Antibody formation. IV. Formation of rapidly and slowly sedimenting antibodies and immunological memory to bacteriophage phi-X 174

Regulation of BCR-mediated Ca2+ mobilization by MIZ1-TMBIM4 safeguards IgG1+ GC B cell-positive selection

The transition from immunoglobulin M (IgM) to affinity-matured IgG antibodies is vital for effective humoral immunity. This is facilitated by germinal centers (GCs) through affinity maturation and preferential maintenance of IgG+ B cells over IgM+ B cells. However, it is not known whether the positive selection of the different Ig isotypes within GCs is dependent on specific transcriptional mechanisms. Here, we explored IgG1+ GC B cell transcription factor dependency using a CRISPR-Cas9 screen and conditional mouse genetics. We found that MIZ1 was specifically required for IgG1+ GC B cell survival during positive selection, whereas IgM+ GC B cells were largely independent. Mechanistically, MIZ1 induced TMBIM4, an ancestral anti-apoptotic protein that regulated inositol trisphosphate receptor (IP3R)-mediated calcium (Ca2+) mobilization downstream of B cell receptor (BCR) signaling in IgG1+ B cells. The MIZ1-TMBIM4 axis prevented mitochondrial dysfunction-induced IgG1+ GC cell death caused by excessive Ca2+ accumulation. This study uncovers a unique Ig isotype-specific dependency on a hitherto unidentified mechanism in GC-positive selection.

Clinical Pharmacology of Bacteriophage Therapy: A Focus on Multidrug-Resistant Pseudomonas aeruginosa Infections

Pseudomonas aeruginosa is one of the most common causes of healthcare-associated diseases and is among the top three priority pathogens listed by the World Health Organization (WHO). This Gram-negative pathogen is especially difficult to eradicate because it displays high intrinsic and acquired resistance to many antibiotics. In addition, growing concerns regarding the scarcity of antibiotics against multidrug-resistant (MDR) and extensively drug-resistant (XDR) P. aeruginosa infections necessitate alternative therapies. Bacteriophages, or phages, are viruses that target and infect bacterial cells, and they represent a promising candidate for combatting MDR infections. The aim of this review was to highlight the clinical pharmacology considerations of phage therapy, such as pharmacokinetics, formulation, and dosing, while addressing several challenges associated with phage therapeutics for MDR P. aeruginosa infections. Further studies assessing phage pharmacokinetics and pharmacodynamics will help to guide interested clinicians and phage researchers towards greater success with phage therapy for MDR P. aeruginosa infections.

Positive selection of IgG+ over IgM+ B cells in the germinal center reaction

Positive selection of high-affinity B cells within germinal centers (GCs) drives affinity maturation of antibody responses. Here, we examined the mechanism underlying the parallel transition from immunoglobulin M (IgM) to IgG. Early GCs contained mostly unswitched IgM⁺ B cells; IgG⁺ B cells subsequently increased in frequency, dominating GC responses 14-21 days after antigen challenge. Somatic hypermutation and generation of high-affinity clones occurred with equal efficiency among IgM⁺ and IgG⁺ GC B cells, and inactivation of Ig class-switch recombination did not prevent depletion of IgM⁺ GC B cells. Instead, high-affinity IgG⁺ GC B cells outcompeted high-affinity IgM⁺ GC B cells via a selective advantage associated with IgG antigen receptor structure but independent of the extended cytoplasmic tail. Thus, two parallel forms of GC B-cell-positive selection, based on antigen receptor variable and constant regions, respectively, operate in tandem to ensure high-affinity IgG antibodies predominate in mature serum antibody responses.

The dark side of the gut: Virome-host interactions in intestinal homeostasis and disease

The diverse enteric viral communities that infect microbes and the animal host collectively constitute the gut virome. Although recent advances in sequencing and analysis of metaviromes have revealed the complexity of the virome and facilitated discovery of new viruses, our understanding of the enteric virome is still incomplete. Recent studies have uncovered how virome–host interactions can contribute to beneficial or detrimental outcomes for the host. Understanding the complex interactions between enteric viruses and the intestinal immune system is a prerequisite for elucidating their role in intestinal diseases. In this review, we provide an overview of the enteric virome composition and summarize recent findings about how enteric viruses are sensed by and, in turn, modulate host immune responses during homeostasis and disease.

Neutralizing antibody response against subcutaneously injected bacteriophages in rabbit model

Bacteriophage therapy is currently experiencing a renaissance. Therapeutic efficacy of bacteriophages depends on phage-bacterial and phage-host interactions. The appearance of neutralizing anti-phage antibody has been speculated to be one of the few reasons for bacteriophage therapy's failure. This study aimed to know whether there is a rise in the neutralizing antibody on the parenteral injection of bacteriophages in an animal model. This study included bacteriophages against five different bacteria, namely Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella Typhi and Staphylococcus aureus. These bacteriophages were isolated, propagated and purified. Bacteriophage specificity was confirmed by spot testing on the respective bacterial lawn. Weekly subcutaneous injection of purified bacteriophages (109PFU) was given to five rabbits for six weeks. Blood samples were collected before administering the next dose every week. The antibody response was tested by phage neutralization followed by plaque assay by using double agar overlay method. The rise in anti-phage neutralizing antibodies was observed usually after the 3rd week after immunization. Complete neutralization of bacteriophages could be seen between 3 and 5 weeks after immunization. A further rise in bacteriophage counts (PFU), especially on 1:1000 and 1:2000 serum dilutions, could be noticed by the end of 6th week against most bacteriophages injected. Background anti-phage neutralizing antibodies were observed against bacteriophage specific to Escherichia coli. However, it was absent against bacteriophages specific to other four bacteria. Bacteriophage interacts with mammalian host and induces anti-phages neutralizing antibody production. However, neutralization of phage depends on repeated administration and duration of therapy. The significant rise in neutralizing antibody could be seen at the end of 3rd week. Therefore, bacteriophage can be effectively used in acute cases where therapy duration is less than 2 weeks. However, for prolonged therapy, bacteriophage cocktail of different antigenicity may be suggested.

Induction of Phage-Specific Antibodies by Two Therapeutic Staphylococcal Bacteriophages Administered per os

In therapeutic phage applications oral administration is a common and well-accepted delivery route. Phages applied per os may elicit a specific humoral response, which may in turn affect phage activity. We present specific anti-phage antibody induction in mice receiving therapeutic staphylococcal bacteriophage A3R or 676Z in drinking water. The schedule comprised: (1) primary exposure to phages for 100 days, followed by (2) diet without phage for 120 days, and (3) secondary exposure to the same phage for 44 days. Both phages induced specific antibodies in blood (IgM, IgG, IgA), even though poor to ineffective translocation of the phages to blood was observed. IgM reached a maximum on day 22, IgG increased from day 22 until the end of the experiment. Specific IgA in the blood and in the gut were induced simultaneously within about 2 months; the IgA level gradually decreased when phage was removed from the diet. Importantly, phage-specific IgA was the limiting factor for phage activity in the gastrointestinal tract. Multicopy proteins (major capsid protein and tail morphogenetic protein H) contributed significantly to phage immunogenicity (IgG), while the baseplate protein gpORF096 did not induce a significant response. Microbiome composition assessment by next-generation sequencing (NGS) revealed that no important changes correlated with phage treatment.

Contribution of the Immune Response to Phage Therapy

Therapeutic phages are being employed for vaccination and treatment of cancer and bacterial infections. Their natural immunogenicity triggers intertwined interactions with innate and adaptive immune cells that might influence therapy. Phage- and bactierial-derived pathogen-associated molecular patterns released after bacterial lysis have been proposed to stimulate local innate immune responses, which could promote antitumor immunity or bacterial clearance. Conversely, immunogenicity of phages induces phage-specific humoral memory, which can hamper therapeutic success. This review outlines the current knowledge on the different types of immune responses elicited by phages and their potential benefits and adverse side effects, when applied therapeutically. This review further summarizes the knowledge gaps and defines the key immunological questions that need to be addressed regarding the clinical application of antibacterial phage therapy.

Immunological memory: What's in a name?

Immunological memory is one of the core topics of contemporary immunology. Yet there are many discussions about what this concept precisely means, which components of the immune system display it, and in which phyla it exists. Recent years have seen the multiplication of claims that immunological memory can be found in "innate" immune cells and in many phyla beyond vertebrates (including invertebrates, plants, but also bacteria and archaea), as well as the multiplication of concepts to account for these phenomena, such as "innate immune memory" or "trained immunity". The aim of this critical review is to analyze these recent claims and concepts, and to distinguish ideas that have often been misleadingly associated, such as memory, adaptive immunity, and specificity. We argue that immunological memory is a gradual and multidimensional phenomenon, irreducible to any simple dichotomy, and we show why adopting this new view matters from an experimental and therapeutic point of view.

Estimating Time of Infection Using Prior Serological and Individual Information Can Greatly Improve Incidence Estimation of Human and Wildlife Infections

Diseases of humans and wildlife are typically tracked and studied through incidence, the number of new infections per time unit. Estimating incidence is not without difficulties, as asymptomatic infections, low sampling intervals and low sample sizes can introduce large estimation errors. After infection, biomarkers such as antibodies or pathogens often change predictably over time, and this temporal pattern can contain information about the time since infection that could improve incidence estimation. Antibody level and avidity have been used to estimate time since infection and to recreate incidence, but the errors on these estimates using currently existing methods are generally large. Using a semi-parametric model in a Bayesian framework, we introduce a method that allows the use of multiple sources of information (such as antibody level, pathogen presence in different organs, individual age, season) for estimating individual time since infection. When sufficient background data are available, this method can greatly improve incidence estimation, which we show using arenavirus infection in multimammate mice as a test case. The method performs well, especially compared to the situation in which seroconversion events between sampling sessions are the main data source. The possibility to implement several sources of information allows the use of data that are in many cases already available, which means that existing incidence data can be improved without the need for additional sampling efforts or laboratory assays.

Targeting the B7 family of co-stimulatory molecules: successes and challenges

As more patient data is cross-referenced with animal models of disease, the primary focus on T(h)1 autoreactive effector cell function in autoimmune diseases, such as rheumatoid arthritis and multiple sclerosis, has shifted towards the role of T(h)17 autoreactive effector cells and the ability of regulatory T cells (T(reg)) to modulate the pro-inflammatory autoimmune response. Therefore, the currently favored hypothesis is that a delicate balance between T(h)1/17 effector cells and T(reg) cell function is critical in the regulation of inflammatory autoimmune disease. An intensive area of research with regard to the T(h)1/17:T(reg) cell balance is the utilization of blockade and/or ligation of various co-stimulatory or co-inhibitory molecules, respectively, during ongoing disease to skew the immune response toward a more tolerogenic/regulatory state. Currently, FDA-approved therapies for multiple sclerosis patients are all aimed at the suppression of immune cell function. The other favored method of treatment is a modulation or deletion of autoreactive immune cells via short-term blockade of activating co-stimulatory receptors via treatment with fusion proteins such as CTLA4-Ig and CTLA4-FasL. Based on the initial success of CTLA4-Ig, there are additional fusion proteins that are currently under development. Examples of the more recently identified B7/CD28 family members are PD-L1, PD-L2, inducible co-stimulatory molecule-ligand (ICOS-L), B7-H3, and B7-H4, all of which may emerge as potential fusion protein therapeutics, each with unique, yet often overlapping functions. The expression of both stimulatory and inhibitory B7 molecules seems to play an essential role in modulating immune cell function through a variety of mechanisms, which is supported by findings that suggest each B7 molecule has developed its own indispensable niche in the immune system. As more data are generated, the diagnostic and therapeutic potential of the above B7 family-member-derived fusion proteins becomes ever more apparent. Besides defining the biology of these B7/CD28 family members in vivo, additional difficulty in the development of these therapies lies in maintaining the normal immune functions of recognition and reaction to non-self-antigens following viral or bacterial infection in the patient. Further complicating the clinical translation of these therapies, the mechanism of action identified for a particular reagent may depend upon the method of immune-cell activation and the subset of immune cells targeted in the study.

Brucella-Agglutinating Antibodies: Relation of Mercaptoethanol Stability to Complement Fixation

Brucella-agglutinating antibodies from selected bovine blood serums and milk samples did not fix complement, and after treatment with 2-mercaptoethanol they lost agglutinating power. After infection of calves with Brucella abortus, strain 19, agglutinins for Brucella that were inactivated by mercaptoethanol appeared earlier than those stable to mercaptoethanol. Under the conditions of these experiments, the appearance and development of complement-fixing capacity coincided closely with the mercaptoethanol stability of the agglutinins for Brucella.

Distribution of echovirus antibody in serum, nasopharynx, rectum, and spinal fluid after natural infection with echovirus type 6

By employing the techniques of radioimmunodiffusion and autoradiography and by using (32)P-labeled echovirus 6 as the antigen, the distribution of echovirus 6 antibody in serum, nasopharynx, rectum, and spinal fluid was studied in a group of children with naturally acquired echovirus type 6 infection, with or without meningeal involvement. The response in serum was characterized by sequential appearance of gammaM, gammaG, and rarely of gammaA antibody. The secretory response in the nasopharynx and rectum was limited to secretory gammaA immunoglobulin. The response in spinal fluid was limited to gammaG immunoglobulin. gammaG echovirus antibody appeared in the spinal fluid with or without demonstrable replication of virus in the spinal fluid. It is suggested that, after short-term acute infection with enteroviruses, the appearance of gammaG antibody in spinal fluid may largely be a reflection of increased transport of serum antibody, particularly of gammaG immunoglobulin class.

Pathogenicity and immunogenicity for mice of temperature-sensitive mutants of vesicular stomatitis virus

Temperature-sensitive (ts) mutants of vesicular stomatitis (VS) virus were tested for their pathogenicity and immunogenicity in weanling mice. Compared with the wild-type virus (ts(+)), ts mutants representing genetic complementation groups I, II, and IV were considerably less pathogenic for mice infected by the intracerebral route and caused few deaths after intranasal inoculation. Mice were completely resistant to ts(+) and ts mutants by the intraperitoneal route. Resistance to intracerebral challenge with ts(+) VS virus was only minimal in mice vaccinated intraperitoneally with ts(+) or ts mutants and only moderate in mice vaccinated intranasally with three ts mutants. Intranasal vaccination, particularly with group IV mutants, resulted in solid immunity within 3 days to intranasal challenge with ts(+) virus. VS viral neutralizing antibody was present in the bronchial secretions of mice by 12 h after intranasal inoculation of mutant ts IV44; the bronchial antibody titers declined to undetectable levels between 3 and 7 days after vaccination. Neutralizing antibody was detected in the serum of mice by the third day after intranasal vaccination with ts IV44 and persisted at high level for at least 11 days. Certain classes of ts mutants would appear to be promising candidates for use as attenuated, live virus vaccines.

HOMEOSTASIS OF ANTIBODY FORMATION IN THE ADULT RAT

Passive immunization of rats with homologous anti-sheep erythrocyte serum markedly inhibited the primary antibody response to various doses of sheep erythrocytes. Inhibition was "specific" and apparently produced by either "19S" or "7S" antibody to the antigen. Passive immunization inhibited splenic hyperplasia associated with the primary antibody response. Passive immunization 24 hours after active immunization effectively inhibited the primary antibody response. The markedly suppressive effect of specific antibody on the primary antibody response contrasted sharply with the absence of this effect on the secondary response. Antigen-antibody complexes formed in vitro elicited no measurable primary antibody response but did elicit a high secondary response. Exposure of normal spleen cells to the antibody in vivo or in vitro suppressed their response to the antigen in x-irradiated recipients. In contrast, cells from previously immunized animals transferred to x-irradiated animals produced antibody in the presence of passively given antibody. Thus, "potential antibody-forming cells" from normal animals were unresponsive to the antigen in the presence of specific antibody, while "antibody-forming cells" from previously immunized animals responded to the antigen in the presence of antibody. Presumably, antibody actively produced in small quantities by a few antibody-forming cells might inhibit antibody formation by potential antibody-forming cells. Confirmation of this suggestion was obtained by showing that some animals initially injected with small doses of antigen failed to produce measurable antibody to subsequent injections of larger doses of the antigen. Low doses of antigen capable of inducing unresponsiveness produced no measurable circulating antibody, but these doses did produce increased numbers of plaque-forming (antibody-releasing) cells in spleens of rats. Thus, the formation of specific antibody may provide a homeostatic or "feed-back" mechanism which controls or limits production of specific antibody to the portion of the antibody-forming system previously stimulated by the antigen. This mechanism may account in part for immunological unresponsiveness produced in certain other related experimental systems.

THE FORMATION AND PROPERTIES OF POLIOVIRUS-NEUTRALIZING ANTIBODY. IV. NORMAL ANTIBODY AND EARLY IMMUNE ANTIBODY OF RABBIT ORIGIN: A COMPARISON OF BIOLOGICAL AND PHYSICOCHEMICAL PROPERTIES

Rabbit sera were found to possess neutralizing activity (normal antibody) to polioviruses and Coxsackie B viruses. This normal antibody showed high specificity in cross-neutralization and absorption tests. It was associated with heat-stable, mercaptan-sensitive, 19S γ₁-β-macroglobulins, which formed weak complexes with the viral antigen. In rare instances, sera with normal macroglobulin antibody, also contained very low activity which was due to 7S γ₂-globulins. The neutralization of poliovirus by normal 19S γ₁-β-antibody appeared to follow first order kinetics, and the thermodynamic parameters of this reaction were the same as those of serological reactions employing immune antibody. The electrophoretic mobility, sedimentation properties, sensitivity to mercaptan, thermostability, and avidity of normal and early (up to day 3) immune antibodies to poliovirus were similar, but differed in several respects from those of late immune antibodies. Thus, the available evidence suggested, that earlier reported differences between normal and immune antibodies reflected differences between antibodies of diverse physicochemical properties rather than between normal and immune antibodies per se. It is proposed that the normal macroglobulin antibody is associated with an immunological response to repeated stimulation with minute amounts of antigen.

THE IMMUNOGLOBULINS OF MICE. I. FOUR MAJOR CLASSES OF IMMUNOGLOBULINS: 7S GAMMA-2-, 7S GAMMA-1-, GAMMA-1A (BETA-2A)-, AND 18S GAMMA-1M-GLOBULINS

Two classes of 7S γ-globulins are identified in normal mouse serum and are designated 7S γ₂-globulins and 7S γ₁-globulins. These two immunoglobulin classes are similar in size. They differ in range of electrophoretic mobility, in specific antigenic determinants, and in genetically determined isoantigens. Four classes of immunoglobulins in mouse serum, i.e. 7S γ₂-, 7S γ₁-, γ_1A (β_2A), and γ_M-globulins, were shown to have antibody activity. Each class was characterized and shown to have distinctive immunochemical and physicochemical properties. The genetically determined isoantigens, Iga-1 and Iga-2, were shown to be present only on 7S γ₂-globulin molecules.

THE ROLE OF DISULFIDE BONDS IN THE COMPLEMENT-FIXING AND PRECIPITATING PROPERTIES OF 7S RABBIT AND SHEEP ANTIBODIES

The number of total disulfide bonds in rabbit and sheep 7S gamma globulin, before and after treatment with 2-mercaptoethanol, has been measured by amperometric titration. Mercaptan reduction could diminish the complement-fixing efficiency of 7S rabbit gamma globulin by no more than 90 per cent without any significant decrease in maximal complement-fixing ability. This was associated with the reduction of only 7 disulfide bonds, including 1 interchain disulfide bond [S—S₍₁₎]. The reduction of 7 disulfide bonds in 7S sheep gamma globulin was associated with a 64 per cent decrease in complement-fixing efficiency, while reduction of 10 to 11 disulfide bonds decreased the complement-fixing efficiency by 90 per cent. Reduction of more disulfide bonds was not associated with any further decrease in complement-fixing efficiency, nor of any decrease in maximal complement-fixing ability. The reduction of more than 10 to 11 disulfide bonds in 7S rabbit and sheep gamma globulins was associated with a decrease in precipitating ability. The disulfide bonds which are more labile to mercaptan reduction appear to be associated with complement-fixing efficiency while the disulfide bonds which are more resistant to mercaptan reduction appear to be associated with precipitating ability. The measurement of interpolypeptide chain disulfide bonds has been discussed. One easily reduced interchain disulfide bond [S—S₍₁₎] appears to be important for the complement-fixing efficiency of 7S rabbit antibody. The integrity of this same bond is essential for the precipitating ability of 5S rabbit antibody and may also be important for its complement-fixing ability.

THE FORMATION AND PROPERTIES OF POLIOVIRUS-NEUTRALIZING ANTIBODY. II. 19S AND 7S ANTIBODY FORMATION: DIFFERENCES IN ANTIGEN DOSE REQUIREMENT FOR SUSTAINED SYNTHESIS, ANAMNESIS, AND SENSITIVITY TO X-IRRADIATION

Transient 19S antibody formation was induced in rabbits by single or repeated stimuli with a small dose of poliovirus. Available evidence indicated that cessation of 19S synthesis was due to lack of continuous antigenic stimulation and not to loss of cells participating in antibody formation. "Immunological memory" in 19S antibody formation was demonstrable only within 2 to 3 days following discontinuation of synthesis but not thereafter. Following stimulation with a high dose of polio-virus both 19S and 7S antibodies were formed. The kinetics of their formation differed in several respects: (a) 19S antibody preceded 7S antibody by ⩾1½ days; (b) 19S antibody rose to peak titers at a rapid exponential rate within 1 week, while 7S antibody increased at a slow decelerating rate for ⩽3 weeks; (c) 19S antibody formation was short-lasting while 7S antibody synthesis endured. A renewed formation of both antibodies occurred following restimulation with a high antigen dose. The secondary 19S and 7S antibody responses were similar to the respective primary responses, and the preexistence of 7S antibody synthesis did not detectably alter the secondary 19S response. Both 19S and 7S antibodies were formed and the kinetics of their formation was similar (a) for infectious and non-infectious (UV-) poliovirus antigen; (b) for the serologically unrelated poliovirus and Coxsackie B-4 virus; (c) when poliovirus was administered by different routes; (d) when 1-day-old or adult rabbits were immunized; (e) in antibody responses to poliovirus in rabbit, guinea pig, and man. Whole body x-irradiation 20 hours prior to antigenic stimulus (high dose) resulted in delayed but markedly prolonged 19S antibody formation and inhibition of 7S antibody synthesis. Thus, the formation of 19S and 7S antibody differed in (a) antigen dose requirements for induction and maintained synthesis; (b) kinetics; (c) retention of memory; and (d) sensitivity to prior x-irradiation. These differences are best explained on the assumption that the two antibodies are produced by different cells.

THE IMMUNOGLOBULINS OF MICE. V. THE METABOLIC (CATABOLIC) PROPERTIES OF FIVE IMMUNOGLOBULIN CLASSES

The metabolic properties of immunoglobulin were investigated by comparing five classes of mouse immunoglobulin. Three forms of 7S immunoglobulin had different rates of catabolism. The fractional rates of catabolism were found to be about 13 per cent per day for 7S γ_2a-globulin; 25 per cent for 7S γ_2b-globulin; and 17 per cent for 7S γ₁-globulin. Catabolism of the three classes of 7S γ-globulin (γ_2a, γ_2b, and γ₁) were prolonged at low serum 7S γ-globulin levels and accelerated at high serum 7S γ-globulin levels. Each of the 7S γ-globulin components was influenced by the serum level of the other mouse 7S γ-globulin components and by exogenously administered human 7S γ-globulin. They were not appreciably altered, however, by the serum level of IgA (γ₁A-, β₂A-globulin). The progressively changing (longer) half-times observed in turnover studies of normal IgG (7S γ-globulin) may be caused by catabolic heterogeneity of normal 7S immunoglobulins which are immunochemically and catabolically related to γ_2a-, γ_2b-, and 7S γ₁-myeloma proteins. These studies indicate that the 7S γ_2a-, 7S γ_2b-, and 7S γ₁-globulins share a common catabolic control mechanism. This mechanism is influenced by the serum level of each of these components, but is independent of the serum level of IgA (γ₁A-globulin) and probably is independent of IgM (γ₁M-globulin). Catabolism of IgA (γ₁A-, β₂A-globulin) and IgM (γ₁M-globulin) was much more rapid than the catabolism of the 7S γ-globulins. The halftimes of the IgA and IgM were approximately 1.2 and 0.5 days respectively. The fractional rate of catabolism of IgA and IgM seemed to be independent of their serum concentration. The rate of catabolism, as well as the rate of synthesis, was shown to play a major role in determining the serum level of each class of immunoglobulin.

THE FORMATION AND PROPERTIES OF POLIOVIRUS-NEUTRALIZING ANTIBODY. III. SEQUENTIAL CHANGES IN ELECTROPHORETIC MOBILITY OF 19S AND 7S ANTIBODIES SYNTHESIZED BY RABBITS AFTER A SINGLE VIRUS INJECTION

Rabbits injected intravenously with a single high dose of poliovirus (type 1) produced two major 19S and two 75 type neutralizing antibody populations, with different electrophoretic mobilities. The first 2 to 2½ days after immunization the antibody was of the 19S type and migrated as a single component in the β-region. In contrast, the major 19S antibody synthesized from day 3 on was a γ₁-globulin. 7S type antibody, appearing on day 4, was contained only in the γ₁-region, while 10 to 14 days following immunization the 7S antibody was associated with both γ₁- and γ₂-globulins. The electrophoretic distribution of antibody in 2-week sera revealed the presence of at least four antibody populations (19S β, 19S γ₁, 7S γ₁, and 7S γ₂). Serum samples collected 1 or 2 weeks following antigenic stimulation often contained small amounts of antibody which sedimented at a rate (11S to 15S) intermediate to that of 7S and 19S antibodies. The neutralizing activity of the 19S type antibodies and the intermediately sedimenting antibody was destroyed by incubation with 0.1 M (5 days) or 0.2 M (1 day) 2-mercaptoethanol at 3°C. The 7S antibody activity was un-affected by treatment with from 0.1 to 0.8 M mercaptan.

ANTIBODY RESPONSE TO IMMUNIZATION BY DIFFERENT ROUTES

Rabbits were injected with human serum albumin once intravenously or intradermally with this antigen plus complete Freund adjuvant. The hemagglutinating titers of the antiserum and of the heavy and light antibody fractions were followed for several months. Circulation of heavy antibody in the intravenously injected group disappeared in 1 month, but in the intradermally injected group, it rose to a maximum titer, then declined, and then showed a second rise in titer. Light antibody showed increasing and then sustained titers over most of the time period. Heavy antibody failed to precipitate with antigen, even when it showed high hemagglutinating titers. Light antibody, in contrast, gave precipitation even when tested at much lower hemagglutination titers

SINGLE CELL STUDIES ON 19S ANTIBODY PRODUCTION

Rats were immunized with Salmonella adelaide flagella. By zone centrifugation of serum samples in sucrose gradients, it was shown that, as in many other systems of antibody formation, the first response was the formation of 19S, mercaptoethanol (ME)-sensitive antibody. This was quickly replaced by 7S, ME-insensitive antibody. Popliteal lymph node cell suspensions were prepared, and cells with antibody on their surface were identified by the method of bacterial adherence. By micromanipulation such cells were washed, placed into microdroplets, examined under high-power phase contrast and broken to release intracellular antibody. These droplets were then studied in either of two ways. In the first method, each droplet was halved and one half treated with ME. Then both halves were titrated for immobilizing antibody through serial twofold dilution of the half microdroplets. Droplets showing destruction of antibody by ME were classified as 19S; those showing no reduction in titer as 7S; and those showing significant (>1 log(2)) reduction as double producers; i.e., cells containing both 7S and 19S antibodies. In the second method, droplets were divided into 4 equal quarters, for testing after treatment with either ME, or a specific rabbit anti-rat 7S globulin serum, or both. In these experiments, cells showing some remaining antibody after treatment with either reagent, but not after treatment with both reagents, were classified as double producers. Of 144 cells tested, 123 contained readily detectable amounts of antibody. These comprised 42 19S cells, 64 7S cells, and 17 double producers. The double producers were frequent at times when the switchover from 19S to 7S antibody production was occurring. All except 4 of the cells in the study could clearly be identified as members of the plasma cell series. Though 7S cells became more frequent as the cell population matured, no clear-cut correlation between cell immaturity and 19S production could be obtained. In the primary response many fully mature plasma cells contained only 19S antibody; conversely, in the secondary response many blasts contained 7S antibody. No morphological difference between 19S and 7S cells could be found. The results suggested that many cells or cell clones go through a sequence whereby each forms first 19S and later 7S antibody with identical combining sites.

THE FORMATION AND PROPERTIES OF POLIOVIRUS-NEUTRALIZING ANTIBODY. I. 19S AND 7S ANTIBODY FORMATION: DIFFERENCES IN KINETICS AND ANTIGEN DOSE REQUIREMENT FOR INDUCTION

Rapid formation of poliovirus-neutralizing antibody was observed in the rabbit. 19S type antibody was detectable 8 to 12 hours following a single intravenous virus injection and the induction period was of the order of 4 to 5 hours or less. The production of 7S antibody had a longer lag phase (1½ to 2 days) and it was formed at slower rate. The observed rate of early 19S and 7S antibody formation as well as the peak titers of the two antibodies were antigen dose dependent. Normal rabbit sera showed low neutralizing activity to several viral antigens in a sensitive assay system. Following intravenous inoculation of poliovirus either transitory (⩽ 1 month) or enduring (¾ to 1½ year) antibody formation resulted depending upon the dose of antigen employed. In transitory responses, which could be induced by a single small antigen dose, only 19S antibody was demonstrable and there was an abrupt cessation of antibody synthesis on day 4 or 5. In enduring responses, both 19S and 7S antibody were formed and the minimum antigen dose required for initiation of such a response was equal to the dose needed for induction of 7S antibody formation. Thus, enduring antibody formation was an all-or-none phenomenon depending upon whether or not 7S antibody formation was induced. The antigen dose requirement for induction of 7S antibody was much higher (by 50-fold or more) than that for 19S antibody. This allowed a determination of antigen dose regions, within which predictably transitory (19S) or enduring (19S + 7S) antibody formation was obtained. These pronounced differences in antigen dose requirement for induction and kinetics of formation of 19S and 7S antibody suggest that the same cells do not participate in the formation of the two antibodies.

ANTIBODY SYNTHESIS AT THE CELLULAR LEVEL. ANTIBODY-INDUCED SUPPRESSION OF 19S AND 7S ANTIBODY RESPONSE

The suppressing activity of passively transferred antibodies on antibody synthesis against sheep red cells was investigated at the cellular level by the agar-plaque technique developed by Jerne. Humoral antibodies injected prior to the antigen suppressed the appearance of plaque-forming spleen cells producing 19S antibodies completely. Antibodies given during the first 4 days after antigen injection also showed such action, but only after a latency period of 40 hours. The inhibiting efficiency of 7S antibodies was about 100 to 200 times greater than that of 19S antibodies. The results support the conclusion that humoral antibodies inhibit the immune response by removing the stimulus for the proliferation of the antibody producing cells and not by directly depressing antibody synthesis in already committed cells. Passively transferred antibodies inhibited the 7S response if given prior to, or 24 hours after the antigen injection, in analogy with previous results concerning 19S response. In contrast to these previous results on 19S synthesis, antibody transfer had no detectable effect during the early exponential phase of 7S production (5 to 7 days after antigen injection). Only limited inhibition was observed 3 days after the antigen. One possible explanation of this difference is that 7S-producing cells do not divide, or divide at a slow rate. Antigen injection would stimulate the proliferation of 19S-producing cells. Subsequently these would switch to the synthesis of 7S antibodies. These would inhibit the initiation of new 19S-producing cells by combining with the antigen. They would thus suppress the recruitment of their own precursors. A steady state of 7S antibody production by cells with a long lifetime would be the result. This hypothesis ascribes an important regulatory function to 7S antibodies. They would be parts of a feed-back system preventing excessive cell multiplication in response to a single antigen.

ANTIGEN-BINDING ACTIVITY OF 6S SUBUNITS OF BETA-2-MACROGLOBULIN ANTIBODY

Direct evidence is provided for the antigen binding activity of the 6S subunits formed by reduction and alkylation of rabbit beta2-macroglobulin antibody. Binding activity of the subunits was clearly demonstrated by radioimmunoelectrophoresis with a preparation of purified rabbit antibody against the p-azobenzenearsonate group, which contained 40 percent of beta2M-antibody. The precipitate arc formed between the subunits and sheep antiserum against rabbit macroglobulin was shown to bind radioactive antigen specifically.

Chicken immunoglobulin mu-chain gene: germline organization and tandem repeats characteristic of class switch recombination

We have isolated the phage clones covering the region spanning from the heavy (H)-chain joining (J) region to the end of the mu-chain gene of the chicken immunoglobulin (Ig). The distance from JH to the first exon of the mu-chain constant (C) region is approximately 13 kb, and introns between the C region exons measure more than 3 kb. These distances are significantly larger than those of known mu-chain genes. We found a region cross-hybridizing to the switch regions of the mouse C mu and C alpha genes just in front of the first exon of C mu. Partial nucleotide sequencing of this region revealed that this region consists of tandem repeats of pentamers (C/T)(C/A)CAG complementary to the mammalian switch repetitive region. These findings suggest that this region is a good candidate for a class switch region of the mu-chain gene of chicken Ig.

Studies of the protective effect of different fractions of sera from pigs immune to Streptococcus suis type 2 infection

Inoculation of mice with high doses of Streptococcus suis type 2 caused depression, anorexia, lethargy and sometimes death. This was prevented by prior inoculation of whole immune pig serum, the IgM and IgG fractions of immune pig serum and serum enriched with antibody to surface antigens. Clinical signs were not prevented by prior inoculation of pre-immune serum or serum depleted of antibody to surface antigens. Serum fractions that were protective in vivo were also opsonic in vitro. Western blot analysis identified two antigens of 44 and 78 kd that were recognized strongly by protective sera and a further four of 86, 94, 130 and 136 kd that were recognized less intensely.

[Pathologico-anatomic findings in sudden, unexpected death in children and adults with influenza A infection]

Thé following observations resulted from studies on forensic autopsy cases: In 76% of the adults and 55% of the infants the cases of unexpected sudden death without morphologically verifiable causes of death showed virologic evidence of recent influenza-A (H3N2)-infection. The pathologic findings corresponded with the findings in lethal infections with influenza-A viruses. Investigation of cases of sudden and unexpected death should always include virologic serum tests. The demonstration of IgM antibodies against influenza-A virus confirms that there was a recent infection. Death from influenza-A infections occurs also in the interepidemic periods.

Simultaneous immunofluorimetric quantitation of IgM and IgG in single splenic lymphoid cells after immunization

The amount of IgM and IgG was determined in individual mouse spleen lymphocytes by double immunofluorimetry after "staining" with dimethylamino-naphthaline sulfonyl chloride-labeled anti-IgM and fluorescein isothiocyanate-labeled anti-IgG. During a single immune response against sheep erythrocytes there was an inverse relationship between the amounts of these two immunoglobulins in individual cells. There was an early steep increase of the cellular amount of IgM during the first 3 days after immunization. Subsequently IgG increased exceeding the initial IgG levels while IgM decreased. Most cells containing high amounts of IgM had a low IgG content and vice versa. The present results directly demonstrate a quantitative switch from IgM to IgG in individual cells on the single cell level after an antigenic stimulus. This indicates simultaneous active production of both immunoglobulins in these cells. For an explanation of this phenomenon differential mRNA splicing rather than DNA rearrangement as an underlying process for immunoglobulin expression may be proposed in these early B-cells.

Optimal strategies in immunology III. The IgM-IgG switch

During a primary immune response generally two classes of antibody are produced, immunoglobulin M (IgM) and immunoglobulin G (IgG). It is currently thought that some lymphocytes which initially produce IgM switch to the production of IgG with the same specificity for antigen. During a secondary immune response IgG is the predominant antibody made throughout the response. In this paper we address the question of why such apparently complicated modes of response should have been adapted by evolution. We construct mathematical models of the immune response to growing antigens which incorporate complement dependent cell lysis. By comparing the times required to eliminate antigen we show that under certain conditions it is advantageous for an animal to switch some of its lymphocytes from IgM to IgG production during a primary response, but yet to secrete only IgG during a secondary response. The sensitivity of such a conclusion to parameter variations is studied and the biological basis and implications of our models are fully discussed.

Induction of a stable hapten-specific immunosuppression by a hapten conjugated to poly(N-vinylpyrrolidone) (PVP)

The ability of a hapten coupled to a clinically permissive synthetic polymer (NIP-PVP) to induce suppression was investigated. NIP coupled to the low molecular weight non-immunogenic form of poly(N-vinylpyrrolidone) (PVP) was found to be capable of inducing a hapten-specific longlasting suppression of both primary and secondary responses. The previous use of PVP as a plasma expander in humans makes this polymer a potentially suitable tool for the induction of specific immunosuppression to a variety of clinically important drug and tissue specific epitopes. The possible use of low molecular weight PVP for that purpose will be investigated further, specifically with larger antigenic components.

Stimulation of antibody synthesis induced by surgical trauma in rats

The effect of a standard laparatomy on antibody synthesis was studied in Wistar R/A rats recieving an intravenous injection of 10(9) sheep red blood cells (SRBC) during the surgical procedure. Anti-SRBC antibody titres were significantly higher in operated animals than in controls. When SRBC were given 2 hr after the surgical procedure, stimulation of antibody synthesis still persisted, but when the antigen was administered 24 hr after laparotomy, no significant difference could be detected between the operated animals and controls. Surgery also enhances the secondary humoral response.

Immunoglobulin M specific for measles in serum and cerebrospinal fluid of patients with multiple sclerosis and other neurological diseases

Serum and cerebrospinal fluid of patients with multiple sclerosis, subacute sclerosing panencephalitis and other neurological disease have been tested by the indirect fluorescent antibody method for immunoglobulin M specific for measles. Only sera of three patients were positive. This feature is of little statistical importance. Nevertheless the authors emphasize the role of a possible viral infection in the pathogenesis of multiple sclerosis.