IMMUNOLOGICAL RELATIONSHIPS OF CELL CONSTITUENTS OF PNEUMOCOCCUS : SECOND PAPER

Decoding capsule synthesis in Streptococcus pneumoniae

Streptococcus pneumoniae synthesizes more than one hundred types of capsular polysaccharides (CPS). While the diversity of the enzymes and transporters involved is enormous, it is not limitless. In this review, we summarized the recent progress on elucidating the structure-function relationships of CPS, the mechanisms by which they are synthesized, how their synthesis is regulated, the host immune response against them, and the development of novel pneumococcal vaccines. Based on the genetic and structural information available, we generated provisional models of the CPS repeating units that remain unsolved. In addition, to facilitate cross-species comparisons and assignment of glycosyltransferases, we illustrated the biosynthetic pathways of the known CPS in a standardized format. Studying the intricate steps of pneumococcal CPS assembly promises to provide novel insights for drug and vaccine development as well as improve our understanding of related pathways in other species.

Streptococcus pneumoniae Capsular Polysaccharide

The polysaccharide capsule of Streptococcus pneumoniae is the dominant surface structure of the organism and plays a critical role in virulence, principally by interfering with host opsonophagocytic clearance mechanisms. The capsule is the target of current pneumococcal vaccines, but there are 98 currently recognised polysaccharide serotypes and protection is strictly serotype-specific. Widespread use of these vaccines is driving changes in serotype prevalence in both carriage and disease. This chapter summarises current knowledge on the role of the capsule and its regulation in pathogenesis, the mechanisms of capsule synthesis, the genetic basis for serotype differences, and provides insights into how so many structurally distinct capsular serotypes have evolved. Such knowledge will inform ongoing refinement of pneumococcal vaccination strategies.

Antigenic Variation and Immune Escape in the MTBC

Microbes that infect other organisms encounter host immune responses, and must overcome or evade innate and adaptive immune responses to successfully establish infection. Highly successful microbial pathogens, including M. tuberculosis, are able to evade adaptive immune responses (mediated by antibodies and/or T lymphocytes) and thereby establish long-term chronic infection. One mechanism that diverse pathogens use to evade adaptive immunity is antigenic variation, in which structural variants emerge that alter recognition by established immune responses and allow those pathogens to persist and/or to infect previously-immune hosts. Despite the wide use of antigenic variation by diverse pathogens, this mechanism appears to be infrequent in M. tuberculosis, as indicated by findings that known and predicted human T cell epitopes in this organism are highly conserved, although there are exceptions. These findings have implications for diagnostic tests that are based on measuring host immune responses, and for vaccine design and development.

CUTANEOUS REACTIONS TO THE POLYSACCHARIDES AND PROTEINS OF PNEUMOCOCCUS IN LOBAR PNEUMONIA

I. a. Pneumococcus polysaccharides, when injected intradermally into patients convalescent from pneumonia, are capable of eliciting a response. The polysaccharide inducing a cutaneous reaction was found always to be homologous in type to that of the pneumococcus causing the infection. b. The character of the reaction incited by the protein-free bacterial sugars is of the immediate wheal and erythema type. c. A patient's capacity to react was found to be intimately associated both with recovery from infection and with the presence of type specific antibodies in the circulating blood. II. a. The so-called nucleo-protein of pneumococcus, when injected intradermally, also causes a local cutaneous reaction in patients during convalescence from lobar pneumonia. b. The local lesion resulting from the injection of protein is tuberculin-like in character, and differs from that evoked by the type-specific polysaccharides in gross appearance, time of development, and duration. c. Individuals, acutely ill with and convalescent from pneumococcus pneumonia, possess in their circulating blood, precipitins reactive with pneumococcus protein. In the observations recorded, the concentration of anti-protein antibodies in the blood serum did not seem to influence the patient's capacity to react to intradermal injection of the protein.

THE PRODUCTION OF PURPURA BY DERIVATIVES OF PNEUMOCOCCUS : III. FURTHER STUDIES ON THE NATURE OF THE PURPURA-PRODUCING PRINCIPLE

1. The purpura-producing principle of Pneumococcus is non-antigenic in the sense that it does not stimulate the formation of antibodies. 2. White mice acquire an increased resistance to purpura as a result of repeated injections of toxic doses of the purpura substance. 3. The serum of rabbits immunized with the purified purpura principle, with "S" and "R" strains of Pneumococcus or with cell extracts, autolysates or the nucleoprotein fraction of the organism does not confer upon white mice protection against purpura. 4. The purpura principle does not exist preformed in the cell, but is rather an autolytic derivative; since it is formed only when pneumococci undergo autolysis, and it is not found when the autolytic ferments are inactivated. 5. The purpura substance is associated with the proteose fraction of active pneumococcus extracts.

THE SOLUBLE SPECIFIC SUBSTANCE OF PNEUMOCOCCUS : THIRD PAPER

1. Refinements in the methods for the isolation of the soluble specific substances of Types II and III pneumococcus are described. These improvements have resulted in the isolation of the end-products in a form free from nitrogen and of enhanced activity with immune serum. 2. The soluble specific substance of Type I pneumococcus is described and shown to differ sharply from the corresponding substances of the other two types, each of which, in turn, differs from the other. 3. Progress is reported on the identification of the sugar units from which the polysaccharides are built up. 4. The evidence so far accumulated is believed to favor strongly the view that the polysaccharides isolated are the actual specific substances of Pneumococcus.

STUDIES ON THE OXIDATION AND REDUCTION OF IMMUNOLOGICAL SUBSTANCES : X. IMMUNOLOGICAL DISTINCTIONS BETWEEN THE HEMOTOXIN AND THE "PROTEIN FRACTION" OF THE PNEUMOCOCCUS CELL

The investigation deals with the immunological differentiation of the hemotoxin and the "protein fraction" of Pneumococcus, and with a like differentiation of the antihemotoxin and the antiprotein precipitins. The distinction is made upon the basis of the following evidence: (1) The antigenic (antibody-invoking and antibody-combining) properties of the hemotoxin were destroyed by heat and oxidation treatments which did not cause the loss of the antigenic effectiveness of the "protein fraction." (2) The removal of the hemotoxin from pneumococcus solutions by combination with erythrocytes caused no loss in the capacity of the solution to invoke the production of antiprotein precipitins nor in its capacity to react with antiprotein immune serum. Titrations of the antihemotoxin content of antipneumococcus horse serum (both diagnostic and therapeutic) indicated that the heating treatment of the immunization material is the most important factor in determining the antihemotoxin content of the immune sera obtained from horses, as well as of that from rabbits. A distinction was also made between the hemotoxin and the toxic substances ("endotoxin") which cause the acute anaphylactoid death of rabbits.

IMMUNOLOGICAL RELATIONSHIPS OF CELL CONSTITUENTS OF ENCAPSULATUS PNEUMONIAE (FRIEDLANDER'S BACILLUS)

1. The soluble specific substance of Friedländer's bacillus is non-antigenic when dissociated from the cell. It is different for each type and it is highly reactive in the corresponding anti-S serum. 2. The nucleoprotein is antigenic, induces the species or protein antibody which reacts with capsule-free cells and protein derived from all types. Antiprotein sera do not react with either the encapsulated cell or the polysaccharide derived from it, and they offer no protection against infection. 3. Anti-R and antiprotein sera are identical in their behavior. 4. The carbohydrate of Friedländer's bacillus is demonstrable in filtrates of actively growing cultures and in the blood and urine of infected animals. 5. The protein is demonstrable in filtrates of only old, disintegrating cultures.

STUDIES ON IMMUNITY TO PNEUMOCOCCUS MUCOSUS (TYPE III) : II. THE INFECTIVITY OF TYPE III PNEUMOCOCCUS FOR RABBITS

The observations recorded in this paper on the infectivity of Type III pneumococci for rabbits may be summarized as follows: 1. Of eleven strains of Type III isolated from human sources, ten were found to possess low virulence for rabbits. This was true despite the fact that all the strains tested possessed large capsules and a high degree of virulence for mice. 2. One strain of Type III pneumococcus was rendered highly virulent for rabbits. Since it possessed no other biological property demonstrably different from the other strains, its virulence must reside in some additional property. 3. An initial decrease in the number of circulating organisms following the injection of virulent bacteria is a well known occurrence, and it was observed in rabbits injected with the rabbit virulent strain of Type III. However, the extent of the reduction was in inverse proportion to the degree of virulence of the strain; a fact which makes mechanical explanations of the phenomenon insufficient. 4. The bacteremia produced in rabbits by Type III pneumococci, avirulent for this species, runs a characteristic course. It differs from that produced by non-encapsulated R forms of pneumococci although in both instances survival of the infected animal ensues. This is evidence that the mechanism of resistance against encapsulated and non-encapsulated pneumococci is not identical. 5. Phagocytosis of Type III pneumococci by circulating rabbit leucocytes was not demonstrable by a vital stain technique, whereas under the same conditions the ingestion of non-encapsulated R forms occurred. This is further evidence that the process whereby non-encapsulated pneumococci are disposed of, is insufficient to explain the natural resistance of rabbits to infection with encapsulated Type III pneumococci.

REACTIONS OF RABBITS TO INTRACUTANEOUS INJECTIONS OF PNEUMOCOCCI AND THEIR PRODUCTS : I. THE ANTIBODY RESPONSE

1. Sixty rabbits were immunized by the repeated injections into the skin of small doses of suspensions of heat-killed Type I pneumococci. In 53 of the rabbits no type-specific antibodies appeared in the serum, and in the remaining seven the titre of these antibodies in the serum was very low. In all cases, however, the sera possessed a high titre of species-specific antibodies. 2. Forty-five rabbits similarly immunized by injections of heat-killed Type III pneumococci also failed to form type-specific antibodies but did form species-specific antibodies. 3. Suspensions of heat-killed R pneumococci and solutions of bacterial substances when injected into the skin stimulated the production of species-specific antibodies, although they failed to stimulate the production of any type-specific antibodies. 4. Animals which had been immunized by intracutaneous injections still possessed the ability to form type-specific antibodies when they were subsequently given intravenous inoculations of type-specific pneumococci.

CHANGES IN HUMORAL IMMUNITY OCCURRING DURING THE EARLY STAGES OF EXPERIMENTAL PNEUMOCOCCUS INFECTION

A study was made of the changes in humoral immunity occurring during the early phases of experimental pneumococcus infection in the dog and cat. The methods devised by Robertson and Sia were employed to demonstrate the presence of anti-pneumococcus properties in the serum of animals naturally resistant to this micro-organism. It was found that with a generalized and overwhelming infection accompanied by early blood invasion, there was a prompt and rapid decrease in the concentration of natural humoral immune bodies which frequently disappeared entirely by the time of death. This same early diminution of humoral immune substances, opsonins, agglutinins, and pneumococcidal-promoting bodies was observed in animals that survived a moderately severe generalized infection but the concentration of immune bodies rose again with the onset of recovery. The decrease in concentration of humoral immune substances during a severe generalized infection appeared to be due to the combination of "S" substance with the normal immune bodies. When the pneumococcus infection was more localized as in the case of true lobar pneumonia a quite different sequence of events was observed to occur. Several animals, in which extensive lobar pneumonia was produced, showed the presence in quantity of humoral immune bodies in the blood throughout the course of an infection terminating fatally. These findings suggest that after the inception of pneumococcus infection in the dog and cat the chief function of natural anti-pneurnococcus substances in the blood is to limit or prevent blood invasion. When pneumococcic infection is localized these circulating antibodies appear to have little effect either in preventing the spread of the process or determining the outcome of the disease.

SPECIFIC CUTANEOUS REACTIONS AND CIRCULATING ANTIBODIES IN THE COURSE OF LOBAR PNEUMONIA : II. CASES TREATED WITH ANTIPNEUMOCOCCIC SERA

1. Characteristic cutaneous responses to the type-specific protein-free carbohydrates of both Type I and Type II pneumococci have been "produced" in cases of lobar pneumonia due to either of these types by the intravenous injection of concentrated bivalent (Types I and II) antipneumococcic sera (Felton). 2. A positive cutaneous response to the specific polysaccharide of Type II pneumococci has been passively transferred from human cases convalescing from this infection to a patient suffering from pneumonia due to this organism. 3. The cutaneous responses to the type-specific polysaccharides and circulating antibodies were studied in 51 cases of lobar pneumonia. Positive cutaneous reactions were, in most instances, associated with recovery, even when purulent complications were present. Failure to elicit a positive reaction was usually followed by a fatal outcome. 4. The positive reactions in patients who were treated with concentrated sera and recovered were most often elicited within 24 hours after the first dose and after a total of 40 cc. had been given. 5. The positive skin reactions obtained after the administration of specific antisera were associated with the presence of mouse protective antibodies and agglutinins in the sera of the patients. 6. The immune reactions in serum treated cases receiving repeated inoculations with the specific carbohydrates disappeared more rapidly than in similar cases receiving no antiserum. It is suggested that the administration of antisera in someway interferes with the production of antibodies by the intracutaneously injected carbohydrates.

STUDIES ON IMMUNITY TO PNEUMOCOCCUS MUCOSUS (TYPE III) : I. ANTIBODY RESPONSE OF RABBITS IMMUNIZED WITH TYPE III PNEUMOCOCCUS

1. Type III pneumococci fail in the majority of instances to stimulate the production of anti-S antibodies. (Type specific agglutinins, type specific precipitins, and antibodies affording type specific protection in mice.) 2. Type III pneumococci are effective in the stimulation of the production of anti-P antibodies (agglutinins for R strains of pneumococci and precipitins for pneumococcus nucleoprotein). These antibodies are ineffectual in the passive protection of mice.

STUDIES ON INDIFFERENT STREPTOCOCCI : I. SEPARATION OF A SEROLOGICAL GROUP-TYPE I

Serological study of a large number of strains of indifferent streptococci has revealed the existence of a large homogeneous group to which the designation Type I has been applied. It is recognized that members of Type I are not necessarily identical, and that further division into subtypes may be feasible. All strains of Type I ferment inulin and salicin. The remaining strains are referred to as belonging to Group X. They are distinguished only by their failure to react strongly with Type I serum. While at present this group must be regarded as quite heterogeneous, further work may reveal the presence of other as yet undefined types now included within its limits. The organisms of this group vary in their fermentative reactions with both inulin and salicin.

VARIATION AND TYPE SPECIFICITY IN THE BACTERIAL SPECIES HEMOPHILUS INFLUENZAE

During the course of a study of different strains of influenza bacilli, fifteen strains have been found to form colonies of a different appearance from that usually considered typical of influenza bacilli. These colonies are smooth, more opaque, and are iridescent in oblique transmitted light. Most of these strains were isolated from patients in whom these organisms seemed to play a pathogenic rô1e. When these strains were grown repeatedly on blood agar, other colonies appeared which were smaller, less smooth, less opaque, and not iridescent, and when subcultures were made from these rough colonies, all of the colonies were of this character. Further study of the cultures obtained from these smooth and rough colonies have shown that one is a variant of the other. The strain from the smooth colony has been called an S strain, that from the rough colony an R strain. Certain differences in the morphology of the organisms in the R and S strains have been observed. Of special importance is the fact that the bacteria of the S strains are possessed of capsules. It has also been found that the S strains are somewhat more virulent for laboratory animals than are the R strains. In the supernatant fluid of broth cultures of S strains, and in the washing fluid of S bacteria grown on agar, there is present a soluble substance which, in the presence of homologous immune serum, gives rise to a precipitate. No reaction of this kind, however, occurs with the cultures of the R strains. By means of cross precipitin reactions, employing antisera against the different S strains, it has been found that the fifteen strains studied may be divided into two distinct immunological groups. Three of these strains belong in one group, Type a, and the remaining twelve in another group, Type b. Seven of the strains studied were isolated from the spinal fluid in cases of meningitis, and all of these strains are of Type b. Agglutination tests performed at 37 degrees C. with these fifteen S strains have revealed the same specific type relationships among the organisms as did the precipitin tests. The R strains on the other hand, exhibit no similar type agglutinations. If the agglutination tests are made at a higher temperature, 47 degrees C., the S strains also fail to show the specific type reactions which occur at 37 degrees C. Certain differences between other biochemical reactions exhibited by the two types of strains have been noted, but it is not believed that they are sufficiently constant to be of great significance. When S strains are grown on artificial media outside the animal body, they tend to be converted into the R form. The rapidity and the readiness with which this conversion occurs depend on certain conditions, such as the kind of media employed, the temperature at which the cultures are kept, and the atmospheric conditions under which they are cultivated. The rate of conversion is increased when the S strains are grown in media containing anti-S immune serum of the homologous type. On the other hand, conversion of R strains into the S form occurs with much less readiness, and then only if very particular conditions are present. On one occasion conversion occurred when an R strain was grown in a medium containing anti-R immune serum. On two other occasions this same strain changed from the R to the S form during passage through animals. With other R strains it has so far been impossible to bring about this transformation. These studies indicate that the bacteria belonging in the group Hemophilus influenzae exhibit changes in pathogenicity and immunological specificity, which are analogous to those shown by the bacteria of the pneumococcus group. It is important to continue this study, with the technique which has been developed, to include a much larger number of strains. On account of the readiness with which the S strains of influenza bacilli lose their type specificity when grown on artificial culture media, it is important that the organisms be studied as soon as possible after removal from their pathological sources. It is not impossible that many strains lose their specificity immediately after removal from the host, and that the specific immunological differentiation of many strains may, for that reason, be very difficult, if not impossible.

AN EXPERIMENTAL ANALYSIS OF BACTERIAL ALLERGY

Our experiments have confirmed the fact that the so called bacterial allergies are dependent upon a mechanism which differs materially from that determining true protein anaphylaxis. Anaphylaxis to protein substances of the bacteria probably occurs but plays a relatively unimportant rôle in the phenomena of infection. The bacterial allergies, however, are of great importance since they develop rapidly and render the infected animal highly vulnerable to products of the bacterial growth which are relatively innocuous for the normal animal. Neither the type-specific carbohydrate "residue antigens" (the "soluble specific substances" of Avery and Heidelberger) nor the antibodies reacting with them play any part whatever in bacterial allergy, and since these type-specific substances represent the haptophore groups of the whole bacteria by which they react with the agglutinins, precipitins, sensitizers, etc., of immune serum, allergy, as previously determined by Mackenzie and Woo, is in no way related to that phase of resistance which is determined by these antibodies. This does not, however, preclude the possibility that allergic hypersusceptibility may not in some way be related to other factors of resistance more definitely associated with cellular rather than with intravascular reactions. Our previous studies with Jennings and Ward in tuberculosis point in this direction (20). Guinea pigs can be actively sensitized with all the bacteria with which we have worked when repeated injections of whole bacteria or of the protein (nucleoprotein) fraction are administered. Large amounts of the latter are necessary since these materials are indifferent antigens, possibly because of the severe manipulations necessary in their production. Sensitiveness develops usually within 10 days after the first dose and increases with continued treatment for 3 or 4 weeks. Sensitiveness is relatively specific, by which we mean that there is a definite specificity which, however, in highly sensitive animals is not absolute and shows considerable overlapping. Continued treatment with considerable quantities of the above substances leads to gradual desensitization in animals in which there are no chronic foci present, which, as in tuberculosis, tends to continue the sensitization. Attempts at passive sensitization have been irregular and inconclusive. When any degree of sensitiveness has developed after the injection of immune sera, it has appeared late and has been of doubtful specificity. Conversely we have failed in any case to neutralize the activity of the active allergic constituents of bacterial extracts by incubation with any type of immune serum. We have failed so far to show any increased fixation of tuberculin material on the part of tuberculous tissues or on that of living tuberculous animals. These failures, however, seem to us of relatively slight importance since quantitative experiments of this nature are extremely difficult in the case of a substance as delicately potent for the tuberculous animal. On the other hand we have obtained definite, though irregular evidence that the incubation of O.T. with fragments of tuberculous lung tissue (less clearly with other tissues) leads to the formation of a substance that produces allergy-like lesions in the skin of normal guinea pigs. With somewhat greater regularity, similar treatment of O.T. has enhanced the potency of the tuberculin for tuberculous animals. And, in these experiments there was evidence that the factor responsible for this action was not easily separable from the cells themselves. When these experimental data are analytically considered they appear in many respects confusing and contradictory. There has been so much work done on the tuberculin reaction, moreover, that, in the face of experimental inconsistencies it would seem foolhardy to formulate more than tentative suggestions to explain the mechanism of these reactions. Nevertheless there are a few outstanding and sufficiently reliable facts which compel a limited number of definite deductions. In the first place there is no question of the complete independence of the true allergic phenomena from the ordinary bacterial antigen-antibody reactions. We know, moreover, that the allergic substance is chemically separable from the carbohydrate "residue" or haptophore group of the bacteria (Mueller, Laidlaw and Dudley). Indeed it has been shown by Long and Seibert (21) that the active allergic substance is either a protein in itself, or at any rate closely associated with the bacterial protein. Furthermore, the distinct, though limited, specificity of the allergic sensitiveness compels the conclusion that we are dealing with an immunological process in which the tissue cells acquire an increased specific capacity to react with this nitrogenous material, a capacity which, in principle, is not far removed from the supposed "sessile receptor" apparatus which is conventionally held responsible for protein anaphylaxis; and this analogy is further amplified by the apparent desensitization which continued treatment produced in many of our own experiments as well as in those of Mackenzie and Woo. Here, however, the analogy with protein anaphylaxis ends. Passive sensitization with any form of immune serum or with the sera of highly sensitized animals is either feeble or entirely unsuccessful and indicates quite convincingly that, whatever the receptor apparatus of the cells may be, it is not easily given up to the blood stream as are ordinary antibodies. Further than this, our tissue-tuberculin experiments, irregular and occasional as they were, nevertheless convinced us that: 1. The contact with the tissues of tuberculous animals results in the production of a toxic factor, not unlike the autolytic toxic materials of some bacteria. 2. The active cell constituent by which this action is wrought, is not easily separated from the cells, even by energetic methods of extraction. This close association of the entire process with the cells themselves is particularly significant in view of the obvious cell injury in which these delayed allergic effects differ from the ordinary urticarial, evanescent reactions associated with protein anaphylaxis. The process of allergy, as far as we can approach it then, may be conceived as follows: A nitrogenous, probably protein, constituent of the bacterial growth or of its body substance stimulates a specific reaction in the tissue cell by which its specific capacity to establish contact with this constituent is enhanced. The cell is thereby enabled to exert a, probably, enzyme-like effect upon this material in consequence of which a toxic substance is liberated, largely upon or possibly within the cell itself. Both processes may be dependent upon one and the same reaction body. But it seems more likely that increased contact and the increased cell activity are separately developed, an assumption which is rendered probable by the association of the highest degrees of allergy with inflammatory cell reactions, and by the fact that moderate and less specific allergic sensitiveness follows 10 or more days after the administration of considerable amounts of indifferent protein substances to guinea pigs. We interpret this as signifying that such injections may non-speciffcally increase cellular activity, a change which many earlier workers have spoken of as "cell irritability." Both processes are closely associated with the altered cell itself and the factors by which the reaction is brought about are not easily given up to the blood stream as are the antibodies formed in response to injections of proteins or whole bacteria. We are confronted, therefore, with an immunological mechanism which has some close analogies to those others in which circulating antibodies are formed, but which differs from these mainly in the intimacy with which the entire reacting system is associated with the cells themselves. It is difficult to conceive that a functional cell alteration, as profound as this, should be entirely unrelated to the phenomena of susceptibility or resistance.

IMMUNOLOGICAL RELATIONSHIPS OF ENCAPSULATED AND CAPSULE-FREE STRAINS OF ENCAPSULATUS PNEUMONIAE (FRIEDLANDER'S BACILLUS)

1. "S" strains of Friedländer's bacillus produce capsules, soluble specific substance, and are of exalted virulence. "S" strains are type-specific and react with only the type-specific antibodies of the homologous types. 2. Immunization with "S" cells induces the formation of antibodies which agglutinate type specifically, precipitate the corresponding soluble specific substance, and protect white mice against infection caused by organisms of the same type. 3. "R" strains of Friedländer's bacillus produce no capsules, produce no soluble specific substance, and are not pathogenic. "R" strains are serologically undifferentiated from each other and react with only the species antibodies. 4. Immunization with "R" cells induces antibodies which do not agglutinate encapsulated organisms, do not precipitate soluble specific substance, and do not afford protection against infection by Friedländer's bacillus. Anti-R serum contains only the species antibody which reacts with any capsule-free organism regardless of its type origin. 5. Decapsulation of "S" cells by heat and acid chemically converts a type-reacting organism into a species-reacting organism.

AN EXAMINATION OF THE MECHANISM OF PNEUMOCOCCUS IMMUNITY BY MEANS OF BACTERICIDAL MEASUREMENTS : II. THE REACTION BETWEEN THE ANTICARBOHYDRATE ANTIBODY AND TYPE-SPECIFIC PRODUCTS OF THE ORGANISM

1. There is in the filtrate of a 5 day broth culture of Type III pneumococcus a type-specific substance which has a very powerful antibactericidal action. If the precipitinogen content of the broth filtrate and the specific carbohydrate is taken as the basis of comparison, it requires approximately one thousand times as much antiserum to neutralize the broth filtrate as is necessary to neutralize the specific carbohydrate. The active substance in the broth filtrate appears to be related to the specific carbohydrate. Its possible nature is discussed. 2. A similar substance, but in stronger concentration, was found in the filtrate of a lung from a Type III pneumonia autopsy. The influence of this substance on the disease is discussed. 3. One specimen of Type III convalescent blood, though comparatively weak in anticarbohydrate antibody (precipitin) was better able to neutralize the broth filtrate and the lung filtrate than a corresponding mixture of normal blood and antiserum. Two other specimens of Type II convalescent blood neutralized the Type III broth filtrate efficiently.

FACTORS INVOLVED IN THE PRODUCTION OF IMMUNITY WITH PNEUMOCOCCUS VACCINE : II. INDUCTION OF ACTIVE IMMUNITY DURING THE COURSE OF LOBAR PNEUMONIA

1. Pneumococcus vaccine was administered to 29 patients with pneumonia to determine whether a state of immunity could be induced during the course of the disease. Twenty patients received an intravenous injection of pneumococcus vaccine or pneumococcus filtrate. Nine pneumonia patients received an intradermal injection of vaccine. Eight patients with miscellaneous disease received an intravenous or intradermal injection of pneumococcus vaccine. 2. Of 23 tests in which the serum of the patient was studied for the appearance of protective substance after intravenous injection of heterologous pneumococcus vaccine, 20 or 87 per cent showed a positive response within 6 days after the administration of the antigen. The average day of onset was 4.4 days after injection. 3. Of 9 tests of the same character following the intravenous injection of pneumococcus filtrate, 8 or 89 per cent showed a positive response. The average day of onset of protective substance was 5.6 days after injection. 4. The appearance of specific protective substance following heterologous injection of pneumococcus vaccine appeared to be due to the introduction of the vaccine and not to the natural course of the disease, as was shown by negative control experiments. 5. Of 24 tests with intradermal injection of vaccine, 10 or 42 per cent developed slight protective substance of irregular degree 4.5 days after injection. 6. No immediate reactions were observed following the intravenous or intradermal injection of pneumococcus vaccine. One chill occurred after injection of pneumococcus filtrate. Of 20 cases with intravenous injection of pneumococcus vaccine or filtrate, 2 died of their disease, one a case in which homologous vaccine was used and one in which heterologous vaccine was administered. 7. Conclusions concerning the therapeutic value of the introduction of pneumococcus vaccine in pneumonia must await further investigation. These studies demonstrate that specific protective substances generally appear 4 to 5 days after intravenous injection of pneumococcus vaccine during the course of lobar or bronchopneumonia.

Mendelian Variation in the Paracolon Mutabile Colon Group and the application of Mendel's Principles to the Theory of Acquired Virulence

It is the thesis of this paper that Mendel's principle of varitaion, formed from the study of the genetics of higher plants and animals, can be applied also to bacteria, and that acquired virulence in bacteria is the result of Mendelian variation.

STUDIES ON THE BIOLOGY OF STREPTOCOCCUS : VII. ALLERGIC REACTIONS WITH STRAINS FROM ERYSIPELAS

Rabbits immunized with filtrates of cultures of hemolytic streptococcus from erysipelas show cutaneous allergy. Two periods of allergy have been observed, an early and a late phase. The earliest reactions occurring in the first period of allergy can be neutralized with erysipelas immune sera. The rash of scarlet fever and the Dick reaction are apparently allergic reactions to products of Streptococcus scarlatinæ.

IN VITRO TRANSFORMATION OF PNEUMOCOCCAL TYPES : I. A TECHNIQUE FOR INDUCING TRANSFORMATION OF PNEUMOCOCCAL TYPES IN VITRO

1. Type-specific S pneumococci may be transformed from one specific S type into other specific S types entirely by in vitro methods. 2. R forms of pneumococci, derived from S forms of one specific type, may be transformed into S forms of other specific types by the following in vitro procedure:—the growth of small inocula of R forms in media containing vaccines prepared from heterologous S cultures. 3. Transformation of type may be effected in this procedure by the use of small quantities of S vaccine,—quantities representing the bacteria from as little as 0.1 cc. of the original culture. 4. Transformation of type, as induced by this procedure, is most readily effected by employing anti-R serum in the culture medium. Transformation of type may be effected, however, in media which do not contain anti-R antibodies. 5. Previous findings on the thermal characteristics of the property of S vaccines responsible for transformation of type have been confirmed and extended.

CHEMICAL STUDIES ON BACTERIAL AGGLUTINATION : IV. QUANTITATIVE DATA ON PNEUMOCOCCUS R (DAWSON S)- ANTI-R (S) SYSTEMS

1. The quantitative, absolute method of agglutinin estimation is extended to the reaction between Types I and II pneumococcus R (S) suspensions prepared in various ways and antisera from rabbits injected with these cells. 2. Quantitative estimations of the amount of antibody to pneumococcus C substance are also given. 3. The significance of the data is discussed.

FACTORS INVOLVED IN THE PRODUCTION OF IMMUNITY WITH PNEUMOCOCCUS VACCINE : I. ACTIVE AND PASSIVE IMMUNITY DURING THE FIRST SEVEN DAYS AFTER INJECTION OF ANTIGEN

1. The antigenic function of a pneumococcus vaccine made from the intact cell was compared with that derived fron a watery extract of the cell free from formed elements. In each instance, the immunity produced was dependent upon type-specific protective substance and not upon the elaboration of the common protein antibody. 2. The vaccine made from the intact cell resulted in both active and passive immunity which began on the 3rd day, increased markedly to the 5th, and remained approximately stationery to the 7th day. In the case of the Berkefeld filtrate of the shaken bacteria and the filtrate of the broth culture, the immunity began on the 4th day, increased to the 5th, and remained approximately stationery to the 7th day. The immunity produced by Pneumococcus Type I vaccine is greater than that produced by Type II. On the 3rd day, mice vaccinated with Type I vaccine resisted 100,000 minimal lethal doses, whereas mice immunized with Type II resisted 10,000 minimal lethal doses. On the 5th day, a larger percentage of mice survived these doses than on the 3rd day. 3. Certain factors related to the preparation and dosage of the vaccine are discussed. 4. As far as the time interval and the degree of immunity produced are concerned, these results suggest the possibility of employing pneumococcus vaccine in suitable doses in the treatment of lobar pneumonia. That an earlier activity of the immunity mechanism could actually be initiated in a patient with lobar pneumonia has still to be demonstrated.

ACTIVE IMMUNIZATION OF MICE WITH THE POLYSACCHARIDES OF PNEUMOCOCCI TYPES I, II AND III

1. Pneumococcus polysaccharides Types I, II and III adsorbed on collodion particles, and Types I and III adsorbed on carbon (norit) are antigenic in mice. 2. Unadsorbed pneumococcus polysaccharide of Type I is antigenic in mice in proper dilution. One preparation of Type II polysaccharide was not antigenic, while another one immunized against Types I and II. Type III polysaccharide was only slightly antigenic against Type III but immunized against Type I. 3. The antigenicity of pneumococcus polysaccharide in optimal dosage is tentatively explained by an adsorption phenomenon taking place in the body in instances in which the polysaccharides had not been adsorbed before injection. 4. The aggressin-like action of large doses of pneumococcus polysaccharides Types I, II and III is further established.

SEROLOGICAL RELATIONSHIPS OF TYPE-SPECIFIC AND DEGRADED PNEUMOCOCCI

1. Immune sera prepared with the degraded or variant forms of pneumococci (R strains) are similar in their reactions to sera prepared with the protein or cell solutions of pneumococci. They contain antibodies reactive with the protein of all types of pneumococci, but no antibodies reactive with the type-specific substances. 2. Pneumococci of the variant or R form, regardless of type derivation, are serologically identical and have the antigenic characteristics of pneumococcus protein. They evoke the species-specific and not the type-specific antibodies. 3. Antipneumococcus sera obtained by immunization with S strains may contain species-specific antibodies in addition to those which are type-specific. Each kind of antibody can be removed separately from these sera by selective absorption with the R or S strains of pneumococci.

AGGLUTINATION BY PRECIPITIN

Serum (antigen) when heated at a temperature sufficient to cause definite clouding reacts more intensely with a specific precipitin than a portion of the unheated serum or samples heated at lower temperatures. The phenomenon is explained on the basis that coagulated protein in suspension is covered with undenatured antigen and the addition of precipitin causes agglutination of the coagulated protein. Similar phenomena are obtained when bacteria or collodion particles are mixed with diluted serum (antigen) and precipitin added; the particles or bacteria agglutinate and increase the visibility of the reaction. Further, it is shown that collodion particles sensitized with cow serum or crystallized egg albumin and subsequently washed until the washing fluid no longer contains the antigenic substance will agglutinate when small quantities of specific precipitin are added. Bacteria sensitized with cow serum and subsequently washed until cow serum no longer remains in the washing solution agglutinate when cow antiserum at fairly low concentration is added. It was not possible to show that bacteria soaked in crystallized egg albumin and subsequently washed retained on their surfaces sufficient undenatured egg albumin to react to crystallized egg albumin precipitin.

THE IDENTITY OF THE MECHANISMS OF TYPE-SPECIFIC AGGLUTININ AND PRECIPITIN REACTIONS WITH PNEUMOCOCCUS

The experimental results which have been described demonstrate the following facts: 1. In the type-specific agglutination reaction, when the organisms are not present in sufficient numbers to absorb completely all the antibodies from the serum, more antibody is bound by cellular S than is required for the process of agglutination. 2. The excess of antibody thus bound can then unite with additional amounts of the specific substance when this is added in soluble form to the agglutinated material. 3. If an excess of the free S is added to an agglutinated mass of antibody and bacteria, the organisms are redispersed and in the suspended state are again specifically agglutinable. 4. When a solution of the specific polysaccharide is added in excess to an homologous immune serum, a prozone is created in which precipitation is inhibited; moreover, if, at this point, type-specific pneumococci are added to the mixture, inhibition of agglutination also occurs. 5. The reactive substance in the type-specific agglutination and precipitation reactions is the same, i.e., the capsular polysaccharide. In the former instance it is combined in the bacterial cell; in the latter, it is in a soluble, chemically purified state and entirely separate from the body of the cell.

A COMPARISON OF CUTANEOUS SENSITIZATION AND ANTIBODY FORMATION IN RABBITS IMMUNIZED BY INTRAVENOUS OR INTRADERMAL INJECTIONS OF INDIFFERENT OR HEMOLYTIC STREPTOCOCCI AND PNEUMOCOCCI

1. Rabbits that had received repeated intravenous injections of heat-killed indifferent streptococci with no resulting sensitization were subsequently made skin-sensitive to them by repeated intracutaneous injection of heat-killed vaccine. 2. Serum agglutinins and precipitins developed earlier in rabbits that had received repeated intravenous injections of killed streptococci and pneumococci than in those injected intracutaneously. However, when such injections were continued over a longer period, the antibodies in both groups of animals reached a similar level. 3. Species specific agglutinins reached about the same level after either intracutaneous or intravenous injections of heat-killed Type I(S) pneumococcus vaccine. Type specific agglutinins were present only in the intravenously injected animals after 33 days but were present in all the animals after 63 days although the titres were somewhat lower in those injected intradermally. Both groups developed precipitins which were only slightly less in the intradermally injected rabbits. 4. These experiments indicate that rabbits intravenously injected with heat-killed streptococci can be made highly skin-sensitive in the same manner as animals injected intracutaneously and that they are not immune or refractory to skin sensitization. When antigen was injected either intracutaneously or intravenously into rabbits for a fairly long time, the amount of circulating antibody in both groups was approximately equal.

A BIOLOGICAL CLASSIFICATION OF ENCAPSULATUS PNEUMONIAE (FRIEDLANDER'S BACILLUS)

A biological classification has been made of thirty strains of Friedländer's bacillus. This study reveals that there exist among these strains three sharply defined and specific types and one heterogeneous group. The three types are Type A, fifteen strains; Type B, six strains; Type C, three strains; and Group X, six strains. The agglutination, agglutinin adsorption, protection, thread, and precipitin reactions have been employed in the working out of this classification, and the types have been proved highly specific by means of each serological test.

THE IMMUNOLOGICAL SPECIFICITY OF STAPHYLOCOCCI : I. THE OCCURRENCE OF SEROLOGICAL TYPES

1. Agglutination is not a precise method for the demonstration of serological types among staphylococci. 2. Precipitation of soluble specific substance derived from these organisms demonstrates the existence of at least two immunologically distinct types. 3. The one type, designated A, is composed of apparently virulent strains, while the other, Type B, contains the avirulent strains. 4. Precipitation tests performed with centrifugates of young broth cultures or with acid extracts of sedimented bacteria may also demonstrate type specificity. 5. Lysis by bacteriophage fails to detect the specific types of Staphylococcus. 6. Immunization by intravenous methods stimulates agglutinin formation in all rabbits and precipitin formation in only one of three or four animals. 7. Immunization by repeated intracutaneous injections of dead staphylococci or living organisms in an agar focus also stimulates agglutinin formation but fails to incite the formation of type specific precipitins.

IMMUNOLOGICAL PROPERTIES OF A TYPICAL (S-PRODUCING) AND A DEGRADED (NON-S-PRODUCING) STRAIN OF TYPE II PNEUMOCOCCUS WITH SPECIAL REFERENCE TO PROTECTIVE ANTIBODIES

The loss of the specialized function of S production by Type II pneumococcus was accompanied by a loss of the antigenic properties involved in both active and passive protection of mice. Absorption of Type II serum with S-producing pneumococci removed all the protective antibodies, as well as the type-specific agglutinins and S precipitins. The same absorption treatment of the serum by non-S-producing pneumococci failed entirely to remove the type-specific antibodies and did not affect the protective value of the serum. Absorption with bacteria-free culture fluids containing the reactive carbohydrate removed the protective antibodies as completely as absorption with the whole bacterial cells of type-specific strains. The results taken as a whole indicate that the antibodies involved in the usual protection of mice against Type II pneumococci are closely related, if not identical, to the specific anticarbohydrate precipitin.

THE ANTIGENIC COMPLEX OF STREPTOCOCCUS HAEMOLYTICUS : I. DEMONSTRATION OF A TYPE-SPECIFIC SUBSTANCE IN EXTRACTS OF STREPTOCOCCUS HAEMOLYTICUS

1. Hydrochloric acid extracts of Streptococcus haemolyticus contain type-specific, as well as non-type-specific, substances. The precipitates formed by these crude extracts with homologous antibacterial serum are flocculent, while those obtained with heterologous serum are usually disc-like. 2. The type-specific substance may be detected by the use of anti-bacterial sera absorbed with heterologous strains of hemolytic streptococci. Such absorbed sera are type-specific: they are precipitated only by extracts of strains of the homologous type. 3. Any heterologous strain of hemolytic streptococcus absorbs the antibodies for all other heterologous strains, but homologous strains absorb type-specific antibodies as well. Numerous repeated absorptions with heterologous hemolytic streptococci tend to lower the titer of the type-specific antibody. A possible explanation of this fact is suggested. 4. Three strains did not yield a type-specific substance; and it seems probable that they had lost this function because of long continued cultivation in artificial media. 5. Classification based on the precipitin test with absorbed serum agrees with that previously determined by agglutination and protection tests. The method is, therefore, applicable to the problem of classification of the hemolytic streptococci.

THE IMMUNOLOGICAL SPECIFICITY OF STAPHYLOCOCCI : III. INTERRELATIONSHIPS OF CELL CONSTITUENTS

1. The carbohydrates derived from Staphylococcus are type specific. 2. The specific carbohydrates fail to induce formation of antibodies in rabbits. 3. Acetylation or adsorption of the carbohydrates on collodion particles does not render them antigenic. 4. The specific carbohydrates may be employed to elicit immediate, type specific, skin reactions in patients with Staphylococcus infection. 5. The protein of Staphylococcus is species specific. 6. The protein is antigenic and stimulates in rabbits species specific antibodies. 7. The protein causes in hypersensitive individuals a species specific, delayed, inflammatory skin reaction.

A TYPE SPECIFIC SUBSTANCE DISTINCT FROM THE SPECIFIC CARBOHYDRATE IN PNEUMOCOCCUS TYPE I

1. Evidence has been presented for the existence of a substance distinct from the specific carbohydrate in the autolytic products of Pneumococcus Type I. 2. The substance reacts specifically by precipitating homologous antiserum which either occurs naturally without antibody against the specific carbohydrate or has been deprived of that antibody artificially. 3. In guinea pigs passively sensitized with such antisera the homologous autolysate containing the substance alone produces typical lethal anaphylactic shock. 4. In weakly alkaline solution the substance is destroyed by boiling. In weakly acid solution it resists a temperature of 100°C. for at least ½ hour. Autoclaving for 1 hour at 15 pounds pressure in either acid or alkaline solution destroys its activity as precipitinogen. 5. The substance is resistant to peptic digestion. 6. The chemical nature and the possible identification of the substance as a haptene have been discussed.

STUDIES ON IMMUNITY TO PNEUMOCOCCUS MUCOSUS (TYPE III) : III. INCREASED RESISTANCE TO TYPE III INFECTION INDUCED IN RABBITS BY IMMUNIZATION WITH R AND S FORMS OF PNEUMOCOCCUS

1. Immunization of rabbits with Type III pneumococci is effective in producing active immunity against infection with a virulent strain of the homologous organism. 2. Immunization of rabbits with Type I or II pneumococci, and with R forms derived from any of the fixed types, is equally effective in producing active immunity against Type III infection. 3. Immunization of rabbits with nucleoprotein or with desoxycholate solutions of heterologous pneumococci, under the experimental conditions described, appears to be ineffective in producing active immunity against Type III infection.

THE TRANSFORMATION OF PNEUMOCOCCAL TYPES : I. THE CONVERSION OF R FORMS OF PNEUMOCOCCUS INTO S FORMS OF THE HOMOLOGOUS TYPE

R forms of Pneumococcus may be converted into S forms of the homologous Type. In addition to the methods previously reported,—(1) animal passage and (2) growth in anti-R sera,—conversion may be effected by the following procedures as employed by Griffith; (1) The subcutaneous injection, in white mice, of large amounts of living R organisms. (2) The subcutaneous injection, in white mice, of small amounts of living R organisms together with the heat-killed bacteria from large amounts of homologous S cultures. There are "varying degrees of constancy of the R variant"; but by these means it has been possible to effect conversion of all R forms selected. Attempts to cause a further "degradation" of R organisms by continued growth in homologous immune serum have been unsuccessful. Type II S and III S vaccines are equally effective in producing conversion when heated for 15' at 60°C., or for 15' at 100°C. Type I S vaccine, however, while effective in causing conversion when heated for 15' at 60°C., apparently loses this property when heated for 15' at 100°C. R vaccines, and vaccines of other organisms, when injected together with live R cultures, have always failed to produce conversion. The causes responsible for conversion under these experimental conditions are discussed and the possibility of the occurrence of a similar process under natural conditions in human beings is indicated.

Paul Ehrlich and O.T. Avery: pathfinders in the search for immunity

This paper is concerned with the use of passive immunity for the prevention and treatment of infections from a historic perspective, particularly in regard to the research of Paul Ehrlich on diphtheria and that of O.T. Avery on pneumonia. It is timely to reexamine this matter, particularly in regard to virus infections, in view of the difficulties in developing antiviral drugs. In addition, specific antibodies can serve as an alternative therapy for antibiotic resistant microbes. It is worth recalling in the history of vaccine development that success in passive immunity has been the key element in devising a successful strategy to develop a vaccine to produce humoral immunity.

The dynamics of conceptual change in twentieth century immunology

I have attempted here to define three distinct eras in the 110-year history of the discipline of immunology. The first, extending from 1880 to about the First World War, centered around the new bacteriology and infectious diseases, and had a distinctly medical orientation. Several of the components of the original research program in immunology failed to maintain their original momentum or to fulfill their initial high promise, and went into decline. These include the development of new vaccines, serotherapeutic approaches, the study of cellular immunity, and the study of diseases that might be mediated by cytotoxic antibodies. Two other subprograms followed a somewhat different course; the study of anaphylaxis and related diseases passed primarily into the hands of clinical allergists, while the development and adaptation of serodiagnostic techniques passed into the hands of the new discipline of serology, both fields out of the mainstream of post-World War I immunology. As interest in the components of the old program was falling away, there developed a new area of interest in immunology. Leadership in the field devolved upon a new group of individuals with a predominantly chemical orientation to the study of antigens and antibodies, who pursued a research program and developed a theoretical base that reflected this orientation well. It may be interesting to examine more closely the forces responsible for this shift in emphasis. When interest in the old areas waned, the medically oriented practitioners did not switch to more immunochemical lines, but went in other directions. Karl Landsteiner was the only prominent "old-timer" who contributed significantly to the newer immunology, and it was his work that set the tone and attracted the new generation of immunochemists who became the reigning Denkkollektiv. A science does not change its precepts and approaches spontaneously; it is moved to the new position by those who explore fertile new areas. This is not to say, however, that there was no longer interesting and important work to be done along the old lines--it was just that such work was no longer "fashionable", as the reception of the work of Dienes, of Rich, of Rivers, and of the early Medawar illustrates. Whereas the earlier immunological program had interacted extensively with many different fields of biology and medicine, the immunochemical era was characterized by a relative introversion, as compared with the broad influence exerted by the earlier immunological program (92). We can date this second era from about the First World War until the late 1950s and early 1960s.(ABSTRACT TRUNCATED AT 400 WORDS)

Analysis of a surface protein of Streptococcus pneumoniae recognised by protective monoclonal antibodies

Using two monoclonal antibodies which protect mice from a fatal challenge with S. pneumoniae, we have identified a surface protein antigen on the pneumococcus. These antibodies recognised components of 84 and 76 kD in a cell wall extract of the nonencapsulated strain, R36A, against which they were made. Absorption experiments indicated that both of the antibodies recognised the same two proteins. The proteins detected by the antibodies in the encapsulated type 2 strain D39 and type 3 strain WU2, exhibited different molecular weights than those proteins detected from R36A. Using a colony blot procedure and a quantitative ELISA, we have shown that these antibodies react with 6 of the 21 pneumococcal strains tested. There was no association between reactivity with these anti-protein antibodies and the capsular serotype of the pneumococcal isolates tested.

Pneumococcal disease and its prevention with polyvalent pneumococcal polysaccharide vaccines--a review

Polyvalent pneumococcal polysaccharide vaccines have been shown to be safe, immunogenic and efficacious and are becoming available for use in patients at high risk of developing pneumococcal infections. Precise estimates of the role of the pneumococcus in human respiratory disease are difficult to obtain, as this organism is also a frequent commensal of the upper respiratory tract; and as the optimal techniques for the identification and proof of its role are not widely used. Nevertheless, the pneumococcus remains the principal cause of adult pneumonia and paediatric otitis media, and is also an important cause of death from bacteremia and meningitis. At present it seems likely that in Australia these vaccines will be most useful amongst people over the age of 50 years, those with chronic systemic disease, alcoholics, splenectomized individuals and disadvantaged groups such as Australian aborigines, all of whom are particularly susceptible to pneumo-coccal bacteremia which has a considerable mortality rate. The possibility of preventing pneumococcal otitis media in childhood is still being evaluated. Studies of the role played by the various pneumococcal serotypes in Australian populations are urgently needed.