EuFMD OS20

1. Introduction
L. Comtet1, A. Carpentier1, F. Donnet1, P. Pourquier1
1 IDvet, FRANCE
Foot and mouth disease (FMD) is one of the most contagious transboundary animal diseases. FMD may be
controlled by zoosanitary measures and vaccination; but this is difficult to do due to the existence of
multiple serotypes (O, A, C, Asia 1, SAT 1,2,3) of the causative virus and the lack of cross-protection
between them.
In a context of an emergency outbreak management in non-vaccinated areas, structural protein (SP)-based
tests serology may be preferred, implying the use of Solid Phase Blocking ELISAs (SPBE) ELISAs related to
the serotype causing the outbreak. Even though many research is being done to understand and predict
the patterns of viral emergence, the risk of an unexpected serotype cannot be excluded.
In this study, we describe the preliminary performance evaluation of a SP pan-serotype SPBE that could
potentially solve these problems.
The specificity was evaluated by testing 264 naïve samples(176 cattle and 88 swine ) from a non-
endemic and unvaccinated area.
The pan-serotype SPBE prototype ELISA kit:
shows high specificity
is able to detect specifically FMVD SP-antibodies regardless of
serotype
has a good analytical specificity, as all SVDV-positive sera tested
were found negative
could be of particular interest for emergency outbreak
management in disease-free and non-vaccinated areas
More validation data is needed to assess test diagnostic sensitivity and
the seroconversion detection window. These preliminary results indicate
the possible use of a pan-serotype SPBE kit for the specific detection of
SP antibodies.
Results
►Specificity
Test principle
Samples to be tested and controls are added to microwells coated with non-infectious FMDV antigen. After washing, an anti pan-serotype monoclonal antibody labeled with horseradish peroxidase (HRP) conjugate
is added. After washes, the substrate solution (TMB) is added and OD ar read at at 450 nm.
For each sample, the S/N % is calculated: ODsample / ODNegativeControl. . Samples with a S/N% <50% are considered as positive.
• Measured specificity for the pan-serotype ELISA = 99.6% (CI95%: 97.88% - 99.93%), n=264
Inclusivity was evaluated by testing infected cattle (from FAO/IAEA) including sera against FMDV
serotypes.
Exclusivity was tested with 5 swine SVDV positive sera, which were previously tested positive with the
IDScreen® SVD Competition ELISA.
Evaluation with infected sera from Vesicular Stomatitis Viruses (VSV) in on-going.
► Inclusivity and exclusivity
• The SP pan-serotype SPBE kit detects all FMD positive sera tested regardless of serotype,
demonstrating a high inclusivity.
Note: Serum containing anti-C FMDV antibodies has still to be tested.
• Despite the small number of samples tested, all SVDV positive sera were found negative,
suggesting high exclusivity of the ELISA.
► Analytical sensitivity
A pan-serotype SPBE prototype for detection of structural protein antibodies:
a solution for emergency supply of FMD SP diagnostic kits?
DISEASE SPECIES SEROTYPE STATUS NUMBER OF SAMPLES TOTAL
FMD
Swine &
cattle
O Positive 5/5
21/21
A Positive 3/3
Asia1 Positive 4/4
SAT 1 Positive 3/3
SAT 2 Positive 3/3
SAT 3 Positive 3/3
SVD Swine NA Negative 5/5 5/5
IDvet, 310 rue Louis Pasteur, 34790 Grabels – France . www.id-vet.com . info@id-vet.com
Conclusion
NA: Not Applicable
ID Screen® FMD competition SP
SPBE cELISA test
Last positive dilution
pan-serotype
Cut Off = 50%
Homologous
serotype cELISA kit
pan-serotype
Cut Off = 50%
Homologous O
serotype
Sample Species Serotype
dilutions
tested
S/N %
Sta
tut
S/N % Statut S/N % Statut S/N % Statut
Sample 1 Swine O
Pur 13 (+) 8 (+)
1:5 1:5
1:5 37 (+) 20 (+)
1:25 100 (-) 55 (-)
1:125 105 (-) 95 (-)
Sample 2 Cattle O
Pur 44 (+) 30 (+)
neat neat
1:5 69 (-) 46 (-)
1:25 94 (-) 80 (-)
1:125 100 (-) 96 (-)
Sample 3
Cattle O
Pur 5 (+) 6 (+)
1:25 1:25
1:5 23 (+) 15 (+)
1:25 45 (+) 31 (+)
1:125 70 (-) 56 (-)
Sample 4 Swine A
pur 40 (+) 11 (+)
1:5 1:25
1:5 47 (+) 20 (+)
1:25 66 (-) 36 (+)
1:125 94 (-) 81 (-)
Sample 5 Swine A
Pur 4 (+) 15 (+)
1:25 1:25
1:5 8 (+) 33 (+)
1:25 34 (+) 48 (+)
1:125 79 (-) 82 (-)
Sample 6
Cattle A
Pur 12 (+) 18 (+)
1:25 1:25
1:5 24 (+) 30 (+)
1:25 45 (+) 44 (+)
1:125 66 (-) 71 (-)
Sample 7 Swine Asia1
pur 9 (+) 14 (+)
1:5 1:5
1:5 44 (+) 46 (+)
1:25 92 (-) 83 (-)
1:125 100 (-) 97 (-)
Sample 8 Cattle Asia1
Pur 8 (+) 4 (+)
1:25 1:25
1:5 12 (+) 9 (+)
1:25 40 (+) 28 (+)
1:125 80 (-) 69 (-)
Sample 9
Swine
Asia1
Pur 2 (+) 6 (+)
1:25 1:25
1:5 12 (+) 18 (+)
1:25 36 (+) 46 (+)
1:125 64 (-) 75 (-)
Analytical sensitivity was assessed by testing in parallel the new panFMD serotype SPBE test and the SP-
serotype specific SPBEs homologous to the serotype of vaccination/immunization test: either
ID Screen® FMD Type O, ID Screen® FMD Type A, ID Screen® FMD Type Asia1 (IDvet, Grabels, France),
Samples tested for this study were serial dilutions of monovalent positive sera from vaccinated or
experimentally immunized animals.
The table below compares the results obtained and the last positive dilution for 9 monovalent samples
with the homologous ID Screen® SP-SPBE:
• The pan-serotype SP SPBE cELISA shows globally comparable analytical sensitivity compared
to the homologous serotype-specific ID Screen® SP-SPBE, regardless of the serotype tested.
Species
Specificity
(number of samples)
CI95%
Swine 100% (88 / 88) 95.82 % - 100 %
Cattle 99.4% (175 / 176) 96.85 % - 99.90 %
TOTAL 99.6% (243 / 244 ) 97.88 % - 99.93 %
Collaboration for field studies
welcome. Contact:
loic.comtet@id-vet.com
and
alix.carpentier@id-vet.com
IDvet team & facilities
Acknowledgements: IDvet would like to thank Sciensano, Brussels, Belgium.