Effect of the injection of an extract of Ascaris suum on macrophage activation during the early phase of Mycobacterium bovis BCG infection in C57Bl/6 mice

ABSTRACT

Injection of an Ascaris suum extract (Asc) affects both the humoral and cellular immune responses to unrelated antigens when it is co-administered with these antigens. In the present study we evaluated the effect of Asc on macrophage activation in the early phase of Mycobacterium bovis BCG (Pasteur strain TMCC 1173) infection in C57Bl/6 mice. C57Bl/6 mice were injected intraperitoneally (ip) with 0.1 mg BCG (BCG group) or BCG plus 1 mg Asc (BCG + Asc group). The peritoneal exudates were obtained at 2, 7 and 14 days after infection. The numbers of IFN-g-secreting cells were assessed by the ELISPOT assay. Nitric oxide (NO) production was measured by the Griess method and by the evaluation of NADPH diaphorase activity in the peritoneal exudates. The administration of Asc extract increased NADPH diaphorase activity (2 days control = 0, BCG = 7 per cent, BCG + Asc = 13 per cent, and Asc = 4 per cent; 7 days control = 4, BCG = 13 per cent, BCG + Asc = 21 per cent, and Asc = 4.5 per cent) and TNF-a levels (mean + or - SD; 2 days control = 0, BCG = 169 + or - 13, BCG + Asc = 202 + or - 37, and Asc = 0; 7 days control = 0, BCG = 545 + or - 15.5, BCG + Asc = 2206 + or - 160.6, and Asc = 126 + or - 26; 14 days control = 10 + or - 1.45, BCG = 9 + or - 1.15, BCG + Asc = 126 + or - 18, and Asc = 880 + or - 47.67 pg/ml) in the early phase of BCG infection. Low levels of NO production were detected at 2 and 7 days after BCG infection, increasing at 14 days (mean + or - SD; 2 days control = 0, BCG = 3.7 + or - 1.59, BCG + Asc = 0.82 + or - 0.005, Asc = 0.48 + or - 0.33; 7 days control = 0, BCG = 2.78 + or - 1.54, BCG + Asc = 3.07 + or - 1.05, Asc = 0; 14 days control = 0, BCG = 9.05 + or - 0.53, BCG + Asc = 9.61 + or - 0.81, Asc = 10.5 + or - 0.2 (2 x 106) cells/ml). Furthermore, we also observed that Asc co-injection induced a decrease of BCG-colony-forming units (CFU) in the spleens of BCG-infected mice during the first week of infection (mean + or - SD; 2 days BCG = 1.13 + or - 0.07 and BCG + Asc = 0.798 + or - 0.305; 7 days BCG = 1.375 + or - 0.194 and BCG + Asc = 0.548 + or - 0.0226; 14 days BCG = 0.473 + or - 0.184 and BCG + Asc = 0.675 + or - 0.065 (x 102) CFU). The present data suggest that Asc induces the enhancement of the immune response in the early phase of BCG infection.