Immunotherapy, passive

In passive immunotherapy immune globulin (Ig) is an effective replacement in most forms of antibody deficiency (14). In the past, plasma was used instead of immune globulin, but plasma is rarely indicated in the 1990s because of the risk of disease, particularly AIDS, transmission. Because plasma contains many factors in addition to immunoglobulins (Igs), plasma is, however, of particular value in patients with protein-losing enteropathy, complement deficiencies, and refractory diarrhea. 

The most widely studied therapeutic proteins produced in plants include monoclonal antibodies for passive immunotherapy and antigens for use as oral vaccines [40]. Antibodies against dental caries, rheumatoid arthritis, cholera, E. coli diarrhea, malaria, certain cancers, Norwalk virus, HIV, rhinovirus, influenza, hepatitis B virus and herpes simplex virus have been produced in transgenic plants. However, the anti-Streptococcus mutans secretory antibody for the prevention of dental caries is the only plant-derived antibody currently in Phase II clinical trials [40]. Until recently, most antibodies were expressed in tobacco, potato, alfalfa, soybean, rice and wheat [9], It has been estimated that for every 170 tons of harvested tobacco, 100 tons represents harvested leaves. A single hectare could thus yield 50 kg of secretory IgA [3, 41]. Furthermore, it has been estimated that the cost of antibody production in plants is half that in transgenic animals and 20 times lower than in mammalian cell cul-... 

Treatment primarily consists of supportive care. Ventilate patient if they have difficulty breathing and administer oxygen. Be prepared to treat for shock. Monitor and support cardiac and respiratory functions as necessary. If the identity of the toxin is known, administer antidote if available. Unlike chemical agents, toxins can cause an immune response. Vaccines are available for some toxins but generally require more than 4 weeks for the body to produce antibodies. Passive immunotherapy is effective for some neurotoxins but must be instituted shortly after exposure. The utility of antibody therapy drops sharply at or shortly after the onset of the first signs of disease. 

Passive immunotherapy or immunoprophylaxis should always be administered as soon as possible after exposure. Prior to the administration of animal sera, patients should be questioned and tested for hypersensitivity. 

Goldman DL, Casadevall A, Zuckier LS. Pharmacokinetics and biodistribution of a monoclonal antibody to Cryptococcus neoformans capsular polysaccharide antigen in a rat model of cryptococcal meningitis implications for passive immunotherapy. J Med Vet Mycol 1997 35(4) 271-8. 

List two advantages of passive immunotherapy over active immunotherapy ... 

Monoclonal antibodies may be used as passive immunotherapy to treat malignancies. They react with specific antigens present on the surface of tumor cells and result in cell destruction. Rituximab was the first MoAb approved in the United States for the treatment of cancer. It is a chimeric MoAb directed against cluster differentiation 20 (CD20) markers, which are expressed on over 90% of B-cell NHL tumors. Rituximab is thought to result in B-cell depletion by a number of mechanisms, including complement-mediated and antibody-dependent cell lysis and induction of apoptosis. 

A. Passive immunotherapy A. Cell-based screening REFERENCES... 

Passive immunotherapy originated over a century ago when it was discovered that sera from one patient affected with diphtheria toxin could cure the diphtheria of an another individual. Antibody treatments have long been viewed as promising potential therapies for a wide variety of diseases... 

Investigational Therapies. As discussed above, the idiotype present on the patient s tumor cells serves as a potential target for immunotherapy. This idiotype can be used to manufacture a patient-specific vaccine. Vaccines would potentially produce both humoral and cellular immune responses, and would also be longer acting than passive immunotherapy. Several vaccines are being evaluated in clinical trials. ... 

C. Prophylaxis. Currently there is no human vaccine for immunization against SEB intoxication. Experimental vaccines are under development. Passive immunotherapy can reduce mortality if given within 4-8 hours post SEB inhalation. 

Passive immunotherapy involves administering preformed antibodies from external sources to the recipient patient, as opposed to therapies like vaccines, which encourage the body to make its own antibodies. Numerous rAbs are specihc to various pathogens (see Table 6.6-2). Pathogens that affect humans, plants, and commercial/ domestic animals are all being looked at for their susceptibility to antibodies. For... 

Numerous variables can lead to a negative result from passive immunotherapy. Too little antibody can result in a lack of protective efficiency. Too much antibody can produce a prozone-like effect, whereby more antibody provides less protection than less antibody. The antibodies used in therapy can also be affected by affin-ity/avidity, specificity, isotype, idiotype, preparation, and route of administration. The genetic background and immune competency of the host can also affect treatment as can route of pathogen infection, genetic background, and inoculum size of the pathogen [114]. A dramatic example of the limitations of passive antibody transfer experiments is provided by the observation that transfer of either too little or too much antibody can result in no protection [114]. 

Monoclonal antibody technology has really rather limited application in agriculture. In general, the uses found for Mabs have been confined to employment in diagnostic tests for various diseases and to a more limited extent in passive immunotherapy. 

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