Understudied, coinfections are more frequent in pig farms than single infections. In pigs, the term "Porcine Respiratory Disease Complex" (PRDC) is often used to describe coinfections involving ...viruses such as swine Influenza A Virus (swIAV), Porcine Reproductive and Respiratory Syndrome Virus (PRRSV), and Porcine CircoVirus type 2 (PCV2) as well as bacteria like Actinobacillus pleuropneumoniae, Mycoplasma hyopneumoniae and Bordetella bronchiseptica. The clinical outcome of the various coinfection or superinfection situations is usually assessed in the studies while in most of cases there is no clear elucidation of the fine mechanisms shaping the complex interactions occurring between microorganisms. In this comprehensive review, we aimed at identifying the studies dealing with coinfections or superinfections in the pig respiratory tract and at presenting the interactions between pathogens and, when possible, the mechanisms controlling them. Coinfections and superinfections involving viruses and bacteria were considered while research articles including protozoan and fungi were excluded. We discuss the main limitations complicating the interpretation of coinfection/superinfection studies, and the high potential perspectives in this fascinating research field, which is expecting to gain more and more interest in the next years for the obvious benefit of animal health.
Porcine dendritic cells (DCs) are relatively well characterized, but a clear-cut identification of all DC subsets combined with full transcriptional profiling was lacking, preventing an unbiased ...insight into the functional specializations of DC subsets. Using a large panel of Abs in multicolor flow cytometry, cell sorting, and RNA sequencing we identified and characterized the porcine equivalent of conventional DCs (cDC) 1 and cDC2 as well as plasmacytoid DCs (pDCs) in the peripheral blood of pigs. We demonstrate that cDC1 are CD135
CD14
CD172a
CADM1
wCD11R1
cells, cDC2 are CD135
CD14
CD172a
CADM1
CD115
wCD11R1
CD1
cells and pDCs are CD4
CD135
CD172a
CD123
CD303
cells. As described in other species, only cDC1 express BATF3 and XCR1, cDC2 express FCER1A and FCGR2B, and only pDCs express TCF4 and NRP1 Nevertheless, despite these cross-species conserved subset-specific transcripts, porcine pDCs differed from the species described so far in many expressed genes and transcriptomic profiling clustered pDCs more distantly from cDCs than monocytes. The response of porcine DC subsets to TLR ligands revealed that pDCs are by far the most important source of TNF-α, IL-12p40, and of course IFN-α, whereas cDCs are most efficient in MHC and costimulatory molecule expression. Nevertheless, upregulation of CD40 and CD86 in cDCs was critically influenced or even dependent on the presence of pDCs, particularly for TLR 7 and 9 ligands. Our data demonstrate that extrapolation of data on DC biology from one species to another has to be done with care, and it shows how functional details have evolved differentially in different species.
Considering that macrophage functions are strongly impacted by the local tissue environment and the type of immune response, the aim of this study was to carefully set the methodological baseline for ...phenotype and functions of polarized porcine monocyte-derived macrophages. To this end, macrophages were generated in autologous serum alone or with colony-stimulating factor (CSF)-1 or CSF-2, and subsequently polarized with interferon (IFN)γ, interleukin-4 or IFNβ. IFNγ promoted expression of MHC class I, MHC class II, CD11a, and CD40 as well as LPS-induced IL-6 and IL-12. A hallmark of interleukin-4 was Arginase 1 and CD203a upregulation, without abrogating pro-inflammatory cytokine production. IFNβ induced CD169, MHC class I, CD40, CD80/86, but suppressed IL-6, IL-12 and tumor-necrosis-factor secretion. CSF-2 alone altered macrophage differentiation and promoted an IFNγ-like polarization. Altogether, the results provide a comprehensive overview of porcine macrophage polarization, and demonstrate commonalities with other species as well as peculiarities of the pig.
•Antigen presentation molecule induction is a hallmark of IFNγ and IFNβ polarization.•IFNγ-priming strongly promotes LPS-induced IL-6 and IL-12 secretion.•IFNβ treatment suppresses LPS-induced TNF responses.•High CD203a expression and IL-12 prevention are hallmarks of IL-4 polarization.•LPS-induced IL-1β, IL-8 and IL-10 are not impacted by polarizing cytokine treatments.
The porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most important swine pathogens and often serves as an entry door for other viral or bacterial pathogens, of which ...Streptococcus suis is one of the most common. Pre-infection with PRRSV leads to exacerbated disease caused by S. suis infection. Very few studies have assessed the immunological mechanisms underlying this higher susceptibility. Since antigen presenting cells play a major role in the initiation of the immune response, the in vitro transcriptional response of bone marrow-derived dendritic cells (BMDCs) and monocytes in the context of PRRSV and S. suis co-infection was investigated. BMDCs were found to be more permissive than monocytes to PRRSV infection; S. suis phagocytosis by PRRSV-infected BMDCs was found to be impaired, whereas no effect was found on bacterial intracellular survival. Transcription profile analysis, with a major focus on inflammatory genes, following S. suis infection, with and without pre-infection with PRRSV, was then performed. While PRRSV pre-infection had little effect on monocytes response to S. suis infection, a significant expression of several pro-inflammatory molecules was observed in BMDCs pre-infected with PRRSV after a subsequent infection with S. suis. While an additive effect could be observed for CCL4, CCL14, CCL20, and IL-15, a distinct synergistic up-regulatory effect was observed for IL-6, CCL5 and TNF-α after co-infection. This increased pro-inflammatory response by DCs could participate in the exacerbation of the disease observed during PRRSV and S. suis co-infection.
•Porcine mycoplasmas induce strong TNF in monocytes and CD40 in cDC1.•Mycoplasmas strongly induce B-cell CD25, proliferation and IgM secretion.•IgMhighCD21− B cells are more responsive to mycoplasma ...than IgM+CD21+ B cells.•M. hyorhinis generally mediates stronger innate responses than M. hyopneumoniae.•M. hyorhinis is highly mitogenic for porcine B cells.
Mycoplasma (M.) hyopneumoniae is the etiological agent of enzootic pneumonia in pigs and is closely related to M. hyorhinis, which can be isolated from the healthy mucosal surfaces of the upper respiratory tract. In rare cases it can also cause arthritis and polyserositis. Since the innate immune system is an important first line of defense and promotes adaptive immune responses, we characterized the innate immune response of various antigen presenting cells (APCs) to M. hyopneumoniae and M. hyorhinis, which differ in their pathogenicity in vivo. Porcine peripheral blood mononuclear cells were infected with different multiplicities of infection (MOI) of live and inactivated porcine mycoplasmas. Both Mycoplasma species induced strong tumour necrosis factor (TNF) responses in monocytes, with a stronger activation by M. hyorhinis. This higher stimulatory activity was also confirmed for CD40 upregulation. Conventional and plasmacytoid dendritic cells (cDC and pDC, respectively) did not or poorly respond to mycoplasmas in terms of TNF expression but more efficiently in terms of CD40 upregulation. Again, these responses were generally stronger with M. hyorhinis than with M. hyopneumoniae. Both Mycoplasma species also activated B cells in terms of CD25 upregulation, proliferation, and IgM secretion. Interestingly, while the induction of CD25 and in particular proliferation was higher with M. hyorhinis, the IgM secretion did not differ between the two species with the exception of the highest dose of M. hyopneumoniae,which appeared to suppress IgM responses. Taken together, our results provide a comparative analysis of innate immune response with different porcine APCs and demonstrate Mycoplasma species-dependent differences, which could relate to their different pathogenicity in vivo.
Small non-coding RNAs have emerged as key modulators of viral infection. However, with the exception of hepatitis C virus, which requires the liver-specific microRNA (miRNA)-122, the interactions of ...RNA viruses with host miRNAs remain poorly characterized. Here, we used crosslinking immunoprecipitation (CLIP) of the Argonaute (AGO) proteins to characterize strengths and specificities of miRNA interactions in the context of 15 different RNA virus infections, including several clinically relevant pathogens. Notably, replication of pestiviruses, a major threat to milk and meat industries, critically depended on the interaction of cellular miR-17 and let-7 with the viral 3′ UTR. Unlike canonical miRNA interactions, miR-17 and let-7 binding enhanced pestivirus translation and RNA stability. miR-17 sequestration by pestiviruses conferred reduced AGO binding and functional de-repression of cellular miR-17 targets, thereby altering the host transcriptome. These findings generalize the concept of RNA virus dependence on cellular miRNAs and connect virus-induced miRNA sequestration to host transcriptome regulation.
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•miRNA binding profiles for 15 different viruses elucidated by Argonaute (AGO)-CLIP•Groups of viruses sequester specific miRNAs or AGO in general•Pestiviruses critically depend on cellular miR-17 and let-7•Pestiviral RNA functionally reduces miR-17 binding on endogenous mRNA targets
To assess the landscape of miRNA interactions on viral RNA, Scheel et al. screened 15 different RNA virus infections using Argonaute crosslinking immunoprecipitation (AGO-CLIP). Unlike canonical miRNA functions, miR-17 and let-7 interact with the pestivirus 3′ UTR to promote virus replication. Pestivirus RNA functionally sequesters miR-17 leading to de-repression of its cellular targets.
New vaccine formulations that include novel strains of Mycoplasma hyopneumoniae and innovative adjuvants designed to induce cellular immunity could improve vaccine efficacy against this pathogen. The ...aim of this experimental study was to assess the efficacy of three experimental bacterin formulations based on M. hyopneumoniae field strain F7.2C which were able to induce cellular immunity. The formulations included a cationic liposome formulation with the Mincle receptor ligand trehalose 6,6-dibehenate (Lipo_DDA:TDB), a squalene-in-water emulsion with Toll-like receptor (TLR) ligands targeting TLR1/2, TLR7/8 and TLR9 (SWE_TLR), and a poly(lactic-co-glycolic acid) micro-particle formulation with the same TLR ligands (PLGA_TLR). Four groups of 12 M. hyopneumoniae-free piglets were primo- (day (D) 0; 39 days of age) and booster vaccinated (D14) intramuscularly with either one of the three experimental bacterin formulations or PBS. The pigs were endotracheally inoculated with a highly and low virulent M. hyopneumoniae strain on D28 and D29, respectively, and euthanized on D56. The main efficacy parameters were: respiratory disease score (RDS; daily), macroscopic lung lesion score (D56) and log copies M. hyopneumoniae DNA determined with qPCR on bronchoalveolar lavage (BAL) fluid (D42, D56). All formulations were able to reduce clinical symptoms, lung lesions and the M. hyopneumoniae DNA load in the lung, with formulation SWE_TLR being the most effective (RDS
-61.90%, macroscopic lung lesions -88.38%, M. hyopneumoniae DNA load in BAL fluid (D42) -67.28%). Further experiments raised under field conditions are needed to confirm these results and to assess the effect of the vaccines on performance parameters.
Streptococcus suis serotype 2 is an extracellular encapsulated bacterium that causes severe septicemia and meningitis in swine and humans. Albeit crucial in the fight against encapsulated bacteria, ...the nature of the capsular polysaccharide (CPS)-specific antibody (Ab) response during S. suis type 2 infection is unknown. We compared for the first time the features of CPS-specific versus protein-specific Ab responses during experimental infections with live virulent S. suis type 2 in mice. The primary protein-specific Ab response was dominated by both type 1 and 2 IgG subclasses, whereas IgM titers were more modest. The secondary protein-specific Ab response showed all of the features of a memory response with faster kinetics and boosted the titers of all Ig isotypes. In contrast, the primary CPS-specific Ab response was either inexistent or had titers only slightly higher than those in noninfected animals and was essentially composed of IgM. A poor CPS-specific memory response was observed, with only a moderate boost in IgM titers and no IgG. Both protein- and CPS-specific Ab responses were Toll-like receptor 2 independent. By using S. suis type 2 strains of European or North American origin, the poor CPS-specific Ab response was demonstrated to be independent of the genotypic/phenotypic diversity of the strain within serotype 2. Finally, the CPS-specific Ab response was also impaired and lacked isotype switching in S. suis-infected pigs, the natural host of the bacterium. The better resistance of preinfected animals to reinfection with the same strain of S. suis type 2 might thus more likely be related to the development of a protein rather than CPS Ab response.
Peste des petits ruminants (PPR) is an acute transboundary infectious viral disease of small ruminants, mainly sheep and goats. Host susceptibility varies considerably depending on the PPR virus ...(PPRV) strain, the host species and breed. The effect of strains with different levels of virulence on the modulation of the immune system has not been thoroughly compared in an experimental setting so far. In this study, we used a multi-omics approach to investigate the host cellular factors involved in different infection phenotypes. Peripheral blood mononuclear cells (PBMCs) from Saanen goats were activated with a T-cell mitogen and infected with PPRV strains of different virulence: Morocco 2008 (high virulence), Ivory Coast 1989 (low virulence) and Nigeria 75/1 (live attenuated vaccine strain). Our results showed that the highly virulent strain replicated better than the other two in PBMCs and rapidly induced cell death and a stronger inhibition of lymphocyte proliferation. However, all the strains affected lymphocyte proliferation and induced upregulation of key antiviral genes and proteins, meaning a classical antiviral response is orchestrated regardless of the virulence of the PPRV strain. On the other hand, the highly virulent strain induced stronger inflammatory responses and activated more genes related to lymphocyte migration and recruitment, and inflammatory processes. Both transcriptomic and proteomic approaches were successful in detecting viral and antiviral effectors under all conditions. The present work identified key immunological factors related to PPRV virulence
.
Dendritic cells (DC) have a main function in innate immunity in that they sense infections and environmental antigens at the skin and mucosal surfaces and thereby critically influence decisions about ...immune activation or tolerance. As professional antigen-presenting cells, they are essential for induction of adaptive immune responses. Consequently, knowledge on this cell type is required to understand the immune systems of veterinary mammals, including cattle, sheep, pigs, dogs, cats, and horses. Recent ontogenic studies define bona fide DC as an independent lineage of hematopoietic cells originating from a common precursor. Distinct transcription factors control the development into the two subsets of classical DC and plasmacytoid DC. These DC subsets express a distinguishable transcriptome, which differs from that of monocyte-derived DC. Using a comparative approach based on phenotype and function, this review attempts to classify DC of veterinary mammals and to describe important knowledge gaps.
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