Immunotherapy

Immunotherapy is the "treatment of disease by inducing, enhancing, or suppressing an immune response". Immunotherapies designed to elicit or amplify an immune response are classified as activation immunotherapies, while immunotherapies that reduce or suppress are classified as suppression immunotherapies.

Immunomodulators

The active agents of immunotherapy are collectively called immunomodulators. They are a diverse array of recombinant, synthetic and natural preparations, often cytokines. Some of these substances, such as granulocyte colony-stimulating factor (G-CSF), interferons, imiquimod and cellular membrane fractions from bacteria are already licensed for use in patients. Others including IL-2, IL-7, IL-12, various chemokines, synthetic cytosine phosphate-guanosine (CpG) oligodeoxynucleotides and glucans are currently being investigated extensively in clinical and preclinical studies. Immunomodulatory regimens offer an attractive approach as they often have fewer side effects than existing drugs, including less potential for creating resistance in microbial diseases.

Cell based Immunotherapies are proven to be effective for some cancers. Immune effector cells such as lymphocytes, macrophages, dendritic cells, natural killer cells (NK Cell), cytotoxic T lymphocytes (CTL), etc., work together to defend the body against cancer by targeting abnormal antigens expressed on the surface of the tumor due to mutation.

Activation immunotherapies

Cancer

Cancer immunotherapy attempts to stimulate the immune system to reject and destroy tumors. Immuno cell therapy for cancer was first introduced by Rosenberg and his colleagues of the National Institutes of Health in the United States. In the late 1980s, they published an article in which they reported a low tumor regression rate (2.6â€"3.3%) in 1205 patients with metastatic cancer who underwent different types of active specific immunotherapy (ASI), and suggested that immuno cell therapy along with specific chemotherapy is the future of cancer immunotherapy. Initially Immunotherapy treatments involved administration of cytokines such as Interleukin. Thereafter the adverse effects of such intravenously administered cytokines lead to the extraction of the lymphocytes from the blood and expanding in vitro against tumour antigen before injecting the cells with appropriate stimulatory cytokines. The cells will then specifically target and destroy the tumor expressing antigen against which they have been raised.

The concept of this treatment started in the US in 1980s and fully fledged clinical treatments on a routine basis have been in practice in Japan since 1990. Randomized controlled studies in different cancers resulting in significant increase in survival and disease free period have been reported and its efficacy is enhanced by 20â€"30% when cell-based immunotherapy is combined with other conventional treatment methods.

BCG immunotherapy for early stage (non-invasive) bladder cancer utilizes instillation of attenuated live bacteria into the bladder, and is effective in preventing recurrence in up to two thirds of cases. Topical immunotherapy utilizes an immune enhancement cream (imiquimod) which is an interferon producer causing the patients own killer T cells to destroy warts, actinic keratoses, basal cell cancer, vaginal intraepithelial neoplasia, squamous cell cancer, cutaneous lymphoma, and superficial malignant melanoma. Injection immunotherapy uses mumps, candida the HPV vaccine or trichophytin antigen injections to treat warts (HPV induced tumors). Lung cancer has been demonstrated to potentially respond to immunotherapy

Dendritic cell-based immunotherapy

Dendritic cells can be stimulated to activate a cytotoxic response towards an antigen. Dendritic cells, a type of antigen presenting cell, are harvested from a patient. These cells are then either pulsed with an antigen or transfected with a viral vector. Upon transfusion back into the patient these activated cells present tumour antigen to effector lymphocytes (CD4+ T cells, CD8+ T cells, and B cells). This initiates a cytotoxic response to occur against cells expressing tumour antigens (against which the adaptive response has now been primed). The cancer vaccine Sipuleucel-T is one example of this approach.

T-cell adoptive transfer

Adoptive cell transfer uses T cell-based cytotoxic responses to attack cancer cells. T cells that have a natural or genetically engineered reactivity to a patient's cancer are generated in vitro and then transferred back into the cancer patient. One study using autologous tumor-infiltrating lymphocytes was an effective treatment for patients with metastatic melanoma;. This can be achieved by taking T cells that are found with the tumor of the patient, which are trained to attack the cancerous cells. These T cells are referred to as tumor-infiltrating lymphocytes (TIL) are then encouraged to multiply in vitro using high concentrations of IL-2, anti-CD3 and allo-reactive feeder cells. These T cells are then transferred back into the patient along with exogenous administration of IL-2 to further boost their anti-cancer activity.

Thus far, a 51% objective response rate has been observed; and in some patients, tumors shrank to undetectable size.

The initial studies of adoptive cell transfer using TIL, however, revealed that persistence of the transferred cells in vivo was too short. Before reinfusion, lymphodepletion of the recipient is required to eliminate regulatory T cells as well as normal endogenous lymphocytes that compete with the transferred cells for homeostatic cytokines. Lymphodepletion was made by total body irradiation prior to transfer of the expanded TIL. The trend for increasing survival as a function of increasing lymphodepletion was highly significant (P=0.007). Transferred cells expanded in vivo and persisted in the peripheral blood in many patients, sometimes achieving levels of 75% of all CD8⁺ T cells at 6â€"12 months after infusion. Clinical trials based on adoptive cell transfer of TILs for patients with metastatic melanoma are currently ongoing at the National Cancer Institute (Bethesda,MD,USA), Moffitt Cancer Center (Tampa,FL,USA), MD Anderson Cancer Center (Houston,TX,USA), Sheba Medical Center (Tel Hashomer,Israel), Herlev University Hospital (Herlev,Denmark) and NKI Antonie van Leeuwenhoek (Amsterdam, Netherlands).

Autologous immune enhancement therapy

The Autologous immune enhancement therapy (AIET) is an autologous immune cell based therapy wherein the patient's own peripheral blood-derived NK cells Cytotoxic T Lymphocytes and other relevant immune cells are expanded in vitro and then reinfused to tackle cancer. There are also studies proving their efficacy against Hepatitis C Viral infection, Chronic fatigue Syndrome and HHV6 infection.

Genetically engineered T cells

Genetically engineered T cells are created by infecting patient's cells with a virus that contain a copy of a T cell receptor (TCR) gene that is specialised to recognise tumour antigens. The virus is not able to reproduce within the cell however integrates into the human genome. This is beneficial as new TCR gene remains stable in the T-cell. A patient's own T cells are exposed to these viruses and then expanded non-specifically or stimulated using the genetically engineered TCR. The cells are then transferred back into the patient and ready to have an immune response against the tumour. Morgan et al. (2006) demonstrated that the adoptive cell transfer of lymphocytes transduced with retrovirus encoding TCRs that recognize a cancer antigen are able to mediate anti-tumour responses in patients with metastatic melanomas. This therapy has been demonstrated to result in objective clinical responses in patients with refractory stage IV cancer. The Surgery Branch of the National Cancer Institute (Bethesda, Maryland) is actively investigating this form of cancer treatment for patients suffering aggressive melanomas. The use of adoptive cell transfer with genetically engineered T cells is a promising new approach to the treatment of a variety of cancers.

In one case study, United States doctors from the Clinical Research Division, led by Dr. Cassian Yee at Fred Hutchinson Cancer Research Center in Seattle had successfully treated a patient with advanced skin cancer by injecting the patient with immune cells cloned from his own immune system. The patient was free from tumours within eight weeks of treatment. Dr. Cassian Yee described the research findings at The Cancer Research Institute International 2008 Symposia Series. Responses, however, were not seen in other patients in this clinical trial. Larger trials are now under way.

Immune recovery

The potential use of immunotherapy is to restore the immune system of patients with immune deficiencies as result of infection or chemotherapy. For example, cytokines have been tested in clinical trials. Interleukin-7 has been in clinical trials for HIV and cancer patients. Interleukin-2 has also been tested in HIV patients.

Vaccination

Anti-microbial immunotherapy, which includes vaccination, involves activating the immune system to respond to an infectious agent.

Suppression immunotherapies

Immune suppression dampens an abnormal immune response in autoimmune diseases or reduces a normal immune response to prevent rejection of transplanted organs or cells.

Immunosuppressive drugs

Immunosuppressive drugs are important tools in the management of organ transplantation and autoimmune disease. Immune responses depend on lymphocyte proliferation, and cytostatic drugs are immunosuppressive. Glucocorticoids are somewhat more specific inhibitors of lymphocyte activation, whereas inhibitors of immunophilins more specifically target T lymphocyte activation. Immunosuppressive antibodies target an increasingly-broad array of steps in the immune response, and there are still other drugs that modulate immune responses.

Immune tolerance

Immune tolerance is the process by which the body naturally does not launch an immune system attack on its own tissues. Immune tolerance therapies seeks to reset the immune system so that the body stops mistakenly attacking its own organs or cells in autoimmune disease or accepts foreign tissue in organ transplantation. A brief treatment should then reduce or eliminate the need for lifelong immunosuppression and the chances of attendant side effects, in the case of transplantation, or preserve the body's own function, at least in part, in cases of type 1 diabetes or other autoimmune disorders.

Allergies

Immunotherapy is also used to treat allergies. While other allergy treatments (such as antihistamines or corticosteroids) treat only the symptoms of allergic disease, immunotherapy is the only available treatment that can modify the natural course of the allergic disease, by reducing sensitivity to allergens.

A one-to-five-year individually tailored regimen of injections may result in long-term benefits. Recent research suggests that patients who complete immunotherapy may continue to see benefits for years to come. Immunotherapy does not work for everyone and is only partly effective in some people, but it offers allergy sufferers the chance to eventually reduce or stop symptomatic/rescue medication.

The therapy is indicated for people who are extremely allergic or who cannot avoid specific allergens. For example, they may not be able to live a normal life and completely avoid pollen, dust mites, mold spores, pet dander, insect venom, and certain other common triggers of allergic reactions. Immunotherapy is generally not indicated for food or medicinal allergies. Immunotherapy is typically individually tailored and administered by an allergist (allergologist) or through specialized physician offices. Injection schedules are available in some healthcare systems and can be prescribed by family physicians. This therapy is particularly useful for people with allergic rhinitis or asthma.

The therapy is particularly likely to be successful if it begins early in life or soon after the allergy develops for the first time. Immunotherapy involves a series of injections (shots) given regularly for several years by a specialist in a hospital clinic. In the past, this was called a serum, but this is an incorrect name. Most allergists now call this mixture an allergy extract. The first shots contain very tiny amounts of the allergen or antigen to which one is allergic. With progressively increasing dosages over time, one's body adjusts to the allergen and becomes less sensitive to it, in a process known as desensitization. A recently approved sublingual tablet (Grazax), containing a grass pollen extract, is similarly effective with few side effects, and can be self-administered at home, including by those patients who also suffer from allergic asthma, a condition which precludes the use of injection-based desensitization. To read more about this topic, see: allergy and Allergen immunotherapy.

Other approaches

Helminthic therapies

Recent research into the clinical effectiveness of Whipworm ova (Trichuris suis) and Hookworm (Necator americanus) for the treatment of certain immunological diseases and allergies means that these organisms must be classified as immuno-therapeutic agents. Helminthic therapy is being investigated as a potentially highly effective treatment for the symptoms and or disease process in disorders such as relapsing remitting multiple sclerosis Crohn’s, allergies and asthma. The precise mechanism of how the helminths modulate the immune response, ensuring their survival in the host and incidentally effectively modulating autoimmune disease processes, is currently unknown. However, several broad mechanisms have been postulated, such as a re-polarisation of the Th1 / Th2 response, and modulation of dendritic cell function The helminths down regulate the pro-inflammatory Th1 cytokines, Interleukin-12 (IL-12), Interferon-Gamma (IFN-γ) and Tumour Necrosis Factor-Alpha (TNF-ά), while promoting the production of regulatory Th2 cytokines such as IL-10, IL-4, IL-5 and IL-13.

That helminths modulate host immune response is proven, as the core assertion of the hygiene hypothesis appears to have been, with the recent publication of a study demonstrating that co-evolution with helminths has shaped at least some of the genes associated with Interleukin expression and immunological disorders, like Crohn's, ulcerative colitis and Celiac Disease. Much of the research that has been published now indicates a key role, for what have been traditionally regarded as disease causing organisms, so that their relationship to humans as hosts should not be classified as parasitic, rather as mutualistic, symbionts.