Biomedical subjects

M A Tomai

Publications and source records attributed to M A Tomai.

At least 19 recordsLinked to original sources

PubMed2006

Immunomodulatory effects of Toll-like receptor-7 activation on chronic lymphocytic leukemia cells.

Weak immunogenicity of chronic lymphocytic leukemia (CLL) cells may contribute to disease progression and inhibit effective immunotherapy. Accordingly, agents that enhance the immunogenicity of CLL cells may be useful in immunotherapeutic approaches to this disease. Since Toll-like receptors (TLRs) are major regulators of innate immunity and initiation of adaptive immunity, we studied the effects of viral pathogen associated molecular pattern agonists (that are recognized by TLRs) on the costimulatory phenotype and function of CLL cells. CLL cells (especially those with high endogenous expression of CD38) responded to TLR7-activating imidazoquinolines and guanosine analogs by increasing costimulatory molecule expression, producing inflammatory cytokines, and becoming more sensitive to killing by cytotoxic effectors. Additional activation of protein kinase C pathways increased the ability to stimulate T-cell proliferation, blocked phosphorylation of the transcription factor, signal transducer and activator of transcription (STAT)3, and resulted in the acquisition of a dendritic cell surface phenotype by TLR7-activated CLL cells. Normal B cells also responded to TLR7 activation by increasing costimulatory molecule expression and cytokine production. These findings suggest a potential role for TLR7 agonists in CLL immunotherapy.

Adult↗

PubMed2002

Immunomodulation as a treatment strategy for genital herpes: review of the evidence.

In this review, we discuss the ongoing development of a new treatment option for genital herpes (GH), the disease caused by herpes simplex virus (HSV) types I and II. Following infection, the virus establishes a latent infection in peripheral neurons, which periodically activates to cause recurrent skin lesions or asymptomatic shedding in the anogenital area. A new class of drugs, the immune response modifiers (IRMs), modulates the immune system against viral infection. This approach is currently being tested as a treatment for GH. We first review the effectiveness of treatment of other viral diseases with imiquimod, the first IRM to be licensed (Aldara, imiquimod 5% cream), and one used for the treatment of external anogenital warts. We then focus on resiquimod, an analog of imiquimod, which shows early promise as a new treatment option for GH. The evidence from in vitro and in vivo studies, in particular the guinea pig model of GH, describing the effectiveness and mode of action of this novel immunopharmacological agent is presented. Resiquimod stimulates specific cells of the innate immune system (including monocytes/macrophages, dendritic cells (DC) and B lymphocytes) to produce cytokines (in particular IFN-alpha, IL-12, TNF-alpha and IFN-gamma) that initiate and drive the development of the Th1 acquired immune response against HSV-infected cells. Recent results from clinical trials and in vivo studies in animal models are consistent with the hypothesis that the development of HSV-specific cell-mediated immunity may prove to be the key in providing a long-lasting protection against GH recurrences.

Adjuvants, Immunologic↗

PubMed2001

The immune response modifier resiquimod mimics CD40-induced B cell activation.

Members of the imidazoquinoline molecule family, including imiquimod and resiquimod (R-848), have potent antiviral and antitumor activities. Imiquimod cream (5%) (Aldara) is currently indicated for treatment of external genital and perianal warts. Previous characterization of these compounds has focused upon their ability to activate monocytes and dendritic cells, but recent studies have shown that resiquimod also stimulates B lymphocytes to proliferate and express an activated phenotype. This suggests that resiquimod could potentially serve as an effective vaccine adjuvant in stimulating a humoral immune response. This study shows that resiquimod mimics effects of the T-dependent CD40 signal in both mouse and human B cell lines. Resiquimod, like CD40, stimulates antibody secretion, cytokine production, protection from apoptosis, and CD80 upregulation. In addition, it shows synergy with signals delivered by the B cell antigen receptor and heightens CD40-mediated B cell activation, demonstrating that resiquimod can enhance antigen-specific responses in B lymphocytes.

Adjuvants, Immunologic↗

PubMed2001

Daily or weekly therapy with resiquimod (R-848) reduces genital recurrences in herpes simplex virus-infected guinea pigs during and after treatment.

The effect of resiquimod (R-848), an immune-response modifier that is similar to imiquimod, on recurrent herpes simplex virus (HSV) was evaluated using the guinea pig model of genital herpes. Guinea pigs were intravaginally infected with HSV-2 and then were randomized on day 14 to receive nothing or 0.1 mL/kg per dose of subcutaneous resiquimod, given either daily, every other day, or weekly from days 15-35. During a 3-week course of therapy, recurrences in all 3 treated groups were reduced by >80%, compared with the control group. After therapy, recurrences remained significantly (P<.05) decreased in all 3 groups for the next 3 weeks. The group treated weekly developed the fewest recurrences. Significant increases in interleukin-2 levels, produced by incubation of mononuclear cells with HSV-2 antigens, but not in circulating antibody also were detected in the treated groups. Resiquimod treatment may offer significant advantages to present antiviral therapies for the control of recurrent genital herpes.

Animals↗

PubMed2000

Molecular mechanisms of B lymphocyte activation by the immune response modifier R-848.

The imidazoquinoline R-848, originally identified as a highly effective antiviral agent, has recently been shown to be capable of potent B lymphocyte activation. The B cell-activating properties of R-848 are strikingly similar to the effects of the CD40 ligand CD154. The present study demonstrates that this similarity extends to the intracellular signaling pathways triggered by the compound, although both overlapping and distinct mechanisms of signaling were seen. Like CD40 ligation, R-848 stimulated activation of the stress-activated protein kinases c-Jun kinase and p38 and activated the NF-kappaB family of transcription factors. Both R-848- and CD40-mediated B cell differentiation were dependent upon NF-kappaB activation, although the relative importance of individual NF-kappaB family members appeared to differ between R-848- and CD40-mediated signals. Both signals were partially dependent upon induction of TNF-alpha and IL-6, and the cytoplasmic adaptor molecule TNF receptor-associated factor 2 is involved in both R-848- and CD40-mediated differentiation.

Adjuvants, Immunologic↗

PubMed2000

Adjuvant activities of immune response modifier R-848: comparison with CpG ODN.

R-848 and imiquimod belong to a class of immune response modifiers that are potent inducers of cytokines, including IFN-alpha, TNF-alpha, IL-12, and IFN-gamma. Many of these cytokines can affect the acquired immune response. This study examines the effects of R-848 on aspects of acquired immunity, including immunoglobulin secretion, in vivo cytokine production, and Ag-specific T cell cytokine production. Results are compared with those of Th1 CpG ODN. R-848 and CpG ODN are effective at skewing immunity in the presence of Alum toward a Th1 Ab response (IgG2a) and away from a Th2 Ab response (IgE). R-848 and CpG ODN are also capable of initiating an immune response in the absence of additional adjuvant by specifically enhancing IgG2a levels. Both R-848 and imiquimod showed activity when given subcutaneously or orally, indicating that the compound mechanism was not through generation of a depot effect. Although CpG ODN behaves similarly to R-848, CpG ODN has a distinct cytokine profile, is more effective than R-848 when given with Alum in the priming dose, and is active only when given by the same route as the Ag. The mechanism of R-848's adjuvant activity is linked to cytokine production, where increases in IgG2a levels are associated with IFN-alpha, TNF-alpha, IL-12, and IFN-gamma induction, and decreases in IgE levels are associated with IFN-alpha and TNF-alpha. Imiquimod also enhances IgG2a production when given with Ag. The above results suggest that the imidazoquinolines R-848 and imiquimod may be attractive compounds for use as vaccine adjuvants and in inhibiting pathological responses mediated by Th2 cytokines.

Adjuvants, Immunologic↗

PubMed2000

The immune response modifiers imiquimod and R-848 are potent activators of B lymphocytes.

Imiquimod and R-848 are members of a family of immune response modifiers that stimulate cytokine production in monocyte/macrophages and dendritic cell cultures. This study evaluated the effects of the imidazoquinolines, imiquimod and R-848, on B lymphocyte activation. Both agents induced proliferation of murine T-cell-depleted and highly purified splenic B cell preparations as well as purified human B cells. Resting and activated B cells responded to these agents, with activated cells responding more efficiently. B cells from the LPS-hyporesponsive C3H/HeJ mice and guanosine-hyporesponsive SJL mice proliferated in response to imiquimod and R-848, indicating a different mechanism of action than lipopolysaccharide and guanine nucleosides. B cells were also stimulated by imiquimod and R-848 to produce increased immunoglobulin levels. Increased expression of a number of B cell activation markers were seen following imiquimod or R-848 stimulation. Finally, R-848 was shown to act as a vaccine adjuvant enhancing OVA-specific IgG2a levels while suppressing total IgE. These results indicate that R-848 and imiquimod are potent activators of B lymphocytes and are capable of augmenting antigen-specific immunoglobulin production.

Adjuvants, Immunologic↗

PubMed2000

Imiquimod, a topical immune response modifier, induces migration of Langerhans cells.

Langerhans cells are bone marrow derived dendritic cells that represent the major antigen-presenting cells in the skin. Langerhans cells take up and process antigen within the epidermis and present processed antigen to T lymphocyte in the regional lymph nodes and thus form an integral part of the cutaneous immune response. The cutaneous immune response can be modified by a number of pharmacologic agents, including corticosteroids, cyclosporine, and retinoids as well as physical agents, such as ultraviolet light. For the most part these agents act by suppressing immune function. A topical immune response modifier, imiquimod has been shown to enhance the cutaneous immune response. Imiquimod has anti-viral and anti-tumor effects in animal models and has been approved for the topical treatment of external genital and perianal warts in humans. The biologic activity of imiquimod in part is due to its effect as a cytokine inducer. Preliminary data suggested that imiquimod could have an effect on Langerhans cells. In order to clarify this effect on Langerhans cells, we examined Langerhans cell morphology and migration in imiquimod-treated skin. The density of Ia + cells decreased 2 d after treatment, falling to approximately 43% by day 10. The Ia positive in cells remaining in the skin appeared larger and more dendritic suggesting an activated state. ATPase staining of epidermal sheet confirmed the decreased number of Langerhans cells. To clarify status of Langerhans cells, the activation of B7 was examined. Activation of B7-1 or B7-2 was not detected. Imiquimod, however, did enhance Langerhans cell migration from skin to draining lymph nodes. This enhanced Langerhans cell migration was also associated with an enhanced allergic contact hypersensitivity. These results suggest that the mechanism of modulation of immune response by imiquimod is in part due to effects on Langerhans cells.

Adenosine Triphosphatases↗

PubMed2000

Correlation between pretreatment levels of interferon response genes and clinical responses to an immune response modifier (Imiquimod) in genital warts.

Imiquimod (IQ) has been successfully used in treatment of genital warts. In clinical settings, patients responded well but wart reduction rates varied. Our aim was to find a correlation between clinical responses and pretreatment (constitutive) levels of genes that might be involved in the molecular action of IQ. Since IQ is a cytokine inducer, we analyzed levels of expression of genes of the JAK/STAT signaling pathway and their inhibitors as well as interferon response factors (IRFs) in pretreatment biopsy specimens from complete responders (99 to 100% wart reduction rate) versus incomplete responders (75 to 92% wart reduction rate) by reverse transcription-PCR. We found that mRNA levels of signal transducer and activator of transcription 1 (STAT1) and IRF1 were higher in complete responders than in incomplete responders. Incomplete responders expressed larger amounts of STAT3, IRF2, and protein inhibitor of activated STAT1 (PIAS1) mRNAs compared to complete responders before IQ treatment. We hypothesize that high-level expression of STAT1 and IRF1 is advantageous for a better IQ response. The observed differences in constitutive mRNA levels of these genes may be the consequence of alterations in cellular differentiation and/or variable expression of endogenous interferons. Previous in vitro studies showed that keratinocyte differentiation coordinates the balance between positive and negative signals along the JAK/STAT pathway by regulating the IRF1:IRF2 and STAT1:PIAS1 ratios and thus affecting induction of IQ-inducible genes. Specifically, differentiation supports constitutive expression of STAT1 and IRF1 mRNAs but not expression of IRF2 and PIAS1. Our data are in good agreement with studies that showed the importance of STAT1 in cytokine induction and activation of interferon-responsive genes by IQ.

Aminoquinolines↗

PubMed1999

Dendritic cell maturation and subsequent enhanced T-cell stimulation induced with the novel synthetic immune response modifier R-848.

Agents that enhance dendritic cell maturation can enhance T-cell activation and therefore may improve the efficiency of vaccines or improve cellular immunotherapy. Previously, we demonstrated that a novel low-molecular-weight synthetic immune response modifier, R-848, induces IL-12 and IFN-alpha secretion from monocytes and macrophages. Here we report that R-848 induces the maturation of human monocyte-derived dendritic cells. Characteristic of dendritic cell maturation, R-848 treatment induces cell surface expression of CD83 and increases cell surface expression of CD80, CD86, CD40, and HLA-DR. Additionally, R-848 induces cytokine (IL-6, IL-12, TNF-alpha, IFN-alpha) and chemokine (IL-8, MIP-1alpha, MCP-1) secretion from dendritic cells. Most significantly, R-848 enhances dendritic cell antigen presenting function, as measured by increased T-cell proliferation and T-cell cytokine secretion in both allogeneic and autologous T-cell systems. Consequently, low-molecular-weight synthetic molecules such as R-848 and its derivatives may be useful as vaccine adjuvants or as ex vivo stimulators of dendritic cells for cellular immunotherapy.

Antigens, CD↗

PubMed1999

Modulation of TH1 and TH2 cytokine production with the immune response modifiers, R-848 and imiquimod.

Cytokines produced by antigen-presenting cells are known to affect the development and cytokine profile of T cells. The immune response modifiers imiquimod and R-848 were previously shown to stimulate human and mouse cultures to secrete interferon-alpha. Results from the present study demonstrate that R-848 and imiquimod are capable of inducing interleukin-12 and interferon-gamma in mouse and human cell cultures. Both CD4(+) and CD8(+) T lymphocytes were responsible for producing IFN-gamma following stimulation with R-848. Macrophages were required for induction of interferon-gamma by R-848 and the cytokines IFN-alpha and IL-12 mediated this response. R-848 and imiquimod were also found to inhibit IL-4 and IL-5 production in mouse and human culture systems. The inhibition of IL-5 in response to R-848 is seen in cultures containing CD4(+) lymphocytes and macrophages and is mediated in part by IFN-alpha. These data suggest that imiquimod and R-848 may have clinical utility in diseases where cell-mediated immune responses are important and in diseases associated with overexpression of IL-4 or IL-5 such as atopic disease.

Adjuvants, Immunologic↗

PubMed1999

Enhancement of the innate and cellular immune response in patients with genital warts treated with topical imiquimod cream 5%.

The mechanism of action of imiquimod 5% cream applied topically to patients with genital warts was evaluated in a double-blind, placebo-controlled study. Imiquimod (16 patients) or placebo (three patients) was applied three times per week for up to 16 weeks. All imiquimod-treated patients had a > or =75% reduction in total wart area while only one of three placebo-treated patients had a similar reduction. Wart biopsies were taken at prestudy, week 6, and end of treatment. Polymerase chain reaction (PCR) for human papillomavirus (HPV) DNA and reverse transcriptase (RT)-PCR for messenger (m)RNAs were used to identify cytokines, cellular markers, viral gene products, and cell cycle markers in these biopsies. Treatment with imiquimod, an immune response modifier, stimulated significant increases in mRNA for interferon (IFN)-alpha, IFN-gamma and 2',5' oligoadenylate synthetase (2',5'-AS) as well as a tendency towards increases in tumor necrosis factor (TNF)-alpha and interleukin-12 p40. Significant increases in mRNA for CD4 and a trend toward increases in CD8 were also observed in imiquimod-treated patients, suggesting activation of a cell mediated immune response. Imiquimod administration was also associated with a significant decrease in viral load as measured by HPV DNA and L1 mRNA. The effects on HPV markers were accompanied by an apparent decrease in mRNA expression for markers of cell proliferation and an increase in mRNA for markers of keratinocyte differentiation and tumor suppressors.

Adolescent↗

PubMed1999

Imiquimod applied topically: a novel immune response modifier and new class of drug.

Imiquimod (S-26308, R-837) (1-(2-methylpropyl)-1H-imidazo[4,5-c]quinolin-4 amine), an immune response modifier, demonstrates potent antiviral and antitumor activity in animal models (see structure in Fig. 1). The drug exhibits no direct antiviral or antiproliferative activity when tested in a number of cell culture systems. Imiquimod's activity was discovered while screening for anti-herpes virus activity. One of the first analogs in the series, S-25059 was tested in the early 1980's and due to slight toxicity, caused slightly reduced herpes cytopathology in Vero cell cultures. Follow-up testing in herpes infected guinea pigs showed complete protection toward lesion development. Activity of these drugs results primarily from interferon alpha (IFN-alpha) induction and other cytokine induction. At least part of the cytokine induction is mediated through NF-kappaB activation. These cytokines stimulate several other aspects of the innate immune response. In addition, imiquimod stimulates acquired immunity, in particular the cellular arm which is important for control of viral infections and various tumors. This effect is mediated by drug induced IFN-alpha and Interleukin-12 (IL-12) and IFN-gamma induced by these cytokines. Imiquimod is expected to be effective where exogenous IFN-alpha has shown utility and where enhancement of cell-mediated immunity is needed. The following is a brief review of the preclinical pharmacology of imiquimod and the clinical results of genital wart trials. The mechanism of action of topically applied imiquimod will likely lead to benefits in several other chronic virus infections and tumors of the skin. Two other reviews on imiquimod that focus mainly on the clinical results have been published (Beutner & Geisse, 1997; Slade, Owens, Tomai & Miller, 1998).

Adjuvants, Immunologic↗

PubMed1999

Development of a topically active imiquimod formulation.

The purpose of this work was to develop a topical formulation of imiquimod, a novel immune response modifier, to induce local cytokine production for the treatment of external genital and perianal warts. A pH-solubility profile and titration data were used to calculate a pKa of 7.3, indicative of a weak base. Solubility experiments were conducted to identify a solvent that dissolves imiquimod to achieve a 5% formulation concentration. Studies to select surfactants, preservatives, and viscosity-enhancing excipients to formulate an oil-in-water cream indicated that fatty acids were the preferred solvent for topical imiquimod formulations, and isostearic acid (ISA) was selected. A relationship existed between the fatty acid composition of four commercially available ISA sources and the solubility of imiquimod. A combination of polysorbate 60, sorbitan monostearate, and xanthan gum was used to produce a physically stable cream. The preservative system included parabens and benzyl alcohol to meet the USP criteria for preservative activity. An in vitro method was developed to demonstrate that imiquimod was released from the formulation. Topical application of the formulation induced local cytokine activity in mice.

Adjuvants, Immunologic↗

PubMed1998

Cytokine induction in hairless mouse and rat skin after topical application of the immune response modifiers imiquimod and S-28463.

ALDARA (imiquimod cream 5%) recently became available for the treatment of genital and perianal warts; however, the topical mechanism of action of imiquimod is not fully understood. Imiquimod, and its analogs R-842, S-27609, and S-28463, are potent anti-viral and anti-tumor agents in animal models. Much of the biologic activity of these compounds can be attributed to the induction of cytokines, including interferon-alpha, tumor necrosis factor-alpha, interleukins-1, -6, -8, and others. This study was performed to characterize the response of mice and rats to topical application of imiquimod and S-28463 and also to evaluate these agents in cultures of murine and human skin cells. Topical administration of imiquimod or S-28463 to the flanks of hairless mice and rats leads to increases in local concentrations of interferon and tumor necrosis factor in the skin. The concentrations of interferon and tumor necrosis factor were higher at the site of drug application than in skin from the contralateral flank or skin from untreated animals. Interferon-alpha mRNA levels were also elevated in the skin of mice after topical application of either imiquimod or S-28463. In vitro, both imiquimod and S-28463 induced increases in interferon and tumor necrosis factor in cultures of cells isolated from hairless mouse skin. Imiquimod also increased interleukin-8 concentrations in human keratinocyte and fibroblast cultures, whereas S-28463 induced increases in tumor necrosis factor in fibroblast cultures. These results demonstrate that imiquimod and S-28463 stimulate production of cytokines in the skin after topical application, which may play a major role in its activity in genital wart patients.

Adjuvants, Immunologic↗

PubMed1998

A randomized, controlled, molecular study of condylomata acuminata clearance during treatment with imiquimod.

Imiquimod, an immune response modifier, has been demonstrated to be safe and effective in the treatment of external genital and perianal warts caused by human papillomavirus (HPV). To identify the molecular mechanism(s) by which condylomata acuminata clear during topical treatment with imiquimod, wart skin biopsies were taken from patients before treatment, at treatment week 6, and at the end of treatment. Tissues were analyzed for HPV DNA and for mRNA of several cytokines and HPV gene products. Wart clearance was associated with evidence of tissue production of interferon-alpha, -beta, and -gamma and tumor necrosis factor-alpha. Regression of warts was strongly associated with a decrease in HPV DNA and in mRNA expression for both early and late viral proteins. Thus, topical imiquimod treatment of anogenital warts led to significant increases in local production of multiple interferon mRNAs and a significant reduction in virus load as measured by decreases in HPV DNA and mRNA for early HPV proteins.

Administration, Topical↗

PubMed1998

Attenuation of virus-induced airway dysfunction in rats treated with imiquimod.

Viral respiratory infections cause acute airway abnormalities consisting of inflammation and physiological dysfunction in both animals and humans. It is likely that inflammatory cell products, such as cytokines, contribute substantially to viral-induced airway dysfunction. We hypothesized that imiquimod, an immune response enhancing agent that induces interferon-alpha, would attenuate the development of airway dysfunction during acute viral illness in rats. Adult Brown Norway rats were inoculated with parainfluenza type 1 (Sendai) virus or sterile vehicle, and treated with either imiquimod or water. Respiratory system resistance (Rrs), arterial oxygen tension (Pa,O2), lung viral titres and bronchoalveolar lavage (BAL) leucocyte counts were measured in anaesthetized, paralysed, ventilated rats. Virus-infected, water-treated rats had a significant decrease in Pa,O2 and had significant increases in leucocyte count and Rrs when compared to both the virus-infected, imiquimod-treated, (Pa,O2, p = 0.03; leucocyte count, p = 0.02; and Rrs, p = 0.009) and noninfected, water-treated rats (Pa,O2, p = 0.007; leucocyte count, p = 0.001; and Rrs, p = 0.01). In addition, imiquimod suppressed BAL eosinophils in both virus-infected (p = 0.02) and noninfected (p = 0.001) groups, and lowered overall virus titres (p = 0.03). Thus, both virus-induced airway inflammation and physiological dysfunction were attenuated significantly by imiquimod treatment in this animal model. By further delineating mechanisms by which infections induce airway dysfunction in animal models, more specific pharmacological interventions can be developed for the treatment of virus-induced asthma.

Adjuvants, Immunologic↗

PubMed1998

Imiquimod 5% cream (Aldara).

Imiquimod is a novel synthetic molecule with potent immune-modifying activities. Formulated in a 5% vanishing cream as Aldara, this self-applied therapy has shown good efficacy and safety in the treatment of external genital and perianal warts caused by human papillomavirus (HPV) infection (Condyloma acuminata). The molecule does not demonstrate direct antiviral activity, but through induction of cytokines results in immune-based resolution of wart tissue and reduction of viral burden. Phase III trials of imiquimod have demonstrated that patients who experience complete clearance of either new or recalcitrant warts tend to remain clear, possibly related to Th1 immune recognition and memory. Self-application, good tolerability and a unique mechanism of action combine to make imiquimod a reasonable first-line therapy for genital warts. The effects of imiquimod on immune function suggest several potential uses. Preclinical studies of infection with herpes simplex virus (HSV), cutaneous leishmaniasis, Rift Valley Fever virus and vesiculostomatitis virus have shown reduced viral persistence, reduced recurrence (HSV) and diminished pathology (Leishmania donovani). In a murine tumour model using the FCB bladder cancer cell line, imiquimod behaves as a potent adjuvant leading to immune-based tumour cell eradication and immunity against subsequent FCB cell challenge. The ability of imiquimod to induce significant production of interferon alpha (IFN-alpha) by monocytes/macrophages suggests that diseases responsive to recombinant interferon therapy, such as basal cell carcinoma, may be reasonable clinical targets. The induction of tumour necrosis factor alpha (TNF-alpha), interferon gamma (IFN-gamma) and interleukin-12 (IL-12) leads to inhibition of IL-5, with animal models demonstrating immune deviation away from Th2 immune responses. The observation that several patients with hepatitis C infection and eosinophilia showed normalisation of elevated eosinophil counts in association with oral imiquimod therapy encourages further exploration of the immune modifying properties of this novel molecule. This review is focused on the use of imiquimod for the treatment of external genital and perianal warts.

Journal Article↗