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Purpose: Immunoregulatory and suppressive mechanisms represent major obstacles to the success of immunotherapy in cancer patients. We have shown that the combination of radiotherapy to the primary tumor and CTL-associated protein 4 (CTLA-4) blockade induces antitumor immunity, inhibiting metastases and extending the survival of mice bearing the poorly immunogenic and highly metastatic 4T1 mammary carcinoma. Similarly to patients with metastatic cancer, however, mice were seldom cured. Here we tested the hypothesis that invariant natural killer T (iNKT) cells, a subset with unique regulatory functions, can regulate the response to radiotherapy and CTLA-4 blockade.Experimental Design: The growth of 4T1 primary tumors and lung metastases was compared in wild-type and iNKT cell–deficient (iNKT-/-) mice. Treatment was started on day 13 when the primary tumors were palpable. Mice received radiotherapy to the primary tumor in two doses of 12 Gy in combination or not with 9H10 monoclonal antibody against CTLA-4. Response to treatment was assessed by measuring primary tumor growth delay/regression, survival, and number of lung metastases.Results: The response to radiotherapy plus 9H10 was markedly enhanced in the absence of iNKT cells, with 50% of iNKT-/- versus 0% of wild-type mice showing complete tumor regression, long-term survival, and resistance to a challenge with 4T1 cells. Administration of the iNKT cell activator α-galactosylceramide did not enhance the response of wild-type mice to radiotherapy plus 9H10. Tumor-infiltrating iNKT cells were markedly reduced in wild-type mice treated with radiotherapy plus 9H10.Conclusions: iNKT cells play a major role in regulating the response to treatment with local radiotherapy and CTLA-4 blockade.

The isolation of Streptococcus pneumoniae serotypes in systemic tissues of patients with invasive disease versus the nasopharynx of healthy individuals with asymptomatic carriage varies widely. Some serotypes are hyper-invasive, particularly serotype 1, but the underlying genetics remain poorly understood due to the rarity of carriage isolates, reducing the power of comparison with invasive isolates. Here, we use a well-controlled genome-wide association study to search for genetic variation associated with invasiveness of serotype 1 pneumococci from a serotype 1 endemic setting in Africa. We found no consensus evidence that certain genomic variation is overrepresented among isolates from patients with invasive disease than asymptomatic carriage. Overall, the genomic variation explained negligible phenotypic variability, suggesting a minimal effect on the disease status. Furthermore, changes in lineage distribution were seen with lineages replacing each other over time, highlighting the importance of continued pathogen surveillance. Our findings suggest that the hyper-invasiveness is an intrinsic property of the serotype 1 strains, not specific for a “disease-associated” subpopulation disproportionately harboring unique genomic variation.

Funder: Joint Programming Initiative on Antimicrobial Resistance; doi: http://dx.doi.org/10.13039/100013281, Funder: UK Medical Research Council, Streptococcus pneumoniae is a devastating global pathogen. Prevalent in sub-Saharan Africa, pneumococcal serotype 1 is atypical in that it is rarely found as a nasopharyngeal coloniser, yet is described as one of the most common causes of invasive pneumococcal disease. Clonal sequence type (ST)-306 and ST615 are representative of the two major serotype 1 lineages A and C, respectively. Here we investigated the virulence properties and haemolytic activities of these 2 clonal types using in vivo mouse models and in vitro assays. A lethal dose of ST615 administered intranasally to mice led to the rapid onset of disease symptoms and resulted in 90% mortality. In contrast, mice exposed to the same infection dose of ST306 or a pneumolysin (Ply)-deficient ST615 failed to develop any disease symptoms. Interestingly, the 2 strains did not differ in their ability to bind the immune complement or to undergo neutrophil-mediated phagocytosis. Upon comparative genomic analysis, we found higher within-ST sequence diversity in ST615 compared with ST306 and determined that ZmpA, ZmpD proteins, and IgA protease, were uniquely found in ST615. Using cell fractionation and cell contact-dependent assay, we made the unexpected finding that ST615 harbours the expression of two haemolytic variants of Ply: a cell-wall restricted fully haemolytic Ply, and a cytosolic pool of Ply void of any detectable haemolytic activity. This is the first time such a phenomenon has been described. We discuss the biological significance of our observation in relation to the aptitude of the pneumococcus for sustaining its human reservoir.

The entry routes and translocation mechanisms of bacterial pathogens into the central nervous system remain obscure. We report here thatStreptococcus pneumoniae(Sp) or polystyrene microspheres, applied to the nose of a mouse, appeared in the meninges of the dorsal cortex within minutes. Recovery of viable bacteria from dissected tissue and fluorescence microscopy showed that up to at least 72h, Sp and microspheres were predominantly in the outer of the two meninges, the pachymeninx. No Sp were found in blood or cerebrospinal fluid. Evidence that this was not an artifact of the method of administration is that in mice infected by horizontal transmission, Sp were also predominantly in the meninges and absent from blood. Intravital imaging through the skull, and flow cytometry showed recruitment and activation of LysM+cells in the dorsal pachymeninx at 5h and 10h following intranasal infection. Imaging of the cribriform plate suggested that both Sp and microspheres entered through its foramina via an inward flow of fluid connecting the nose to the pachymeninx. Our findings bring further insight into the invasion mechanisms of bacterial pathogens such as Sp into the central nervous system, but are also pertinent to the delivery of drugs to the brain, and the entry of air-borne particles into the cranium.

The pneumococcus causes serious diseases such as pneumonia, sepsis, and meningitis and is a major cause of morbidity and mortality worldwide. Serotype 1 accounts for the majority of invasive pneumococcal disease cases in sub-Saharan Africa but is rarely found during nasopharyngeal carriage., Streptococcus pneumoniae is a frequent colonizer of the human nasopharynx and a major cause of life-threating invasive infections such as pneumonia, meningitis and sepsis. Over 1 million people die every year due to invasive pneumococcal disease (IPD), mainly in developing countries. Serotype 1 is a common cause of IPD; however, unlike other serotypes, it is rarely found in the carrier state in the nasopharynx, which is often considered a prerequisite for disease. The aim of this study was to understand this dichotomy. We used murine models of carriage and IPD to characterize the pathogenesis of African serotype 1 (sequence type 217) pneumococcal strains obtained from the Queen Elizabeth Central Hospital in Blantyre, Malawi. We found that ST217 pneumococcal strains were highly virulent in a mouse model of invasive pneumonia, but in contrast to the generally accepted assumption, can also successfully establish nasopharyngeal carriage. Interestingly, we found that cocolonizing serotypes may proliferate in the presence of serotype 1, suggesting that acquisition of serotype 1 carriage could increase the risk of developing IPD by other serotypes. RNA sequencing analysis confirmed that key virulence genes associated with inflammation and tissue invasiveness were upregulated in serotype 1. These data reveal important new insights into serotype 1 pathogenesis, with implications for carriage potential and risk of invasive disease through interactions with other cocolonizing serotypes, an often-overlooked factor in transmission and disease progression.

Streptococcus pneumoniae (the pneumococcus) is a major cause of mortality and morbidity globally, and the leading cause of death in children under 5 years old. The pneumococcal cytolysin pneumolysin (PLY) is a major virulence determinant known to induce pore-dependent pro-inflammatory responses. These inflammatory responses are driven by PLY–host cell membrane cholesterol interactions, but binding to a host cell receptor has not been previously demonstrated. Here, we discovered a receptor for PLY, whereby pro-inflammatory cytokine responses and Toll-like receptor signalling are inhibited following PLY binding to the mannose receptor C type 1 (MRC-1) in human dendritic cells and mouse alveolar macrophages. The cytokine suppressor SOCS1 is also upregulated. Moreover, PLY–MRC-1 interactions mediate pneumococcal internalization into non-lysosomal compartments and polarize naive T cells into an interferon-γlow, interleukin-4high and FoxP3+ immunoregulatory phenotype. In mice, PLY-expressing pneumococci colocalize with MRC-1 in alveolar macrophages, induce lower pro-inflammatory cytokine responses and reduce neutrophil infiltration compared with a PLY mutant. In vivo, reduced bacterial loads occur in the airways of MRC-1-deficient mice and in mice in which MRC-1 is inhibited using blocking antibodies. In conclusion, we show that pneumococci use PLY–MRC-1 interactions to downregulate inflammation and enhance bacterial survival in the airways. These findings have important implications for future vaccine design. A Streptococcus pneumoniae toxin, pneumolysin, binds to MRC-1 on phagocytes to dampen immune responses and promote infection.

Hyper-virulent Streptococcus pneumoniae serotype 1 strains are endemic in Sub-Saharan Africa and frequently cause lethal meningitis outbreaks. It remains unknown whether genetic variation in serotype 1 strains modulates tropism into cerebrospinal fluid to cause central nervous system (CNS) infections, particularly meningitis. Here, we address this question through a large-scale linear mixed model genome-wide association study of 909 African pneumococcal serotype 1 isolates collected from CNS and non-CNS human samples. By controlling for host age, geography, and strain population structure, we identify genome-wide statistically significant genotype-phenotype associations in surface-exposed choline-binding (P = 5.00 × 10−08) and helicase proteins (P = 1.32 × 10−06) important for invasion, immune evasion and pneumococcal tropism to CNS. The small effect sizes and negligible heritability indicated that causation of CNS infection requires multiple genetic and other factors reflecting a complex and polygenic aetiology. Our findings suggest that certain pathogen genetic variation modulate pneumococcal survival and tropism to CNS tissue, and therefore, virulence for meningitis., Using a genome-wide association study approach, Chaguza et al. identify significant genotype-phenotype associations relevant to Streptococcus pneumoniae infection. These findings indicate genetic variations in the pathogen attributed to pneumococcal tropism to central nervous system tissues, with implications for meningitis virulence.

Streptococcus pneumoniae (S.p.) and Respiratory Syncytial Virus (RSV) are two major pathogens commonly found to coexist in respiratory secretions in patients with acute respiratory infection. Though there is increasing evidence of a synergistic interplay between these two pathobionts, the exact mechanisms remain obscure. The aim of our study was to decipher how coinfection with RSV alter pneumococcal growth dynamics and host immune response and how this impact on the colonisation and invasive properties of S.p. Using in vivo mouse model, we made the key observation that upon coinfection with RSV, the density of pneumococcal colonisation in the nasopharynx and dissemination to the lower respiratory tract were significantly higher in mice previously colonised with S.p. These mice also presented more severe weight loss and delayed recovery compared to mono-infected animals as well as significantly heightened pro-inflammatory cytokine profiles. Measurement of in vitro transepithelial electrical resistance (TEER) showed that, upon RSV coinfection, S.p. transmigrate through the epithelial barrier without altering epithelial integrity suggesting a transcellular mechanism rather than paracellular migration. Moreover, RSV-pneumococcal coinfection of human primary nasal epithelial cell demonstrated major changes in host protein expression involved in the catalytic activity, ubiquitination, cytoskeletal organisation, and endocytosis. Simultaneously, significant upregulation observed in bacterial proteins involved in the ribosomal activity, streptococcus-induced tissue inflammation, DNA supercoiling, and bacterial viability during oxidative stress, affecting both the survival and the virulence of S.p. Our results explain the complex interactions between pneumococci, RSV and host and help towards further understanding the significance of viral-bacterial co-infection in clinical settings.

In this study we provide important evidence to show that changes in the epidemiology of pneumococcal serotype 1 sequence types in The Gambia may be a direct consequence of differences in virulence and increased ability to colonize hosts over time., Streptococcus pneumoniae serotype 1 is one of the leading causes of invasive pneumococcal disease (IPD) in West Africa, with ST618 being the dominant cause of IPD in The Gambia. Recently however, a rare example of clonal replacement was observed, where the ST3081 clone of serotype 1 replaced the predominant ST618 clone as the main cause of IPD. In the current study, we sought to find the reasons for this unusual replacement event. Using whole-genome sequence analysis and clinically relevant models of in vivo infection, we identified distinct genetic and phenotypic characteristics of the emerging ST3081 clone. We show that ST3081 is significantly more virulent than ST618 in models of invasive pneumonia, and is carried at higher densities than ST618 during nasopharyngeal carriage. We also observe sequence type–specific accessory genes and a unique sequence type–specific fixed mutation in the pneumococcal toxin pneumolysin, which is associated with increased hemolytic activity in ST3081 and may contribute to increased virulence in this clone. Our study provides evidence that, within the same serotype 1 clonal complex, biological properties differ significantly from one clone to another in terms of virulence and host invasiveness, and that these differences may be the result of key genetic differences within the genome.

For all newborn mammals, mother's milk is the perfect nourishment crucial for their postnatal development. However, the mechanisms underlying the metabolic control of lactation and milk composition are not well understood. In this study, Wan and colleagues show that consumption of a western diet containing extra fat, cholesterol, and sucrose by maternal mice can trigger the secretion of inflammatory milk that leads to a TLR2/4-dependent neonatal toxicity, manifested as alopecia. This neonatal toxicity requires Toll-like-receptors (TLRs), but not gut microbiota, because TLR2/4 deletion or TLR4 inhibition confers resistance, whereas germ-free mice remain sensitive. Thus, this study provides novel insights into metabolic disorders at the maternal offspring interface.

Purpose: Immunoregulatory and suppressive mechanisms represent major obstacles to the success of immunotherapy in cancer patients. We have shown that the combination of radiotherapy to the primary tumor and CTL-associated protein 4 (CTLA-4) blockade induces antitumor immunity, inhibiting metastases and extending the survival of mice bearing the poorly immunogenic and highly metastatic 4T1 mammary carcinoma. Similarly to patients with metastatic cancer, however, mice were seldom cured. Here we tested the hypothesis that invariant natural killer T (iNKT) cells, a subset with unique regulatory functions, can regulate the response to radiotherapy and CTLA-4 blockade.Experimental Design: The growth of 4T1 primary tumors and lung metastases was compared in wild-type and iNKT cell–deficient (iNKT-/-) mice. Treatment was started on day 13 when the primary tumors were palpable. Mice received radiotherapy to the primary tumor in two doses of 12 Gy in combination or not with 9H10 monoclonal antibody against CTLA-4. Response to treatment was assessed by measuring primary tumor growth delay/regression, survival, and number of lung metastases.Results: The response to radiotherapy plus 9H10 was markedly enhanced in the absence of iNKT cells, with 50% of iNKT-/- versus 0% of wild-type mice showing complete tumor regression, long-term survival, and resistance to a challenge with 4T1 cells. Administration of the iNKT cell activator α-galactosylceramide did not enhance the response of wild-type mice to radiotherapy plus 9H10. Tumor-infiltrating iNKT cells were markedly reduced in wild-type mice treated with radiotherapy plus 9H10.Conclusions: iNKT cells play a major role in regulating the response to treatment with local radiotherapy and CTLA-4 blockade.

Dendrite arbor structure is a critical determinant of nervous system function that must be actively maintained throughout life, but the signaling pathways that regulate dendrite maintenance are essentially unknown. We report that the Abelson (Abl) and Abl-related gene (Arg) nonreceptor tyrosine kinases are required for maintenance of cortical dendrites in the mouse brain.arg-/-cortical dendrites initially develop normally and are indistinguishable from wild-type dendrites at postnatal day 21. Dendrite branches are not efficiently maintained inarg-/-neurons, leading to a reduction in dendrite arbor size by early adulthood. More severe dendrite loss is observed inabl-/-arg-/-neurons. Elevation of Arg kinase activity in primary cortical neurons promotes axon and dendrite branching. Activation of integrin receptors by adhesion to laminin-1 or Semaphorin 7A also promotes neurite branching in cortical neurons, but this response is absent inarg-/-neurons because of the reduced dynamic behavior of mutant neurite branches. These data suggest that integrin signaling through Abl and Arg support cortical dendrite branch maintenance by promoting dendrite branch dynamics in response to adhesive cues.

Purpose: Ionizing radiation therapy (RT) is an important component in the management of breast cancer. Although the primary tumor can be successfully treated by surgery and RT, metastatic breast cancer remains a therapeutic challenge. Here we tested the hypothesis that the combination of RT to the primary tumor with CTLA-4 blockade can elicit antitumor immunity inhibiting the metastases.Experimental Design: The poorly immunogenic metastatic mouse mammary carcinoma 4T1 was used as a model. Mice were injected s.c. with 4T1 cells, and treatment was started 13 days later when the primary tumors measured 5 mm in average diameter. Mice were randomly assigned to four treatment groups receiving: (1) control IgG (IgG), (2) RT + IgG, (3) 9H10 monoclonal antibody against CTLA-4, (4) RT + 9H10. RT was delivered to the primary tumor by one or two fractions of 12 Gy. 9H10 and IgG were given i.p. thrice after RT.Results: Consistent with the fact that 4T1 is poorly immunogenic, 9H10 alone did not have any effect on primary tumor growth or survival. RT was able to delay the growth of the primary irradiated tumor, but in the absence of 9H10 survival was similar to that of control mice. In contrast, mice treated with RT + 9H10 had a statistically significant survival advantage. The increased survival correlated with inhibition of lung metastases formation and required CD8+ but not CD4+ T cells.Conclusions: The combination of local RT with CTLA-4 blockade is a promising new immunotherapeutic strategy against poorly immunogenic metastatic cancers.

Abl family nonreceptor tyrosine kinases regulate cell morphogenesis through functional interactions with the actin cytoskeleton. The vertebrate Abl family kinases, Abl and Arg, are expressed in the adult mouse brain, where they may regulate actin cytoskeletal dynamics in mature neurons. Using immunoelectron microscopy, we have localized Abl and Arg to the pre- and postsynaptic compartments of synapses in the mouse hippocampal area CA1. Paired-pulse facilitation (PPF) was significantly reduced at the Schaffer collateral-CA1 (SC-CA1) excitatory synapses in hippocampal slices from abl−/− and arg−/− mice as compared with wild-type mice. Furthermore, treatment of wild-type slices with the specific Abl family kinase inhibitor STI571 also reduced PPF. Basal synaptic transmission, posttetanic potentiation (PTP), long-term potentiation (LTP), and long-term depression (LTD) were similar to wild-type controls in abl−/− and arg−/− slices and in STI571-treated wild-type slices. These results indicate that an important function of Abl and Arg is to modulate synaptic efficacy via a presynaptic mechanism during repetitive activation.

Summary Mitochondrial complex I (CI) deficiency is associated with multiple neurological and metabolic disorders. However, its effect on innate immunity and bone remodeling is unclear. Using deletion of the essential CI subunit Ndufs4 as a model for mitochondrial dysfunction, we report that mitochondria suppress macrophage activation and inflammation while promoting osteoclast differentiation and bone resorption via both cell-autonomous and systemic regulation. Global Ndufs4 deletion causes systemic inflammation and osteopetrosis. Hematopoietic Ndufs4 deletion causes an intrinsic lineage shift from osteoclast to macrophage. Liver Ndufs4 deletion causes a metabolic shift from fatty acid oxidation to glycolysis, accumulating fatty acids and lactate (FA/LAC) in the circulation. FA/LAC further activates Ndufs4 −/− macrophages via reactive oxygen species induction and diminishes osteoclast lineage commitment in Ndufs4 −/− progenitors; both inflammation and osteopetrosis in Ndufs4 −/− mice are attenuated by TLR4/2 deletion. Together, these findings reveal mitochondrial CI as a critical rheostat of innate immunity and skeletal homeostasis.

Porous silicon (pSi) microparticles, in diverse sizes and shapes, can be functionalized to present pathogen-associated molecular patterns that activate dendritic cells. Intraperitoneal injection of MPL-adsorbed pSi microparticles, in contrast to free MPL, resulted in the induction of local inflammation, reflected in the recruitment of neutrophils, eosinophils and proinflammatory monocytes, and the depletion of resident macrophages and mast cells at the injection site. Injection of microparticle-bound MPL resulted in enhanced secretion of the T helper 1 associated cytokines IFN-γ and TNF-α by peritoneal exudate and lymph node cells in response to secondary stimuli while decreasing the anti-inflammatory cytokine IL-10. MPL-pSi microparticles independently exhibited anti-tumor effects and enhanced tumor suppression by low dose doxorubicin nanoliposomes. Intravascular injection of the MPL-bound microparticles increased serum IL-1β levels, which was blocked by the IL-1 receptor antagonist Anakinra. The microparticles also potentiated tumor infiltration by dendritic cells, cytotoxic T lymphocytes, and F4/80+ macrophages, however, a specific reduction was observed in CD204+ macrophages.

The recent description of an early T-lineage progenitor (ETP) population in adult mouse thymus implies the presence of a bone marrow predecessor that has not yet been identified. Here we describe a LinNeg Sca-1Pos c-kitHi Thy-1.1Neg L-selectinPos adult mouse bone marrow population that resembles the thymic ETP in both antigen expression phenotype and posttransplantation lineage potential. These cells produce wavelike kinetics of thymic seeding and reconstitute the irradiated thymus with kinetics comparable to a thymocyte graft after intravenous transplantation. Transient B-lineage reconstitution is also observed, but little myeloid potential can be detected in transplant experiments. A second subset of progenitors is L-selectinNeg and is highly enriched for rapid and persistent T- and B-lineage potential, as well as some myeloid potential. L-selectin (CD62L) is therefore an effective marker for separating lymphoid progenitors from myeloid progenitors and hematopoietic stem cells in mouse bone marrow. (Blood. 2004;103: 2990-2996)

The Atm−/− mice recapitulate most of the defects observed in ataxia-telangiectasia (A-T) patients, including a high incidence of lymphoid tumors and immune defects characterized by defective T cell differentiation, thymus hypoplasia, and defective T-dependent immune responses. To understand the basis of the T cell developmental defects in Atm−/− mice, a functional TCRαβ transgene was introduced into these mutant mice. Analysis of the Atm−/−TCRαβ+ mice indicated that the transgenic TCRαβ can rescue the defective T cell differentiation and partially rescue the thymus hypoplasia in Atm−/− mice, indicating that thymocyte positive selection is normal in the Atm−/− mice. In addition, cell cycle analysis of the thymocytes derived from Atm−/−TCRαβ+ and control mice suggested that Atm is involved in the thymocyte expansion. Finally, evaluation of the T-dependent immune responses in Atm−/−TCRαβ+ mice indicated that Atm is dispensable for normal T cell function. Therefore, the defective T-dependent immune responses in Atm−/− mice must be secondary to greatly reduced T cell numbers in these mutant mice.

Disruption of the mouse Atm gene, whose human counterpart is consistently mutated in ataxia-telangiectasia (A-T) patients, creates an A-T mouse model exhibiting most of the A-T-related systematic and cellular defects. While ATM plays a major role in signaling the p53 response to DNA strand break damage, Atm-/- p53(-/-) mice develop lymphomas earlier than Atm-/- or p53(-/-) mice, indicating that mutations in these two genes lead to synergy in tumorigenesis. The cell cycle G1/S checkpoint is abolished in Atm-/- p53(-/-) mouse embryonic fibroblasts (MEFs) following gamma-irradiation, suggesting that the partial G1 cell cycle arrest in Atm-/- cells following gamma-irradiation is due to the residual p53 response in these cells. In addition, the Atm-/- p21(-/-) MEFs are more severely defective in their cell cycle G1 arrest following gamma-irradiation than Atm-/- and p21(-/-) MEFs. The Atm-/- MEFs exhibit multiple cellular proliferative defects in culture, and an increased constitutive level of p21 in these cells might account for these cellular proliferation defects. Consistent with this notion, Atm-/- p21(-/-) MEFs proliferate similarly to wild-type MEFs and exhibit no premature senescence. These cellular proliferative defects are also rescued in Atm-/- p53(-/-) MEFs and little p21 can be detected in these cells, indicating that the abnormal p21 protein level in Atm-/- cells is also p53 dependent and leads to the cellular proliferative defects in these cells. However, the p21 mRNA level in Atm-/- MEFs is lower than that in Atm+/+ MEFs, suggesting that the higher level of constitutive p21 protein in Atm-/- MEFs is likely due to increased stability of the p21 protein.

Nanoparticles, such as polymeric delivery platforms, can exhibit intrinsic immunostimulant properties, dependent on size, charge, surface modification, and composition. To function as effective adjuvants, a balance between immunostimulatory properties and biocompatibility is essential. We have demonstrated that porous silicon (pSi) microparticles are effective delivery vehicles, with uptake by target cell populations. A peritonitis mouse model was used to access early innate immune responses 24 hours following administration of pSi microparticles. C57BL/6 mice were injected intraperitoneally with microparticles of various shapes and sizes and cytokine production and cell infiltration were assessed. pSi microparticles were found to have proinflammatory effects. The microparticles induced significant leukocyte infiltration into the site of injection and elevated IL-1β levels in lavage fluid. As cancer progresses, immune responses become more tolerant and cancer cells become more refractory to chemotherapies. Select chemotherapeutics, including cyclophosphamide, doxorubicin, and paclitaxel, have immunodulatory effects. Based on the immunopotentiating effects of pSi microparticles, and the ability of monophosphoryl lipid A (MPL) adsorbed pSi microparticles to activate antigen presenting cells, we sought to potentiate the doxorubicin-mediated immune response through co-delivery of MPL-pSi microparticles. When tumors in mice bearing intramammary 4T1-luc breast tumors reached a volume of 100 mm3, mice were injected with doxorubicin loaded liposomes (5 mg/kg) and MPL-pSi microparticles (5x108 microparticles; 10 µg MPL equivalent) by means of tail vein injection. Tumor growth was monitored by calipher measurements and luciferase expression using the IVIS Imaging System 200. While MPL-pSi microparticle-treated mice exhibited reduced tumor growth, mice receiving MPL-pSi microparticles and doxorubicin-loaded liposomes exhibited arrest of tumor growth. Thus pSi microparticles are an attractive immunopotentiating platform, with applications for both drug and antigen delivery. Citation Format: Ismail M. Meraz, Laura Williams, Marie Yang, Edward C. Lavelle, Rita E. Serda. Porous silicon microparticles exhibit immunomodulatory effects leading to suppression of tumor growth. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology: Multidisciplinary Science Driving Basic and Clinical Advances; Dec 2-5, 2012; Miami, FL. Philadelphia (PA): AACR; Cancer Res 2013;73(1 Suppl):Abstract nr B25.

Mother's milk is widely accepted as nutritious and protective to the newborn mammals by providing not only macronutrients but also immune-defensive factors. However, the mechanisms accounting for these benefits are not fully understood. Here we show that maternal very-low-density-lipoprotein (VLDL) receptor deletion in mice causes the production of defective milk containing diminished levels of platelet-activating factor acetylhydrolase (PAFAH). As a consequence, the nursing neonates suffer from alopecia, anaemia and growth retardation owing to elevated levels of pro-inflammatory platelet-activating factors. VLDL receptor deletion significantly impairs the expression of phospholipase A2 group 7 (Pla2g7) in macrophages, which decreases PAFAH secretion. Exogenous oral supplementation of neonates with PAFAH effectively rescues the toxicity. These findings not only reveal a novel role of VLDL receptor in suppressing inflammation by maintaining macrophage PAFAH secretion, but also identify the maternal VLDL receptor as a key genetic program that ensures milk quality and protects the newborns.

Long-term usage of rosiglitazone, a synthetic PPARgamma agonist, increases fracture rates among diabetic patients. PPARgamma suppresses osteoblastogenesis while activating osteoclastogenesis, suggesting that rosiglitazone decreases bone formation while sustaining or increasing bone resorption. Using mouse models with genetically altered PPARgamma, PGC1beta, or ERRalpha, here we show that PGC1beta is required for the resorption-enhancing effects of rosiglitazone. PPARgamma activation indirectly induces PGC1beta expression by downregulating beta-catenin and derepressing c-jun. PGC1beta, in turn, functions as a PPARgamma coactivator to stimulate osteoclast differentiation. Complementarily, PPARgamma also induces ERRalpha expression, which coordinates with PGC1beta to enhance mitochondrial biogenesis and osteoclast function. ERRalpha knockout mice exhibit osteoclast defects, revealing ERRalpha as an important regulator of osteoclastogenesis. Strikingly, PGC1beta deletion in osteoclasts confers complete resistance to rosiglitazone-induced bone loss. These findings identify PGC1beta as an essential mediator for the PPARgamma stimulation of osteoclastogenesis by targeting both PPARgamma itself and ERRalpha, thus activating two distinct transcriptional programs.