Abstract
The potD gene, belonging to the well-conserved ABC (ATP-binding cassette) transport system potABCD, encodes the bacterial substrate-binding subunit of the polyamine transport system. In this study, we found PotD in Haemophilus (Glaesserella) parasuis could actively stimulate both humoral immune and cellular immune responses and elevate lymphocyte proliferation, thus eliciting a Th1-type immune response in a murine immunity and infection model. Stimulation of Raw 264.7 macrophages with PotD validated that Toll-like receptor 4, rather than 2, participated in the positive transcription and expression of pro-inflammatory cytokines IL–1β, IL–6, and TNF–α using qPCR and ELISA. Blocking signal-regulated JNK–MAPK and RelA(p65) pathways significantly decreased PotD-induced pro-inflammatory cytokine production. Overall, we conclude that vaccination of PotD could induce both humoral and cellular immune responses and provide immunoprotection against H. parasuis challenge. The data also suggest that Glaesserella PotD is a novel pro-inflammatory mediator and induces TLR4-dependent pro-inflammatory activity in Raw 264.7 macrophages through JNK–MAPK and RelA(p65) pathways.
Highlights
Haemophilus (Glaesserella) parasuis is a pleomorphic, nonmotile, nicotinamide adenine dinucleotide (NAD)-dependent bacterium belonging to the family Pasteurellaceae and causes Glasser’s disease (GD)in piglets [1]
We found mice that survived in the recombinant protein of PotD (rPotD)+adjuvant presented less severe clinical severe clinical symptoms than the mice in the PBS/rPotD-alone/adjuvant-alone groups
In the anti-Toll-Like Receptors 2 (TLR2) or anti-TLR2/4 group, secreted levels of all of the three pro-inflammatory cytokines had no significant changes (p > 0.05). These results indicated that TLR4, rather than TLR2, mediated PotD-induced expression of pro-inflammatory cytokines in macrophages in H. parasuis infection
Summary
Haemophilus (Glaesserella) parasuis is a pleomorphic, nonmotile, nicotinamide adenine dinucleotide (NAD)-dependent bacterium belonging to the family Pasteurellaceae and causes Glasser’s disease (GD)in piglets [1]. H. parasuis is primarily readily isolated in weaner pigs, followed by finisher pigs and sows [2]. It normally colonizes the upper respiratory tract of swine and includes strains with diverse genetics and pathogenicities [3]. Vaccines 2019, 7, 216 signs of GD are characterized by pneumonia, meningitis, polyarthritis, and fibrinous polyserositis, giving rise to significant economic losses in the pork industry throughout the world [5,6]. The current regimen of curing this disease relies heavily on antibiotic therapy, and it is difficult to prevent this disease by immunization of inactivated vaccines due to the lack of crossprotection between different serotypes [4]. It is urgent to determine the mechanism of its pathogenesis in depth, and to find an effective protective vaccine [10]
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