Field study conducted in Tunisia to evaluate efficacy of an O-BFS vaccine FAO/OIE Reference Lab for FMD Emiliana Brocchi Institut de la Recherche Vétérinaire de Tunisie - Service Virologie Soufien Sghaier Istituto Zooprofilattico Sperimentale della Lombardia e dell'emilia-romagna Brescia - Italy
Vaccine matching for O/ME-SA/Ind-2001 Performed at WRL Pirbright Field isolate VACCINE STRAIN O-3039 O/TUR/5/09 O Manisa O BFS LIB 1/2013 0,51 >0,84 0,14 LIB 7/2013 >0,85 >0,86 0,16 LIB 17/2013 0,41 0,45 0,14 LIB 22/2013 >0,90 >1,0 0,50 O TUN/01/14 0.27 (VN=182) 0.56 (91) 0.12 (64) 0.15 (72) O ALG/01/14 0.28 (VN=190) 0.49 (82) 0.14 (72) 0.13 (57) NEP 18/2013 NEP 1/2014 SAU 1/2014 UAE 1/2014 UAE 2/2014 Key for results: MATCH (r 1 0.3), NO MATCH (r 1 <0.3), Borderline result (0.28-0.32) In brackets neutralizing titres produced by heterologous vaccine strains 2 JPC REMESA Heraklion 16 th March 2015 Emiliana Brocchi
ObjecBve Predict efficacy of O- BFS vaccine in the Tunisian context METHOD: Evaluate the level of neutralizing anbbodies against the vaccine strain O- BFS and against the FMD circulabng virus in Tunisia (O Tunisia 2014) elicited by one vaccinabon with the O BFS vaccine. Concept: virus neutralizing anbbodies are able to inacbvate virus infecbvity and can be interpreted as esbmate of protecbon. 3 JPC REMESA Heraklion 16 th March 2015 Emiliana Brocchi
Experimental design and criteria Two groups of animals, not exposed to infection, selected for vaccination with O-BFS vaccine Naïve cattle and sheep: non-vaccinated, ideally without maternal antibodies Cattle and sheep previously vaccinated with the Tunisian vaccine (O Manisa + O Tunisa 1999) - five cattle out of 40 and 4 sheeps out of 40 kept as sentinels Sampling scheme Before vaccination (day 0) 5 days post vaccination (5 DPV) : evaluation of early immune-response to vaccine 21 days post-vaccination (21 DPV) : standard time to assess vaccine-induced immune response 4 JPC REMESA Heraklion 16 th March 2015 Emiliana Brocchi
AREAS SELECTED for the vaccination trial OTD MATEUR cattle & sheep prev. vaccinated Beja (cattle) and Medenine (sheep) non-vacc animals
MEDENINE LANDSCAPE SAMPLING
Mateur sheep 7 JPC REMESA Heraklion 16 th March 2015 Emiliana Brocchi
DR. SGHAIER SAMPLING SHEEP in MATEUR 8 JPC REMESA Heraklion 16 th March 2015 Emiliana Brocchi
9 PROF. HAMMAMI VACCINATING SHEEP in MATEUR JPC REMESA Heraklion 16 th March 2015 Emiliana Brocchi
11 JPC REMESA Heraklion 16 th March 2015 Emiliana Brocchi
Testing scheme Parallel titration of sera by Virus Neutralization Test (VNT) against both: Ø the vaccine strain O-BFS (homologous titres) Ø the Tunisian circulating virus (heterologous titres) In addition to VNT, sera were analysed by ELISA kits for measurement of antibodies to NSP (marker of infection) and to serotype O. 12 JPC REMESA Heraklion 16 th March 2015 Emiliana Brocchi
PREVIOUSLY VACCINATED ANIMALS MEAN VNT TITRES (log2) N. 40 CATTLE (5 sentinels) - N. 40 SHEEP (4 sentinels) Threshold protecbon Threshold protecbon Both cattle and sheep showed low level of antibodies residual from previous vaccination (day 0) The vaccination with O-BFS vaccine elicited a strong and fast (5 DPV) increase of protecting antibodies against both type O strains Homologous titres (O-BFS) are only 2-fold higher than heterologous (field virus) Assuming a VN titre of log 2 6 (1/128) as indicative of protection, the results show that in the vaccinated population a booster vaccination with O-BFS elicits a protective immune-response as soon as 5 DPV 13 JPC REMESA Heraklion 16 th March 2015 Emiliana Brocchi
RESULTS OF INDIVIDUAL ANIMALS (vaccinated cattle) ODT Mateur Cattle (1-10) -------- threshold +/- -------- threshold protection log2 VN titre 0 5 10 15 sentinel sentinel day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV ODT Mateur Cattle (11-20) log2 VN titre 0 5 10 15 sentinel day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV 14 JPC REMESA Heraklion 16 th March 2015 Emiliana Brocchi
RESULTS OF INDIVIDUAL ANIMALS (vaccinated cattle) -------- threshold +/- -------- threshold protection ODT Mateur Cattle (21-30) log2 VN titre 0 5 10 15 sentinel day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV ODT Mateur Cattle ( 31-40) log2 VN titre 0 5 10 15 sentinel day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV 15 JPC REMESA Heraklion 16 th March 2015 Emiliana Brocchi
RESULTS OF INDIVIDUAL ANIMALS (vaccinated sheep) -------- threshold +/- -------- threshold protection ODT Mateur Sheep (1-10) log2 VN titre 0 5 10 15 day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV ODT Mateur Sheep (11-20) log2 VN titre 0 5 10 15 day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV 16 JPC REMESA Heraklion 16 th March 2015 Emiliana Brocchi
RESULTS OF INDIVIDUAL ANIMALS (vaccinated sheep) log2 VN titre 0 5 10 15 sentinel ODT Mateur Sheep (21-30) sentinel -------- threshold +/- -------- threshold protection day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV sentinel ODT Mateur Sheep ( 31-40) sentinel log2 VN titre 0 5 10 15 day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV 17 JPC REMESA Heraklion 16 th March 2015 Emiliana Brocchi
Other assays ELISA for type O antibodies : ü overall the results correlate and confirm those of VNT NSP-Abs (marker of infection): ü all seronegative at day 0 ü sero-conversion (low Ab level) in 5 cattle and 5 sheep at day 21 PV Hypothesis: ü immune-response to residual NSP in vaccine detectable only in few plurivaccinated animals ü circulation of FMD infection at low level few heads infected, no clinical signs (thanks to vaccine immunity) None of the NSP-seropositive animals corresponded to the sentinels, which might have been more susceptible to infection in the case of virus circulation 18 JPC REMESA Heraklion 16 th March 2015 Emiliana Brocchi
NAÏVE ANIMALS NON VACCINATED MEAN VNT TITRES 13 cattle and 21 sheep seronegative for SP and NSP Abs Threshold protecbon Threshold protecbon ü 21 days post-single vaccination cattle and sheep showed a significant sero-conversion ü Heterologous (O Tunisia 14) mean titres were 2-3 fold lower than homologous (O-BFS) ü Antibody levels achieved by this primary immune response were much lower (5-7 fold) than in boosted-vaccinated animals ü Nevertheless, 21 days after a single vaccination, the mean titres towards the field virus overcome the value log 2 7 (1/128), estimated to confer protection. 19 JPC REMESA Heraklion 16 th March 2015 Emiliana Brocchi
RESULTS OF INDIVIDUAL ANIMALS (non vaccinated CATTLE) M Beja Bovine (1-7) -------- threshold +/- -------- threshold protection log2 VN titre 0 5 10 15 day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV M Beja Bovine (8-13) log2 VN titre 0 5 10 15 day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV All cattle showed a sero-conversion, but 2 out of 13 (ie 15% cattle) did not reach a protective immunity against the circulating virus after a single vaccination with O-BFS vaccine 20 JPC REMESA Heraklion 16 th March 2015 Emiliana Brocchi
RESULTS OF INDIVIDUAL ANIMALS (non vaccinated SHEEP) Madeneine Sheep (1-10) -------- threshold +/- -------- threshold protection log2 VN titre 0 5 10 15 day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV Madeneine Sheep (11-20) log2 VN titre 0 5 10 15 day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV 21 JPC REMESA Heraklion 16 th March 2015 Emiliana Brocchi
RESULTS OF INDIVIDUAL ANIMALS (non vaccinated SHEEP) -------- threshold +/- -------- threshold protection Madeneine Sheep (21-29) log2 VN titre 0 5 10 15 day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV day 0 5DPV 21DPV Similarly to cattle: ü all sheep showed sero-conversion at different levels 21 DPV ü all sheep reached protective immunity against the administered vaccine (strain O-BFS) ü but only 70% sheep reached the estimated protective titre against the circulating virus Therefore, one single vaccination with O-BFS is not expected to confer protection to all animals which will be vaccinated for the first time. 22 JPC REMESA Heraklion 16 th March 2015 Emiliana Brocchi
Other assays (non-vaccinated animals) ELISA for type O antibodies ü Overall the results correlate and confirm those of VNT NSP-Abs (marker of infection) ü All animals remained negative for anti-nsp antibodies for the duration of the experiment, proving absence of FMDV circulation 23 JPC REMESA Heraklion 16 th March 2015 Emiliana Brocchi
Direct comparison vaccinated vs naïve PREVIOUSLY VACCINATED SHEEP NAIVE Threshold protecbon Threshold protecbon ü the trend of immune response in the two groups is the same ü focalizing on Abs to the field virus, it is evident that the O-BFS mono-vaccinated sheep reached average titres about 3 log 2, i.e. 8-fold less, than the booster-vaccinated sheep ü 30% of sheep did not achieve a protective immunity against the field Tunisian virus 24 JPC REMESA Heraklion 16 th March 2015 Emiliana Brocchi
Direct comparison vaccinated vs naïve PREVIOUSLY VACCINATED CATTLE NAIVE 14 13 CATTLE - OTD Mateur 14 13 CATTLE - BEJA Mean VN titre (log2) 12 11 10 9 8 7 6 5 4 day 0 5 DPV 21 DPV 12 11 10 9 8 7 6 5 4 day 0 21 DPV Threshold protecbon threshold +/- ü MEAN titre of single-vaccinated animals overcome the estimated protecting level (log 2 = 7, 1/128) also for the field virus, BUT it is about 6-fold less than in the group of booster vaccinated CATTLE ü 15% of cattle did not achieve a protective immunity 25 JPC REMESA Heraklion 16 th March 2015 Emiliana Brocchi
OVERALL CONCLUSIONS The vaccination with O BFS vaccine is expected to induce a good immunity against the O Tunisia 2014 field virus in previously vaccinated animals (thanks to booster effect). However a proportion of naïve animals will not probably achieve a protective immunity with a single vaccination. The results observed at day 0 (before vaccination with O BFS) in the Mateur group (representing the situation of vaccinated farms) reflect the FMD immune status in the Tunisian context during the 2014 outbreak: approximately 50% cattle and 75% sheep showed neutralizing Ab titres against the field circulating virus lower than the estimated threshold of protection, thus indicative of a low protection level in the population. Also distance from last vaccination should be considered among factors that influence population immunity. 26 JPC REMESA Heraklion 16 th March 2015 Emiliana Brocchi
GENERAL CONCEPTS ü Protective immunity lasts up to 6 months after an initial course of vaccination, depending on the vaccine potency and the antigenic relationship between vaccine and outbreak strains ü An initial course of two vaccinations improves the strength and duration of the antibody response ü Longer lasting protection may develop once animals have received multiple vaccine doses 27 JPC REMESA Heraklion 16 th March 2015 Emiliana Brocchi