Predicting antigenic sites on the FMDV. F.F. Maree, R. Reeve, B. Blignaut, J.J. Esterhuysen, E. Fry, T. de Beer, E. Rieder and D.

Size: px

Start display at page:

Download "Predicting antigenic sites on the FMDV. F.F. Maree, R. Reeve, B. Blignaut, J.J. Esterhuysen, E. Fry, T. de Beer, E. Rieder and D."

Melanie Owens
5 years ago
Views:

1 Predicting antigenic sites on the FMDV capsid from cross-reactivity reactivity data F.F. Maree, R. Reeve, B. Blignaut, J.J. Esterhuysen, E. Fry, T. de Beer, E. Rieder and D.Haydon

2 Introduction The SAT types display appreciably greater intratypic genomic and antigenic variation than the traditional Euro-Asian types. Serious implications for the control of the disease by vaccination The ability to predict vaccine efficacy would be valuable tool in an effective control strategy. Antigenic variation results from changes to the viral capsid. Identification of epitopes for the SAT viruses may help to predict the protection afforded by a vaccine against a specific outbreak. Traditionally, evaluating the suitability of existing vaccine strains against outbreak strains is based on VNT s.

3 Objectives To investigated the genetic variation of the complete capsid-coding region of representative SAT strains in sub-saharan Africa. Determine the antigenic variation within SAT1 and SAT2 serotypes across the African continent. Assess whether a statistical correlation exist between genetic distance and serological relatedness (r-values). Identification of antigenically significant, surface-exposed regions on the capsid of SAT1 and SAT2 viruses. Applying the knowledge of putative epitopes to predict whether a vaccine will protect against newly circulating outbreak strains.

4 Conclusion Molecular epidemiology indicates that large variation exist between topotypes within the SAT serotypes which has severe implications for vaccination. Vast antigenic variation was observed among SAT1 and especially SAT2 viruses with serious implications for the choice of vaccine strain. Linear mixed-effects model of virus neutralisation titre. Assess the protection afforded by a vaccine against a heterologous challenge. Evaluate the likely efficacy of potential vaccine strains against a group of challenge strains when a new vaccine is required. Identified the antigenic regions which are strongly correlated with protection for the SAT1 and SAT2 serotypes. Applied to any FMDV serotype with available cross-protection data.

5 P1 Phylogeny Minimum evolution tree depicting gene relationships for P1-coding regions of SAT1, 2 and 3 viruses. Topotypes based on 1D phylogeny are indicated. Jukes-Cantor distances and 0 bootstrap replications were applied. Bootstrap support is indicated KNP/02/89/2 KNP/19/89/2 KNP/51/93/2 SAR/16/83/2 ZIM/08/94/2 ZIM/GN/10/91 RHO/01/48/2 KEN/08/99/2 ANG/04/74/2 ZIM/07/83/2 ZIM/01/88/2 ZIM/34/90/2 ZIM/14/90/2 ZIM/17/91/2 KEN/03/57/2 UGA/02/02/2 ZAI/01/74/2 RWA/02/01/2 ERI/12/89/2 SAU/06/00/2 SEN/05/75/2 GHA/08/91/2 SEN/07/83/2 KNP/196/91/1 KNP/148/91/1 ZIM/HV/03/90 SAR/09/81/1 KNP/41/95/1 ZIM/GN/13/90 MOZ/03/02/1 ZIM/25/90/1 ZAM/02/93/1 KEN/05/98/1 TAN/37/99/1 ZIM/06/94/1 NAM/307/98/1 UGA/03/99/1 UGA/01/97/1 SUD/03/76/1 NIG/05/81/1 NIG/08/76/1 NIG/06/76/1 NIG/15/75/1 KNP/10/90/3 ZIM/05/91/3 BEC/16/53/3 ZAM/04/96/3 UGA/02/97/3 A22 A12 O1Kauf O1Tai Southern Africa East Africa West Africa Southern Africa East Africa West Africa SAT3 SAT2 SAT1 European A and O types

6 SAT1 antigenic variation SAT1 antigenic variation SAT1 antigenic variation I II III IV V VII VIII SAR/9/ KNP/196/ NIG/5/81 KNP 196/91/1 SAR 9/81 GN 13/91 HV 3/90 KNP 148/91/1 KNP 41/95/1 NAM 307/98/1 ZIM 6/94/1 MOZ 3/02/1 ZIM 25/90/1 TAN 1/99/1 ZAM 2/93/1 KEN 5/98/1 UGA 3/99/1 UGA 1/97/1 SUD 3/76/1 NIG 5/81/1 NIG 15/75/1 TAN 37/99/1 NIG 6/76/1 NIG 8/76/1 r-values of SAT-1 isolates from different topotypes compared to antiserum prepared to strains SAR9/81, KNP196/91/1 (both topotype I) and NIG/5/81 (VII).

7 SAT2 antigenic variation SAT2 antigenic variation SAT2 antigenic variation II I II IV-XII ZIM/7/ KNP/19/89 RWA/2/01 KNP/19/89/2 KNP/2/98/2 KNP/51/93/2 SAR/16/83/2 ZIM/8/94/2 ZIM/GN/10/91 ZIM/7/83/2 ZIM/14/90/2 ZIM/17/91/2 ZIM/1/88/2 ZIM/34/90/2 RHO/1/48 KEN/8/99/2 GHA/8/91/2 LBR/1/74/2 SEN/5/75/2 SEN/7/83/2 SAU/6/00/2 RWA/2/01/2 ANG/4/74/2 UGA/02/02/2 ZAI/01/74/2 0 ERI/12/89 ERI/12/89/2 r-values of SAT-2 virus isolates from different topotypes compared to antiserum prepared to the reference strains KNP19/89 (I), ZIM7/83 (II), RWA/2/01 (VIII) and ERI/12/89 (X).

8 r-values vs genetic distance SAT2 r-value distance SAT2 average r-values were plotted against genetic distance (non-synonymous mutations).

9 Prediction of antigenically significant regions SAT1 virion VP2 H-I loop VP2 B-C loop A surface view of the crystallographic structure of a SAT1 virion showing a putative VP2 conformational epitope.

10 Prediction of antigenically significant regions VP1 VP2 VP3 most significant regions significant regions other regions A surface view of the crystallographic structure of a modelled (FunGIMS) SAT2 pentamer showing the outer capsid proteins around the pore at the 5-fold axis. The SAT2 significant antigenic regions are indicated. Four of the six regions correlate to previously identified epitopes on other serotypes.

11 Prediction of neutralising titres SAT1 SAT2 estimated r-values estimated r-values actual r-values actual r-values Prediction of the log(titre) for SAT1 and SAT2 isolates vs. real values during cross-validation: prediction of neutralisation titre was satisfactory for SAT1 viruses and even better for SAT2 viruses.

Unique features of foot and mouth disease in Southern Africa

Unique features of foot and mouth disease in Southern Africa Gavin Thomson Commodity-based trade and enhanced market access: The vital role of the Department of Veterinary Services Gaborone; 6-7 February