Acute hypotensive transfusion reactions are potentially harmful adverse effects of transfusion attributable to bradykinin generation. They are most often seen in patients taking angiotensin-converting enzyme (ACE) inhibitors (ACE-Is) because of the role ACE plays in metabolizing bradykinin. However, a number of acute hypotensive transfusion reactions occur in patients not taking ACE-Is. Aminopeptidase P (APP), another important enzyme responsible for bradykinin degradation, is encoded by the polymorphic XPNPEP2 gene. Some polymorphisms in XPNPEP2 have been associated with decreased APP activity. However, the role that APP polymorphisms play in acute hypotensive transfusion reactions has never been investigated.
To develop a molecular assay to examine for the C-2399A single-nucleotide polymorphism (SNP) in the APP gene, XPNPEP2, in patients experiencing acute hypotensive transfusion reactions unassociated with ACE-Is.
We developed an assay using polymerase chain reaction and DNA sequencing with primers targeted at XPNPEP2 (5'-GAGTATTATGTGGGGACCATCC-3' and 5'-ATGCCTCGCAGAGACAAGAG-3'). Polymorphism zygosity was determined by comparing the sense/antisense sequencing results. This assay was then applied to patients with acute hypotensive transfusion reactions not taking ACE-Is (n  =  4).
A C-2399A SNP assay was successfully developed and applied to patients with acute hypotensive transfusion reactions. In a pilot study, 2 patients (50%) were found to possess C-2399A polymorphisms. One was found to be homozygous, and the other was heterozygous.
Our C-2399A SNP assay can be used to study acute hypotensive transfusion reactions in patients not taking ACE-Is. Initial data indicate that the C-2399A polymorphism may be a contributing factor in such reactions. However, further studies are necessary to better define the role of APP polymorphisms in relation to acute hypotensive transfusion reactions unassociated with ACE-Is.