Prion strains associated with iatrogenic CJD in French and UK human growth hormone recipients

Abstract

Treatment with human pituitary-derived growth hormone (hGH) was responsible for a significant proportion of iatrogenic Creutzfeldt-Jakob disease (iCJD) cases. France and the UK experienced the largest case numbers of hGH-iCJD, with 122 and 81 cases respectively. Differences in the frequency of the three PRNP codon 129 polymorphisms (MM, MV and VV) and the estimated incubation periods associated with each of these genotypes in the French and the UK hGH-iCJD cohorts led to the suggestion that the prion strains responsible for these two hGH-iCJD cohorts were different. In this study, we characterized the prion strains responsible for hGH-iCJD cases originating from UK (n = 11) and France (n = 11) using human PrP expressing mouse models. The cases included PRNP MM, MV and VV genotypes from both countries. UK and French sporadic CJD (sCJD) cases were included as controls. The prion strains identified following inoculation with hGH-iCJD homogenates corresponded to the two most frequently observed sCJD prion strains (M1^CJD and V2^CJD). However, in clear contradiction to the initial hypothesis, the prion strains that were identified in the UK and the French hGH-iCJD cases were not radically different. In the vast majority of the cases originating from both countries, the V2^CJD strain or a mixture of M1^CJD + V2^CJD strains were identified. These data strongly support the contention that the differences in the epidemiological and genetic profiles observed in the UK and France hGH-iCJD cohorts cannot be attributed only to the transmission of different prion strains.

Keywords: Growth hormone; Iatrogenic CJD; Prion disease.

Fig. 1

Survival times of human PrP-expressing mice (tgHu) inoculated with growth hormone CJD cases originating from France and UK. Transgenic mice that express the Met₁₂₉ (tgMet), Val₁₂₉ (tgVal) human PrP were inoculated intra-cerebrally (6 mice, 20µL per mouse) with a 10% brain homogenate from hGH-iCJD cases of French and UK origin. Two iterative passages were performed in each mouse line (Table 1). For each passage, results are presented according to the country of origin (Fr and UK) and the PRNP codon 129 genotype of patients (homozygous Met129: MM—heterozygous Met129/Val129: MV—homozygous Val129: VV). Survival time (mean ± SD in days post inoculation) in tg Met (○) and tg Val (∆). White/black symbols correspond to a type 1/type 2 PrP^res (as assessed by Western blot) in the brain of the mice respectively. Survival times in tgMet and TgVal associated with M1^CJD and V2^CJD cloned strains as well as an artificial mixture of V2^CJD + M1^CJD (10^–4 diluted) are included as reference (see Table 2)

Fig. 2

PrP^res western blot profiles in the brains of human PrP-expressing mice (TgHu) inoculated with human growth hormone iatrogenic CJD (hGH-iCJD) cases. Transgenic mice that express the Met₁₂₉ (tgMet) or Val₁₂₉ (tgVal) human PrP were inoculated intra-cerebrally (6 mice, 20µL per mouse) with a 10% brain homogenate from hGH- iCJD cases of French and UK origin. Two iterative passages were performed in each line (Table 1). After each passage and in each mouse line the isoform (type 1/type 2) of the PrP^res was determined in mice brain by SDS-PAGE and WB with the anti-PrP monoclonal antibody Sha31 (epitope YEDRYYRE). A PrP^res type 1 isoform (MM1 sCJD isolate) and type 2 isoform (VV2 sCJD isolate) were included as controls on each gel. The WB results obtain in each line are reported in Table 1

Fig. 3

Vacuolar lesion profiles in the brain of human PrP-expressing mice (tgHu) inoculated with human growth hormone iatrogenic CJD cases originating from France and UK. French (Fr) and UK hGH- iCJD isolates were inoculated in transgenic mice that express Met₁₂₉ (tgMet) or Val₁₂₉ (tgVal) human PrP (intra-cerebral route, 6 mice, 20µL per mouse). After two iterative passages standardized vacuolar lesion profiles were established in the brains of the mice. Lesion profiles corresponding to M1^CJD (○) and V2^CJD (●) strains are presented for comparison. Results are presented according to the origin (Fr and UK) and the genotype of patients (homozygous Met129: MM—heterozygous Met129/Val129: MV—homozygous Val129: VV°). Fr MM cases: case 1 (∇), case 2 (∆), case 5 (○). UK MM: case 6 (○), case 7 (∇). Fr MV: case 10 (○), case 12 (∆). UK MV: case 11: case 9 (∇), cases 9 (○), case 13(∆). Fr VV cases: case 18 (∆), case 19 (∇), case 22 (○). UK VV cases: case 14 (○), case 15 (∆), case 22 (∇). For the Fr VV cases 18 and 19, second passage in tgMet were not available at the moment of writing (see Table1)