Immunophenotype and functions of fetal baboon bone-marrow derived dendritic cells

Dendritic cell-based immunization induces Coccidioides Ag2/PRA-specific immune response

Valley Fever, or coccidioidomycosis, is caused by a soil-borne, highly virulent fungal pathogen, Coccidioides spp. Infection with Coccidioides can be life-threatening. Since an effective treatment is not available and the T cell-mediated immune response is protective, vaccine development is of interest. In this study, a primary dendritic cell (DC)-vaccine was evaluated for its ability to stimulate Coccidioides antigen-specific immune response in an extremely susceptible BALB/c mouse model. The DC-vaccine (Ag2-DC) was prepared by non-virally transfecting the primary bone marrow-derived DCs with a plasmid DNA encoding Ag2/PRA (protective epitope of Coccidioides). Mice were intranasally immunized with Ag2-DC on days 2 and 10. Immunized mice were necropsied on days 8, 32, and 44. Major organs and blood samples were harvested. The most common indicators of injury (protein, lactate, and albumin), Ag/PRA-specific cytokine-secreting cells, and IgG and its isotypes were determined by biochemical and immunologic assays, respectively. No signs of sickness were noted. Similarly, no significant changes were observed in the levels of total lung protein, lactate, and albumin, in immunized mice compared with healthy control mice. Interferon (IFN-γ), and interleukin (IL)-4 and IL-17 cytokine-secreting cells were observed in lung and lymph nodes upon Ag2-DC immunization. Our results showed that the levels of serum IgG and its isotypes were increased in Ag2-DC-immunized mice. This report provides evidence of DC immunization-stimulated Ag2/PRA-specific immune responses.

Lung dendritic cell developmental programming, environmental stimuli, and asthma in early periods of life

Dendritic cells (DCs) are important cells of our innate immune system. Their role is critical in inducing adaptive immunity, tolerance, or allergic response in peripheral organs—lung and skin. The lung DCs are not developed prenatally before birth. The DCs develop after birth presumably during the first year of life; exposures to any foreign antigen or infectious organisms during this period can significantly affect DC developmental programming and generation of distinct DC phenotypes and functions. These changes can have both short-term and long-term health effects which may be very relevant in childhood asthma and predisposition for a persistent response in adulthood. An understanding of DC development at molecular and cellular levels can help in protecting neonates and infants against problematic environmental exposures and developmental immunotoxicity. This knowledge can eventually help in designing novel pharmacological modulators to skew the DC characteristics and immune responses to benefit the host across a lifetime.

Non-human primate dendritic cells

Non-human primates (NHP) are essential translational models for biomedical research. Dendritic cells (DC) are a group of antigen presenting cells (APC) that play pivotal roles in the immunobiology of health and disease and are attractive cells for adoptive immunotherapy to stimulate and suppress immunity. DC have been studied extensively in humans and mice but until recently, have not been well characterized in NHP. This review considers the available data about DC across a range of NHP species and summarizes the understanding of in vitro-propagated DC and in vivo-isolated DC, which is now established. It is clear that although NHP DC exist within the paradigm of human DC, there are important functional and phenotypic differences when compared with human DC subsets. These differences need to be taken into account when designing preclinical, translational studies of DC therapy using NHP models.

Surfactant protein-A and toll-like receptor-4 modulate immune functions of preterm baboon lung dendritic cell precursor cells

Lung infections are important risk factors for an increased morbidity and mortality in prematurely-delivered babies. Immaturity of the innate immune components makes them extremely susceptible to infection. Recently, we isolated lung dendritic cell (DC)-precursor cells from preterm fetal baboons. The isolated cells were found to be defective in phagocytosing Escherichia coli under basal conditions. In this study, we investigated the effects of exogenously-added purified native lung surfactant protein (SP)-A and recombinant toll-like receptor (TLR)-4-MD2 proteins on phagocytic uptake and cytokine secreting ability of fetal baboon lung DC-precursor cells. The cells were pulsed with SP-A and/or TLR4-MD2 proteins and the phagocytic function was investigated by incubating the cells with fluorescent-labeled E. coli bioparticles and analyzed by spectrofluorometry. The amounts of TNF-α secreted in cell-free supernatants were measured by ELISA. Our results demonstrate that SP-A and TLR4-MD2 proteins, whether added alone or together, induce phagocytosis of E. coli (p<0.05). The SP-A does not affect TNF-α secretion, while the TLR4-MD2 protein induces TNF-α. However, simultaneous addition of SP-A with TLR4-MD2 protein reduces the TLR4-MD2-protein induced TNF-α to basal level. In conclusion, our results indicate that an exogenous administration of SP-A can potentially induce phagocytic activity and anti-inflammatory effect in preterm babies, and help control infection and inflammation.

In vivo trafficking and immunostimulatory potential of an intranasally-administered primary dendritic cell-based vaccine

BACKGROUND

Coccidioidomycosis or Valley fever is caused by a highly virulent fungal pathogen: Coccidioides posadasii or immitis. Vaccine development against Coccidioides is of contemporary interest because a large number of relapses and clinical failures are reported with antifungal agents. An efficient Th1 response engenders protection. Thus, we have focused on developing a dendritic cell (DC)-based vaccine for coccidioidomycosis. In this study, we investigated the immunostimulatory characteristics of an intranasal primary DC-vaccine in BALB/c mouse strain that is most susceptible to coccidioidomycosis. The DCs were transfected nonvirally with Coccidioides-Ag2/PRA-cDNA. Expression of DC-markers, Ag2/PRA and cytokines were studied by flow cytometry, dot-immunoblotting and cytometric bead array methods, respectively. The T cell activation was studied by assessing the upregulation of activation markers in a DC-T cell co-culture assay. For trafficking, the DCs were co-transfected with a plasmid DNA encoding HSV1 thymidine kinase (TK) and administered intranasally into syngeneic mice. The trafficking and homing of TK-expressing DCs were monitored with positron emission tomography (PET) using 18F-FIAU probe. Based on the PET-probe accumulation in vaccinated mice, selected tissues were studied for antigen-specific response and T cell phenotypes using ELISPOT and flow cytometry, respectively.

RESULTS

We found that the primary DCs transfected with Coccidioides-Ag2/PRA-cDNA were of immature immunophenotype, expressed Ag2/PRA and activated naïve T cells. In PET images and subsequent biodistribution, intranasally-administered DCs were found to migrate in blood, lung and thymus; lymphocytes showed generation of T effector memory cell population (T(EM)) and IFN-γ release.

CONCLUSIONS

In conclusion, our results demonstrate that the intranasally-administered primary DC vaccine is capable of inducing Ag2/PRA-specific T cell response. Unique approaches utilized in our study represent an attractive and novel means of producing and evaluating an autologous DC-based vaccine.

Ontogeny and phagocytic function of baboon lung dendritic cells

Dendritic cells (DCs) are the most potent antigen-presenting cells, but the ontogeny and functions of lung DCs are not known during prenatal period. Here, we isolated lung DC population from fetal (125 −175dGA) and adult baboons. The cells were stained with fluorochrome-conjugated-HLA-DP, DQ, DR, CD1a, CD11c, CD14, CD40, CD80, CD86, CD209, CMKLR1, ILT7-specific antibodies, and staining was analyzed by Flow-cytometry. The phagocytic function was investigated by incubating the cells with fluorescent-labeled Escherichia coli bioparticles and analyzed by Flow-cytometry and fluorescence microscopy. The fetal baboon lung DCs expressed low levels of HLA-DP, DQ, DR, CD11c and CD86 as compared to adult baboon lung DCs and showed distinct DC morphology. The fetal lung DCs were also less capable of phagocytosing E. coli as compared to the adult lung DCs (p<0.05). In conclusion, the fetal lung DCs are not only phenotypically immature, but also less efficient in phagocytosing E. coli.

Transgenic zebrafish reporter lines reveal conserved Toll-like receptor signaling potential in embryonic myeloid leukocytes and adult immune cell lineages

The immune response of a host to an invading pathogen is dependent on the capacity of its immune cell compartment to recognize highly conserved pathogen components using an ancient class of pattern recognition receptors known as Toll-like receptors (TLRs). Initiation of TLR-mediated signaling results in the induction of proinflammatory cytokines that help govern the scale and duration of any ensuing response. Specificity for TLR signaling is, in part, a result of the differential recruitment of intracellular adaptor molecules. Of these, MyD88 is required for the majority of TLR signaling. Zebrafish have been shown to possess TLRs and adaptor molecules throughout early development, including MyD88, strongly suggesting conservation of this ancient defense mechanism. However, information about which embryonic cells/tissues possess this conserved signaling potential is lacking. To help define which embryonic cells, in particular, those of the innate immune system, have the potential for MyD88-dependent, TLR-mediated signaling, we generated transgenic reporter lines using regulatory elements of the myd88 gene to drive the fluorescent reporters enhanced GFP and Discosoma red fluorescent protein 2 within live zebrafish. These lines possess fluorescently marked cells/tissues consistent with endogenous myd88 expression, including a subset of myeloid leukocytes. These innate immune cells were confirmed to express other TLR adaptors including Mal, trif, and Sarm. Live wound-healing and infection assays validated the potential of these myd88-expressing leukocytes to participate in immune responses. These lines will provide a valuable resource for further resolving the contribution of MyD88 to early vertebrate immunity.

Effects of Saccharomyces boulardii on cytokine secretion from intraepithelial lymphocytes infected by Escherichia coli and Candida albicans

Saccharomyces boulardii (S. boulardii) is a probiotic and used in the prevention or treatment of diarrhoea. Saccharomyces boulardii has many mechanisms to protect the host against diarrhoeal pathogens. It might modulate the immune system. In this study, the influence of S. boulardii on the secretion of cytokines from intraepithelial lymphocytes (IELs) infected with Escherichia coli (E. coli) and Candida albicans (C. albicans) was investigated in vitro. Cytokine levels were determined by enzyme-linked immunosorbent assay. The secretion of proinflammatory cytokines such as interleukin (IL)-1beta was decreased in the infected IELs incubated with S. boulardii, but different from it, anti-inflammatory cytokine levels such as IL-4 and IL-10, however, were found to be higher. These findings demonstrated that S. boulardii may have protective effects against diarrhoeal pathogens by reducing the proinflammatory response.

Developmental expression of Toll-like receptors-2 and -4 in preterm baboon lung

Preterm babies are susceptible to respiratory infection due to immature lung and immune system. Immune cells express Toll-like receptors (TLRs), which may be important in local host defense of preterm infants. We studied the expression of TLR2 and TLR4 in lung tissues of fetal baboons delivered at 125, 140, and 175 days of gestation (dGA; term=185+/-2 days) and preterm baboons that became naturally infected with bacterial/fungal pathogens. The TLR-mRNA and protein were quantified by Northern and Western blotting, respectively. The expression of both TLRs was significantly low at 125 and 140dGA. At 175dGA, the levels reached equivalent to those in adult baboons. However, in naturally infected baboons, the TLR4-mRNA was reduced (p<0.05); TLR2-mRNA expression remained unaltered. The protein expression of both TLRs was found increased in naturally infected baboons. Our results suggest that the lung TLR expression is developmentally regulated and altered during respiratory infection in preterm babies.