CORDIS provides links to public deliverables and publications of HORIZON projects.
Links to deliverables and publications from FP7 projects, as well as links to some specific result types such as dataset and software, are dynamically retrieved from OpenAIRE .
Deliverables
Currently, the detection of specific antibodies (serology) is used to detect individuals that harbour persistent Small Ruminant Lentivirus infections (SRLV). However, some animals fail to produce such antibodies and thus escape detection. This project aims to develop a test (PCR) that detects the genetic material of the virus instead of antibodies against it. The SRLVs in Europe and other parts of the world are known for their genetic heterogeneity. European tests that detect the virus genetic material must therefore encompass this heterogeneity. We studied a part of the viral genome of a number of European strains in order to identify homogenous sites that can serve as a uniform target for a PCR-test, i.e. the potential primer/probe sites. Results were combined with the limited genetic information that already existed in the literature; 3 different primer/probe combinations with the potential for encompassing the heterogeneity could be established, leading to 3 of the prototype tests.
Before this project, some of the RTD-partners had already developed SRLV-PCR tests on a local basis. The European potential of these tests was evaluated by exchanging small sets of - blinded- local samples between these partners. It appeared that three of these local tests which target different parts of the viral genome happened to have the potential of encompassing the European SRLV genetic heterogeneity. The consortium decided to also include these 3 tests in the set of prototype tests, leading to a total of 6 prototype tests. Early February 2003, the consortium decided on the exact nature of the 6 prototype tests that have been produced by one of the SME-partners and whose performance on European sheep/goat blood samples has been compared in each RTD laboratory using the specially collected local sample banks.
Two prototypes have been developed in the scope of SRLV-Control project. One prototype is specific for goats and the other is specific for sheep. Further developments are necessary in order to improve the sensitivity of both of them. However, these prototypes already allow to detect the viruses in false sero-negative animals. The reliability of these tests is to be further tested.
The new kit is a great interest for the actors of goat and sheep field: For the semen producers, the first effect of the project will be to know earlier if the young bucks are infected or not, reduce the quarantine delay that has to be respected today, and the time to be waited before use of the semen stocks. It would be an important asset for the development of their business. Considering the potential volume of the market, it is clear that the SMEs will cover a large market.
The sheep/goat breeding SMEs can exploit the results following three principal directions:
- For SRLV-free flocks/herds, the result will enable to keep the health status secured, even if new animals are imported from other flocks.
- For flocks/herds that are almost SRLV-free, it will offer the possibility to efficiently eliminate the last source of infection; i.e. the sero-negative but infected individuals.
- For the infected flocks/herds, it will offer the possibility to detect infection more efficiently and thus accelerate the eradication of the infection.
Because a negative result with this new test is more reliable than the common serology, flocks/herds with an established SRLV-free status will be able to maintain this status at lower cost. For both sheep and goat, an effective control of the infection will enable the safe application of AI, which in itself is essential to the further development of the sector. For the test producer, the test for blood developed in this project will be commercially available to laboratories all over Europe and beyond.
Knowledge of the availability of monocytes in blood:
Monocytes are the only peripheral blood cells carrying the SRLVs -genetic material and it is estimated that this is the case in only 0.1% of these cells. Hence it is of crucial importance to know if these cells, which form a very small part (literature: 0-4%) of the white blood cell fraction, are available in any given blood sample. Studies in goats and sheep of different ages, gender, health and SRLV-infection status demonstrated that every 8ml blood contains a sufficient number of monocytes to allow reliable testing. This means that blood is a reliable (and a practical) substrate for testing.
Expertise with methods to obtain these monocytes:
In view of the low percentage of monocytes carrying the viral genes it is important to obtain all the monocytes from the blood sample in the highest possible concentration. Several options have been compared for efficiency and practicality. It appeared that the best results were obtained by differential centrifugation, yielding a fraction containing lymphocytes and monocytes (PBMCs) followed by separation of the monocytes using their property to engulf particles that can be trapped in a magnetic field. The efficacy of different particles and engulfing conditions was compared, leading to an optimum monocytes collection protocol, which can be maintained as the gold standard method.
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