Antibody production to adrenal cytochrome P450-dependent enzymes using acid-treated bacteria as immune carriers.

Abstract

The cytochromes P450 of the adrenal cortex are responsible for the production of glucocorticoids, mineralocorticoids and androgen precursors. Recent investigations of these hemoproteins have focused on their regulation and expression in normal as well as pathological adrenal glands in order to obtain a better understanding of the mechanism and regulation of steroid hormone biosynthesis. Comparative studies of these enzymes in different species have also yielded invaluable information in this regard. Modern biotechnological techniques have been essential in the study of this labile group of enzymes and immunology in particular has made an important contribution to our knowledge of cytochrome P450 expression and regulation iri vivo. We have recently reported on a novel method for antibody production in which acid-treated Salmonella miririesota R595 are utilized as immune carriers [l]. Here we wish to report on the application of this technique in raising antibodies to a variety of ovine cytochrome P450-dependent enzymes. Subsequently, the specificities of these antibodies with other ovine adrenal cytochrome P450-dependent enzymes and the interspecies crossreactivities of these antibodies with a variety of bovine, baboon and porcine adrenal cytochrome P450dependent enzymes were determined. Cytochrome P450-dependent enzymes were isolated from ovine adrenals. The enzymes and the reference to the method by which they were respectively isolated, follow: P45Oc17 [2], P450cll [3], P45Oscc [3] and P450c21 [4]. Acid-treated Salmorzella mirzfiesorrr R595 bacteria (so-called naked bacteria, NB) were prepared from phenol-killed bacteria of this strain as described [l]. The abovementioned enzymes in their respective isolation buffers were used directly for adsorption to NB. Prior to adsorption, the protein concentration of each of the respective preparations was determined. A fine suspension of NB ( I mdml in H20) was prepared by homogenizing the lyophilized NB in a homogenizer with a loosely fitting Teflon plunger. Each of the isolated enzymes was added to respective preparations of finely suspended NB in a mass ratio of 1 to 5. This mixture was placed in ii peared-shaped flask and reduced to dryness on a rotary evaporator. The complexes thus formed were resuspended in PBS and used for immunization. Rabbits (two per antigen) were injected intravenously into the peripheral ear vein. On day I rabbits were immunized with 60 pg of antigeniNB complex in 0.25 ml PBS, on day 4 with 120 pg in 0.5 mi PBS and with 240pg in 0.5 ml PBS on days 7 and 11. The initial immunizations were followed up by booster injections of 240 pg in 0.5 ml PBS on days 18, 21, 25, 32, 35 and 39. The rabbits were test bled on days 1 I , 18, 25, 32, 39 and on day 46 a large volume of blood was collected. All sera were tested for antibody activity by enzyme-linked immunosorbent assay as described [ l ] using the respective antigens for coating purposes. The abovementioned wine P450-dependent enzymes were subjected to SDS-PAGE after which the proteins were transferred by electrotransfer to a nitrocellulose membrane. A separate Western blot analysis was then performed with each of the antisera raised to detect their specificity. To this end, the nitrocellulose membrane was blocked with casein buffer and incubated overnight with optimally diluted rabbit antiserum in casein buffer. A washing step with PBS-Tween 20 followed, which was repeated after each of the successive steps. Subsequently, the membrane was incubated with sheep antirabbit antibodies and thereafter rabbit-PAP. Bands were visualized by the addition of substrate solution which consisted of 4-chloro-1-naphtol and H202 in PBS. In order to detect the crossreactivity of the respective antisera, bovine, baboon and porcine cytochrome P450-de endent enzymes were also separated by the same SDg-PAGE, electrotransfer and Western blotting procedures as described above. Table 1: Specificities of antibodies to ovine P450c17. P450c21, P-450scc and P-450cll.