developed by academic founder, Prof Luke Alphey, now at the Pirbright institute) is newer, smarter, more effective – it is based on an older ‘sterile insect technique’ that relied upon irradiation of male mosquitoes (Alphey et al., 2010).

High energy ionizing radiation triggers DNA breaks that result in random mutations and rearrangements – radically altering the genome. The males are neutered, genetically.

With just the right dose, the mutant flies can make it for long enough after release to mate with a female. Ultimately, females that mate with irradiated males produced fewer eggs. Unsurprisingly though, the irradiated males aren’t up to much in terms of competing with their native competitors. It works, but not particularly well…

The Oxitec approach is based on a genetically engineered ‘tTAV’ gene that is inserted into the mosquito. It is much more effective. tTAV chokes up the cellular machinery, preventing gene expression. It also works through a positive feeback loop. When tTAV is expressed, it will bind to linked ‘tetO operators’ that will steadily and increasingly pump up the volume on tTAV expression and cellular dysregulation. Once that happens, there is no coming back. The mosquito will die. The action is mosquito-specific, and safe according to all regulatory tests and guidelines.

Tetracycline (an antibiotic) inhibits tTAV activity in the laboratory, preventing a population crash during production. When they are released into the environment, they no longer have continuous access to the antibiotic. They have time to find a mate and reproduce, and pass the tTAV gene to the next generation, just before things get very ugly and they all die – engineered friendly males, and all of the offspring.

Insect control by genomic inception (you’ll need to see the Leo DiCaprio film to understand that I expect) – Rachel Carson alluded to it in Silent Spring when discussing approaches to control:

“Some of the most fascinating of the new methods are those that seek to turn the strength of a species against itself, to use the drive of an insect’s life forces to destroy it. The most specialized of these approaches is the male sterilization technique.”

The irradiation approach of the 1970’s was a faint whisper of what was to come. Field trials of the self-limiting OX513A mosquito clock an astonishing 90% kill rate, translating into tangible disease suppression. It is all very impressive. I wanted to see the mosquitoes. So, I put Hadyn Parry’s never-say-no mantra to the test.

Oxitec? Never heard of’em mate…

Pupae emerging V2
An adult Aedes aegypti emerges from the aquatic pupal stage (Oxitec Ltd)

I was heading to Abingdon, just south of Oxford, in a taxi. The driver, Juan, is an Iraqi with a psychology doctorate. He had never heard of Oxitec before. I told him about the genetically engineered mosquitoes, and he was not pleased. What happens when the mosquitoes die and other animals eat them – do they get the toxin. Where does it all end? I had a shot at convincing him, but I don’t think he was persuaded. We agreed to disagree and shook hands. I can only imagine what he’ll be telling folks about the GMO mosquitoes and their toxins, down in Abingdon.

Oxitec HQ is pleasantly situated, beside a small pond and picnic area. Red ivy fades to green around the external brickwork – making the best of a fairly unassuming industrial facade.

“Monday isn’t great for lab visits – we transfer eggs from the adult cages, and females can escape into the lab” – Christa (Oxitec researcher)

It’s a Monday, and I’m walking into a cloud of hungry mosquitoes. Hungry, genetically engineered mosquitoes. I could see several engorged females in the lab, abdomens swollen with their ruby red prize  – some poor sap had been fed upon.

But it wasn’t me…

Sarah (PR sharp-shooter) and Christa are swooping around me with electrified tennis rackets (…really) – ripping mosquitoes out of the air – and there’s me, writing my notes and asking dumb questions, utterly untouchable dystopic-sultan-for-a-day. It felt good. The most dangerous animal on the planet coming for me, and striking out time and again. Whilst I had to run the gauntlet that morning, the females never make it out of the secure culture facility. Multiple barriers, decontamination rooms and electrified sentinels make sure of it.

Only the males see light of day, and they don’t bite. The females need the high-protein diet of blood to produce eggs – the males will gain their sustenance from flower nectar.

Friendly mosquitoes – public health re-imagined 

The real promise of the friendly insect control concept is in responsiveness to new public health emergencies. The unexpected and aggressive emergence of Zika virus for example, coupled to previously unappreciated pathology highlights this. Significant investment was committed to vaccine development, which was then abandoned when the crisis began to subside.

The Sanofi Pasteur-led Zika vaccine project deflated without so much as a whimper on September 1st 2017. The Biomedical Advanced Research and Development Authority (BARDA – within the Department of Health and Human Services) rang the death knell by “de-scoping” (they wanted their money back) the development contract with Sanofi on August 17th. Whilst the Sanofi press release was written with the usual dis-impassioned sterility, you can tell they were not happy – “In February 2016, Sanofi Pasteur urgently responded to the WHO’s declaration of a public-health emergency of international concern (PHEIC). In doing so, we assumed significant opportunity costs and delayed other internal pipeline priorities to lend our expertise to the Zika global public-health threat”.

Large companies refocus their business mission to respond, huge amounts of funding are committed, the plug is pulled, and it all circles the drain…

Oxitec stand in the breach, with an intervention that is demonstrably effective.

Many mosquitoes, especially Aedes aegypti, are extremely promiscuous hosts for a wide range of disease causing agents. One genetically engineered mosquito species can represent a viable intervention for a number of diseases simultaneously. Dengue virus has been the initial target. It infects 50-100 million people each year, with 2.5 billion people at risk annually. Symptoms vary widely from asymptomatic, through flu-like and haemorrhagic fever (think EBOLA) and so-called shock syndrome. Some 500,000 hospitalisations occur due to associated haemorrhagic fever, with a fatality rate of 5% or more. Those that know Dengue best, call it Breakbone fever, with good cause.

Mosquito control for malaria prevention is trickier – several mosquito species can host the Plasmodium parasite. That requires a substantial coordinated effort to control multiple species. Hadyn had a glint in his eye as he told me about plans to go after several Anophleles species simultaneously…

It was a fascinating morning. The ideas and approaches being pioneered at Oxitec are no longer aspirational, they are reality. Their staff are scary-smart and excited to be working there. They are now a fully commercial proposition in Brazil, and trials are ongoing elsewhere. They are also making moves into agriculture and animal welfare.

Oxitec are a lean operation. They have had to be in order to make it through the political and regulatory vortex, without the financial beef of big industry. It is truly remarkable that they have achieved so much in such a small space of time.

I’m officially excited about what comes next for Oxitec, especially following the news of significant new investment and jobs. Oxitec is escalating with intent.

For more information on the Oxitec mosquito, and the diseases that it can indirectly control, check out the video, references and links below…


***If you can’t access the papers – email me and I will send them***

Arthur et al. Mosquito (Aedes aegypti) flight tones: Frequency, harmonicity, spherical spreading, and phase relationships. The Journal of the Acoustical Society of America 2014 Feb; 135(2): 933–941. doi: 10.1121/1.4861233

Alphey et al. Sterile-Insect Methods for Control of Mosquito-Borne Diseases: An Analysis. Vector Borne Zoonotic Dis. 2010 Apr; 10(3): 295–311. doi: 10.1089/vbz.2009.0014

More information on mosquito-borne diseases

More information on the Oxitec mosquito

Keep up to date with Oxitec’s work