O. Sheils, P. Smyth, C. Martin, J.J. O'Leary.
Development of an 'allelic discrimination' type assay to differentiate between the strain origins of measles virus detected in intestinal tissues of children wtih ileocolonic lymphonodular hyperplasia and concomitant developmental disorder.
Department of Histopathology, Trinity College Dublin Ireland
In a recent study, our group described the presence of measles virus RNA genes in a new form of inflammatory bowel disease with concimitant developmental disorder. (1) One of the many questions raised by this study asked if measles virus detected was wild or vaccine type in origin. The objective of this pilot study was to address this point.
Several conserved amino acid coding changes have been identified in measles virus strains in the Edmonston Vaccine lineage, and it has been suggested these represent a vaccine 'strain signature'.(2) One such site (nucleic acid position 7901, amino acid position 211) displays a consistent A-G mutation in Edmonston derived vaccines compared with wild type strains. This site is located in the H gene region of the measles genome and is associated with cellular CD46 interaction.
This single base mutation was used as the basis for the design of an allelic discrimination assay using TaqMan MGB probes (FAM labeled for wild type and VIC labeled for Vaccine Type). The assay was run on an ABI 7000 sequence detection system using total RNA extracted from intestinal biopsies amplified with TaqMan one step RT-PCR kit.
Synthetic oligonucleotides representing wild and vaccine strains were designed using published sequences from the NCBI database, and used as controls in the assay system.
The assay identified wild type measles in three brain blocks from an SSPE patient, while 12 gut biopsies from affected children were deemed to have vaccine strain present. This pilot study further corroborates our previous findings of an association between the presence of measles virus and gut abnormalities in children with developmental disorder, and indicates the origins of the virus to be vaccine strain.
(1) Potential viral pathogenic mechanism for new variant inflammatory bowel disease. Uhlmann V, Martin C, Sheils O et al. J Clin Pathol Mol Pathol 2002;55: 0-6
(2) Comparison of predicted amino acid sequences of measles virus strains in the Edmonston Vaccine Lineage. Parks CL, Lerc, RA, Walpita P et al. J Virol 2001; (75):2,910-920.