Date of Award

2000

Document Type

Doctoral Thesis

Degree Name

Doctor of Philosophy

Department

Biological Sciences

First Advisor

Dr. Séamus Fanning

Abstract

Between 1997 and 1998, 3,136 cases of rotavirus diarrhoea were detected in Irish children less than 2 years of age. Hospital inpatients accounted for 80% of these infections, with the remainder being diagnosed in general practice. A large percentage of infections were detected in neonates, suggesting a possible inadequate maternal derived protection from existing indigenous strains. This feature suggested the possible existence of ‘novel’ strains circulating in Ireland. No data describing the epidemiology of rotavirus strains in this country currently exists. Furthermore no assessment of the potential health-economic impact or quantitation of potential disease burden was ever undertaken

Three hundred and thirty rotavirus positive stool samples were isolated from Irish children presenting with confirmed diarrhoea in the southern and eastern regions of Ireland over a three-year period, from 1997 to 1999. These strains were characterised using polyacrylamide gel electrophoresis and polymerase chain reaction (PCR) mediated-typing. The predominant types identified in Ireland included G1P[8], G2P[4] and G4P[8]. However, novel strains, not previously detected in Irish children, were also identified. Significantly, two strains normally associated with infections in animals were recovered from Irish children as part of mixed infections.

The major rotavirus neutralisation viral protein (VP7) is encoded by gene segment 9 in group A human strains. A restriction fragment length polymorphic (RFLP)- detecting assay was developed to examine the genetic variability and/or similarity between the VP7-encoding genes from Irish rotavirus strains and a random selection of global strains taken fronn the current databases. VP7 protein encoding genes of 130 strains were analysed by RFLP using three restriction enzymes. These data showed the Irish rotavirus wild-type population to be homogenous, being distinguished from global isolates of the same serotype by these methods.

Nucleic acid and the deduced amino acid sequences of six VP7 protein encoded genes were determined. Specific amino acid substitutions were identified among the Irish rotavirus strains providing evidence of true reassortment between these isolates. Furthermore, careful analysis of the amino acid sequences within known hyperyariable regions of the VP7-encoding gene, confirmed the existence of two genetic lineages within G1-serotypes. The latter is a useful strategy to monitor the “real-time” evolution of these viruses. When taken together with the previously identified unusual G-types, these findings predict a more genetically diverse, complex and dynamic rotavirus pool existing in this country. This knowledge will in the future facilitate the development of a suitable vaccine for the Irish population.

Access Level

info:eu-repo/semantics/openAccess

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