Toxicity of a GM3 cancer vaccine in Macaca fascicularis monkey: a 12-month study.

GM3 is a ganglioside that has been biochemically identified as dominating the cell surface of several human tumours, but is also found on human normal cells at much lower density. Since GM3 is widely distributed in essentially all types of animal cells, there is a conflict with the concepts of tumour-associated antigen, immunogen, and toxicity. We have designed a GM3-based cancer vaccine for the treatment of human breast and melanoma tumours. Prior to the Phase I clinical trial, we carried out a 12-month dose repeated toxicity study in five male Macaca fascicularis monkeys. Four male monkeys were treated with placebo in a similar way. During the study, no differences were observed between control and treated monkeys related to daily clinical observations (other than local damage) including rectal temperature, blood pressure, respiratory and cardiac rates, weight gain, biochemical and hematological parameters (with the exception of transitory pathological changes), and anti-DNA and anti-nuclear antibodies, although treated monkeys consistently developed both IgM- and IgG-specific anti-GM3 antibodies. Sixty per cent of treated monkeys developed moderate local reactions at the injection site, which disappeared without sequels. We concluded that this GM3 cancer vaccine overcame in monkeys the natural tolerance to GM3 ganglioside evidenced by a strong immune response, while the local reactions elicited-were transitory without apparent important systemic toxicity effects.

Role of chemical mediators in bronchoconstriction induced by kerosene.

Kerosene is a by product of petroleum used in some countries for cleaning, lighting and cooking purposes. Rodriguez de la Vega et al (1981) have presented evidences of the relation between bronchial asthma and the manipulation of kerosene. Since the experiments performed by our group showed that the acute inhalation of the aerosol of kerosene induces bronchoconstriction in rabbits (Casacó et al 1982), we investigated its effect on guinea pig respiratory physiology. In order to elucidate the implication of histamine and arachidonic acid metabolites in kerosene induced bronchoconstriction, we investigated the influence of the administration to guinea pig of a single dose of the histamine H1 antagonist mepyramine (0.1 mg/kg i.v.) 10 minutes before the aerosol and also the effect of the steroidal antinflammatory drug triamcinolone in rabbits (5 mg/kg i.m.) daily during 4 days before the inhalation of kerosene. The histamine concentrations in guinea pig blood before and after the aerosol were also compared. The inhalation of kerosene during 5 min. (20.4 mg/L) by guinea pigs resulted in an increase of airway resistance without increase of blood histamine concentration. On the other hand, the bronchoconstrictive effect of kerosene in guinea pigs and rabbits was not modified by the previous treatment with mepyramine or triamcinolone respectively. The results suggest that the acute bronchoconstriction induced by kerosene is mediated neither by stimulation of histamine H1 receptors nor by the release of chemical mediators.

Biochemical mechanisms in the effects of kerosene on airways of experimental animals.

The biochemical mechanisms involved in the bronchoconstriction and airway hyperresponsiveness induced by the acute inhalation of aerosol of kerosene in experimental animals and the inflammatory changes induced by subchronic inhalation of the aerosol or smoke of kerosene were investigated. The results obtained indicate that the inhibition of the acetylcholinesterase activity in airways and the decrease in the efficiency of the calcium uptake by the sarcoplasmic reticulum are some of the mechanisms involved in the airway hyperreactivity induced by kerosene. The levels of cyclic nucleotides in lungs and trachea and the histamine concentration in blood did not change in the animals exposed to the aerosol of kerosene. The subchronic exposure to vapors of kerosene or its combustion fumes, induced an increase in the activity of lysosomal enzymes in lungs which can be an explanation of the inflammatory response induced in lungs by this agent.

Venous return as stimulus for respiration in rabbit.

The "exercise hyperpnoea" problem was studied in 44 anaesthetized rabbits by increasing the cardiac output by: a) tilting by 12 degrees the hindlimbs up; b) injecting into the right heart 15 ml of dextran; c) normocapnic or d) hypocapnic blood. In all cases there was an increase in minute ventilation, VE, independently of the presence or absence of an increase in CO2 flux to the lungs. We decreased the cardiac output by tilting up the head by 10 degrees; this elicited a decrease in VE accompanied by an increase in the fractional end-tidal CO2. For elucidating the role played by carotid body chemoreceptors in eleven rabbits the legs were tilted up before and while the animals breathed pure oxygen. The results were very similar. When the hindlimbs were tilted up after cervical bilateral vagotomy the VE response diminished about fifty per cent. We conclude that: a) hyperpnoea and hypopnoea elicited by a change in cardiac output are due to stimulation or depression of mechanoreceptors localized in the pulmonary circulation, b) carotid body chemoreceptors are not required for these responses, c) fifty per cent of the VE response depends on the integrity of the vagus nerves, d) it is probable that the increase in venous return plays an important role in the hyperpnoea at the onset of muscular exercise.

Reversal of oxygen difference between arterial blood and cerebrospinal fluid in the rabbit.

The experiments were carried out in rabbits under general anaesthesia with muscle relaxation and artificial ventilation with atmospheric air. Samples of arterial blood and cerebrospinal fluid were obtained. Of particular interest was reversal of the oxygen gradient, that is PaO2 less than PCSFO2 at arterial blood hypoxia below 65 Torr. The animals were given then acetazolamide intravenously which was followed by acidification and increased partial oxygen pressure in the arterial blood. At the same time the oxygen gradient between the arterial blood and cerebrospinal fluid (CSF) practically disappeared. Administration of a hypoxic breathing mixture reversed again the oxygen gradient. It is worth stressing that the pH of the arterial blood showed no statistically significant fall. In view of this it is postulated that Bohr's effect is not responsible for the reversal of the oxygen gradient although it has been suggested by Jankowska and Grieb [13]. We put forward the hypothesis that the rate of oxygen passage on the arterial side of the blood-brain barrier is not identical in both directions, and its passage from the blood into the CSF decreases with increasing arterial hypoxia. This mechanism of "oxygen trap" may be the cause of reversal of the oxygen gradient between the arterial blood and CSF in hypoxia.