Bovine monocytes induce immunoglobulin production in peripheral blood B lymphocytes

Analysis of Bovine Viral Diarrhea Viruses-infected monocytes: identification of cytopathic and non-cytopathic biotype differences

Background

Bovine Viral Diarrhea Virus (BVDV) infection is widespread in cattle worldwide, causing important economic losses. Pathogenesis of the disease caused by BVDV is complex, as each BVDV strain has two biotypes: non-cytopathic (ncp) and cytopathic (cp). BVDV can cause a persistent latent infection and immune suppression if animals are infected with an ncp biotype during early gestation, followed by a subsequent infection of the cp biotype. The molecular mechanisms that underscore the complex disease etiology leading to immune suppression in cattle caused by BVDV are not well understood.

Results

Using proteomics, we evaluated the effect of cp and ncp BVDV infection of bovine monocytes to determine their role in viral immune suppression and uncontrolled inflammation. Proteins were isolated by differential detergent fractionation and identified by 2D-LC ESI MS/MS. We identified 137 and 228 significantly altered bovine proteins due to ncp and cp BVDV infection, respectively. Functional analysis of these proteins using the Gene Ontology (GO) showed multiple under- and over- represented GO functions in molecular function, biological process and cellular component between the two BVDV biotypes. Analysis of the top immunological pathways affected by BVDV infection revealed that pathways representing macropinocytosis signalling, virus entry via endocytic pathway, integrin signalling and primary immunodeficiency signalling were identified only in ncp BVDV-infected monocytes. In contrast, pathways like actin cytoskeleton signalling, RhoA signalling, clathrin-mediated endocytosis signalling and interferon signalling were identified only in cp BDVD-infected cells. Of the six common pathways involved in cp and ncp BVDV infection, acute phase response signalling was the most significant for both BVDV biotypes. Although, most shared altered host proteins between both BVDV biotypes showed the same type of change, integrin alpha 2b (ITGA2B) and integrin beta 3 (ITGB3) were down- regulated by ncp BVDV and up- regulated by cp BVDV infection.

Conclusions

This study shows that, as we expected, there are significant functional differences in the host proteins that respond to cp or ncp BVDV infection. The combined use of GO and systems biology network modelling facilitated a better understanding of host-pathogen interactions.

Bovine viral diarrhea virus infection affects the expression of proteins related to professional antigen presentation in bovine monocytes

The complete annotation of the cattle genome allows reliable protein identification by tandem mass spectrometry (MS(2)) and greatly facilitates proteomics. Previously, we reported that differential detergent fractionation (DDF) analysis of bovine monocytes reveals proteins related to antigen pattern recognition, uptake and presentation to immunocompetent lymphocytes. Here we have identified 47 bovine proteins, involved in immune function of professional antigen-presenting cells (APC) that have been significantly altered after cytopathic (cp) Bovine Viral Diarrhea Virus (BVDV) infection. In particular, proteins related to immune responses such as cell adhesion, apoptosis, antigen uptake, processing and presentation, acute phase response proteins, MHC class I- and II-related proteins and other molecules involved in immune function of professional antigen presentation have been significantly altered after BVDV infection. Our data suggest that cp BVDV, while promoting monocyte activation and differentiation, is inhibiting their antigen presentation to immunocompetent T cells, thus resulting in the uncontrolled inflammation mediated by activated macrophages, enhanced viral spread, and impaired anti-viral defense mechanisms in the host.

Bovine viral diarrhea viruses modulate toll-like receptors, cytokines and co-stimulatory molecules genes expression in bovine peripheral blood monocytes

We have used noncytopathic (ncp) and cytopathic (cp) Bovine Viral Diarrhea Viruses (BVDV) to determine the expression levels of TLR genes, type I IFN, pro-inflammatory and Th1/Th2 cytokine gene expression in bovine monocytes. In general, both BVDV strains had similar effects. However, we found some significant differences that could be due to biological differences between cp and ncp BVDV strains. TLR3 was significantly up-regulated in 1h ncp, but not in cp BVDV- infected monocytes, whereas TLR7 expression dominated in 24h infection with both BVDV strains. Type I IFN and IL-12 gene expression was also significantly up-regulated in 1h ncp, but not cp BVDV infection that correlated with the enhanced TLR3 gene expression. Both BVDV biotypes suppressed pro-inflammatory cytokines TNF-alpha, IL-1beta, and IL-6, co-stimulatory molecules CD80 and CD86, but did not change Th1 type cytokine IL-12 and INF-gamma, gene expression after 24h infection. We hypothesize that BVDV may escape immune responses by altering the expression of TLR 3 and 7 and their signaling pathways.

Growth, weaning performance and blood indicators of humoral immunity in Holstein calves fed supplemental flavonoids

The primary objective was to test the hypothesis that flavonoids mediate immune response and affect calf performance. Twenty Holstein calves [7 +/- 2 days age; 41.4 +/- 0.7 kg body weight (BW)] were randomly assigned to four treatments of (i) no; (ii) low (7.3 x 10(-5) g/kg BW); (iii) medium (7.3 x 10(-4) g/kg BW); and (iv) high (3.6 x 10(-3) g/kg BW) doses of flavonoids intake in a completely randomized design. Calves received the treatments as a tablet until weaning or a daily intake of 680 g starter. After weaning, calves received no supplemental flavonoids and monitored until 120 days of age. The flavonoids were extracted from propolis. Treatments did not affect body length, wither height and the severity of scours. At week 5 of age, BW was higher when calves fed the high compared to the low dose of flavonoids. At week 6, calves fed the high dose of flavonoids had higher BW than those fed no or low doses of flavonoids. The serum immunoglobulin G (IgG) concentrations remained lower at the first 3 weeks of the experiment when calves received the low but not the high doses of flavonoids. At week 4, both medium and low doses of flavonoids moderated serum IgG. At week 8, the medium and high but not the low doses of flavonoids lowered serum IgG. At week 6, calves fed high and medium flavonoids doses had lower blood immunoglobulin M (IgM) than control calves. Results suggest that flavonoids affect the humoral immune response and can improve growth in young calves. This response depended on calf age. Future studies are needed to further evaluate the premise that dietary forages or the main source of flavonoids are helpful for a less stressful weaning in the modern calf raising.

The bovine antibody repertoire

Cattle are able to produce a full range of Ig classes including the long-elusive IgD through rearrangement of their germline genes. Several IgL groupings have been reported but as in several other livestock species (e.g. sheep, rabbits, chickens), rearrangement per se fails to generate significant IgH diversity. This is largely because of the modest number of bovine VH segments that participate in rearrangement and their conserved sequences. Perhaps in compensation, bovine Ig heavy chains carry CDR3 sequences of exceptional length. Processes that operate post-rearrangement to generate diversity remain ill defined as are the location, timing and triggers to these events. Reagents are needed to understand better the maturation of B lymphocytes, their responses to antigens and cytokines, and to provide standards for the quantitation of Ig responses in cattle; recombinant methods may help meet this need as Ab engineering technologies become more widely used.

Differential detergent fractionation for non-electrophoretic bovine peripheral blood monocyte proteomics reveals proteins involved in professional antigen presentation

Professional antigen presenting cells (APC), dendritic cells (DC) and their myeloid progenitors, monocytes/macrophages are critical controllers of innate and adaptive immunity. Here we show that differential detergent fractionation (DDF) analysis of bovine monocytes reveals proteins related to antigen pattern recognition, uptake and presentation to immunocompetent lymphocytes. We identify 53 bovine proteins involved in immune function of professional APC. In particular, 13 adhesion molecules, three toll-like receptors (TLR1, 6 and 8), three antigen uptake-related proteins (including mannose receptor [MR] precursor), and eight actin-like proteins involved in active endocytosis were identified. In addition, MHC class I and II-related proteins, cytokines, active substances and growth factors have been identified. We conclude that the DDF approach can provide interpretable and meaningful functional information concerning protein expression profiles associated with monocyte activation, transformation into macrophages and/or immature DC, and maturation of monocyte-derived DC in the presence of multiple bovine pathogens.

Cytopathic and non-cytopathic bovine viral diarrhoea virus biotypes affect fluid phase uptake and mannose receptor-mediated endocytosis in bovine monocytes

We have used non-cytopathic (ncp) and cytopathic (cp) bovine viral diarrhoea viruses (BVDV) to determine how the two biotypes affect mannose receptor (MR)-mediated endocytosis and fluid phase uptake in bovine monocytes. We have demonstrated that endocytosis in uninfected monocytes after 1 h of culture was mediated by the MR and fluid phase uptake, and after 24 h of culture it was mediated via fluid phase uptake only. Both cp and ncp BVDV affected the mechanisms of antigen uptake in monocytes. Endocytosis in BVDV infected monocytes, unlike in uninfected cells, was MR-independent and mediated by fluid phase uptake after 1 h of infection. The 24-h-BVDV infection changed the antigen uptake mechanisms to become MR- and fluid phase uptake-dependent. We conclude that antigen uptake, an important antigen presenting cell (APC) function, is affected in the early stage of BVDV infection during the first 24 h, with both BVDV biotypes, cp and ncp, having similar effects on monocyte antigen uptake in cattle. By influencing the early antigen uptake function of APC, BVDV might disrupt the function of monocytes as professional APC and contribute to the specific immunotolerance to BVDV.