Immunostimulatory CpG oligodeoxynucleotides enhance the induction of bovine CD4+ cytotoxic T-lymphocyte responses against the polymorphic immunodominant molecule of the protozoan parasite Theileria parva

Evidence for the existence of regulatory and effector B cell populations in Peyer's patches of sheep

IL-10 secreting CD21(+) B cells exist in sheep Peyer's patches (PP). It's not known however, whether all PP B cells are regulatory or whether an effector population also exists in this tissue. To further characterize the subpopulations of B cells in PP's, highly purified B cells were negatively sorted from jejunal PP and fractionated according to co-expression of CD72(+)CD21(+)or CD72(+)CD21(-) molecules and then stimulated with the TLR9-agonist, CpG ODN. IL-10, IL-12, IFN-γ, and IgM production were then assayed. We observed that only highly purified CD72(+)CD21(+) B cells spontaneously secreted high levels of IL-10, but they did not produce any IL-12, IFN-γ or IgM suggesting that this cell population contains regulatory B cells. In contrast, CD72(+)CD21(-) B cells did not secrete IL-10, but secreted IL-12, IFN-γ, and IgM, suggesting they include effector cells. In addition, B cells expressing surface IgA, IgM and IgG1 all secreted similar levels of IL-10. We further confirmed that only B cells produce IL-10, while other cells in the PP including DCs and T cells do not. Our investigations may provide evidence for the existence of two sub-populations in sheep PP; IL-10 secreting regulatory (CD72(+)CD21(+)) cells, and IL-12/IFN-γ/IgM-secreting effector (CD72(+)CD21(-)) cells.

IL-10 secreting CD21⁺ B cells are present in jejunal Peyer's patches of sheep during fetal development

We recently reported a novel interleukin-10 (IL-10)-secreting CD21(+) B cell population in jejunal Peyer's patches (JPP) of sheep with a regulatory function (Bregs) suppressing Toll-like receptor 9 (TLR9)-induced cytokine responses. However, little is known about the development of these cells. Therefore, we investigate their existence in JPP cells from fetal and newborn lambs. CD21(+) B cells were purified from JPP cells by magnetic cell sorting and subsequently stimulated with the TLR9 agonist, CpG ODN (CpG oligodeoxynucleotide). Lymphocyte proliferative responses, cytokine production (IL-10, IL-12 and interferon-γ [INF-γ]) and antibody secretion were assayed. We found that fetal and neonatal CD21(+) B cells spontaneously secreted high levels of IL-10 regardless of CpG stimulation but that these cells did not produce any IL-12 or INF-γ upon stimulation with CpG. The observed responses are consistent with those previously reported for Bregs characterized in JPP of older lambs. Surprisingly, unlike in older lambs, fetal and neonatal JPP CD21(+) B cells proliferated in response to CpG stimulation. Our investigations of fetal and neonatal lambs provide evidence for the development of IL-10-secreting CD21(+) B cells in PPs prior to antigen exposure.

Stress, acute phase proteins and immune modulation in calves

Acute phase and inflammatory responses are triggered by a variety of intrinsic and extrinsic stressors that come at a cost through suppressing the normal function of tissues and organs of domestic animals. Recently, with growing attention placed on global warming and animal welfare, there has been an increased interest in improving our understanding of the relationships between different classes of stress, the expression of acute phase proteins (APPs), the stress-related endocrine system and immunomodulation. Immune function is compromised by all forms of stress including poor nutrition, weaning, extreme thermal conditions, injury and infection in calves. Proinflammatory cytokines, APPs and hormones of the hypothalamic–pituitary adrenal axis as well as the composition of immune cells can all be characterised in culture supernatants and peripheral blood. APPs have been used as biomarkers for the stress status of ruminants both experimentally and in field studies. Therefore detailed studies of the mechanisms of action of these APPs and their interactions in ameliorating different stress responses are warranted. The focus of this review is on the aetiology of the responses in calves under severe stress and its impact on growth and immune status. Possible strategies to alleviate this condition including the role of specific feed additives are presented.

Cytosine-phosphate-guanine oligodeoxynucleotides containing GACGTT motifs enhance the immune responses elicited by keyhole limpet hemocyanin antigen in dairy cattle

Adjuvants are important components of vaccine formulations. Effective adjuvants line innate and adaptive immunity by signaling through pathogen recognition receptors. Synthetic cytosine-phosphate-guanine (CpG) oligodeoxynucleotides (ODNs) have been shown to have potentials as adjuvants for vaccines. However, the immunostimulatory effect of CpG is species-specific and depends on the sequence of CpG motifs. A CpG ODN (2135), containing 3 identical copies of GTCGTT motif, was previously reported to have the strongest effects on bovine peripheral blood mononuclear cells (PBMC). Based on the sequence of 2135, we replaced the GTCGTT motif with 11 other sequences containing CG and investigated their effects on bovine lymphocyte proliferation. Results showed that the CpG ODNs containing 3 copies of GACGTT motif had the highest lymphocyte stimulation index (7.91±1.18), which was significantly (P<0.05) higher than that of 2135 (4.25±0.56). The CpG ODNs containing 3 copies of GACGTT motif also significantly increased the mRNA expression of interferon (IFN)-α, interleukin (IL)-12, and IL-21 in bovine PBMC. When dairy cows were immunized with the keyhole limpet hemocyanin (KLH) antigen formulated with CpG ODNs containing 3 copies of GACGTT, production of KLH-specific antibodies in serum and in milk whey was significantly (P<0.05) enhanced. IFN-γ in whole blood stimulated by KLH was also significantly (P<0.05) increased in cows immunized with KLH plus CpG ODNs. Our results indicate that CpG ODNs containing 3 copies of the GACGTT motifs is a potential adjuvant for bovine vaccines.

CpG oligodeoxynucleotide and montanide ISA 206 adjuvant combination augments the immune responses of a recombinant FMDV vaccine in cattle

Foot-and-mouth disease (FMD) is a highly contagious disease of cloven-hoofed animals. To prevent the spread of FMDV, inactivated virus vaccines are used to immunize animals in developing countries. However, there are safety concerns. In addition, it is difficult to distinguish the vaccinated animals from those naturally infected ones. In our lab, we have developed a recombinant FMDV vaccine named A7. A7 contained multiple B cell and T cell epitopes, which reside in a capsid protein (VP1) of FMDV. To enhance its immunogenicity, A7 was formulated with CpG ODN RW03 in combination with Montanide ISA 206 (ISA), and the resultant vaccine (A7+ISA+CpG ODN RW03) was used to immunize mice and cattle. It was found that CpG ODN RW03 and ISA combination could facilitate A7 to induce a vigorous and long-lasting specific antibody response in mice and cattle. After FMDV challenge, 80% (4/5) of the calves immunized with A7+ISA+CpG ODN RW03 were protected, which was superior to those immunized with A7+ISA (25%, 1/4) or inactivated FMDV vaccine (50%, 2/4). These findings suggest that CpG ODN RW03 could be used with Montanide ISA 206 as a potent adjuvant for recombinant FMDV in cattle.

Reduced efficacy of multiple doses of CpG-matured dendritic cell tumor vaccine in an experimental model

CpG motifs have been advanced as agents that stimulate the maturation of DCs for immunotherapy. The present study tested the hypothesis that multiple doses of CpG-matured DC vaccine would be efficacious for complete eradication of experimentally-induced tumor. Accordingly, WEHI164 cells were implanted subcutaneously in the flank of BALB/c mice. During DC culture, tumor lysate was added to immature DCs followed by addition of CpG or non-CpG control 4-6h later. A total of three doses of CpG or non-CpG control-matured DCs were injected around tumors. The results showed that multiple doses of CpG-matured DCs led to considerable decrease in cytotoxicity of lymphocytes and significantly increased tumor growth rate compared to a single dose. Further, mice which received three doses of the vaccine also displayed significant FoxP3 in tumor tissue. In conclusion, multiple doses of CpG-matured DCs exhibited decreased anti-tumor immunity in association with increased expression of FoxP3.

Mesenteric lymph node cells from neonates present a prominent IL-12 response to CpG oligodeoxynucleotide via an IL-15 feedback loop of amplification

At birth, the immune system is still in development making neonates more susceptible to infections. The recognition of microbial ligands is a key step in the initiation of immune responses. It can be mimicked to stimulate the immune system by the use of synthetic ligands recognising pattern recognition receptors. In human and mouse, it has been found that neonatal cytokine responses to toll-like receptor (TLR) ligands differ in many ways from those of adults but the relevant studies have been limited to cord blood and spleen cells. In this study, we compared the responses in neonate and adult sheep to CpG oligodeoxynucleotides (ODN), a TLR9 ligand, in both a mucosal and a systemic organ. We observed that in response to CpG-ODN more IL-12 was produced by neonatal than adult sheep cells from mesenteric lymph nodes (MLN) and spleen. This higher IL-12 response was limited to the first 20 days after birth for MLN cells but persisted for a longer period for spleen cells. The major IL-12-producing cells were identified as CD14⁺CD11b⁺. These cells were poor producers of IL-12 in response to direct stimulation with CpG-ODN and required the cooperation of other MLN cells. The difference in response to CpG-ODN between neonates and adults can be attributed to both a higher proportion of CD14⁺CD11b⁺ cells in neonate lambs and their higher capacity to produce IL-15. The IL-15 increases IL-12 production by an amplifying feedback loop involving CD40.