Rodgers, Jackie Michele; (1993) The immunology of hydrocephalus shunt infections. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

A serological test suitable for the detection of agglutinating antibody in ventriculoatrial (VA) shunt colonisation, developed twenty years ago, does not however, detect rising titres in ventriculoperitoneal (VP) shunt infections. Diagnosis of VP shunt colonisation depends upon clinical presentation which is variable and often unhelpful. A suitable serological test is therefore required as VP shunts now constitute the majority. Different antigens which included polysaccharide B extracted from the cell walls of coagulase negative staphylococci (CNSt) by buffers of differing pH, and a whole cell protein antigen obtained by sonication were used in an ELISA test. Both antigens were found to detect antibody in those with infected VA and VP shunts. Differences in the IgM and IgG response to infection could also be assessed. SDS-PAGE and immunoblotting studies were made to determine important epitopes involved in shunt infection due to CNSt. Three strains of St. epidermidis. two slime positive (F743 & FI 1) and one slime negative (F544) as determined by a quantitative assay were utilised. No bands were found in uninfected cases, but bands did appear in response to infection in both VA and VP shunts. Bands of between 29 and 205KDa were found in those with VA shunt infection but were limited to a molecular weight of up to 97KDa in those with VP shunts. The dissimilarity in band response suggests a difference in antigen processing and presentation. No major difference in band response using immunoblotting was noted between slime-producers and non-slime producers, although increased absorbance values were seen in those producing slime using ELISA, The antigenicity of purified slime was investigated by IV inoculation into rabbits. Antibody to slime was detected by ELISA but only in combination with other molecules indicating its role as a hapten. The excretion of slime in urine was also investigated by electrophoresis but results were disappointing. Bands were seen upon electrophoresis in those who were infected but could not be used to differentiate between different gram positive infections. These bands were thought to be peptidoglycan in nature. The agglutinating test was further examined and an IgM response defined. The action of proteolytic enzymes on the antigen used did not alter titres of known positive sera, but antibiotics affecting cell polysaccharide production did so, suggesting the importance of such an epitope in the immune response in this test. The importance of serology in shunt nephritis due to immune complexes was also reviewed.

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