DETECTION OF HUMAN PROTEINS IN BURIED BLOOD USING ELISA AND MONOCLONAL-ANTIBODIES - TOWARDS THE RELIABLE SPECIES INDENTIFICATION OF BLOOD STAINS ON BURIED MATERIAL

The survival of human proteins in blood stains on fragments of cloth buried in exposed soil was examined in a 15-month investigation carried out from September 1990 to December 1991. During this period there was a wide variety of weather conditions. Samples were exhumed at 4-weekly intervals for 16 weeks and finally at 65 weeks; extracts of the stains were tested for albumin and IgG using a highly specific and sensitive enzyme-linked immunosorbent assay (ELISA) performed with monoclonal antibodies. Human albumin survived well throughout the 15 months of study, but IgG could be detected only in the 4- and 8-week samples. The reactions for IgG were weaker than those for albumin, although the method's sensitivity (10 ng) was the same for each protein. Appropriate buried and non-buried control experiments were carried out using cloth, either unstained or stained with human blood or animal sera; there was no cross-reactivity between human and the other species investigated and soil did not affect the assay; under laboratory conditions, IgG and albumin survived equally well. The system's versatility was illustrated by using monoclonal anti-bovine-albumin to detect specific albumin in the extracts of buried cloth which had been stained with bovine serum. It was concluded that ELISA performed with monoclonal antibodies could be of great value in identifying blood stains for forensic purposes. The method has several advantages other than sensitivity and specificity: by using Terasaki plates, very small 5 mul-aliquots of extract can be tested as opposed to the 50 mul-samples required for conventional micro-ELISA plates; cross reactivity from environmental factors is avoided and, compared with radioimmunoassay and standard ELISA, the technique does not require complicated measuring equipment to provide a result. Decreased antigen survival with time and exposure suggests that it will be better to test for the more abundant blood proteins such as albumin. The system would be ideal for experimental forensic work, for example for examining the effects of different variables such as soil composition on protein survival.