Monoclonal antibodies in the treatment of cancer

Potential uses of monoclonal antibodies in anti-cancer treatment include passive serotherapy, radioisotope conjugates, toxin-linked conjugates, and chemotherapy-monoclonal antibody conjugates. The bases for these applications have been founded in research with heterologous antisera, and in some cases with monoclonal antibodies in animal tumor models. Human trials with passive serotherapy have already begun in both hematopoietic and solid tumor malignancies. Promising results have been reported in cutaneous T cell lymphoma with anti-T cell monoclonal antibody, and in nodular lymphoma with anti-idiotype monoclonal antibody. Radioisotope conjugate work appears promising for imaging in both animals and humans, and this work will lay the foundation for possible therapeutic application of radio-immunotherapy. Toxin-linked conjugates are promising in vitro and may have application in autologous bone marrow transplantation. Research with chemotherapy conjugates is also underway. Preliminary results suggest that murine monoclonal antibodies will be well tolerated clinically except in the setting of circulating cells which bear the target antigen, where rapid infusions may be associated with intolerable side effects. In certain diseases, production of endogenous anti-mouse antibodies may also limit application. Advances in the technology for human-human hybridoma production may help solve some of these problems.

Characteristics of mastadenovirus h 8, the causative agent of epidemic keratoconjunctivitis

Adenovirus 8 (Ad 8, strain 1127) has the general structural features of an adenovirus; it produces the genus-specific hexon antigen. The fiber length of 12 nm corresponds to that of other subgenus D adenoviruses. In hemagglutination-inhibition, Ad 8 is related to Ad9 and Ad 15/H9. The slow multiplication, compared to most other subgenus D viruses, was shown not to be caused by an extended growth cycle, but appears to be due to an inefficient virus release into the medium. After restriction analysis with the enzymes Sma I and Bgl II, the typical fragment patterns of species from subgenus D were obtained, while very different patterns emerged from the analysis with Hind III, Bam HI, and Bst E II endonucleases. Several strains of Ad 8 produced more penton-associated toxin than Ad 15/H9 used as reference virus from subgenus D, which could explain the "clumping CPE" caused by Ad 8. Ad 8 toxin was neutralized by antisera from many adenovirus species. The poor virus yield of Ad 8 was not improved by removing soluble viral or cellular substances; all other attempts to improve virus yield by varying the conditions of cell culture also failed.

Immunization of rabbits to produce high serum titres of neutralizing antibodies and immunity to the paralyzing toxin of Ixodes holocyclus

Rabbits have been immunized against the effects of the paralyzing toxin of the Australian paralysis tick Ixodes holocyclus by injecting them with preparations extracted from tick salivary glands. Immunized rabbits were able to withstand doses of toxin known to kill unimmunized rabbits. Neutralizing antibodies were detectable in serum after 2-4 doses of the crude extract or of the relatively pure antigenic fraction. When injections were continued at intervals of from 2-7 weeks, hyperimmunity was retained for at least 68 weeks. Hyperimmune serum, reaching a very high titre of neutralizing antibodies, was obtained after 3-6 injections. Titres tended to decline when boosting ceased, but after a "rest period' high titres were restored by further boosting with normally lethal doses of toxin. No symptoms of tick paralysis developed despite low titres prior to boosting. Thus, once hyperimmunity had been established, high titres of circulating antibodies were not immediately essential for immunity to tick paralysis. An IgG fraction was obtained from rabbit serum using a Protein A-Sepharose method; 33.4 micrograms of IgG protein fully neutralized, and 19.5 micrograms IgG half neutralized, 1 micrograms of crude toxin protein. This procedure with rabbits may permit the production of a purified tick-paralysis antitoxin more suitable for human use than the existing antitoxin based on canine hyperimmune serum.

Burn toxin and its competitin

A "toxic factor' has been isolated and purified from scalded normal human skin; it is lethal to mice and toxic to HeLa and HEP2 cell lines in tissue culture. The toxic factor in both crude and purified form is antigenic in rabbits, producing an antisera that neutralizes the in vivo and in vitro effects of "burn toxin', similar to that of the convalescent sera of burned human subjects. The sonicate of the toxic glycoprotein named competitin is relatively non-lethal and protects against the lethal effect of the toxic factor. The action of the purified burn toxic factor and its competitin is at the ATP site of actomyosin preparations. The data presented suggests that the purified burn toxic factor and its competitin compete for the same receptor sites in the myocardium. A thesis is presented that states that it is vital to neutralize the toxic effects of burn breakdown tissue products in severely burned subjects before the vicious cycle of depressed immunological function and malnutrition ensues. Competitin produced in vitro from toxic factor(s) generated scalded normal human skin is offered as a means of neutralizing the toxic factors(s).

Dialysis for psoriasis - preliminary remarks concerning mode of action

In one patient treated by peritoneal dialysis for psoriasis the skin lesions cleared completely. In two persons hemodialysis gave unsatisfactory results. In treated and another three untreated patients cellular immunity was evidently suppressed. This phenomenon is similar to the immunologic changes in persons with uremia. Solutes in middle molecular weight range (SMMWR) suppress cellular immunity. These compounds were therefore investigated in psoriatics. The level of SMMWR was lower before than after each dialysis, although their concentration increased slightly during the dialytic treatment. This suggests that solutes in middle molecular weight are fixed in the epidermis and/or in the walls of the skin capillaries and that dialysis liberates them from these places. Peritoneal dialysis seems to be a more effective method of treating psoriasis than hemodialysis. Solutes in middle molecular weight range might play an important role in the pathomechanisms of this multifactorial disease.

The present status of research in burn toxins

Modern intensive care combined with current improvements in the specific, systemic and local therapy of burns has delayed the mortal effects of severe burns. Nor has there been any significant improvement in this mortality during the last decade. The occurrence of uncontrollable infection and sepsis due to gram-negative bacteria or fungi as the basic cause of death was not a satisfactory explanation. So, progress should only be expected from a new concept in burn treatment. This new concept should be to view the burn disease as being caused by toxic factors induced by thermal injury to the skin. Electron-microscope studies in mice and rats have revealed similar mitochondrial alterations in hepatocytes after either a sublethal controlled burn injury or an intraperitoneal application of an equivalent dose, of a cutaneous burn toxin. The intraperitoneal injection of different amounts of the burn toxin indicated, that the extent of the mitochondrial changes correlated directly with the dose of toxin. Investigations of liver metabolism suggested an inhibition of the oxygenation chain. The incubation of isolated liver cells together with the burn toxin demonstrated by scanning electron microscopy a direct cytotoxic effect of the burn toxin. In animal tests the pathogenic effect of the burn toxin could be prevented by treatment with an antitoxic IgG generated in sheep. The fatal sepsis of severely burned patients is the consequence of a decreased host defence against infections, which is caused by a primary and general toxic alteration of the whole organism. One important aspect of treatment should therefore be the elimination of burn toxins. To achieve this management should include primary excision of the burns, local application of nonabsorbable protein-complex-binding substances and specific passive immunotherapy with an antitoxic IgG.

Evidence for the role of toxin A in the pathogenesis of infection with Pseudomonas aeruginosa in humans

Levels of antibody to toxin A of Pseudomonas aeruginosa were determined by a solid-phase radioimmunoassay. Mean (+/- SEM) peak levels of IgG in 24 normal soldiers were 2.6 +/- 0.5 microgram/ml, white mean peak levels in 12 patients colonized with and 13 patients infected in sites other than the blood with toxin A-producing strains were 16.7 +/- 7.0 and 17.1 +/- 4.4 microgram/ml, respectively. Levels of IgG were determined in 52 patients with pseudomonas bacteremia, and those surviving and those dying of bacteremia due to toxin A-producing strains had mean peak levels of 25.8 +/- 5.5 and 4.6 +/- 2.0 microgram/ml, respectively. The antitoxin response in sequential bacteremic sera began shortly after onset of bacteremia and decreased gradually, but antitoxin could be recalled promptly upon reinfection with Pseudomonas. Death from pseudomonas bacteremia was significantly associated with infection by a toxin A-producing strain, presence of underlying disease, hypotension, and antitoxin level of < 2 microgram/ml.

Neutralizing activity against Clostridium difficile toxin in the supernatants of cultured colostral cells

Human colostral specimens were obtained from 60 Japanese postpartum women within the first 3 days after delivery. Neutralizing activity against Clostridium difficile toxin was evaluated with Y1 adrenal cells in miniculture. When Y1 adrenal cells were exposed briefly to the toxin, they showed a rounding response in culture, resembling that effected by Escherichia coli enterotoxin; however, preincubation of the toxin with aqueous phase of colostrum significantly reduced its cytopathic effect on Y1 adrenal cells. Of 60 colostral specimens, 17 samples had neutralizing activity against the toxin. Cell-free supernatants of colostral cells cultured for 7 days without mitogens contained significant amounts of both immunoglobulin A (IgA) and IgM, but very small amounts of IgG. Neutralizing activity of cell-free supernatants of cultured colostral cells was evaluated as described above. Neutralizing activity against the toxin was identified in five samples of culture supernatants out of 60 colostral cell specimens. In all five cases, the aqueous phase of colostrum also had a neutralizing effect against C. difficile toxin. Neutralizing activity against the toxin found in five supernatants of cultured colostral cells was completely abolished only by anti-human IgA antibody as assessed by immune precipitation.

Identification of staphylococcal Panton-Valentine leukocidin as a potent dermonecrotic toxin

The Panton-Valentine leukocidin of Staphylococcus aureus was shown to exhibit a potent dermonecrotic effect when injected intradermally into rabbits. This effect could be abrogated by immunizing animals with the F component or both components, but immunization with the S component appeared to exacerbate certain of the intradermal responses.

Biochemical and pharmacological properties of a cardiotoxic factor isolated from the blood serum of burned patients

Blood serum of severely burned patients contains several substances which are not present in normal sera. One of these substances, a small protein of an approximate molecular weight of 12 to 14,000 daltons displayed a toxic action on the circulatory system. This cardiotoxic factor was obtained in a purified form by alcohol precipitation followed by gel filtration and carboxymethyl cellulose chromatography. The purified preparation seems to be a low molecular weight protein of about 8000 daltons. The biological effects of this substance consist essentially of alterations of the ECG pattern, indicating decreased cardiac output and ischaemia of the cardial muscle. The blood pressure decreases and respiratory function is also altered. The presence of such a toxic factor in sufficient concentration in the blood serum may explain the cardiovascular complications observed in some burned patients.

Neutralization of Clostridium difficile toxin by Clostridium sordellii antitoxins

Neutralization of Clostridium difficile toxin by Clostridium sordellii antitoxin was studied by cytotoxicity assay in tissue culture. The sources of toxin were stools from two patients with pseudomembranous colitis and a culture filtrate of C. difficile isolated from one of the patients. C. sordellii antitoxin was available either in monovalent form or as gas gangrene polyvalent antitoxin. The potency of antitoxins against C. difficile determined by cytotoxicity assay did not correlate with the established values reported for mouse protection tests against C. sordellii toxin. An equivalent zone of optimal neutralization was demonstrated for stool toxin, and a slightly different one for culture toxin. The rate of neutralization appeared to be instantaneous, either at 24 or at 37 degrees C. The efficacy of antitoxin in preventing cytotoxicity in cultured cells preexposed to toxin decreased rapidly with preexposure time. The union between toxin and antitoxin could be readily dissociated by simple dilution or by ammonium sulfate precipitation followed by dissociated by simple dilution or by ammonium sulfate precipitation followed by dilution. Continued incubation of toxin-antitoxin mixture did not increase the firmness of the union; on the contrary, more dissociation occurred. The unusual looseness of the toxin-antitoxin union is probably relatd to lack of serological specificity or affinity. Based on these observations, a practical diagnostic method for antibiotic-induced colitis is outlined.