The French Epidemic Intelligence System: comparing disease surveillance at the national and international level using data from the Program for Monitoring Emerging Diseases.

In a context of globalisation and climate change, the risk of emerging infectious diseases spreading around the world has significantly increased in the past decades. In response to this growing threat, an epidemic intelligence team has been set up within the framework of the French animal health epidemiological surveillance platform (ESA platform). The French Epidemic Intelligence System (FEIS) monitors animal health risks in Europe and beyond that threaten animal populations in France (emerging and exotic diseases not yet present). The FEIS expert network covers all 53 category 1 health hazards identified as priority diseases by the French authorities. From January 2016 to December 2017, the FEIS published 126 reports on animal health events related to infectious diseases, of which 76.2% were related to events in Europe. When comparing FEIS reports to posts from the Program for Monitoring Emerging Diseases (ProMED), an FEIS report was produced for 52.6% of ProMED themes (combinations of disease and country) posted in 2016-2017 on events in Europe. The remaining European ProMED themes did not meet the criterion for the production of an FEIS report because either the disease was already present in France, the risk of introduction into France was considered low or negligible, or the introduction of the pathogen would have low or negligible economic and societal impacts. The FEIS efficiently detected and reported on all health hazards identified by ProMED to alert health authorities and stakeholders when needed (according to the criterion). Compared with international epidemic intelligence systems such as ProMED, which provide general information, the FEIS adds another layer of filtering and interpretation to available information on animal health threats tailored to France's specific needs, in order to communicate only essential information to health authorities.

Dans un contexte caractérisé par la mondialisation et le changement climatique, le risque de propagation mondiale des maladies infectieuses émergentes s'est significativement accru en quelques décennies. Pour répondre à cette menace croissante, une équipe de veille épidémique a été mise en place dans le cadre de la Plateforme française d'épidémiosurveillance en santé animale (Plateforme ESA). Le système de Veille sanitaire internationale (VSI) surveille les risques sanitaires en santé animale présents en Europe, voire au-delà, dès lors qu'ils représentent une menace pour les populations animales sur le territoire français (maladies émergentes et maladies exotiques jamais introduites en France). Le réseau d'experts de la VSI couvre les 53 risques sanitaires de catégorie 1 définis par les autorités françaises comme maladies prioritaires. De janvier 2016 à décembre 2017, 126 rapports de la VSI ont été publiés sur des événements de santé animale liés à des maladies infectieuses, dont 76,2 % concernaient des événements survenus en Europe. La comparaison entre les rapports émanant de la VSI et ceux du Programme de suivi des maladies émergentes (ProMED) fait apparaître que 52,6 % des thématiques publiées en 2016-2017 par ProMED (associant une maladie et un pays) relatives à des événements survenus en Europe avaient également fait l'objet d'un rapport par la VSI. Les thématiques restantes sur ProMED correspondant à des événements européens ne répondaient pas aux critères de la VSI, soit parce qu'il s'agissait d'une maladie déjà présente en France, soit parce que le risque d'introduction de l'agent pathogène en France était considéré comme faible ou négligeable, soit enfin parce que l'impact économique et sociétal d'une telle introduction, si elle survenait, aurait été faible ou négligeable. La VSI a détecté (en fonction de ses critères) l'ensemble des risques sanitaires identifiés par ProMED et les a notifiés avec efficacité aux autorités et acteurs en charge de la santé, chaque fois que nécessaire. Par rapport aux systèmes de veille sanitaire internationaux tels que ProMED qui fournissent des informations générales, la VSI, qui est spécifiquement adaptée aux besoins français, ajoute une strate supplémentaire de filtrage et d'interprétation des données disponibles sur les menaces de santé animale, afin de ne transmettre aux autorités sanitaires que les informations qui leur sont essentielles.

De unos decenios a esta parte, en un contexto marcado por la mundialización y el cambio climático, ha aumentado sustancialmente el riesgo de propagación por todo el mundo de enfermedades infecciosas emergentes. Para responder a esta creciente amenaza se ha establecido, dentro del dispositivo francés de vigilancia epidemiológica zoosanitaria (plataforma ESA), un equipo de inteligencia epidemiológica. El Sistema Francés de Información Epidemiológica (épidémiologique) está dedicado a seguir de cerca los riesgos zoosanitarios que, desde Europa u otras partes del mundo, amenacen a las poblaciones animales de Francia (enfermedades emergentes y exóticas que aún no estén presentes en el país). La red de especialistas de la VSI cubre la totalidad de los 53 peligros sanitarios de categoría 1 que las autoridades francesas tienen definidos como enfermedades prioritarias. Entre enero de 2016 y diciembre de 2017, la VSI publicó 126 informes sobre episodios zoosanitarios relacionados con enfermedades infecciosas, de los que un 76,2% tenían que ver con episodios ocurridos en Europa. Al comparar los informes de la VSI con las notas publicadas por el Programa de Vigilancia de Enfermedades Emergentes (ProMED) se constató que ela VSI había elaborado un informe en relación con el 52,6% de los temas (combinación de enfermedades y países) tratados por el ProMED en sus notas de 2016 y 2017 sobre episodios ocurridos en suelo europeo. Los restantes temas europeos tratados por el ProMED no cumplían el criterio de que hubiera un informe de la VSI al respecto, ya fuera porque la enfermedad ya estaba presente en Francia, porque se consideró bajo o insignificante el riesgo de penetración en Francia o porque la llegada del patógeno tendría una repercusión escasa o insignificante en la economía o la sociedad. La VSI detectó y comunicó con eficacia todos los peligros sanitarios identificados por el ProMED para alertar a las autoridades sanitarias y demás interlocutores cada vez que fue necesario (con arreglo al criterio). En comparación con los sistemas internacionales de información epidemiológica, como el ProMED, que proporcionan información general, la VSI agrega un filtro y un nivel de interpretación suplementarios a la información disponible sobre amenazas zoosanitarias, adaptándola así a las necesidades específicas de Francia, con el fin de comunicar únicamente información esencial a las autoridades sanitarias.

Biosurveillance: a systematic review of global infectious disease surveillance systems from 1900 to 2016.

Biosurveillance is crucial to detect, identify and minimise the negative consequences of infectious disease. Its value to society and importance to global public health and global health security are growing. Despite the long history and global importance of biosurveillance, a systematic review of all existing biosurveillance systems across the 'One Health' spectrum has not yet been published. This study conducted a systematic review to identify all extant and defunct biosurveillance systems from 1900 to 2016. Of the 815 systems examined, the majority surveyed human, animal or plant data discretely. Some 105 collected human and animal data, whereas only 31 collected data on all three categories. The authors found a large increase in the number of global biosurveillance systems between 1900 and 2008, but a reduction in the number of biosurveillance systems from 2008 to the present. The number of syndromic systems created, versus laboratory-based biosurveillance systems, increased rapidly after 1980 across the globe.

La surveillance biologique est un procédé essentiel pour détecter, caractériser et minimiser les effets négatifs des maladies infectieuses. Son rôle à l'égard de la société et son importance pour la santé publique et la sécurité sanitaire mondiale ne cessent de croître. Malgré l'histoire déjà longue et l'importance mondiale de la surveillance biologique, aucun inventaire systématique des systèmes de surveillance biologique mis en œuvre dans une perspective « Une seule santé ¼ n'avait été publié jusqu'à ce jour. La présente étude résume les résultats d'un examen systématique portant sur tous les systèmes de surveillance biologique appliqués entre 1900 et 2016, qu'ils aient été arrêtés ou qu'ils soient encore utilisés aujourd'hui. La majorité des 815 systèmes examinés exploite des données relatives soit aux êtres humains, soit aux animaux, soit aux plantes. Près de 105 systèmes recueillent à la fois des données sur l'être humain et sur les animaux et 31 systèmes seulement recueillent des données sur les trois catégories en même temps. Les auteurs ont constaté une forte augmentation du nombre de systèmes de surveillance biologique dans le monde entre 1900 à 2008, puis un déclin de ce nombre entre 2008 et aujourd'hui. Le nombre de systèmes syndromiques, par opposition aux systèmes de surveillance biologique basés sur les examens de laboratoire a connu une augmentation rapide dans le monde entier à partir de 1980.

La vigilancia biológica (o biovigilancia), indispensable para discernir, detectar y reducir al mínimo las consecuencias negativas de una enfermedad infecciosa, reviste cada vez más interés para la sociedad y más importancia para la salud pública y la seguridad sanitaria mundiales. Pese a la dilatada historia y a la relevancia mundial de la vigilancia biológica, hasta ahora nunca se había publicado un examen sistemático de todos los sistemas de biovigilancia existentes dentro del espectro de «Una sola salud¼. Los autores describen un estudio encaminado a examinar de forma sistemática todos los sistemas de vigilancia biológica, aún vigentes o ya extintos, instaurados entre 1900 y 2016. La mayoría de los 815 sistemas examinados estaban dedicados a la vigilancia específica de las personas, los animales o las plantas. En unos 105 se obtenían datos de humanos y anímales, y solo en 31 de ellos se recogían datos de las tres categorías. Los autores observaron un marcado incremento del número de sistemas mundiales de biovigilancia entre 1900 y 2008, número que en cambio se fue reduciendo a partir de 2008. De 1980 en adelante se aceleró en todo el globo la creación de sistemas sindrómicos, por oposición a sistemas de biovigilancia basados en el trabajo en laboratorio.

Maternal immunization of mice with group B streptococcal type III polysaccharide-beta C protein conjugate elicits protective antibody to multiple serotypes.

Group B streptococcal infection is a major cause of neonatal mortality. Antibody to the capsular polysaccharide protects against invasive neonatal disease, but immunization with capsular polysaccharides fails to elicit protective antibody in many recipients. Conjugation of the polysaccharide to tetanus toxoid has been shown to increase immune response to the polysaccharide. In animal models, C proteins of group B streptococci are also protective determinants. We examined the ability of the beta C protein to serve in the dual role of carrier for the polysaccharide and protective immunogen. Type III polysaccharide was covalently coupled to beta C protein by reductive amination. Immunization of rabbits with the polysaccharide-protein conjugate elicited high titers of antibody to both components, and the serum induced opsonophagocytic killing of type III, Ia/C, and Ib/C strains of group B streptococci. Female mice were immunized with the conjugate vaccine and then bred; 93% of neonatal pups born to these dams vaccinated with conjugate survived type III group B streptococcal challenge and 76% survived type Ia/C challenge, compared with 3% and 8% survival, respectively, in controls (P < 0.001). The beta C protein acted as an effective carrier for the type III polysaccharide while simultaneously induced protective immunity against beta C protein--containing strains of group B streptococci.

Biopsy diagnosis of Creutzfeldt-Jakob disease by western blot: a case report.

Creutzfeldt-Jakob disease is a clinically and pathologically heterogeneous disorder that often requires brain biopsy for definitive diagnosis. We report the case of a 62-year-old man who underwent brain biopsy for progressive neurological deterioration. Histopathologically, there was minimal spongiform change that could not be unequivocally attributed to Creutzfeldt-Jakob disease. A 16 mg portion of gray matter saved frozen was subsequently analyzed by Western blot and showed definitive protease-resistant prion protein. This case illustrates applicability, ease in interpretation, and accuracy of Western blot analysis for protease-resistant prion protein in small brain biopsy specimens. Given the importance of accurate diagnosis in suspected prion disease, we recommend that a small portion of tissue from any brain biopsy performed in this setting be kept frozen for possible biochemical studies.

Pyogenic liver abscesses.

Pyogenic liver abscess is a classic clinical entity whose presentation and management have evolved significantly with the advent of potent antimicrobials and the availability of improved diagnostic imaging. The classic triad of fever, upper right quadrant pain or fullness, and jaundice resulting from advanced pylephlebitis is now seldom seen. Despite these changes, pyogenic liver abscess remains an important clinical entity for which prompt recognition and treatment are essential to achieve a favorable outcome. This article discusses the presentation and diagnosis of and current therapy for liver abscesses.

Cloning and expression in Escherichia coli of a protective surface protein from type V group B streptococci.

This report describes a trypsin-resistant laddering protein purified from a type V strain, a serotype of important emerging clinical significance. This protein is present in a majority of type V clinical strains, elicits protective antibody in an animal model, and is cross-reactive with the alpha C protein and R1. The gene encoding this protein has been cloned; preliminary nucleotide sequence analysis reveals significant homology, though not identity, with the alpha C protein gene. These data support the hypothesis that there exists a family of related but distinct GBS surface proteins which may play a role in immunity to GBS infection.

An overview of internet biosurveillance.

Internet biosurveillance utilizes unstructured data from diverse web-based sources to provide early warning and situational awareness of public health threats. The scope of source coverage ranges from local media in the vernacular to international media in widely read languages. Internet biosurveillance is a timely modality that is available to government and public health officials, healthcare workers, and the public and private sector, serving as a real-time complementary approach to traditional indicator-based public health disease surveillance methods. Internet biosurveillance also supports the broader activity of epidemic intelligence. This overview covers the current state of the field of Internet biosurveillance, and provides a perspective on the future of the field.

Landscape of international event-based biosurveillance.

Event-based biosurveillance is a scientific discipline in which diverse sources of data, many of which are available from the Internet, are characterized prospectively to provide information on infectious disease events. Biosurveillance complements traditional public health surveillance to provide both early warning of infectious disease events and situational awareness. The Global Health Security Action Group of the Global Health Security Initiative is developing a biosurveillance capability that integrates and leverages component systems from member nations. This work discusses these biosurveillance systems and identifies needed future studies.

A protective surface protein from type V group B streptococci shares N-terminal sequence homology with the alpha C protein.

Infection by group B streptococci (GBS) is an important cause of bacterial disease in neonates, pregnant women, and nonpregnant adults. Historically, serotypes Ia, Ib, II, and III have been most prevalent among disease cases; recently, type V strains have emerged as important strains in the United States and elsewhere. In addition to type-specific capsular polysaccharides, many GBS strains possess surface proteins which demonstrate a laddering pattern on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and resistance to trypsin digestion. These include the alpha C protein, the R proteins, and protein Rib. Some of these proteins elicit protective antibodies in animals. We demonstrate a trypsin-resistant laddering protein purified from a type V GBS strain by mutanolysin extraction and column chromatography. This protein contains a major 90-kDa band and a series of smaller bands spaced approximately 10 kDa apart on SDS-PAGE. Cross-reactivity of the type V protein with the alpha C protein and with R1 was demonstrated on Western blot (immunoblot). N-terminal sequence analysis of the protein revealed residue identity with 17 of 18 residues at corresponding positions on the alpha protein. Western blot of SDS extracts of 41 clinical type V isolates with rabbit antiserum to the protein demonstrated a homologous protein in 25 isolates (61%); two additional strains exhibited a heterologous pattern which was also demonstrated with 4G8, a monoclonal antibody directed to the alpha C protein repeat region. Rabbit antiserum raised to the type V protein conferred protection in neonatal mice against a type V strain bearing a homologous protein. These data support the hypothesis that there exists a family of trypsin-resistant, laddering GBS surface proteins which may play a role in immunity to GBS infection.

Regulation of cell component production by growth rate in the group B Streptococcus.

Group B Streptococcus (GBS) is the leading cause of bacterial sepsis and meningitis among neonates. While the capsular polysaccharide (CPS) is an important virulence factor of GBS, other cell surface components, such as C proteins, may also play a role in GBS disease. CPS production by GBS type III strain M781 was greater when cells were held at a fast (1.4-h mass-doubling time [td]) than at a slow (11-h td) rate of growth. To further investigate growth rate regulation of CPS production and to investigate production of other cell components, different serotypes and strains of GBS were grown in continuous culture in a semidefined and a complex medium. Samples were obtained after at least five generations at the selected growth rate. Cells and cell-free supernatants were processed immediately, and results from all assays were normalized for cell dry weight. All serotypes (Ia, Ib, and III) and strains (one or two strains per serotype) tested produced at least 3.6-fold more CPS at a td of 1. 4 h than at a td of 11 h. Production of beta C protein by GBS type Ia strain A909 and type Ib strain H36B was also shown to increase at least 5.5-fold with increased growth rate (production at a td of 1. 4 h versus 11 h). The production of alpha C protein by the same strains did not significantly change with increased growth rate. The effect of growth rate on other cell components was also investigated. Production of group B antigen did not change with growth rate, while alkaline phosphatase decreased with increased growth rate. Both CAMP factor and beta-hemolysin production increased fourfold with increased growth rate. Growth rate regulation is specific for select cell components in GBS, including beta C protein, alkaline phosphatase, beta-hemolysin, and CPS production.

Deletion of repeats in the alpha C protein enhances the pathogenicity of group B streptococci in immune mice.

The alpha C protein is a protective surface-associated antigen of group B streptococci (GBS). The prototype alpha C protein of GBS (strain A909) contains nine identical tandem repeats, each comprising 82 amino acids, flanked by N- and C-terminal domains. Clinical isolates of GBS show variable numbers of repeats with a normal distribution and a median of 9 to 10 repeats. Here, we show that escape mutants of GBS expressing one-repeat alpha C protein were 100-fold more pathogenic than GBS expressing wild-type nine-repeat alpha C protein in neonatal mice whose dams were immunized with antiserum elicited to nine-repeat alpha C protein (50% lethal doses of 1.6 x 10(3) and 1.8 x 10(5), respectively; P = 0.0073). There was no difference in pathogenicity in nonimmune mice. Enzyme-linked immunosorbent assay inhibition showed that nine-repeat but not one-repeat alpha C protein is readily available for antibody binding on the surface of intact GBS. Immune electron microscopy studies with antibodies to the capsular polysaccharide (CPS) and to the alpha C protein demonstrated localization of the nine-repeat alpha C protein and the CPS at similar distances from the cell wall. The one-repeat alpha C protein was visualized poorly and only in close proximity to the cell wall, thus suggesting that antibody binding to the protein was hindered by CPS or other cell surface components. We concluded that deletion in the repeat region of the alpha C protein enhanced the pathogenicity of GBS in immune mice by (i) loss of a protective (conformational) epitope(s) and (ii) loss of antibody binding to the alpha C protein due to a decrease in antigen size relative to cell wall components and/or CPS.

A monoclonal antibody identifies a protective C-protein alpha-antigen epitope in group B streptococci.

Group B streptococci (GBS) are the leading causes of neonatal sepsis and meningitis in the United States, with a high rate of fatality and serious morbidity despite appropriate therapy. The C-protein antigens of GBS appear to be important in immunity to experimental infection, yet these antigens remain incompletely characterized with respect to their number, structure, and function. None of these proteins has yet been purified to homogeneity. We have developed a novel method for extraction of surface proteins from the A909 (Ia/c) strain of GBS by using mutanolysin. Antibodies raised in rabbits against these partially purified proteins conferred passive protection to lethal GBS infection in mice challenged with a GBS strain expressing C proteins with a heterologous capsule type. In addition, mouse monoclonal antibodies were produced and identified by reactivity with the mutanolysin-extracted proteins. One of these monoclonal antibodies (4G8) identifies an epitope on the alpha-antigen of the GBS C proteins (identified by protease susceptibility and mouse protection). On sodium dodecyl sulfate-polyacrylamide gels, this epitope appears as a series of regularly spaced bands ranging in apparent molecular mass from 160,000 to 30,000 Da. The monoclonal antibody 4G8 induces opsonic killing of GBS and protects mice from lethal challenge with GBS. Thus, the 4G8 monoclonal antibody identifies a fully protective epitope on the C-protein alpha-antigen of GBS.

Mosaicism in the alpha-like protein genes of group B streptococci.

Members of a family of repeat-containing surface proteins of group B streptococci (GBS) defined by the alpha C and Rib proteins exhibit size variability and cross-reactivity and have been studied as potential vaccine components. We report evidence of horizontal DNA transfer with subsequent recombination as a mechanism generating diversity within this antigen family. Alp2 and Alp3 are additional members of the alpha C protein family identified in strains of the emerging GBS serotypes V and VIII. Each contains an overall genetic organization highly similar to that of the alpha C and Rib proteins, including a tandem repeat region and conserved N- and C-terminal regions. Among different strains, protein size varies according to the number of tandem repeats within the corresponding gene. Unlike the alpha C and Rib proteins, however, the newly described alpha-like proteins contain other regions, including one similar to the IgA-binding region of the GBS beta C protein, a nontandem repeat region, and an isolated repeat highly homologous to the alpha C repeat. Sequence analysis of the regions flanking the alpha C protein gene on a 13.7-kb insert reveals several ORFs that are likely to be involved in basic metabolic pathways. Analysis of corresponding flanking regions in other GBS strains, including the parent strains of the newly described alpha-like proteins, shows striking conservation among all strains studied. These findings indicate that the alpha-like proteins are encoded by mosaic variants at a single genomic locus and suggest that recombination after horizontal DNA transfer is a means of generating diversity within this protein family.

Phenotypic diversity in the alpha C protein of group B streptococci.

Group B streptococci (GBS) is the leading cause of neonatal sepsis and meningitis. C proteins are an immunologically important group of surface-associated antigens in GBS that remain incompletely characterized. Two C proteins have been designated alpha and beta on the basis of protease susceptibility. We recently used a monoclonal antibody to describe a protective epitope of the GBS alpha (or trypsin-resistant) C protein in the prototype Ia/c GBS strain. In the present study, we examined 51 GBS isolates for expression of C-protein alpha and beta antigens. The alpha antigen, as detected with monoclonal antibody in sodium dodecyl sulfate (SDS) extracts, appears as a heterogeneous series of proteins spaced 8 kDa apart on SDS-polyacrylamide gel electrophoresis, but has a maximum molecular mass that varies among strains from 62.5 to 167 kDa. By immunoblotting with human immunoglobulin A, polyclonal antiserum, or monoclonal antibody, the beta antigen, in contrast, appears as a single protein of molecular mass between 124 and 134 kDa. The amount of alpha antigen expressed by each strain was quantified by enzyme immunoassay inhibition and was found to vary markedly from strain to strain. The susceptibility of strains of GBS to opsonization and killing by human polymorphonuclear leukocytes in the presence of either complement alone or complement with alpha-specific monoclonal antibody was examined. Strains expressing the alpha antigen were less readily killed in the absence of specific antibody than were alpha-negative strains. Killing in the presence of alpha-specific monoclonal antibody was found to correlate directly with the maximum molecular mass of the alpha antigen and with the quantity of antigen on the bacterial cell surface. Isolates of GBS that express the alpha C protein vary widely in the quantity and molecular mass of the alpha antigen produced, and this heterogeneity appears to have biologic importance.

Alpha C protein as a carrier for type III capsular polysaccharide and as a protective protein in group B streptococcal vaccines.

The alpha C protein, a protective surface protein of group B streptococci (GBS), is present in most non-type III GBS strains. Conjugate vaccines composed of the alpha C protein and type III capsular polysaccharide (CPS) might be protective against most GBS infections. In this study, the type III CPS was covalently coupled to full-length, nine-repeat alpha C protein (resulting in III-alpha9r conjugate vaccine) or to two-repeat alpha C protein (resulting in III-alpha2r conjugate vaccine) by reductive amination. Initial experiments with the III-alpha9r vaccine showed that it was poorly immunogenic in mice with respect to both vaccine antigens and was suboptimally efficacious in providing protection in mice against challenge with GBS. Therefore, modified vaccination protocols were used with the III-alpha2r vaccine. Female mice were immunized three times with 0.5, 5, or 20 microgram of the III-alpha2r vaccine with an aluminum hydroxide adjuvant and bred. Ninety-five percent of neonatal mice born to dams immunized with the III-alpha2r vaccine survived challenge with GBS expressing type III CPS, and 60% survived challenge with GBS expressing wild-type (nine-repeat) alpha C protein; 18 and 17%, respectively, of mice in the negative control groups survived (P, <0.0001). These protection levels did not differ significantly from those obtained with the type III CPS-tetanus toxoid conjugate vaccine and the unconjugated two-repeat alpha C protein, which protected 98 and 58% of neonates from infection with GBS expressing type III CPS or the alpha C protein, respectively. Thus, the two-repeat alpha C protein in the vaccine was immunogenic and simultaneously enhanced the immunogenicity of type III CPS. III-alpha vaccines may be alternatives to GBS polysaccharide-tetanus toxoid vaccines, eliciting additional antibodies protective against GBS infection.

The development of acute myelomonocytic leukemia in a patient with acute lymphocytic leukemia.

A diagnosis of acute lymphocytic leukemia (ALL) was made from a peripheral blood and bone marrow specimen from a 59-year-old woman. Typical-appearing lymphoblasts were positive for periodic acid-Schiff (PAS) reaction, but negative for peroxidase, Sudan black B (SBB) and non-specific esterase (NSE) stains. Lymphoblasts failed to form non-immune rosettes and had no surface membrane immunoglobulins. However, lymphoblasts exhibited an "Ia-like" membrane antigen and markedly stimulated allogeneic lymphocytes in a mixed lymphocyte reaction (MLR). These cytochemical and immunologic studies were considered characteristic of null-cell subtype of ALL. Thirteen months later, the peripheral blood and bone marrow specimens contained numerous myelomonoblasts characterized by a weak or negative PAS stain and strongly positive peroxidase, SBB, and NSE reactions. Electron micrographs of the bone marrow suggested that the majority of leukemic cells were myelomonocytic and a minority of cells were lymphoblasts. In addition, myelomonoblasts in liquid cultures appeared to differentiate into mature macrophages. These data suggest the development of acute myelomonocyte leukemia in a previous case of ALL.

Variation in repeat number within the alpha C protein of group B streptococci alters antigenicity and protective epitopes.

Variable expression of repeating units of the protective alpha C proteins among clinical isolates of group B streptococci (GBS) may have implications for vaccine development. In this study, alpha C protein genes containing various numbers of repeats (1,2,9, and 16) were cloned in a T7 overexpression vector in Escherichia coli. Expression was induced by isopropyl-beta-D-thiogalactopyranoside, and proteins were purified by anion-exchange, gel filtration, or affinity chromatography or by isoelectric focusing. Rabbits were immunized with purified 1-,2-,9-, or 16-repeat proteins. All proteins appeared to be highly immunogenic. Enzyme-linked immunosorbent assay inhibition with 9-repeat protein as the coating antigen and 9-repeat-antigen-elicited antiserum showed that a 200-fold-higher concentration of 1-repeat antigen than of 9- or 16-repeat antigen was required for 50% inhibition of antibody-antigen binding. The concentration of 2-repeat antigen required for 50% inhibition was intermediate relative to the concentrations of 1- and 9-repeat antigens. These results suggested that antibodies to 9-repeat antigen recognized predominantly a conformational epitope(s) contained in proteins with higher numbers of repeats (9 or 16) but lost considerable binding affinities for an epitope(s) contained in alpha C proteins with fewer repeats (1 or 2). Similar results were obtained with antiserum to 16-repeat antigen. However, antibodies to 1- and 2-repeat antigens recognized 1-,2-,9-,and 16-repeat antigens with equal binding affinities. This finding suggested that 1- and 2-repeat-elicited antibodies recognized an epitope(s) on individual repeats. Loss of repeating units from the alpha C proteins may result in decreased protection because the loss of epitopes (including conformational epitopes) gives the microorganisms the opportunity to escape host antibodies. If 1- and 2-repeat-elicited antibodies bind all alpha C proteins with equal affinity, regardless of their repeat number, they may prevent GBS strains with fewer repeats from escaping host immunity. Protection data obtained with antisera to the proteins with different repeat numbers support this hypothesis: mouse pups challenged with GBS strain A909 were better protected when immunized with 1- or 2-repeat-elicited antiserum (76 and 75%, respectively) than when immunized with 9- or 16-repeat-elicited antiserum (41 and 48%, respectively).