Sarah L. Young

Bifidobacterial Species Differentially Affect Expression of Cell Surface Markers and Cytokines of Dendritic Cells Harvested from Cord Blood

ABSTRACT The gut microbiota may be important in the postnatal development of the immune system and hence may influence the prevalence of atopic diseases. Bifidobacteria are the most numerous bacteria in the guts of infants, and the presence or absence of certain species could be important in determining the geographic incidence of atopic diseases. We compared the fecal populations of bifidobacteria from children aged 25 to 35 days in Ghana (which has a low prevalence of atopy), New Zealand, and the United Kingdom (high-prevalence countries). Natal origin influenced the detection of bifidobacterial species in that fecal samples from Ghana almost all contained Bifidobacterium infantis whereas those of the other children did not. Choosing species on the basis of our bacteriological results, we tested bifidobacterial preparations for their effects on cell surface markers and cytokine production by dendritic cells harvested from cord blood. Species-specific effects on the expression of the dendritic-cell activation marker CD83 and the production of interleukin-10 (IL-10) were observed. Whereas CD83 expression was increased and IL-10 production was induced by Bifidobacterium bifidum, Bifidobacterium longum, and Bifidobacterium pseudocatenulatum, B. infantis failed to produce these effects. We concluded that B. infantis does not trigger the activation of dendritic cells to the degree necessary to initiate an immune response but that B. bifidum, B. longum, and B. pseudocatenulatum induce a Th2-driven immune response. A hypothesis is presented to link our observations to the prevalence of atopic diseases in different countries.

Obesity During Pregnancy Disrupts Placental Morphology, Cell Proliferation, and Inflammation in a Sex-Specific Manner Across Gestation in the Mouse

ABSTRACT It is well-accepted that maternal obesity affects fetal development to elevate the risk of offspring disease, but how this happens is unclear. Understanding placental alterations during gestation as a consequence of maternal obesity is critical to understanding the impact of maternal obesity on fetal programming. Here, we used histological criteria, flow cytometry, quantitative PCR, and multiplex cytokine assays to examine changes in cell proliferation and inflammation in the placenta during gestation in a mouse model of maternal high-fat diet-induced obesity. We focused on mouse mid- to late gestation (approximately human late first and third trimester) because previous literature has indicated that this is when important regulators of metabolism, including that of the brain and endocrine pancreas, are forming. These studies were undertaken in order to understand how maternal obesity changes the placenta during this period, which might suggest a causal link to later-life metabolic dysfunction. We found that labyrinth thickness and cell proliferation were decreased at both pregnancy stages in obese compared to normal weight pregnancies. Inflammation was also altered in late pregnancy with increased macrophage activation and elevated cytokine gene expression in the placenta as well as increased abundance of some cytokines in the fetal circulation in obese compared to normal weight pregnancies. These changes in macrophage activation and cytokine gene expression were of greater magnitude and significance in placentas accompanying male fetuses. These data provide insight into placental changes in obesity and identify potential links between placental inflammation and programming of offspring disease by maternal obesity.

Cross-presentation of epitopes on virus-like particles via the MHC I receptor recycling pathway

Effective vaccines and immunotherapies against cancer require professional antigen‐presenting cells to cross‐present exogenous antigen to initiate cytotoxic T‐cell responses to destroy tumors. Virus‐like particles (VLPs), containing tumor antigens, which can immunize against cancers, are cross‐presented by dendritic cell (DC) but the mechanism by which this occurs is not fully understood. Here, we used VLPs, derived from rabbit hemorrhagic disease virus (RHDV) with both murine and human DCs, to elucidate these pathways. We have employed inhibitors to demonstrate that these VLPs are taken up by clathrin‐dependent macropinocytosis and phagocytosis before being degraded in acidic lysosomal compartments. VLP‐derived peptides are loaded onto major histocompatibility complex I that have been recycled from the cell surface. Antigen‐coupled VLPs and murine ovalbumin‐specific and human melanoma‐associated antigen recognized by T cells (MART‐1)‐specific CD8+ T cells were used to demonstrate cross‐presentation via this alternate, receptor recycling pathway, which operated independently of the proteasome and the transporter‐associated with antigen presentation. Finally, we found that cross‐presentation of VLPs in vivo was not confined to CD8α+ DC subsets. These data define the cross‐presentation pathway for RHDV VLPs and may lead to improved cancer immunotherapies.

Manipulation of immune responses to Mycobacterium bovis by vaccination with IL-2- and IL-18-secreting recombinant bacillus Calmette Guerin.

Bacillus Calmette Guerin (BCG) has been reported to show variable efficacy as a vaccine against tuberculosis. We demonstrated that the secretion of biologically active IL‐2 (rBCG/IL‐2), but not IL‐18 (rBCG/IL‐18), by BCG improves its ability to induce and maintain a strong type 1 immune response in BALB/c mice. rBCG/IL‐2 induced significantly higher Ag‐specific proliferative responses, high IFN‐γ production and serum titres of IgG2a 16 weeks after vaccination. This immune profile was correlated to an increased rate of clearance of non‐pathogenic mycobacteria (live BCG delivered intranasally). Surprisingly, however, this strong type 1 immune profile induced no greater protective immunity against aerosol challenge with virulent Mycobacterium bovis than that induced by normal BCG (nBCG). By comparison, vaccination with rBCG/IL‐18 was found to induce significantly less IFN‐γ production in splenic lymphocytes than nBCG. This impaired induction of IFN‐γ was correlated to a significantly lower protective efficacy against M. bovis challenge, as compared to nBCG. The data suggest that manipulation of the immune response to tuberculosis and tuberculosis vaccines will require a more complete understanding of the factors that are important in generating a protective immune response.

Utility of interleukin-12 and interleukin-10 in comparison with other cytokines and acute-phase reactants in the diagnosis of neonatal sepsis.

We compared the test characteristics of interleukin (IL)-1 beta, IL-6, IL-8, IL-10, IL-12(p-70), tumor necrosis factor-alpha (TNF-alpha), procalcitonin (PCT), C-reactive protein (CRP), and full blood count (FBC) in the diagnosis of neonatal sepsis. This prospective cohort study in the Neonatal Intensive Care Unit of Dunedin hospital of patients between July 1, 2002 and February 28, 2007 included 117 neonates commenced on antibiotics for 164 episodes of suspected sepsis. Blood cultures, FBC, CRP, IL-1 beta, IL-6, IL-8, IL-10, IL-12(p-70), TNF-alpha, and PCT were obtained at the time sepsis was first suspected and for the following 3 days. Receiver operator characteristics (ROC) plots and test characteristics were determined using culture-positive sepsis as the gold standard. At the time sepsis was first suspected, the most promising individual test was IL-12(p70) with an area under the curve (95% confidence interval [CI]) for the ROC of 0.74 (0.63 to 0.86), which (with a cutoff at 75 pg/mL) had a sensitivity (95% CI) of 28% (20 to 36%) and a specificity of 98% (96 to 100%). IL-10 had a sensitivity of 17% (10 to 23%) and a specificity of 99% (97 to 100%). IL-10 and IL-12(p70) are promising diagnostic tests that can be used to confirm sepsis in neonates.

Environmental Strains of Mycobacterium avium Interfere with Immune Responses Associated with Mycobacterium bovis BCG Vaccination

ABSTRACT Prior exposure of a vaccinee to certain species of environmental mycobacteria can prime the immune system against common mycobacterial antigens, which can in turn reduce the subsequent efficacy of live attenuated mycobacterial vaccines (such as Mycobacterium bovis BCG), in both human and livestock vaccination programs. In this study, two strains of Mycobacterium avium, both isolated from New Zealand livestock, were investigated to determine their growth characteristics and effects on the immune system in murine models. Markedly different effects on the immune system were observed; an IS901-negative strain (WAg 207) induced significant up-regulation of cell surface activation markers (major histocompatibility complex II, CD80, and CD86) on in vitro-derived dendritic cells and induced the release of proinflammatory monokines (interleukin-1β [IL-1β], IL-6, and tumor necrosis factor alpha) in dendritic cell-macrophage cocultures following direct in vitro contact of cells with bacteria. In contrast, an IS901-positive strain (WAg 206) had none of these effects. When mice were exposed to M. avium via oral infection prior to BCG parenteral immunization, both strains were shown to be capable of decreasing subsequent antigen-stimulated gamma interferon secretion by splenic lymphocytes, although this effect was more significant for strain WAg 206. Both strains also induced a mycobacterial antigen-specific serological response in M. avium-sensitized and BCG-immunized mice; this response was greater in WAg 206-sensitized mice, and there was a predominance of immunoglobulin G1 antibody. The down-regulation of IFN-γ responses and the up-regulation of antibody responses are characteristic of a switch to a type 2 immune response. The different results may be linked to the inherent growth characteristics of the two strains, since WAg 206 was shown to grow slowly in murine macrophages in vitro and to cause a persistent systemic infection following infection in vivo, while WAg 207 grew fast and did not persist in mice. The implications of these findings for BCG vaccination protocols are discussed.

Virus-like particles from rabbit hemorrhagic disease virus can induce an anti-tumor response

Recombinant virus-like particles (VLP) expressing heterologous tumor antigens have recently been investigated for use as vaccines. We have chemically conjugated ovalbumin (OVA) or OVA-derived CD4 (OTII) and CD8 (OTI) epitopes, to rabbit hemorrhagic disease virus (RHDV) VLP. VLP conjugated with OVA were able to cross-prime CD8+ cells from OT1 mice transgenic for the OVA T cell receptor. VLP.OTI was able to induce higher antigen-specific cytotoxicity in vivo than VLP mixed with either the protein or the peptide. Furthermore we have shown that the growth of the aggressive B16.OVA melanoma in mice was significantly delayed in those animals that had been vaccinated with VLP.OVA or with VLP coupled with both OTI and OTII peptides prior to the introduction of the tumor. Neither VLP.OTI nor VLP.OTII alone were capable of inhibiting tumor growth. This work suggests that RHDV VLP offer a versatile scaffold for multiple vaccine epitopes, enabling cross-presentation of the antigen to elicit potent cell-mediated and anti-tumor responses.

Cytokine-modified Mycobacterium smegmatis as a novel anticancer immunotherapy

Intravesical administration of live M. bovis BCG organisms for carcinoma in situ of the urinary bladder is the most successful immunotherapy for solid malignancy. Nevertheless BCG‐therapy is associated with significant toxicity and is ineffective in 30–40% of cases. Recently it has been proposed that cytokine‐modified mycobacteria may give greater efficacy. As any immunotherapy involving administration of live BCG organisms (wild‐type or recombinant) is likely to have associated toxicity (notably in the immunocompromised), we examined the anti‐tumour potential of the closely related nonpathogenic organism, Mycobacterium smegmatis, and a TNFα gene‐modified recombinant M. smegmatis. When wild‐type M. smegmatis were delivered to immunocompetent C57Bl/6 mice bearing the transplantable MB49 bladder tumour, efficacy comparable to live BCG was observed with 10–20% long‐term survival. However, this effect was lost in both Nude and Beige mice, lacking functional T and NK cells, respectively. Recombinant M. smegmatis secreting TNFα, however, gave a 70% durable tumour‐free survival. Lymphocytes from draining lymph‐nodes and spleens of these mice exhibited pronounced IFNγ production to mycobacterial‐antigen and tumour‐lysate, indicating a bias towards cell‐mediated immunity. This was further supported by histopathological examination of the tumour site, which revealed significantly increased numbers of CD3+ lymphocytes in animals receiving the recombinant vaccine, but not in those receiving wild‐type bacteria. Importantly, tumour rejection following M. smegmatis/TNFα was independent of T lymphocytes, as athymic Nude mice efficiently eradicated MB49 tumours. In contrast, the therapeutic efficacy of M. smegmatis/TNFα was reduced in animals deficient in NK cytolytic function, suggesting a role for NK‐cells in initial tumour destruction. Furthermore the absence of NK‐function in Beige mice did not prevent the establishment of tumour‐protective memory. No toxicity was observed with wild‐type or recombinant M. smegmatis in immunocompetent, T‐deficient or NK‐deficient models. We demonstrate for the first time that recombinant mycobacteria expressing mammalian cytokines have markedly increased anti‐tumour properties. The lack of toxicity suggests that M. smegmatis is a “safe” vehicle for use in immunocompromised patients.

Virus-like particles and α-galactosylceramide form a self-adjuvanting composite particle that elicits anti-tumor responses.

Virus-like particles (VLP) are effective vehicles for delivery of heterologous antigen to antigen-presenting cells. However VLP alone are insufficiently stimulatory to generate the signals required to facilitate effective priming of naïve T cells. We show that the VLP derived from rabbit hemorrhagic disease virus can bind the galactose-containing adjuvant α-galactosylceramide to form a composite particle for co-delivery of antigen and adjuvant to the same antigen-presenting cell. Vaccination with VLP and α-galactosylceramide activated splenic iNKT cells to produce IFN-γ and IL-4, led to the generation of antigen-specific T cells that protected prophylactically against subcutaneous tumor challenge, and was more effective at generating anti-tumor immune responses than either component individually. These data demonstrate a novel method for immunopotentiating VLP to increase their efficacy in the generation of anti-tumor responses via the innate ligand recognition properties of calicivirus-derived nanoparticles.

An enhanced heterologous virus-like particle for human papillomavirus type 16 tumour immunotherapy.

Cervical cancer is caused by high-risk, cancer-causing human papillomaviruses (HPV) and is the second highest cause of cancer deaths in women globally. The majority of cervical cancers express well-characterized HPV oncogenes, which are potential targets for immunotherapeutic vaccination. Here we develop a rabbit haemorrhagic disease virus (RHDV) virus-like particle (VLP)-based vaccine designed for immunotherapy against HPV16 positive tumours. An RHDV-VLP, modified to contain the universal helper T cell epitope PADRE and decorated with an MHC I-restricted peptide (aa 48–57) from the HPV16 E6, was tested for its immunotherapeutic efficacy against the TC-1 HPV16 E6 and E7-expressing tumour in mice. The E6-RHDV-VLP-PADRE was administered therapeutically for the treatment of a pre-existing TC-1 tumour and was delivered with antibodies either to deplete regulatory T cells (anti-CD25) or to block T cell suppression mediated through CTLA-4. As a result, the tumour burden was reduced by around 50% and the median survival time of mice to the humane endpoint was almost doubled the compared to controls. The incorporation of PADRE into the RHDV-VLP was necessary for an E6-specific enhancement of the anti-tumour response and the co-administration of the immune modifying antibodies contributed to the overall efficacy of the immunotherapy. The E6-RHDV-VLP-PADRE shows immunotherapeutic efficacy, prolonging survival for HPV tumour-bearing mice. This was enhanced by the systemic administration of immune-modifying antibodies that are commercially available for use in humans. There is potential to further modify these particles for even greater efficacy in the path to development of an immunotherapeutic treatment for HPV precancerous and cancer stages.