Effects of intravenous and subcutaneous heartworm homogenate from doxycycline-treated and untreated donor dogs on bronchial reactivity and lung in cats

A controlled, blind research study was conducted to define the innate response of lungs in specific pathogen free (SPF) cats to intravenous (n=10) or subcutaneous (n=4) administration of homogenate of adult Dirofilaria immitis from donor dogs compared with lung response in control cats (n=6). There was no difference in cats that received heartworm homogenate IV for 18 days from donor dogs treated with doxycycline for 1 month compared with cats given heartworm homogenate from untreated donor dogs. Cats did not develop clinical signs, and no radiographic changes were noted. Cats given SC heartworm homogenate at lower concentration than IV groups did not develop histologic changes. Cats that received IV heartworm homogenate for 18 days developed mild interstitial and peribronchial myofibrocyte proliferation and smooth muscle proliferation of the pulmonary arteries. Bronchial ring contractility in vitro was blunted in the IV homogenate cats to the agonists acetylcholine and 5-hydroxytryptamine. Cats in the SC group had increased sensitivity to histamine at high concentrations but normal contractility and relaxation responses to other agonists. No increase in mast cells was noted in lung tissues of cats given homogenate. In the absence of bronchial wall remodeling, cats given IV homogenate had blunted responses to bronchial constriction, but normal relaxation to nitroprusside and substance P and increased sensitivity to histamine. In the absence adult heartworms, the homogenate of adult heartworms in the circulation of SPF cats induced a direct effect on lung parenchyma and altered bronchial ring reactivity.

THE NEUTRALIZATION OF ANTIPNEUMOCOCCUS IMMUNE BODIES BY INFECTED EXUDATES AND SERA

1. In empyema fluids resulting from infection with pneumococci there are present large amounts of soluble substances which have the property of neutralizing pneumococcus antibodies. 2. Similar substances are found in the blood of infected rabbits. 3. When immune serum is injected into infected rabbits the immune substances disappear very quickly, and therefore are prevented from activity in overcoming the infection. 4. When immune serum is administered to patients severely infected with pneumococci, the immune bodies may also disappear very rapidly, and this disappearance is probably associated with the presence of such soluble substances in the blood. 5. The serum only becomes effective when these substances are neutralized. 6. The study of agglutination curves is of value in showing why in certain instances favorable results have not followed the use of immune serum. 7. It is important that in severely injected patients the serum be administered early in the disease and that the initial dosage be large.

TOXIC SUBSTANCES PRODUCED BY PNEUMOCOCCUS

1. The filtered blood serum of rabbits infected with pneumococci is not toxic. 2. Extracts of pneumococci prepared by keeping emulsions of the bacteria in salt solution at 37 degrees C. for varying periods of time may be toxic, and when injected intravenously into guinea pigs, may produce a train of symptoms followed by acute death resembling that seen in acute anaphylaxis. Such extracts, however, are not uniformly toxic and it has been impossible to discover the exact conditions under which such extracts become toxic. 3. When the centrifugalized peritoneal washings of guinea pigs infected with pneumococci are injected into the circulation of normal guinea pigs, these animals very frequently exhibit symptoms like those seen in acute anaphylaxis, and a considerable proportion of the animals die acutely. 4. When pneumococci are dissolved in dilute solutions of bile salts and the solution resulting is injected intravenously into rabbits and guinea pigs, these animals show with great constancy the same symptoms that are seen in acute anaphylaxis. The solution of pneumococci in bile may occur in ten minutes at 37 degrees C. or in half an hour on ice. This is considered evidence that the toxicity of the solution does not result from digestion of the bacterial protein, but is due to substances preformed in the bacterial cells and set free on their solution. The toxicity of the solution is diminished or destroyed by heating to 55 degrees C. or over.

A FILTERABLE VIRUS PRESENT IN THE SUBMAXILLARY GLANDS OF GUINEA PIGS

In the lesions of herpes simplex and similar conditions due to filterable viruses, cells are present which show characteristic alterations, particularly in the nucleus. The nucleus of these cells contains a mass which stains with acid dyes. Surrounding this mass is a clear space or halo, within which there are large granules staining with basic stains. These cells are little if at all enlarged. In a few human cases, especially in infants, enlarged cells have been found which contain nuclei showing changes similar to those seen in the abnormal cells of herpes simplex. In the ducts of the submaxillary glands of guinea pigs, Jackson observed structures which she considered to be protozoan parasites. Our own studies indicate, however, that these structures are greatly swollen epithelial cells with nuclei having the same characters as the nuclei of the atypical cells in the lesions of herpes simplex. These cells are usually surrounded by a mononuclear cellular reaction. They were found in 84 per cent of the full grown guinea pigs examined but they were present in only three of forty-three young guinea pigs less than 1 month old. The resemblance of these cells, except as regards size, to the atypical cells present in lesions due to filterable viruses suggested that they also may be the result of an infection with a similar agent. That they are usually not present in guinea pigs less than 1 month old indicates that natural infection usually occurs after this period. Experiments were therefore undertaken to determine whether or not an infective agent is concerned in this condition and if so to learn something of its nature. When an emulsion of the submaxillary glands of full grown guinea pigs is injected into the brains of young guinea pigs the animals have fever and exhibit symptoms of cerebral irritation. They usually die in 5 to 7 days and in sections of the brain a diffuse subacute meningitis is found. In the exudate there are large numbers of cells having all the characteristics of the abnormal cells of herpes simplex. Similar cells are present in the lesions resulting from the injection of the same emulsion into the testicle, lung, tongue, and submaxillary glands of young guinea pigs. In none of these lesions, however, are the cells greatly enlarged as they are in the lesions in old guinea pigs. These results support the view that the lesion in the submaxillary gland of old guinea pigs is due to an infective agent. Attempts were therefore made to transmit this agent through a series of young guinea pigs. When the injections were all made into the same organ all the experiments but one gave negative results, but when the site of injection was changed at each transfer it was possible in a number of instances to reproduce the lesions through two animals in series and in one experiment through three animals in series. By modifying the technique, efforts were made to transmit the infection indefinitely but these attempts were unsuccessful. No explanation can be offered for this failure. Studies made to determine some of the properties of the infective agent have shown that it is destroyed by heating at 54° for 1 hour, and that it is not injured by preservation in 50 per cent glycerol for as long as 11 days. After the material had remained in 50 per cent glycerol for 28 days, however, it was found to be no longer infective. The infective agent was not held back by a Berkefeld N filter which was impermeable to bacteria. It seems probable therefore that the infective agent belongs in the group of filterable viruses, though further work will be necessary to learn more of its exact nature. These observations present additional evidence that the presence of cells with nuclear inclusions in any lesion indicates that the injury is probably due to an infective agent belonging in the group of filterable viruses.

PNEUMOCOCCUS HEMOTOXIN

Solutions of the bodies of pneumococci, obtained by dissolving them in dilute solutions of sodium cholate, by permitting them to undergo autolysis, or by first freezing, drying, and then grinding in salt solution, are actively hemolytic for rabbit, sheep, guinea pig, and human red blood corpuscles. The substance on which this hemolytic property depends is very labile, much of its activity is lost on passing through a filter, and it is destroyed by the action of trypsin. In its properties it corresponds to the substance contained in such solutions which causes the death of guinea pigs on intravenous injection. Its activity is prevented by the presence of minute amounts of cholesterin. Following the injection of this solution into rabbits and sheep, the sera of these animals acquire increased power of inhibiting its hemolytic action. It therefore possesses antigenic properties. It may therefore be concluded that the bodies of pneumococci contain a toxin that is hemolytic for red blood corpuscles. This substance is not simply a product of autolysis but undoubtedly exists preformed in the bacterial cell. However, it is not given up to the surrounding fluid as long as the bodies of the bacteria are intact. It may therefore be considered a hemolytic endotoxin.

THE PRODUCTION OF ANTIPNEUMOCOCCIC SERUM

In the production of immune serum for therapeutic purposes strict attention must be paid to the immunological specificity of the bacteria used for immunization. At present the only serum of which the therapeutic value has been proven is that effective against Type I pneumococcus infection. This serum should have agglutinating power for Type I pneumococcus and should have the power of protecting mice against large amounts of virulent culture. Experiments have shown that for producing the primary immunity most rapidly several series of small doses of dead cultures should be given, the injections being made daily for 6 to 7 days, followed by a week in which no injections are made. To produce the highest type of immunity probably living organisms are required. These should be given in moderate doses daily for 3 days, with an interval of a week between each series of injections. By following accurately the methods described, horses may be made to produce rapidly a high grade of specific serum. The observations so far made indicate the importance of employing small doses of culture frequently repeated in this form of immunization.

THE PRODUCTION OF METHEMOGLOBIN BY PNEUMOCOCCI

1. Pneumococci in contact with hemoglobin transform this into methemoglobin. This reaction occurs only when the pneumococci are living; it is not induced by the culture fluid or by extracts of the bacteria. 2. The reaction does not occur when hemoglobin is added to an emulsion of washed pneumococci in salt solution. However, if minute traces of dextrose be added to such a mixture, the reaction quickly occurs. The dextrose may be replaced by any one of a number of other sugars, and also by certain other organic substances, if the latter are added in large amounts. Certain other organic substances are not able to replace dextrose, but it has been impossible to determine any special molecular configuration on which this property depends. 3. The formation of methemoglobin by pneumococci probably resembles the formation of methemoglobin by certain chemical substances, such as aminophenol. 4. From the work of others it is probable that the formation of methemoglobin is always a reaction of oxidation. In the formation of methemoglobin by reducing agents, the latter are first oxidized, this occurring better in the presence of oxyhemoglobin. In certain instances an alternate oxidative and reduction of the transforming agent occurs, so that the reaction is continuous. The effect which the presence or absence of free oxygen has on the reaction with pneumococci suggests that this follows similar lines. 5. The reaction does not occur in the absence of oxygen. If the free oxygen be first removed, and then replaced, the reaction occurs more rapidly than if the oxygen had not been removed. The presence of free oxygen in excess slightly delays the reaction, possibly because of the inhibition of the reduction process which forms the first part of the reaction. 6. The explanation of this phenomenon of methemoglobin production is not only of importance so far as this special reaction is concerned, but also because it suggests an explanation for the manner in which pathological effects are produced by those bacteria which apparently produce no soluble toxin.

THE PROBLEM OF THE ETIOLOGY OF HERPES ZOSTER

Attempts were made to produce lesions in. animals by the injection of material obtained from the vesicles and involved skin of nine cases of herpes zoster. All the cases, with the exception of one (Case II), were characteristic cases of idiopathic herpes zoster and the question of their being cases of so called zosteriform herpes or symptomatic herpes zoster can hardly be raised. As regards Case II, if this case occurred alone, there might be some doubt as to its nature on account of the mildness of the symptoms and the small area of skin involvement. Taken in connection with Cases III and IV, however, which occurred in the same ward and in patients who were quite closely in contact with Patient II, it seems fairly reasonable to assume that they were all of the same character. Cases of herpes zoster have been extremely rare in this hospital and the occurrence of three cases in the same ward within a very short period of time suggests very strongly a transference of infection from one case to the other. That Case II was not one of herpes simplex also seems fairly certain from the negative results obtained by inoculation of rabbits' eyes with vesicle material. In making the animal experiments we employed various methods which were suggested largely by the technique used by previous observers, especially by those who have reported results which were considered positive. In making inoculations into the corneas the technique recommended by Lipschütz was employed as far as possible. Young rabbits were used and the material was obtained from fresh vesicles early in the disease and inoculated with as little delay as possible. The material injected into rabbits' eyes was obtained from seven cases and twenty-four rabbits were used. In judging of the results obtained in this kind of experimentation great caution must be observed. Our experience convinces us that slight opacities occurring along the lines of scarification and mild conjunctivitis cannot be held to indicate the effect of a specific virus. As regards the interpretation of the microscopic changes found, we were quite familiar with the appearance of intranuclear inclusion bodies as seen in the lesions of experimental herpes simplex and the filterable virus (Virus III) indigenous to rabbits described by Rivers and Tillett (5). We also had no difficulty in imding intranuclear inclusions in the sections of skin removed from patients. It is not likely, therefore, that these structures were overlooked in our study of the sections. Briefly stated, although the material studied was satisfactory and in spite of the fact that a considerable number of animals were used for each case, we have been unable to confirm the observations of Lipschütz regarding the experimental production of specific lesions in the corneas of rabbits. We realize that this is only negative evidence and therefore not of conclusive importance in view of Lipschütz's observations. It indicates, however, that the production of specific lesions in rabbits' eyes with material from herpes zoster vesicles is extremely difficult and that successful results may be a matter of chance, depending, possibly, on peculiar susceptibility on the part of the rabbits. In view of the fact, however, that a careful analysis of the positive results reported by other observers shows that the conclusions were based on insufficient evidence, we believe that further work is necessary before the successful inoculation of the rabbits' corneas with herpes zoster virus can be accepted as fully demonstrated. To make the evidence convincing specific lesions should be obtained with a fair degree of regularity and the virus should be successfully transmitted through at least two generations. Apparently the latter was not attempted by Lipschütz. Intracerebral inoculations into three rabbits with material from two cases (Nos. I and IV) were made. Two rabbits were also inoculated intraspinally with material from one case (No. IV). None of these animals showed any reaction. In the case of one of the animals inoculated into the brain (Case I) although this rabbit showed no symptoms, we thought it conceivable that the susceptibility of the species for the virus might be so slight that no obvious lesion had been produced. Nevertheless it was thought that the virus might possibly remain alive at the seat of inoculation and by repeated transfers become adapted to the rabbit. This phenomenon has been observed by Noguchi with vaccine virus, and by Rivers and Tillett with the rabbit virus isolated by these workers. This possibility was tested by us by making serial corneal and brain inoculations. Corneal transfers were carried through fourteen animals in series, and brain transfers through ten. No specific lesions developed in any of the animals. The work of Teague and Goodpasture suggested that the skin might be rendered more susceptible to infection by previous treatment with tar. Material from two cases (Nos. I and VIII) was inoculated into the tarred skin of guinea pigs and rabbits. The material was injected intracutaneously and also rubbed into the scarified skin. No reaction was obtained in any of the animals. Finally, the transmission of herpes zoster to monkeys was attempted. Blanc and Caminopetros, and Bastai and Busacca, as discussed in the review of the literature, inoculated monkeys (Macacus) in various ways, without success. It was thought possible that although monkeys of the genus Macacus might be refractory, monkeys of another genus might prove susceptible. Consequently, besides the inoculation of two Macacus monkeys, attempts were made to infect five vervets. Moreover, in view of the fact that the virus of vaccinia and the rabbit virus of Rivers and Tillett could be successfully cultivated in the testicle, intratesticular inoculations were employed. The testicles were removed at varying periods following inoculation. Numerous sections of these testicles were made and examined, but in no instance were any lesions found which could be interpreted as specific. No cells containing intranuclear inclusion bodies were found. These experiments, therefore, have also led to purely negative results. This report of our work is made at the present time because a considerable amount of literature has been published which gives the impression that herpes zoster has been successfully transmitted to animals. Although the observations of Lipschütz are suggestive, it is important that they be confirmed by further investigations. Until herpes zoster can be regularly transmitted to animals and cross-immunity tests be carried out, the relation of the virus of herpes zoster to that of herpes simplex remains a matter of speculation. In view of the fact that herpes simplex can be easily and regularly transmitted to rabbits, whereas in the hands of a large number of investigators similar experiments with herpes zoster are completely negative, it does not seem likely that the etiological agent concerned in these two diseases can be absolutely identical. The question of the identity or non-identity of herpes zoster and varicella is even more difficult to answer, because at present neither of these infections is readily transmissible to animals. The work of Kundratitz is extremely interesting. His observations, aside from indicating a close immunological relationship between herpes zoster and varicella, are important in that they seem to show the presence of a transmissible virus in the vesicles of herpes zoster. The only question that arises is whether the cases of herpes zoster from which Kundratitz was able to make successful transfers were true cases of idiopathic herpes zoster.