Avacta Group plc has announced it has identified three Affimer proteins capable of binding to a recombinant form of a secreted Zika virus NS1 protein (Non-Structural protein 1), which is diagnostic of Zika virus infection at the early, acute stage.

These Affimer binders were identified and characterised within just thirteen weeks of receiving the virus target and have the potential to be developed into new rapid point-of-care diagnostic tests for Zika infection.

The three Affimer binders are highly specific to the Zika NS1 protein and can differentiate in human serum from five other closely related viruses that give similar symptoms: Dengue, Yellow Fever, West Nile, and Japanese and Tick-borne Encephalitis. Since these viruses are very similar, there is currently no validated antibody that detects Zika virus specifically, which is a limiting factor in the development of a reliable, quick diagnostic test.

The ability to rapidly generate new diagnostic reagents in response to outbreaks of infectious agents is critical to meeting an urgent medical need, as recently evidenced by the SARS and Ebola virus outbreaks. The very high specificity of Avacta’s Affimer technology, together with the speed with which new Affimer binders can be identified and characterised, makes the technology ideal for rapidly responding to the need for detection and monitoring of new outbreaks. The Group intends to commercialise Affimer based rapid diagnostics through co-development and licensing to third party diagnostics developers an example of which is Mologic, a UK rapid diagnostics developer, with whom a research and product development collaboration was recently announced.  

Dr Alastair Smith, Chief Executive Officer, Avacta, said: “Avacta’s Affimer technology offers a distinct advantage over antibodies in infectious disease diagnostics in terms of both rapid development times and specificity. The identification of these three Affimer binders means that new diagnostic tests could be developed that have the potential to diagnose a Zika infection from its early stages, and would be suitable for low cost, rapid point-of-care diagnostics that could be deployed widely in the field or at US transport hubs for example.

At the half year we set out three initial strategic priorities for the Affimer technology, outside of therapeutic applications, in which we believe that the technology has key competitive advantages. Rapid diagnostics is one of those strategic priorities and the news that we have been able to generate highly specific Affimer binders to a significant emerging health threat in such a short space of time is strong validation of those advantages.

The success of this work shows that the Affimer technology is a platform that can be applied more broadly to generate highly specific binders rapidly. We continue to execute our strategy of developing Affimer reagents for third party products as well as developing our in-house therapeutics pipeline focused on immuno-oncology.  I look forward to the next opportunity to update the market.” 

About Zika Virus Diagnostics

The Zika NS1 protein used in the study, together with the other NS1 proteins used for screening, was provided by the Native Antigen Company (https://thenativeantigencompany.com/). This recombinant protein was identified as the best reagent available for the selection of Affimers for Zika diagnostics as it is uniquely produced in mammalian cells, and is therefore chemically and structurally very similar to the native viral antigen. It may also be used as a reference standard in future diagnostic kits.

Existing tests for Zika and the related flaviviruses use PCR to detect the viral DNA or use antigens to detect the patients’ own antibodies raised against the viral infection. PCR tests are only effective for a short period of a few days after symptoms begin and detecting the patients’ antibodies to the virus only work after the immune response has occurred. These tests suffer from cross reactivity when a patient has been infected in the past with another flavivirus and vaccination against one flavivirus, yellow fever for example, can confound the antibody based tests making it appear that the patient has Zika.  NS1 is a protein that is produced by active flaviviruses from the earliest stages of infection and therefore, if it is possible to differentiate between the different NS1 proteins that are specific to each flavivirus, then an effective and specific diagnostic can be developed. The Affimer binders that have been generated by Avacta make this possible for the first time. 

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