AU-PANVAC Advances Recombinant Antigen Development to Strengthen PPR Diagnostics

 Refining HPPR-bELISA production and exploring diagnostic approaches to support the next stages of PPR eradication.

The African Union Pan African Veterinary Vaccine Centre (AU-PANVAC) is working to refine its HPPR-bELISA assay through the development of a recombinant PPR haemagglutinin (H) protein using a baculovirus expression system. This initiative aims to improve antigen production, strengthen biorisk management and support a more scalable supply of diagnostic kits for African Union Member States.

The current assay uses inactivated PPR vaccine strain Nigeria 75/1 as its antigen source. Activities to clone and express the recombinant H protein have begun, with the objective of developing an alternative antigen for use in ELISA-based diagnostic assays.

Developing a suitable recombinant antigen could reduce dependence on conventional antigen sources and support the expansion of HPPR-bELISA kit production. This would help AU-PANVAC respond to growing diagnostic requirements as countries strengthen surveillance and advance their PPR eradication programmes.

The transition will require assessment of the recombinant antigen’s suitability and validation of the resulting assay’s performance. The intended outcome is a reliable production approach that maintains diagnostic quality while improving the capacity to supply national laboratories.

Alongside assay refinement, AU-PANVAC is exploring diagnostic development relevant to a DIVA strategy Differentiating Infected from Vaccinated Animals. Such a strategy would help distinguish evidence of natural PPR infection from responses associated with vaccination.

This distinction becomes particularly important as vaccination programmes progress and countries seek stronger evidence on whether the virus continues to circulate. A validated DIVA system could support epidemiological surveillance, inform investigations and contribute to the assessment of eradication progress.

However, developing a recombinant H protein antigen does not, by itself, establish that an assay can differentiate infected from vaccinated animals. That capability must be demonstrated through a suitable diagnostic design and validation in relation to the vaccines used. The recombinant antigen work therefore represents a development step, while DIVA remains a research objective requiring further evidence.

From research to tools for Member States

The next stages will focus on assessing antigen expression, evaluating its suitability for ELISA applications and establishing assay performance. Any proposed DIVA application will require specific evaluation using samples with well-characterised infection and vaccination histories.

If successfully developed and validated, these diagnostic advances could provide Member States with additional tools to strengthen surveillance and generate evidence supporting progress towards PPR-free status. Their contribution would complement vaccination records, field investigations and other surveillance findings.

Through this initiative, AU-PANVAC is investing in African diagnostic capacity for both current testing needs and the evolving demands of eradication. More scalable kit production and carefully validated diagnostic innovation can help countries sustain surveillance and build the evidence needed to demonstrate progress.