LIMITED EFFECT OF RECOMBINANT PORCINE INTERLEUKIN-12 ON PORCINE LYMPHOCYTESDUE TO A LOW EXPRESSION OF IL-12 BETA2 RECEPTOR

Authors: Solano-Aguilar, Gloria; Zarlenga, Dante; Beshah, Ethiopia; VENGROSKI, K - ARS, USDA, BELTSVILLE,MD; Gasbarre, Louis; JUNKER, D - SCHERING PLOUGH; COCHRAN, M - SCHERING PLOUGH; WESTON, C - SCHERING PLOUGH; VALENCIA, D - SCHERING PLOUGH; Lunney, Joan

Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/3/2002
Publication Date: 10/28/2002
Citation: SOLANO AGUILAR, G., ZARLENGA, D.S., BESHAH, E., VENGROSKI, K., GASBARRE, L.C., JUNKER, D., COCHRAN, M., WESTON, C., VALENCIA, D., LUNNEY, J.K. LIMITED EFFECT OF RECOMBINANT PORCINE INTERLEUKIN-12 ON PORCINE LYMPHOCYTESDUE TO A LOW EXPRESSION OF IL-12 BETA2 RECEPTOR. VETERINARY IMMUNOLOGY AND IMMUNOPATHOLOGY. vol. 89, pp. 133-48, 2002.

Interpretive Summary: Stimulating protective responses against infectious diseases is essential for animal health. Thus our laboratory investigated the immune stimulator interleukin-12 (IL-12) for its effectiveness in swine. With collaborators at Schering Plough the two chains of IL-12 were cloned and expressed in mammalian systems. To our surprise swine IL-12 was ineffective in stimulating swine cells to proliferate or produce interferon-gamma (IFNg), a potent anti-viral protein. However, the same swine IL-12 was able to stimulate cattle cells. To determine why the pig IL-12 was ineffective for swine cells we cloned the IL-12 receptor (IL-12R) and developed an assay to assess it regulation. Our results show that swine IL-12 will stimulate cattle cells to express more IL-12R but will not stimulate swine cells to do the same. Testing purified swine IL-12 gave the same results. In vivo tests, with injection of purified swine IL-12 into the hind legs of young piglets, were also negative. Thus, the immune stimulator IL-12 is not effective in swine because it does not up-regulate receptor expression; then the pig cannot respond by making IFNg. Thus, we recommend that other immune stimulants be pursued for pigs for treating infectious diseases.

Technical Abstract: The cytokine interleukin 12 (IL-12) is a key molecule in the regulation of CD4 + T cell development and specifically potentiates T helper 1 responses in mouse and man. However, biological effects mediated by IL-12 have not been well defined in porcine. Herein, recombinant porcine IL-12 (rPoIL-12) was expressed in a swine poxvirus system as a biologically active heterodimer and used to stimulate bovine or swine lymphoblast cells. After three days of incubation, only bovine blasts were responsive to the rPoIL- 12 treatment as monitored by cell proliferation and Interferon gamma (IFNg) production in three independent trials. Porcine lymphoblasts proliferated in the presence of filtered supernatants from PMA-ConA stimulated cells ruling out the possibility of unresponsive cells. Similarly, intramuscular administration of rPoIL-12 in the hind leg of three-week old pigs indicated minimal proliferation of lymphoid cells, or enhancement in the number of IFNg producing lymphocytes isolated from inguinal lymph nodes. The IL- 12Rbeta2 receptor [IL12Rb2] sequence was cloned and results from competitive RT-PCR demonstrated that the expression of IL-12R on porcine cells as measured by the transcription of IL12Rb2 was relatively less than that transcribed in bovine cells. This observation is in agreement with the reduced proliferation response of swine blast cells to rPoIL-12. These data support a mechanism for IL-12 stimulation in swine inconsistent with that observed in conventional models. 115GSATech