The applicability of ELISA detection of gastric mucosa-expressing proteins for the identification of vomit.

The identification of vomit stains may be helpful for crime scene reconstruction. However, there is no specific and convenient method for identifying vomit stain. Therefore, to establish the procedure for forensic identification of vomit stains, we focused on four gastric mucosa-expressing proteins, pepsinogen I (PGA), pepsinogen II (PGC), gastrin (GAST), and mucin 5AC (MUC5AC). We developed enzyme-linked immunosorbent assay (ELISA) procedures for the detection of these four candidate proteins. The specificity and sensitivity of ELISA detection of these proteins were analyzed, and applicability for the identification of vomit in forensic casework samples was also investigated. We found the sensitivities of ELISA for detection of PGA, PGC, GAST, and MUC5AC from the standard protein (peptide) and from diluted gastric mucosa extract were 10.0-100.0 ng/ml and 1:200-1:1600, respectively. PGA and PGC were successfully detected in stomach contents and gastric mucosa samples; however, these also cross-reacted with some urine and semen samples, respectively, because of low level expression in these fluids. MUC5AC was positive for most gastric mucosa samples; however, it was difficult to detect in stomach contents. ELISA detection of GAST was not suitable for the identification of vomit. All aged samples stored up to 90 days gave positive results for ELISA procedures for PGA, PGC, and MUC5AC. Therefore, ELISA detection of these proteins might be applicable to aged samples. PGA was also detected in all actual vomit samples tested. These results suggest that ELISA for the detection of gastric mucosa-expressing proteins, especially PGA, could be an effective tool for the forensic identification of vomit.