Preliminary trial of poly ICLC in chronic progressive multiple sclerosis

The route of administration dictates the immunogenicity of peptide-based cancer vaccines in mice

Vaccines consisting of synthetic peptides representing cytotoxic T-lymphocyte (CTL) epitopes have long been considered as a simple and cost-effective approach to treat cancer. However, the efficacy of these vaccines in the clinic in patients with measurable disease remains questionable. We believe that the poor performance of peptide vaccines is due to their inability to generate sufficiently large CTL responses that are required to have a positive impact against established tumors. Peptide vaccines to elicit CTLs in the clinic have routinely been administered in the same manner as vaccines designed to induce antibody responses: injected subcutaneously and in many instances using Freund's adjuvant. We report here that peptide vaccines and poly-ICLC adjuvant administered via the unconventional intravenous route of immunization generate substantially higher CTL responses as compared to conventional subcutaneous injections, resulting in more successful antitumor effects in mice. Furthermore, amphiphilic antigen constructs such as palmitoylated peptides were shown to be better immunogens than long peptide constructs, which now are in vogue in the clinic. The present findings if translated into the clinical setting could help dissipate the wide-spread skepticism of whether peptide vaccines will ever work to treat cancer.

TLR3 agonism re-establishes CNS immune competence during α4-integrin deficiency

OBJECTIVE

Natalizumab blocks α4-integrin-mediated leukocyte migration into the central nervous system (CNS). It diminishes disease activity in multiple sclerosis (MS), but carries a high risk of progressive multifocal encephalopathy (PML), an opportunistic infection with JV virus that may be prompted by diminished CNS immune surveillance. The initial host response to viral infections entails the synthesis of type I interferons (IFN) upon engagement of TLR3 receptors. We hypothesized that TLR3 agonism reestablishes CNS immune competence in the setting of α4-integrin deficiency.

METHOD

We generated the conditional knock out mouse strain Mx1.Cre+ α4-integrinfl/fl, in which the α4-integrin gene is ablated upon treatment with the TLR3 agonist poly I:C. Adoptive transfer of purified lymphocytes from poly I:C-treated Mx1.Cre+ α4-integrinfl/fl donors into naive recipients recapitulates immunosuppression under natalizumab. Active experimental autoimmune encephalomyelitis (EAE) in Mx1.Cre+ α4-integrinfl/fl mice treated with poly I:C represents immune-reconstitution.

RESULTS

Adoptive transfer of T cells from poly I:C treated Mx1.Cre+ α4-integrinfl/fl mice causes minimal EAE. The in vitro migratory capability of CD45+ splenocytes from these mice is reduced. In contrast, actively-induced EAE after poly I:C treatment results in full disease susceptibility of Mx1.Cre+ α4-integrinfl/fl mice, and the number and composition of CNS leukocytes is similar to controls. Extravasation of Evans Blue indicates a compromised blood-brain barrier. Poly I:C treatment results in a 2-fold increase in IFN β transcription in the spinal cord.

INTERPRETATION

Our data suggest that TLR3 agonism in the setting of relative α4-integrin deficiency can reestablish CNS immune surveillance in an experimental model. This pathway may present a feasible treatment strategy to treat and prevent PML under natalizumab therapy and should be considered for further experimental evaluation in a controlled setting.

TLR3 Agonist Poly-IC Induces IL-33 and Promotes Myelin Repair

Background

Impaired remyelination of demyelinated axons is a major cause of neurological disability. In inflammatory demyelinating disease of the central nervous system (CNS), although remyelination does happen, it is often incomplete, resulting in poor clinical recovery. Poly-IC a known TLR3 agonist and IL-33, a cytokine which is induced by poly-IC are known to influence recovery and promote repair in experimental models of CNS demyelination.

Methodology and Principal Findings

We examined the effect of addition of poly-IC and IL-33 on the differentiation and maturation of oligodendrocyte precursor cells (OPC) cultured in vitro. Both Poly-IC and IL-33 induced transcription of myelin genes and the differentiation of OPC to mature myelin forming cells. Poly-IC induced IL-33 in OPC and addition of IL-33 to in vitro cultures, amplified further, IL-33 expression suggesting an autocrine regulation of IL-33. Poly-IC and IL-33 also induced phosphorylation of p38MAPK, a signaling molecule involved in myelination. Following the induction of gliotoxic injury with lysolecithin to the corpus callosum (CC), treatment of animals with poly-IC resulted in greater recruitment of OPC and increased staining for myelin in areas of demyelination. Also, poly-IC treated animals showed greater expression of IL-33 and higher expression of M2 phenotype macrophages in the CC.

Conclusion/Significance

Our studies suggest that poly-IC and IL-33 play a role in myelin repair by enhancing expression of myelin genes and are therefore attractive therapeutic agents for use as remyelinating agents in human demyelinating disease.

Role for MyD88, TLR2 and TLR9 but not TLR1, TLR4 or TLR6 in experimental autoimmune encephalomyelitis

The potential roles of TLRs in the cause and pathogenesis of autoimmune CNS inflammation remain contentious. In this study, we examined the effects of targeted deletions of TLR1, TLR2, TLR4, TLR6, TLR9, and MyD88 on the induction of myelin oligodendrocyte glycoprotein 35-55 (MOG(35-55)) peptide/CFA/pertussis toxin-induced autoimmune encephalomyelitis. Although C57BL/6.Tlr1(-/-), C57BL/6.Tlr4(-/-) and C57BL/6.Tlr6(-/-) mice showed normal susceptibility to disease, signs were alleviated in female C57BL/6.Tlr2(-/-) and C57BL/6.Tlr9(-/-) mice and C57BL/6.Tlr2/9(-/-) mice of both sexes. C57BL/6.Myd88(-/-) mice were completely protected. Lower clinical scores were associated with reduced leukocyte infiltrates. These results were confirmed by passive adoptive transfer of disease into female C57BL/6.Tlr2(-/-) and C57BL/6.Tlr9(-/-) mice, where protection in the absence of TLR2 was associated with fewer infiltrating CD4(+) cells in the CNS, reduced prevalence of detectable circulating IL-6, and increased proportions of central (CD62L(+)) CD4(+)CD25(+)Foxp3(+) regulatory T cells. These results provide a potential molecular mechanism for the observed effects of TLR signaling on the severity of autoimmune CNS inflammation.

Synthetic double-stranded RNAs are adjuvants for the induction of T helper 1 and humoral immune responses to human papillomavirus in rhesus macaques

Toll-like receptor (TLR) ligands are being considered as adjuvants for the induction of antigen-specific immune responses, as in the design of vaccines. Polyriboinosinic-polyribocytoidylic acid (poly I:C), a synthetic double-stranded RNA (dsRNA), is recognized by TLR3 and other intracellular receptors. Poly ICLC is a poly I:C analogue, which has been stabilized against the serum nucleases that are present in the plasma of primates. Poly I:C₁₂U, another analogue, is less toxic but also less stable in vivo than poly I:C, and TLR3 is essential for its recognition. To study the effects of these compounds on the induction of protein-specific immune responses in an animal model relevant to humans, rhesus macaques were immunized subcutaneously (s.c.) with keyhole limpet hemocyanin (KLH) or human papillomavirus (HPV)16 capsomeres with or without dsRNA or a control adjuvant, the TLR9 ligand CpG-C. All dsRNA compounds served as adjuvants for KLH-specific cellular immune responses, with the highest proliferative responses being observed with 2 mg/animal poly ICLC (p = 0.002) or 6 mg/animal poly I:C₁₂U (p = 0.001) when compared with immunization with KLH alone. Notably, poly ICLC—but not CpG-C given at the same dose—also helped to induce HPV16-specific Th1 immune responses while both adjuvants supported the induction of strong anti-HPV16 L1 antibody responses as determined by ELISA and neutralization assay. In contrast, control animals injected with HPV16 capsomeres alone did not develop substantial HPV16-specific immune responses. Injection of dsRNA led to increased numbers of cells producing the T cell–activating chemokines CXCL9 and CXCL10 as detected by in situ hybridization in draining lymph nodes 18 hours after injections, and to increased serum levels of CXCL10 (p = 0.01). This was paralleled by the reduced production of the homeostatic T cell–attracting chemokine CCL21. Thus, synthetic dsRNAs induce an innate chemokine response and act as adjuvants for virus-specific Th1 and humoral immune responses in nonhuman primates.

Novel adjuvants that facilitate the induction of strong cellular immunity could be of help in the design of vaccine strategies to combat infections such as HIV or tuberculosis. Our immune cells possess archaic receptors recognizing structures of infectious pathogens, and the interaction of these receptors with their ligands results in an activation of the immune system. Here we exploited synthetic forms of one of these ligands, i.e., dsRNA, to define an adjuvant for the induction of cellular immune responses in primates. We injected model and viral proteins together with three different forms of dsRNA subcutaneously (s.c.) in rhesus macaques, and all compounds served as adjuvants for the induction of cellular immunity without the incidence of major side effects. These adjuvant effects depended on the adjuvant dose and coincided with profound alterations in the chemokine production in the draining lymph nodes. dsRNA also helped to induce cellular and humoral immune responses against capsomeres of low immunogenicity derived from the human papillomavirus 16, the causative agent in about 50% of all cases of cervical cancer worldwide. Therefore, formulations involving synthetic dsRNA are promising candidates for development of novel vaccines.

Nasal immunization with the mixture of PA63, LF, and a PGA conjugate induced strong antibody responses against all three antigens

A new generation anthrax vaccine is expected to target not only the anthrax protective antigen (PA) protein, but also other virulent factors of Bacillus anthracis. It is also expected to be amenable for rapid mass immunization of a large number of people. This study aimed to address these needs by designing a prototypic triantigen nasal anthrax vaccine candidate that contained a truncated PA (rPA63), the anthrax lethal factor (LF), and the capsular poly-gamma-D-glutamic acid (gammaDPGA) as the antigens and a synthetic double-stranded RNA (dsRNA), polyriboinosinic-polyribocytodylic acid (poly(I:C)) as the adjuvant. This study identified the optimal dose of nasal poly(I:C) in mice, demonstrated that nasal immunization of mice with the LF was capable of inducing functional anti-LF antibodies (Abs), and showed that nasal immunization of mice with the prototypic triantigen vaccine candidate induced strong immune responses against all three antigens. The immune responses protected macrophages against an anthrax lethal toxin challenge in vitro and enabled the immunized mice to survive a lethal dose of anthrax lethal toxin challenge in vivo. The anti-PGA Abs were shown to have complement-mediated bacteriolytic activity. After further optimization, this triantigen nasal vaccine candidate is expected to become one of the newer generation anthrax vaccines.

Poly ICLC inhibits Plasmodium cynomolgi B malaria infection in rhesus monkeys

Prophylatic treatment with a single dose of 1.0 or 2.0 mg/kg (body weight) of polyinosinic-polycytidylic acid stabilized with polylysine and carboxymethylcellulose (Poly ICLC), a potent interferon (IFN) inducer and immune enhancer, 18 h before intravenous inoculation of sporozoites (1.04 x 10(5)-0.70 x 10(6) sporozoites) of Plasmodium cynomolgi B in the rhesus monkey, completely abolished the infectivity of sporozoites. The inhibitory effect of Poly ICLC is dose dependent in monkeys infected with P. cynomolgi B sporozoites. Treatment with lower doses of Poly ICLC (0.5 mg/kg) provided significant protection, but the lowest dose of Poly ICLC used (0.1 mg/kg) failed to provide any protection. Prophylactic treatment with Poly ICLC, however, had no protective effect against trophozoite-induced infection.

Clinical trials of interferons in multiple sclerosis. What have we learned?

Although multiple sclerosis (MS) is generally believed to be an immune-mediated disease, conventional therapy with ACTH, corticosteroids, or immunosuppressive drugs is unsatisfactory. Aside from their unpredictable therapeutic effects, these agents are potentially hazardous and can only be given for short periods of time. There is an urgent need for less toxic yet effective immunotherapy, that that can be administered early in the disease and continued indefinitely. Clinical trials of the interferons (IFNs) have not only led to a promising new approach to treatment, but have also stimulated basic research in the immunological mechanisms of underlying disease activity. Administration of IFN-gamma promotes exacerbations of MS, whereas recombinant IFN-beta has been shown, in controlled clinical trials, to suppress them. Other ongoing studies are likely to provide further information about its long-term therapeutic value. More importantly, laboratory studies performed in conjunction with these clinical trials have provided fresh insights into the pathogenesis of MS by revealing immunoregulatory mechanisms in which endogenous IFN-gamma, TNF-alpha, and other cytokines appear to play central roles. The 'Decade of the Brain' may therefore see answers both to the therapeutic dilemma of MS, and to more basic questions about the function of IFNs and other cytokines in activation and regulation of the disease process.

Changes in leukocyte recirculation, NK cell activity, and HLA-DR expression in peripheral blood mononuclear cells of MS patients treated with Poly ICLC

To investigate the cellular immune effects of the interferon inducer, Poly ICLC, in humans, peripheral blood mononuclear cells from patients with multiple sclerosis receiving Poly ICLC as part of a preliminary clinical trial were studied. Peripheral blood mononuclear cell phenotype analysis using fluoresceinated monoclonal antibodies and flow microfluorometry showed decreases in the percentages and absolute numbers of all lymphocyte subsets 24 h after infusion. These changes returned toward baseline at 48 h except the percentage of CD-4 positive cell which increased above baseline levels. The percentage of HLA-DR antigen positive cells and CD-16 (Leu 11a) positive cells were increased 24 h after infusion but returned to baseline at 48 h. NK activity as determined by chromium release from K562 target cells was decreased at 24 h but increased 48 h after drug infusion. The increases in percentages of HLA-DR antigen and CD-16 positive cells at 24 h and NK activity at 48 h are consistent with the in vitro effects of IFN while the decreases in peripheral blood mononuclear cells are suggestive of changes in cell recirculation.

The kinetics of interferon induction by poly ICLC in humans

A preliminary trial of the interferon (IFN) inducer polyriboinosinic acid-polyribocytidylic acid in poly-L-lysine and carboxymethylcellulose (poly ICLC) was conducted in patients with chronic progressive multiple sclerosis (MS). Because IFN induction in men is greater than in women, the kinetics of IFN induction were studied. As no significant differences were found in the serum half-life of IFN, sex-linked differences in IFN clearance or degradation are not likely to be responsible for the differences noted. Because fever was the major limiting side effect in MS patient, the relationship of fever to IFN levels was assessed. Changes in temperature were not related to changes in IFN levels, suggesting that fever might be blocked without reducing IFN levels.

Cortisol induction by poly ICLC: implications for clinical trials of interferon

Because interferon injections have recently been reported to induce cortisol in cancer patients, we retrospectively reviewed cortisol levels obtained during a preliminary trial of the interferon inducer polyriboinosinic polyribocytidylic acid in poly-L-lysine and carboxymethylcellulose (poly ICLC) in multiple sclerosis patients to determine if significant cortisol induction occurred. Analysis of data from 51 poly ICLC infusions in 6 men and 4 women showed elevated cortisol levels 4 to 16 hours after infusion, with hematological changes consistent with steroid effect. The highest cortisol levels observed were in 2 patients who improved during the treatment period, but there was no clear relationship between cortisol levels and clinical outcome in the group as a whole.