Fig 1.
Schematic representation of the experimental design of the sheep blood transfusion experiments.
Sheep used as blood donors were orally infected with 5g BSE-infected cattle brain homogenate. Two units of blood (450-500ml each) were collected from each donor at 10 months post-infection (mpi). Group A–one unit was transfused as whole blood; the second unit was processed to components, before transfusion to individual recipient sheep (total of 5 recipients per donor). Group B–both units were processed to components, and one set of components was leucodepleted, before transfusion to recipients (total of 7 recipients per donor). Group C–negative control donors were orally dosed with 5g normal cattle brain homogenate (i.e. mock-infected), and one unit of whole blood was collected from each sheep at 10 mpi and transfused into recipients. To assess secondary transmission of infection by transfusion, one unit of whole blood was collected from 18 primary recipients of whole blood (n = 8) and buffy coat (n = 10) at 15 mpi, and transfused into individual secondary recipients.
Table 1.
Efficiency of transmission of BSE by different blood components following transfusion in sheep.
Table 2.
Titres of infectivity in sheep blood components estimated by bioassay in TgshpXI mice.
Table 3.
Transmission of BSE by transfusion of leucodepleted and non-leucodepleted blood components from the same donor.
Fig 2.
Relationship between donor genotype, stage of infection and transfusion transmission rate.
Each point on the chart represents an individual infected donor sheep, showing the number of corresponding transfusion recipients infected (all components) plotted against the stage of survival period at which blood was collected (%SP = time from infection to blood collection x 100/time from infection to culling). The donor PRNP codon 141 genotypes are represented by different symbols: 141LL–open diamonds; 141FF–closed triangles; 141LF–open circles. The longer survival periods of 141FF and 141LF compared to 141LL sheep mean that they were at an earlier stage of infection when they donated blood for transfusion (10 months post infection for all donors).
Table 4.
Association of donor PRNP genotype with transfusion transmission.
Table 5.
Detection of PrPSc by PMCA in buffy coat samples BSE-infected donor sheep at 10 months post infection (preclinical).
Fig 3.
Detection of PrPSc in preclinical buffy coat samples from BSE-infected donor and recipient sheep.
Longitudinal series of buffy coat samples from three donors (N178, N226, N257; upper panel A) and three recipients (P263, N224, P453; lower panel B) were used undiluted to seed PMCA reactions. All three possible PRNP codon 141 genotypes (LL, FF, LF) are represented. Numbers at the top of each panel indicate the stage of infection at each sampling point in months post-infection (mpi), with T (terminal) representing the final sampling point when sheep were culled with clinical signs of disease. The image shows representative results from a single experimental run after 2 rounds (R2) of PMCA (dextran sulphate added to final concentration of 0.5% w/v). C–positive control; BSE-infected sheep brain homogenate (PK digested; 1.7mg brain equivalent). B–blank lane.
Table 6.
Time course of detection of PrPSc by PMCA in blood samples from BSE-infected donor sheep.
Table 7.
Time course of detection of PrPSc by PMCA in blood samples from BSE-infected recipient sheep.