Interleukin-1 blockade overcomes erlotinib resistance in head and neck squamous cell carcinoma

Erlotinib has demonstrated poor clinical response rates for head and neck squamous cell carcinoma (HNSCC) to date and the majority of respondents acquire resistance to erlotinib relatively quickly. To elucidate novel pathways involved in erlotinib resistance, we compared the gene expression profiles of erlotinib-resistant (ER) vs. erlotinib-sensitive (ES) HNSCC cell lines. Enrichment analysis of microarray data revealed a deregulation of the IL-1 signaling pathway in ER versus ES-HNSCC cells. Gene expression of interleukin-1 alpha (IL1A) and interleukin-1 beta (IL1B) were significantly upregulated by > 2 fold in ER-SQ20B and ER-CAL 27 cells compared to their respective ES-cells. Secretion of the IL-1 receptor antagonist (IL-1RA) was significantly reduced in ER-cells compared to ES-cells. Blockade of IL-1 signaling using a recombinant IL-1R antagonist (anakinra) was able to inhibit the growth of ER-SQ20B and ER-CAL 27 but not ES-SQ20B and ES-CAL 27 xenografts as a single agent and in combination with erlotinib. ER-SQ20B xenografts treated with anakinra ± erlotinib were found to be less vascularized than ER-SQ20B xenografts treated with water or erlotinib. Mice bearing ER-SQ20B xenografts had significantly lesser circulating levels of G-CSF and IL-1β when treated with anakinra ± erlotinib compared to those treated with water or erlotinib alone. Furthermore, augmented mRNA levels of IL1A or interleukin-1 receptor accessory protein (IL1RAP) were associated with shortened survival in HNSCC patients. Altogether, blockade of the IL-1 pathway using anakinra overcame erlotinib resistance in HNSCC xenografts and may represent a novel strategy to overcome EGFR inhibitor resistance for treatment of HNSCC patients.

2-Deoxy-d-glucose Suppresses the In Vivo Antitumor Efficacy of Erlotinib in Head and Neck Squamous Cell Carcinoma Cells

Poor tumor response to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) is a significant challenge for effective treatment of head and neck squamous cell carcinoma (HNSCC). Therefore, strategies that may increase tumor response to EGFR TKIs are warranted in order to improve HNSCC patient treatment and overall survival. HNSCC tumors are highly glycolytic, and increased EGFR signaling has been found to promote glucose metabolism through various mechanisms. We have previously shown that inhibition of glycolysis with 2-deoxy-d-glucose (2DG) significantly enhanced the antitumor effects of cisplatin and radiation, which are commonly used to treat HNSCC. The goal of the current studies is to determine if 2DG will enhance the antitumor activity of the EGFR TKI erlotinib in HNSCC. Erlotinib transiently suppressed glucose consumption accompanied by alterations in pyruvate kinase M2 (PKM2) expression. 2DG enhanced the cytotoxic effect of erlotinib in vitro but reversed the antitumor effect of erlotinib in vivo. 2DG altered the N-glycosylation status of EGFR and induced the endoplasmic reticulum (ER) stress markers CHOP and BiP in vitro. Additionally, the effects of 2DG + erlotinib on cytotoxicity and ER stress in vitro were reversed by mannose but not glucose or antioxidant enzymes. Lastly, the protective effect of 2DG on erlotinib-induced cytotoxicity in vivo was reversed by chloroquine. Altogether, 2DG suppressed the antitumor efficacy of erlotinib in a HNSCC xenograft mouse model, which may be due to increased cytoprotective autophagy mediated by ER stress activation.

Abstract 5505: MyD88-dependent signaling decreases the anti-tumor efficacy of epidermal growth factor receptor inhibition in head and neck cancer cells

Epidermal growth factor receptor (EGFR) is upregulated in the majority of head and neck squamous cell carcinomas (HNSCC). However many HNSCC patients respond poorly to EGFR inhibitors (EGFRIs) despite tumor expression of EGFR. Gene expression analysis of erlotinib-treated HNSCC cell lines revealed an upregulation of genes involved in MyD88-dependent interleukin-6 (IL-6) expression compared to their respective vehicle treated cell lines. We therefore proposed that MyD88-dependent signaling may reduce the anti-tumor efficacy of the EGFR inhibitor erlotinib in HNSCC. Erlotinib significantly upregulated IL-6 secretion which we have previously reported to result in reduced drug efficacy and drug resistance (Fletcher et al, 2013). Suppression of MyD88 expression significantly blocked erlotinib-induced IL-6 secretion in vitro and increased the anti-tumor activity of erlotinib in vivo. There was little to no evidence of toll-like receptor (TLR) or interleukin-18 receptor (IL-18R) involvement in erlotinib-induced IL-6 secretion. However, suppression of the interleukin-1 receptor (IL-1R) signaling through pharmacologic and genetic methods significantly reduced erlotinib-induced IL-6 production and increased HNSCC cell sensitivity to erlotinib in vitro. A time-dependent increase of IL-1 alpha (IL-1α) but not IL-1 beta (IL-1β) was observed in response to erlotinib treatment and IL-1α blockade significantly increased the anti-tumor activity of erlotinib and the EGFR antibody inhibitor cetuximab in vivo. Pre-treatment with a pan-caspase inhibitor but not a caspase-1 inhibitor reduced erlotinib-induced IL-1α secretion suggesting that IL-1α was released due to cell death. Human HNSCC tumors showed higher IL-1α mRNA levels compared to matched normal tissue, and IL-1α was found to be negatively correlated with survival in HNSCC patients. Overall, the IL-1α/IL-1R/MYD88/IL-6 pathway may be responsible for the reduced anti-tumor efficacy of erlotinib and other EGFRIs; and blockade of the MyD88-dependent signaling may improve the efficacy of EGFRIs in the treatment of HNSCC.

Citation Format: Andrean L. Simons-Burnett, Adam T. Koch, Laurie Love-Homan, Aditya Stanam. MyD88-dependent signaling decreases the anti-tumor efficacy of epidermal growth factor receptor inhibition in head and neck cancer cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5505. doi:10.1158/1538-7445.AM2015-5505

Upregulated interleukin-6 expression contributes to erlotinib resistance in head and neck squamous cell carcinoma

Despite the role of epidermal growth factor receptor (EGFR) signaling in head and neck squamous cell carcinoma (HNSCC) development and progression, clinical trials involving EGFR tyrosine kinase inhibitors (TKIs) have yielded poor results in HNSCC patients. Mechanisms of acquired resistance to the EGFR TKI erlotinib was investigated by developing erlotinib-resistant HNSCC cell lines and comparing their gene expression profiles with their parental erlotinib-sensitive HNSCC cell lines using microarray analyses and subsequent pathway and network analyses. Erlotinib-resistant HNSCC cells displayed a significant upregulation in immune response and inflammatory pathways compared to parental cells. Interleukin-6 (IL-6) was one of thirteen genes that was significantly differentially expressed in all erlotinib-resistant HNSCC cell lines, which was validated using RT-PCR and ELISA. Blockade of IL-6 signaling using the IL-6 receptor antagonist tocilizumab, was able to overcome erlotinib-resistance in erlotinib-resistant SQ20B tumors in vivo. Overall, erlotinib-resistant HNSCC cells display elevated IL-6 expression levels compared to erlotinib-sensitive HNSCC cells and blockade of the IL-6 signaling pathway may be an effective strategy to overcome resistance to erlotinib and possibly other EGFR TKIs for HNSCC therapy.

MyD88-Dependent Signaling Decreases the Antitumor Efficacy of Epidermal Growth Factor Receptor Inhibition in Head and Neck Cancer Cells

EGFR is upregulated in the majority of head and neck squamous cell carcinomas (HNSCC). However, many patients with HNSCC respond poorly to the EGFR inhibitors (EGFRI) cetuximab and erlotinib, despite tumor expression of EGFR. Gene expression analysis of erlotinib-treated HNSCC cells revealed an upregulation of genes involved in MyD88-dependent signaling compared with their respective vehicle-treated cell lines. We therefore investigated whether MyD88-dependent signaling may reduce the antitumor efficacy of EGFRIs in HNSCC. Erlotinib significantly upregulated IL6 secretion in HNSCC cell lines, which our laboratory previously reported to result in reduced drug efficacy. Suppression of MyD88 expression blocked erlotinib-induced IL6 secretion in vitro and increased the antitumor activity of erlotinib in vivo. There was little evidence of Toll-like receptor or IL18 receptor involvement in erlotinib-induced IL6 secretion. However, suppression of IL1R signaling significantly reduced erlotinib-induced IL6 production. A time-dependent increase of IL1α but not IL1β was observed in response to erlotinib treatment, and IL1α blockade significantly increased the antitumor activity of erlotinib and cetuximab in vivo. A pan-caspase inhibitor reduced erlotinib-induced IL1α secretion, suggesting that IL1α was released because of cell death. Human HNSCC tumors showed higher IL1α mRNA levels compared with matched normal tissue, and IL1α was found to be negatively correlated with survival in patients with HNSCC. Overall, the IL1α/IL1R/MYD88/IL6 pathway may be responsible for the reduced antitumor efficacy of erlotinib and other EGFRIs, and blockade of IL1 signaling may improve the efficacy of EGFRIs in the treatment of HNSCC.

Abstract B29: The role of MYD88-dependent signaling in the anti-tumor efficacy of the EGFR inhibitor erlotinib in head and neck cancer cells

Epidermal growth factor receptor (EGFR) is upregulated in the majority of head and neck squamous cell carcinomas (HNSCC). Unfortunately, the incorporation of EGFR inhibitors (EGFRIs) into the management of HNSCC has not improved long-term survival rates in patients with advanced stage HNSCC tumors. Therefore, the identification and understanding of strategies that will improve the efficacy of EGFRIs may potentially improve patient treatment and survival.

Using microarray analysis, our laboratory has observed a profound increase in genes involved in MYD88-dependent pro-inflammatory pathways in EGFRI-treated HNSCC cell lines compared to their respective vehicle-treated cell lines. Additionally, we have previously shown that EGFRIs induce production of the inflammatory cytokine interleukin-6 (IL-6), leading to the reduced efficacy and acquired resistance to EGFRIs in HNSCC cells. Since MYD88-dependent signaling may lead to IL-6 production and secretion, the purpose of these studies is to determine if MYD88-dependent pathways such as Toll-like receptor (TLR), interleukin-1 receptor (IL-1R) and interleukin-18 receptor (IL-18R) pathways are responsible for the IL-6 production induced by EGFRIs.

We found that knockdown of MYD88 (using siRNA and shRNA) significantly inhibited IL-6 secretion induced by the EGFRI erlotinib in Cal-27 and SQ20B HNSCC cells in vitro, increased the anti-tumor activity of erlotinib in vitro and enhanced the anti-tumor efficacy of erlotinib in a HNSCC xenograft mouse model. These results suggested that MYD88-dependent signaling was involved in IL-6 production and in the reduced efficacy of erlotinib.

In order to elucidate which MYD88-dependent pathway was involved in erlotinib-induced IL-6 production, we investigated the involvement of TLR, IL-1R or IL-18R-mediated signaling. Although TLRs and the IL-18R were expressed and active on our HNSCC cells, we found little to no evidence of their involvement in erlotinib-induced IL-6 production. However, inhibition of the IL-1R through pharmacologic (anakinra) or genetic (siRNA and shRNA transfection) methods significantly reduced erlotinib-induced IL-6 production and increased HNSCC cell sensitivity to erlotinib in vitro. These observations point to the IL-1R/MYD88 pathway being involved in IL-6 production and in the reduced efficacy of erlotinib. We observed a time-dependent increase of IL-1 alpha (IL-1α) but not IL-1 beta (IL-1β) in response to erlotinib treatment implicating IL-1α as the damage associated molecular pattern (DAMP) responsible for activating the IL-1R. Furthermore, suppression of cell death with a pan-caspase inhibitor reduced erlotinib-induced IL-1α secretion.

Finally, human HNSCC tumors were found to have higher IL-1α mRNA levels than matched normal tissue, and comparison of high and low IL-1α expressing HNSCC tumors (from the TCGA PANCAN databank) showed IL-1α to be negatively correlated with survival. Altogether, erlotinib-induced cell death may result in the release of IL-1α which activates IL-1R on adjacent surviving cells resulting in MYD88-mediated IL-6 secretion and the development of acquired resistance to erlotinib. In summary, the IL-1α/IL-1R/MYD88/IL-6 pathway may be responsible for the reduced anti-tumor efficacy of erlotinib and other EGFRIs; and blockade of the IL-1 pathway may improve the efficacy of EGFRIs in the treatment of HNSCC. This work was supported by the grants NIH K01CA134941 and ACS IRG7700434.

Citation Format: Andrean L. Simons, Adam T. Koch, Laurie Love-Homan, Aditya Stanam. The role of MYD88-dependent signaling in the anti-tumor efficacy of the EGFR inhibitor erlotinib in head and neck cancer cells. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Drug Sensitivity and Resistance: Improving Cancer Therapy; Jun 18-21, 2014; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(4 Suppl): Abstract nr B29.

EGFR inhibition induces proinflammatory cytokines via NOX4 in HNSCC

Chronic inflammation plays a fundamental role in tumor promotion, migration, and invasion. With the use of microarray profiling, a profound increase was observed for those transcripts involved in proinflammatory signaling in epidermal growth factor receptor (EGFR) inhibitor-treated head and neck squamous cell carcinoma (HNSCC) cells as compared with their respective controls. As such, it was hypothesized that EGFR inhibitor efficacy is offset by the proinflammatory response that these therapeutics conjure in HNSCC. Systematic evaluation of the clinical EGFR inhibitors-erlotinib, cetuximab, lapatinib, and panitumumab-revealed increased secretion of proinflammatory cytokines such as interleukins (IL-2, IL-4, IL-6, IL-8), granulocyte-macrophage colony-stimulating factor, TNF-α, and IFN-γ. Mechanistic focus on IL-6 revealed that erlotinib induced a time-dependent increase in IL-6 mRNA and protein expression. Importantly, exogenous IL-6 protected HNSCC cells from erlotinib-induced cytotoxicity, whereas tocilizumab, an IL-6 receptor antagonist, sensitized cells to erlotinib in vitro and in vivo. Inhibitors of NF-κB, p38, and JNK suppressed erlotinib-induced IL-6 expression, suggesting critical roles for NF-κB and MAPK in IL-6 regulation. Furthermore, knockdown of NADPH oxidase 4 (NOX4) suppressed erlotinib-induced proinflammatory cytokine expression. Taken together, these results demonstrate that clinical EGFR inhibitors induce the expression of proinflammatory cytokines via NOX4.

IMPLICATIONS

The antitumor activity of EGFR inhibitors is reduced by activation of NOX4-mediated proinflammatory pathways in HNSCC.

NOX4 mediates cytoprotective autophagy induced by the EGFR inhibitor erlotinib in head and neck cancer cells

Most head and neck squamous cell carcinomas (HNSCCs) overexpress epidermal growth factor receptor (EGFR) and EGFR inhibitors are routinely used in the treatment of HNSCC. However, many HNSCC tumors do not respond or become refractory to EGFR inhibitors. Autophagy, which is a stress-induced cellular self-degradation process, has been reported to reduce the efficacy of chemotherapy in various disease models. The purpose of this study is to determine if the efficacy of the EGFR inhibitor erlotinib is reduced by activation of autophagy via NOX4-mediated oxidative stress in HNSCC cells. Erlotinib induced the expression of the autophagy marker LC3B-II and autophagosome formation in FaDu and Cal-27 cells. Inhibition of autophagy by chloroquine and knockdown of autophagy pathway genes Beclin-1 and Atg5 sensitized both cell lines to erlotinib-induced cytotoxicity, suggesting that autophagy may serve as a protective mechanism. Treatment with catalase (CAT) and diphenylene iodonium (DPI) in the presence of erlotinib suppressed the increase in LC3B-II expression in FaDu and Cal-27 cells. Erlotinib increased NOX4 mRNA and protein expression by increasing its promoter activity and mRNA stability in FaDu cells. Knockdown of NOX4 using adenoviral siNOX4 partially suppressed erlotinib-induced LC3B-II expression, while overexpression of NOX4 increased expression of LC3B-II. These studies suggest that erlotinib may activate autophagy in HNSCC cells as a pro-survival mechanism, and NOX4 may play a role in mediating this effect.

Susceptibility of human head and neck cancer cells to combined inhibition of glutathione and thioredoxin metabolism

Increased glutathione (GSH) and thioredoxin (Trx) metabolism are mechanisms that are widely implicated in resistance of cancer cells to chemotherapy. The current study determined if simultaneous inhibition of GSH and Trx metabolism enhanced cell killing of human head and neck squamous cell carcinoma (HNSCC) cells by a mechanism involving oxidative stress. Inhibition of GSH and Trx metabolism with buthionine sulfoximine (BSO) and auranofin (AUR), respectively, induced significant decreases in clonogenic survival compared to either drug alone in FaDu, Cal-27 and SCC-25 HNSCC cells in vitro and in vivo in Cal-27 xenografts. BSO+AUR significantly increased glutathione and thioredoxin oxidation and suppressed peroxiredoxin activity in vitro. Pre-treatment with N-acetylcysteine completely reversed BSO+AUR-induced cell killing in FaDu and Cal-27 cells, while catalase and selenium supplementation only inhibited BSO+AUR-induced cell killing in FaDu cells. BSO+AUR decreased caspase 3/7 activity in HNSCC cells and significantly reduced the viability of both Bax/Bak double knockout (DKO) and DKO-Bax reconstituted hematopoietic cells suggesting that necrosis was involved. BSO+AUR also significantly sensitized FaDu, Cal-27, SCC-25 and SQ20B cells to cell killing induced by the EGFR inhibitor Erlotinib in vitro. These results support the conclusion that simultaneous inhibition of GSH and Trx metabolism pathways induces oxidative stress and clonogenic killing in HNSCCs and this strategy may be useful in sensitizing HNSCCs to EGFR inhibitors.

Evaluation of a novel photoactive and biotinylated dehydroepiandrosterone analog

To characterize the cell surface receptor for dehydroepiandrosterone (DHEA), we synthesized a DHEA analog containing biotin and benzophenone groups (DHEA-BP-Bt). DHEA-BP-Bt was equipotent with DHEA in competing with [(3)H]DHEA for binding to solubilized plasma membranes of bovine aortic endothelial cells (BAEC). Additionally, DHEA-BP-Bt pre-conjugated to avidin and immobilized on agarose, also inhibited plasma membrane binding of [(3)H]DHEA. Furthermore, DHEA-BP-Bt activated endothelial nitric oxide synthase, similar to DHEA. Confocal micrographs showed that, upon photoirradiation, DHEA-BP-Bt bound to sites on the cell surface of BAEC in a DHEA inhibitable manner. Finally, DHEA-BP-Bt bound specifically to proteins of approximately 55 kDa and 80 kDa, either when live cells were UV irradiated with the analog and plasma membrane proteins separated by SDS-PAGE or in a ligand blot analysis. These data confirm the successful synthesis of a photoactive, biotinylated DHEA analog which is capable of cross-linking to and identifying plasma membrane DHEA binding sites and which will allow us to further purify this receptor.

In vivo imaging of transgenic Leishmania parasites in a live host

Distinct species of Leishmania, a protozoan parasite of the family Trypanosomatidae, typically cause different human disease manifestations. The most common forms of disease are visceral leishmaniasis (VL) and cutaneous leishmaniasis (CL). Mouse models of leishmaniasis are widely used, but quantification of parasite burdens during murine disease requires mice to be euthanized at various times after infection. Parasite loads are then measured either by microscopy, limiting dilution assay, or qPCR amplification of parasite DNA. The in vivo imaging system (IVIS) has an integrated software package that allows the detection of a bioluminescent signal associated with cells in living organisms. Both to minimize animal usage and to follow infection longitudinally in individuals, in vivo models for imaging Leishmania spp. causing VL or CL were established. Parasites were engineered to express luciferase, and these were introduced into mice either intradermally or intravenously. Quantitative measurements of the luciferase driving bioluminescence of the transgenic Leishmania parasites within the mouse were made using IVIS. Individual mice can be imaged multiple times during longitudinal studies, allowing us to assess the inter-animal variation in the initial experimental parasite inocula, and to assess the multiplication of parasites in mouse tissues. Parasites are detected with high sensitivity in cutaneous locations. Although it is very likely that the signal (photons/second/parasite) is lower in deeper visceral organs than the skin, but quantitative comparisons of signals in superficial versus deep sites have not been done. It is possible that parasite numbers between body sites cannot be directly compared, although parasite loads in the same tissues can be compared between mice. Examples of one visceralizing species (L. infantum chagasi) and one species causing cutaneous leishmaniasis (L. mexicana) are shown. The IVIS procedure can be used for monitoring and analyzing small animal models of a wide variety of Leishmania species causing the different forms of human leishmaniasis.

Dehydroepiandrosterone inhibits intracellular calcium release in beta-cells by a plasma membrane-dependent mechanism

Both dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEAS) affect glucose stimulated insulin secretion, though their cellular mechanisms of action are not well characterized. We tested the hypothesis that human physiological concentrations of DHEA alter insulin secretion by an action initiated at the plasma membrane of beta-cells. DHEA alone had no effect on intracellular calcium concentration ([Ca(2+)](i)) in a rat beta-cell line (INS-1). However, it caused an immediate and dose-dependent inhibition of carbachol-induced Ca(2+) release from intracellular stores, with a 25% inhibition at zero. One nanometer DHEA. DHEA also inhibited the Ca(2+) mobilizing effect of bombesin (29% decrease), but did not inhibit the influx of extracellular Ca(2+) evoked by glyburide (100 microM) or glucose (15 mM). The steroids (androstenedione, 17-alpha-hydroxypregnenolone, and DHEAS) had no inhibitory effect on carbachol-induced intracellular Ca(2+) release. The action of DHEA depended on a signal initiated at the plasma membrane, since membrane impermeant DHEA-BSA complexes also inhibited the carbachol effect on [Ca(2+)](i) (39% decrease). The inhibition of carbachol-induced Ca(2+) release by DHEA was blocked by pertussis toxin (PTX). DHEA also inhibited the carbachol induction of phosphoinositide generation, with a maximal inhibition at 0.1 nM DHEA. Furthermore, DHEA inhibited insulin secretion induced by carbachol in INS-1 cells by 25%, and in human pancreatic islets by 53%. Taken together, this is the first report showing that human physiological concentrations of DHEA decrease agonist-induced Ca(2+) release by a rapid, non-genomic mechanism in INS-1 cells. Furthermore, these data provide evidence consistent with the existence of a specific plasma membrane DHEA receptor, mediating this signal transduction pathway by pertussis toxin-sensitive G-proteins.

Immunostimulatory oligodeoxynucleotides promote protective immunity and provide systemic therapy for leishmaniasis via IL-12- and IFN-gamma-dependent mechanisms

Resistance to murine leishmaniasis correlates with development of a CD4(+) T helper 1 (Th1)-predominant immune response. To determine whether immunostimulatory CpG-containing oligodeoxynucleotides (CpG-ODN), known to promote a Th1 immune response, could provide protection from Leishmania infection, CpG-ODN and freeze-thawed (F/T) Leishmania major were coinjected intradermally into susceptible BALB/c mice. A Leishmania-specific Th1-predominant immune response was induced, and 40% of animals were protected from subsequent challenge with infectious organisms, with 0% protection of animals injected with F/T Leishmania organisms and PBS, F/T organisms and control ODN, or F/T organisms alone. More striking protection (65-95%) was seen in mice first infected with intact Leishmania organisms and then injected with CpG-ODN, either at the site of infection or at a remote site. To determine whether the therapeutic protection provided by CpG-ODN depended on IL-12 and IFN-gamma production, both IFN-gamma-deficient BALB/c mice and BALB/c mice treated with neutralizing anti-IL-12 mAb were first inoculated with Leishmania and then treated with either CpG-ODN, ODN, or PBS. None of these IFN-gamma-deficient mice survived (0/20, 0/20, and 0/20 respectively). Furthermore, neutralization of IL-12 completely abolished the therapeutic protection provided by CpG-ODN (0/20 mice surviving). We conclude that immunostimulatory DNA sequences likely exert systemic effects via IL-12 and IFN-gamma-dependent mechanisms and hold considerable promise as both vaccine adjuvants and potential therapeutic agents in the prevention and treatment of leishmaniasis.

CpG oligodeoxynucleotides can circumvent the Th2 polarization of neonatal responses to vaccines but may fail to fully redirect Th2 responses established by neonatal priming

Neonatal murine responses to a panel of conventional vaccines differ qualitatively from adult responses by a particular polarization toward a Th2 pattern and a frequent limitation of the Th1 and CTL responses required for protection against intracellular microorganisms. In contrast, DNA vaccines induce adult-like Th1/CTL neonatal responses against the same vaccine Ags. In this report, we show that this can be related to their content in unmethylated CpG motifs. Oligodeoxynucleotides (ODN) containing CpG motifs activate neonatal APCs to produce IL-12 in vitro and induce adult-like Th1 responses to tetanus toxoid and measles Ags in vivo, with production of IgG2a-specific Abs and adult-like secretion of IFN-gamma and IL-5 by Ag-specific T cells. However, in spite of their capacity to trigger neonatal B cell proliferation in vitro, CpG-ODN only partially enhanced early life Ab responses. Finally, using Th1-driving CpG-ODN with the boosting dose of a protein vaccine was sufficient to redirect adult but not neonatally primed Th2 responses. These observations could be important for the development of novel vaccines that will have to be effective early in life.

CpG Oligodeoxynucleotides Can Circumvent the Th2 Polarization of Neonatal Responses to Vaccines But May Fail to Fully Redirect Th2 Responses Established by Neonatal Priming

Neonatal murine responses to a panel of conventional vaccines differ qualitatively from adult responses by a particular polarization toward a Th2 pattern and a frequent limitation of the Th1 and CTL responses required for protection against intracellular microorganisms. In contrast, DNA vaccines induce adult-like Th1/CTL neonatal responses against the same vaccine Ags. In this report, we show that this can be related to their content in unmethylated CpG motifs. Oligodeoxynucleotides (ODN) containing CpG motifs activate neonatal APCs to produce IL-12 in vitro and induce adult-like Th1 responses to tetanus toxoid and measles Ags in vivo, with production of IgG2a-specific Abs and adult-like secretion of IFN-γ and IL-5 by Ag-specific T cells. However, in spite of their capacity to trigger neonatal B cell proliferation in vitro, CpG-ODN only partially enhanced early life Ab responses. Finally, using Th1-driving CpG-ODN with the boosting dose of a protein vaccine was sufficient to redirect adult but not neonatally primed Th2 responses. These observations could be important for the development of novel vaccines that will have to be effective early in life.

Sequence motifs in adenoviral DNA block immune activation by stimulatory CpG motifs

Unmethylated CpG dinucleotides in particular base contexts (CpG-S motifs) are relatively common in bacterial DNA but are rare in vertebrate DNA. B cells and monocytes have the ability to detect such CpG-S motifs that trigger innate immune defenses with production of Th1-like cytokines. Despite comparable levels of unmethylated CpG dinucleotides, DNA from serotype 12 adenovirus is immune-stimulatory, but serotype 2 is nonstimulatory and can even inhibit activation by bacterial DNA. In type 12 genomes, the distribution of CpG-flanking bases is similar to that predicted by chance. However, in type 2 adenoviral DNA the immune stimulatory CpG-S motifs are outnumbered by a 15- to 30-fold excess of CpG dinucleotides in clusters of direct repeats or with a C on the 5' side or a G on the 3' side. Synthetic oligodeoxynucleotides containing these putative neutralizing (CpG-N) motifs block immune activation by CpG-S motifs in vitro and in vivo. Eliminating 52 of the 134 CpG-N motifs present in a DNA vaccine markedly enhanced its Th1-like function in vivo, which was increased further by the addition of CpG-S motifs. Thus, depending on the CpG motif, prokaryotic DNA can be either immune-stimulatory or neutralizing. These results have important implications for understanding microbial pathogenesis and molecular evolution and for the clinical development of DNA vaccines and gene therapy vectors.

CpG DNA Induces Sustained IL-12 Expression In Vivo and Resistance to Listeria monocytogenes Challenge

Vertebrates have evolved innate immune defense mechanisms that recognize and respond to structural patterns that are specific to microbial molecules. One such pattern recognition system is based on unmethylated CpG dinucleotides in particular sequence contexts (CpG motifs); these motifs are common in bacterial DNA but are under-represented (“CpG suppression”) and methylated in vertebrate DNA. Mice that are injected with bacterial DNA or synthetic oligodeoxynucleotides (ODNs) containing CpG motifs respond with a rapid production of IL-12 and IFN-γ. The serum levels of IL-12 were increased for at least 8 days after a single injection of CpG ODNs, but IFN-γ levels returned to baseline within 24 h. This Th1-like cytokine response to CpG motifs induces a state of resistance to infection by Listeria monocytogenes in susceptible specific pathogen-free BALB/c mice. Resistance developed within 48 h of pretreatment with CpG ODNs, persisted for at least 2 wk, and was dependent upon IFN-γ secretion. These data support the hypothesis that CpG DNA motifs are a “danger signal” that activates protective innate immune defenses and may have therapeutic potential.

CpG DNA induces sustained IL-12 expression in vivo and resistance to Listeria monocytogenes challenge

Vertebrates have evolved innate immune defense mechanisms that recognize and respond to structural patterns that are specific to microbial molecules. One such pattern recognition system is based on unmethylated CpG dinucleotides in particular sequence contexts (CpG motifs); these motifs are common in bacterial DNA but are under-represented ("CpG suppression") and methylated in vertebrate DNA. Mice that are injected with bacterial DNA or synthetic oligodeoxynucleotides (ODNs) containing CpG motifs respond with a rapid production of IL-12 and IFN-gamma. The serum levels of IL-12 were increased for at least 8 days after a single injection of CpG ODNs, but IFN-gamma levels returned to baseline within 24 h. This Th1-like cytokine response to CpG motifs induces a state of resistance to infection by Listeria monocytogenes in susceptible specific pathogen-free BALB/c mice. Resistance developed within 48 h of pretreatment with CpG ODNs, persisted for at least 2 wk, and was dependent upon IFN-gamma secretion. These data support the hypothesis that CpG DNA motifs are a "danger signal" that activates protective innate immune defenses and may have therapeutic potential.

CpG DNA, a novel immune enhancer for systemic and mucosal immunization with influenza virus

Bacterial DNA causes B cell proliferation, immunoglobulin secretion, and Th1-like cytokine secretion, due to unmethylated CpG dinucleotides in particular base contexts (CpG motifs), which are far more common in bacterial DNA than in vertebrate DNA. Synthetic oligodeoxynucleotides (ODN) containing CpG motifs also trigger immune activation, suggesting possible utility as vaccine enhancers. Mice systemically primed with formalin-inactivated influenza virus mixed with CpG ODN, generated virus-specific serum antibodies at titres approximately seven times higher than mice immunized without CpG; the titres were further increased following an identical second injection. To determine whether CpG could be absorbed through mucosae and enhance vaccination responses, mice were immunized intranasally (IN) with the same preparation of virus with or without CpG ODN or Escherichia coli DNA. Following IN immunization, CpG ODN or E. coli DNA promoted increased production of influenza-specific antibodies in serum, saliva and the genital tract, compared with the control groups. These studies indicate that stimulatory CpG ODN are promising new immune enhancers for vaccination applications.

Induction of hepatic pathology in SCID-Hu mice engrafted with peripheral blood lymphocytes of patients with Schistosomiasis japonica

SCID mice were engrafted with peripheral blood lymphocytes (PBL) derived from persons currently or previously infected with Schistosoma japonicum. After immunization with soluble worm antigenic preparation, the SCID-Hu mice were analyzed for a human immune response. ELISA revealed a low titer of human antibody recognizing soluble egg antigens in 2 of 10 mice. One mouse had detectable levels of interleukin (IL)-2 and gamma-interferon, TH1 phenotype cytokines. All mice had elevated levels of IL-4, a TH2 phenotype cytokine. The human cytokine profile of the mice paralleled the patient's serum profile at clinical examination. In addition, all mice had substantial hepatic pathology, including inflammatory cell infiltrates and macrovesicular fat deposition. The data indicate that activation of PBL from patients with a history of schistosomiasis japonica infection can result in focal hepatic pathology, which may be driven by specific cytokines.

Brain microvascular smooth muscle and endothelial cells produce granulocyte macrophage colony-stimulating factor and support colony formation of granulocyte-macrophage-like cells

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a potent stimulator of macrophages and neutrophils and plays a role in inflammatory diseases. In this article, we report that mouse brain-derived microvascular smooth muscle cells (SM) and endothelial cells (En) in coculture with splenocytes support the colony proliferation of immature granulocyte-macrophage-like (GM) cells. Unstimulated SM and En cells release GM-CSF as shown by ELISA assay and SM expresses mRNA for GM-CSF by polymerase chain reaction (PCR). Stimulation of SM and En by a nonspecific activator (lipopolysaccharide) results in upregulation of GM-CSF production. GM colonies cannot be grown on cultured astrocytes or on extracellular matrix alone prepared from smooth muscle or endothelium. However, colonies form on the extracellular matrix and on astrocytes, either in the presence of SM- or En-conditioned medium or after the addition of recombinant GM-CSF. The GM cells are positive for nonspecific esterase, peroxidase, and MAC-1 markers but are negative for FC gamma receptors and for Thy 1.2, CD8, CD4, MHC class II, and Asialo GM1 markers. These observations emphasize the possibility for active participation of brain microvasculature SM and En in acute inflammatory reactions of the central nervous system.

Adhesion molecules on murine brain microvascular endothelial cells: expression and regulation of ICAM-1 and Lgp 55

The mechanisms for the initiation of immune reactions in the central nervous system are poorly understood. In this report, we describe the presence of intercellular adhesion molecule-1 (ICAM-1) and Lgp 55 (suggested mouse homologue of human intercellular adhesion molecule-2, ICAM-2) on the surface of brain microvessel endothelium (EN) cells and show in vitro induction of ICAM-1 molecules on EN cells with pro-inflammatory cytokines. ICAM-1 expression was detected using flow cytometry analysis with biotinylated anti-ICAM-1 antibody (YN1/1.7.4). Lgp 55 expression was characterized using PA3 monoclonal antibody. According to our results, 30-40% of the non-activated brain EN cells expressed ICAM-1 and 15-20% expressed Lgp 55 molecules. The ICAM-1 molecule expression was increased after the activation of the cells with recombinant murine gamma interferon (IFN-gamma), tumor necrosis factor (TNF-alpha), and interleukin-1 alpha (IL1-alpha) in a dose-dependent manner. The increased ICAM-1 expression was detected as early as 2 h following the cytokine treatment and reached its maximum after 24 h. Transforming growth factor-beta (TGF-beta) did not influence the expression of ICAM-1 molecule. Lgp 55 molecule does not seem to be regulated by pro-inflammatory cytokines. ICAM-1 and Lgp 55 expression was found to be polarized on the luminal surface of EN by confocal laser microscopy suggesting accessibility for leukocytes. Inducible ICAM-1 expression may play a critical role in formation of inflammatory reactions inside the central nervous system.

Adhesion of splenocytes to brain microvascular endothelium in the BALB/c and SJL/j mouse systems

Adhesion of hematopoietic cells to endothelial (En) cells plays an important role in their migration into extravascular tissue. This report characterizes the adhesion properties of naive splenocytes to syngeneic and allogeneic mouse brain microvascular endothelium isolated from the BALB/c or SJL/j mouse strains. Syngeneic adhesion reaches maximum levels by 60 min at 37 degrees C, but is more pronounced in the BALB/c system (mean adhesion = 10.7% +/- 1.0) compared to adhesion seen in the SJL/j (mean adhesion = 4.3% +/- 0.6). BALB/c, but not SJL/j adhesion, seems to be mediated, at least in part, by the interaction of CD11a/CD18 (lymphocyte function-associated antigen 1 (LFA-1] with one of its ligands, because BALB/c adhesion is partially inhibited when the assay is carried out either in the presence of chelating agents or with antibodies to the CD11a/CD18 molecule. Activation of the endothelium with recombinant interferon-gamma (rIFN-gamma), recombinant interleukin-1 alpha (rIL-1 alpha), and recombinant tumor necrosis factor-alpha (rTNF-alpha), enhances adhesion in both BALB/c and SJL/j. IFN-gamma and IL-1 alpha mediated adhesion enhancement is abrogated by antibodies to the CD11a/CD18 molecules in the BALB/c but not in the SJL/j system. The adhesion of splenocytes to mouse brain En clearly has unique properties, and whether or not the differences seen in the SJL/j system in any way influences its susceptibility to the autoimmune demyelinating disease, experimental autoimmune encephalitis, remains to be determined.