The characterisation and identification of body fluid proteins for forensic purposes

• Main Author: Vincini, Louisa
• Other Authors: Kong Thoo Lin, Paul : McIntosh, Lesley : Wilson, Theresa
• Published: Robert Gordon University 2010
• Subjects: 614.1
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.519359

Advances in DNA technology have led to the extremely sensitive and rapid analysis methods used in forensic science. It can often be crucial to a criminal case to unequivocally identify the body fluid source of DNA. This is of particular importance in rape cases where the defence may argue that the source of a female DNA profile might be from a casual touch or from saliva. In this study, proteomics has been employed in an attempt to identify potential biomarkers that are specific to a range of body fluids. Many publications cite the use of proteomics to identify biomarkers of disease such as cancer. In these reports, diseased and healthy tissues or tissues that have been treated or not treated with a drug are compared and the expressed proteins are compared by 2D electrophoresis. Human body fluids differ in function, composition and protein expression. Proteomics therefore seemed an ideal application to isolate the proteins that are characteristic of and specific to, different fluid types. Both saliva and vaginal fluid proteomic methodologies were optimised for sample preparation, IPG strip pH range and protein load, and post-electrophoretic staining. Seventeen isolated protein spots from saliva and vaginal fluid samples were submitted for LC-MS/MS analysis. Nine saliva spots and eleven vaginal spots were identified as known proteins on the MASCOT database. Of those thought to be specific to saliva or vaginal fluid six candidate biomarkers were tested further against a panel of body fluids for specificity using ELISA or Dot Blot. Zinc-α-2 glycoprotein (ZA2G) was detected and present in all body fluid samples thus could be used as a human body fluid positive control in a future assay. SCC (Squamous cell carcinoma) ELISA was capable of distinguishing samples of vaginal origin by detection of SCCA (Squamous cell carcinoma antigen). This antigen could be used in conjunction with a menstrual blood marker to distinguish between vaginal fluid and menstrual blood. Antibody specificity was a limiting factor in the success of the dot blots performed and hence the analysis of Cystatin SA, Cystatin SN and SERPIN B1 was inconclusive.