Current Pharmaceutical Design - Volume 9, Issue 24, 2003

The spleen plays a paramount role in the host protection against invading microrganisms. In support of the above concept, in splenectomized patients there is increasing evidence of overwhelming postsplenectomy infections (OPSI). OPSI are caused by Streptococcus pneumoniae in about 80% of cases, but also Gram-negative bacteria are implicated in a certain number of cases. Therapeutically, penicillin and pneumococcal vaccines represent valid therapeutic approaches in Gram-positive OPSI. However, the effectiveness of polyvalent polysaccharide pneumococcal vaccines is still debated and, thus, other therapeutic strategies should be validated for combating OPSI. According to our personal data, a deficit of phagocytic activities and of T helper (h)-1 cells is very frequent in splenectomized patients. In sera, we found reduced levels of both Interferon-γ and Interleukin (IL)-4. These data are in accordance with the recent observation on the protective role of T cells against S. pneumoniae. In fact, patients deficient in IL-12 develop severe pneumococcal infections and undergo apoptosis of Th1 cells.

It is well known that inappropriate nutrient intake accounts for the maintenance of the immunological equilibrium, in humans and animals. Vitamins, elements, lipids, proteins and nucleic acids play an important role in the regulation of cellular and humoral immune responses since single or multiple deficits of these food components have been shown to cause immune abnormalities. For instance, in the course of protein-calorie malnutrition bacterial and / or viral infections represent the major cause of death. Ageing is characterized by a decline of many immune functions, and this process is called immunosenescence. Here, we report novel findings on the inability of superantigens to activate old CD8+, natural killer and B cells, as an expression of cell amnesia. In the elderly, this lack of activation could lead to lethal effects in the case of severe staphylococcal infections. Quite interestingly, recent findings outlined some similarities between human immune deficiency virus (HIV)-1 infection and ageing in terms of immune changes. The model of HIV-infection may be useful for the interpretation of ageing mechanisms and possible therapeutical interventions. Finally, the role of nutrition in different pathological conditions and the use of medical foods for correcting of immune deficits will be described.

Recently a possible cross talk about the relationship between p53 and beta-catenin has been suggested by the observation that colorectal cancers accumulating beta-catenin (as a result of APC mutations) also exhibit high frequency p53 mutations. Our aim was to evaluate the pattern of both the proteins and match these with the morphological changes in colorectal carcinogenesis. Immunohistochemical patterns of p53 and beta catenin were studied using the natural carcinogenetic model of malignant colorectal sporadic adenoma in 27 formalin-fixed paraffinembedded polyps. We found a progressive increase of p53 and beta-catenin staining from normal, to dysplastic, and to cancerous epithelium. We noted, in dysplastic and cancerous epithelium, but not in normal tissue, the translocation of beta-catenin from the cytoplasm to the nucleus, and in dysplastic epithelium, a significant correlation between p53 over expression and betacatenin patterns. Beta-catenin cytoplasmic accumulation seemed to drive p53 over expression already in the early stages of carcinogenesis, while nuclear beta-catenin translocation appeared to be related to a pattern of invasion of neoplastic cells.

Proinflammatory cytokines released from monocytes / macrophages, in particular tumor necrosis factor (TNF)-α, interleukin (IL)-1, IL-6, and IL-8 seem to play an important role in Inflammatory Bowel Disease (ulcerative colitis and Crohn's disease). Endotoxins or lipopolysaccharides, derived from the outer membrane of Gram-negative bacteria interact with CD14 on surface membrane of macrophages, thus triggering a signal cascade, which leads to the production and release of proinflammatory cytokines, particularly TNF-α. Therefore, in IBD, lipopolysaccharides could play a pathogenic role. In this respect, plasma endotoxins have been demonstrated in a not negligible percentage of patients with ulcerative colitis and in their unaffected relatives. The presence of circulating endotoxins could be due, at least in part, to the impaired natural immunity in either patients with ulcerative colitis or in their first degree unaffected relatives. Lactoferrin is an iron-binding glycoprotein, which binds to the lipid A region of lipopolysaccharide with a high affinity and this interaction prevents the binding of lipopolysaccharide to CD14, thus inhibiting the release of proinflammatory cytokines. Therefore, based on the possible pathogenic role exerted by endotoxins in ulcerative colitis, lactoferrin may deserve attention as a possible therapeutical agent in experimental models of Inflammatory Bowel Disease.

Hashimoto's thyroiditis, the most common form of autoimmune thyroid disease, is characterised by lymphocytic infiltration of the thyroid gland, gradual destruction of the organ and production of thyroid specific auto antibodies (antithyroid peroxidase and antithyroglobulin antibodies). There are evidences that cast doubt on the pathogenetic role of these antibodies in thyroid autoimmunity. It is very likely that cellular destruction is mediated by other cellular mechanisms, such as auto reactive T-lymphocytes, natural killer and cytokines. However, other studies performed in animal models have led to the conclusion that organ specific autoimmune thyroiditis should be regarded as a polygenic disease with a penetrance that is strongly influenced by environmental factors. According to our recent results, patients affected by autoimmune thyroiditis exhibited a decreased percentage of NK and CD25 + bearing cells significantly in comparison to normal controls. Altogether these data indicated that in the patients with autoimmune thyroid disease a certain degree of peripheral immune deficiency was present.

Several lines of evidence support a mutual relationship between the nervous system and the immune system. Therefore, it is not surprising that some neuropsychiatric disorders are also characterized by immune abnormalities. In patients with phobic disorders and in patients with migraine without aura some common immune abnormalities have been detected and, in particular, natural immunity deficits, exaggerated release of proinflammatory cytokines and circulating bacterial endotoxins have been found. In other neurological disease, some etiologic factors have been detected as in the case of Guillain-Barrè syndrome in which molecular mimicry between Campylobacter jejuni endotoxin and GM1 ganglioside may cause an acute inflammatory polyneuropathy. On the other hand, attempts to identify an antigen have been made in patients with Alzheimer's disease and schizophrenia. Finally, the chronic fatigue syndrome, an old illness in search for an antigen, risk factors and precipitating agents have been described but evidence for a specific antigen is still lacking.

Glucocorticoids (GCs) represent the most effective treatment for autoimmune and allergic diseases, even if collateral effects are not rare, especially endocrine and immunosuppressive manifestations. Moreover, these drugs can develop adverse immunological reactions of I, III or IV type. Though immediate adverse reactions caused by systemic therapy with GCs are not very frequent, the possible beginning of anaphylactic and pseudo-anaphylactic manifestations in patients undergoing therapy with these drugs has to be considered. It has been observed that immediate adverse reactions usually are happened in asthmatic patients and in patients obliged to assume GCs again and again because of their pathology (e.g, kidney transplant). Other risk factors resulted to be female sex and hypersensibility to acetylsalicylic acid (ASA). Both in the cases of pseudo-allergic and allergic reactions, the pharmacological principle is hardly the responsible agent for the reaction; instead the excipients in drugs are often implicated (succinate salt, sulphites and carboxy-methyl-cellulose). It is possible that the IgE-response is highly specific for a fixed GC molecule as well depending on the way of administration and its salification. Moreover, it has been hypothesized that in patients with a first type allergic reaction to GCs there is a fourth type, sensitization to GCs, which is not usually diagnosed and even comes before IgE sensitization. Third type hypersensibility reactions may occur, too. Since GCs are large-scale drugs, also in emergency medicine and reanimation, allergic sensitization towards them, although infrequent, gives many interventionist problems. In the light of this feature, it seems of crucial importance to verify the tolerance toward other GC molecules. And in particular, it has been noted that patients presenting immediate reactions to hydrocortisone (HC) and methylprednisolone (MP) could tolerate prednisone and prednisolone per os and second-generation GCs, such as desamathazone and betamethazone. Nevertheless, second-generation GCs must not be considered safe; in fact, the beginning of allergic manifestations has been pointed out even towards them.

The mucosal immune system has evolved alongside, but separate, from the general systemic immune system. As a major consequence of this dichotomy, only immune responses initiated in mucosal inductive sites can result in effective immunity in mucosal tissues themselves. Oral tolerance, as usually assessed as orally-induced systemic unresponsiveness, contributes to mucosal homoeostasis by preventing unwanted immune reactions to food or environmental antigens. It is now established that tolerance can also be induced by the nasal route and mucosally-induced tolerance is being actively investigated for immune therapy against a number of diseases. Nontoxic derivatives of cholera toxin and the heat labile toxin of Escherichi coli as well as chimeric enterotoxins have been developed. These molecules retain the mucosal adjuvant activity of native enterotoxins and are effective at inducing targeted Th1 or Th2- type immune responses. Mucosal delivery of cytokines as adjuvants represents a safer alternative to parenteral cytokine injection. Nasally administered cytokines such as IL-1 and IL-12 or chemokines including RANTES, lymphotactin, MIP-1β, all act as mucosal adjuvants for co-administered antigens. Each of these cytokines promote specific pattern of CD4+ T helper cell cytokine responses that could be exploited for targeted immune therapy. Although GALT and NALT are both parts of the Common Mucosal Immune System, there are major differences between orally and nasally induced immune responses. Nasal vaccines more effectively promote protective immunity in the genitourinary tract than do oral vaccines. In addition, aging affects mucosal tolerance or immunity in GALT more than is seen in NALT. Therapeutic manipulation of mucosal immunity involves regulation of CD4+ T cell cytokine responses and thus, should require a careful examination of the host status, including the occurrence of inflammatory bowel diseases.

Inflammatory bowel disease, such as ulcerative colitis and Crohn's disease, results from an interaction between susceptibility genes, the host's bacterial environment, gut barrier defects, and immunological factors. New management approaches have been evolved from advances in our understanding of the pathobiology of this common gut disorder In particular, the therapeutic manipulation of the bacterial microenvironment in the gut seems to offer an innovative tool for the treatment of those patients. Since the gut is a highly sensitizing organ that contributes to the systemic imune response, potent treatments need to be developed to reduce gut inflammation in this disorder. Recent studies have demonstrated that probiotic lactobacilli, and also immunostimulatory DNA sequences from those same bacteria have an important antiinflammatory potential in this context. Future research should better define among patients with inflammatory bowel disease the various clinical phenotypes with the greatest potential of response to probiotic treatment. Identification of the genes leading to the disease and a rather better understanding of the underlying immunoregulatory abnormalities will be crucial steps to define the different profiles of interaction between endogenous digestive bacterial flora and the immune system in each individual patient. Such advances will probably lead to targeting of effective treatments, including bacteriotherapy with probiotic lactobacilli, to subsets of patients with inflammatory bowel disease.

IL-12 has demonstrated remarkable antitumor activity when used directly as a recombinant protein or when different viral or non-viral vectors transfer its genes. At enhancing tumor immunity, IL-12 acts as a bridge between innate and adaptive immune responses due to its ability to induce proliferation and activation of NK, NKT, and T cells. In addition, IL-12 inhibits tumor angiogenesis mainly through IFNγ-dependent production of the chemokine IP10. As a result, IL-12 can eliminate several types of tumors developed in rodents. Pre-clinical experience forecasted a quick and successful clinical translation, but the encouraging results observed in animals were not reproduced in patients. Moreover, unacceptable toxicity resulting from IFNγ overproduction was observed in 2 renal carcinoma patients included in a phase II clinical trial that consisted in systemic administration of rIL-12. As a consequence, development of IL-12 as an antitumor agent was temporarily halted while the high expectations raised among clinicians faded away. Gene transfer methods are designed to confine IL-12 production in the tumor environment preventing systemic toxicity. Tumor cells, dendritic cells, or autologous fibroblasts have been transfected with recombinant adenoviruses or retroviruses to secrete IL-12 locally, showing good efficacy and safety profiles. IL-12 combination with other immunotherapy approaches synergizes to achieve even better results. Encouraging pilot clinical results have been recently obtained from the first phase I trial studying adenovirus mediated in vivo gene transfer of IL-12 into lesions of advanced cancer patients. Further improvements will follow from: i) increases in the efficacy of gene transduction; ii) development of tumor specific promoters; iii) development of regulatable and long-term expression vectors and iv) combination with other immunological and non-immunological anticancer therapies.

The application of immunotherapy for the treatment of malignant diseases has attracted growing interest in recent years. Because T-cell immunity plays a major part in the control of tumor growth, strategies have been developed to specifically target and activate T-cells towards tumor cells by circumventing major histocompatibility complex (MHC)- restricted antigen recognition. Here we review the immunoreceptor (“T-body”) strategy based on grafting cytolytic T-cells with an antigen-specific, recombinant receptor with signalling properties. The extracellular domain of the receptor molecule consists of a single-chain antibody fragment (scFv) derived from a monoclonal antibody that binds to a tumor associated antigen. The intracellular domain is derived from a signalling receptor for cellular activation, e.g., the FcεRI receptor γ-chain or the CD3 σ-chain. Thereby, the immunoreceptor strategy combines the advantages of MHCindependent binding of antibodies to antigens with efficient T-cell activation. Due to the receptor design, T-cells grafted with immunoreceptors can be directed virtually against every cell defined by the particular antigen, including tumor cells and virally infected cells. This review summarizes the current knowledge about redirecting T-cell functions by grafting in recombinant immunoreceptors with specificity for tumor associated antigens and discusses the limitations and perspectives of the strategy for use in adoptive immunotherapy of malignant diseases.

Selective interference with immune processes in the central nervous system (CNS) is a very difficult task because of the limitations associated with the delivery of immuno modulatory molecules across the blood brain barrier. Systemic administration of immune-mediators, either by conventional routes or by intramuscularly or intravenous gene therapy, is hampered by severe side effects and alters immune-system functions also in peripheral organs. To overcome these problems, different gene therapy strategies have been developed to deliver immuno modulatory molecules directly within the central nervous system. The use of engineered CNS antigenspecific circulating cells as selective delivery vehicles, the direct injection of gene vectors into the brain parenchyma, or also the ependymal route, have been proposed as possible alternative gene therapy protocols to selectively interfere with immuno-pathological processes in the CNS. We will review the use of these CNS-targeted gene therapy protocols for the treatment of experimental autoimmune encephalomyelitis (EAE), the prototypical experimental immune-mediated disease of the CNS, and therefore discuss the relevance of these results for the therapy of multiple sclerosis (MS) the most common, immune-mediated, demyelinating disease of the CNS in humans.