In vitro and in vivo effects of an immunomodulator composed of Escherichia coli lipopolysaccharide and Propionibacterium granulosum-inactivated cells in pigs

The in vitro cytokine profiles of porcine alveolar macrophages and peripheral blood mononuclear cells (PBMC) were examined by reverse transcription-polymerase chain reaction or enzyme-linked immunosorbent assay after stimulation with the immunomodulatory compound INMD [lipopolysaccharide (LPS) and Propionibacterium granulosum]. Expression of interleukin-1 (IL-1), IL-6, IL-12 and tumour necrosis factor-α (TNF-α), but not of IL-10, was detected in INMD-stimulated alveolar macrophages. Stimulated PBMC expressed IL-1, IL-2, IL-4, IL-6, IL-10 and IL-12 and secreted interferon-γ (IFN-γ). In all cases, the level of response was lower with INMD than with E. coli LPS alone, except for IFN which was secreted in higher levels in INMD-stimulated cells. In a second experiment, the ex vivo effect of the administration of INMD was evaluated using the product as a coadjuvant of a live attenuated Aujeszky's disease virus (ADV) vaccine. For this purpose, 85 8-10-week-old crossbred pigs were assigned to two groups (group A = 43 and group B = 42) and vaccinated with ADV. Group B received, simultaneously with the first dose of vaccine, an intramuscular dose of INMD equivalent to 20 μg/ml LPS and 250 μg/ml P. granulosum, while group A was given sterile saline solution as a placebo. At the time of vaccination, 97.6 % (42 of 43) and 95.2 % (40 of 42) of animals of groups A and B, respectively, had anti-gB maternal antibodies. Of those animals, anti-gE ADV antibodies were detected in 11.6 % of animals of group A (five of 43) and 19 % of group B (eight of 42). All animals were boosted with ADV vaccine alone 4 weeks later. Pigs to which INMD was administered together with the vaccine showed higher primary humoral responses than the vaccine-alone animals (P < 0.005). However, after boosting significant differences disappeared (P > 0.05).