Localization of the regions on the C-terminal domain of the heavy chain of botulinum A recognized by T lymphocytes and by antibodies after immunization of mice with pentavalent toxoid

We have mapped the regions recognized by T and/or B cells (Abs) on the C-terminal domain (Hc) of the heavy chain of botulinum neurotoxin serotype A (BoNT/A) after immunization of two inbred mouse strains with pentavalent toxoid (BoNTs A, B, C, D and E). Using a set of synthetic overlapping peptides, encompassing the entire Hc domain (residues 855-1296), we demonstrated that T cells of Balb/c (H-2d) mice, primed with one injection of toxoid, recognized two major regions within residues 897-915 and 939-957. After multiple inoculations with toxoid, T cells of Balb/c expanded their recognition ability and responded very well to challenge with peptide 1261-1279 and moderately to stimulation with peptide 1149-1167. Unlike Balb/c T cells, those of toxoid-primed SJL (H-2s) mice exhibited a more complex profile and responded to challenge with a large number of overlapping peptides. After one toxoid injection, however, three peptides, 897-915, 939-957/953-971 overlap and 1051-1069, were the most potent T cells stimulators. After three toxoid injections, peptides 897-915 and 1051-1069 remained immunodominant while the third region was shifted upstream to 925-943/939-957 overlap. The immunodominant epitope within peptide 897-915 was recognized exclusively by T cells, since no Abs were detected against this region. The Ab binding profiles of the two mouse strains were quite similar, showing only small quantitative differences. Both, Balb/c and SJL anti-toxoid Abs displayed strong binding mainly to peptide 1177-1195, followed by peptides 869-887/883-901 overlap and 1275-1296. In addition, a significant amount of Balb/c anti-toxoid Abs was bound to peptide 1135-1153. Unlike Balb/c Abs, that interacted weakly with peptides 995-1013 and 1051-1069, the anti-toxoid Abs of SJL mice exhibited strong binding toward both peptides. The results showed that, in a given strain, the regions recognized by anti-toxoid Abs and T cells may coincide or may be uniquely B or T cell determinants.

Bacterial surface display: trends and progress

Heterologous surface display on Gram-negative bacterial was first described a decade ago and is now an active research area. More recently, strategies for surface display on Gram-positive bacterial have also been devised and these carry some inherent advantages. Bacterial surface display has found a range of applications in the expression of various antigenic determinants, heterologous enzymes, single-chain antibodies, polyhistidyl tags and even entire peptide libraries. This article explains the basis of bacterial surface display and discusses current uses and possible future trends of this emerging technology.

Recombinant Opc meningococcal protein, folded in vitro, elicits bactericidal antibodies after immunization

The meningococcal Opc protein has been expressed as inclusion bodies in Escherichia coli. After cell disruption and successive washing of the insoluble fraction, insoluble proteins were solubilized in presence of the chaotropic agent guanidium hydrochloride. The extract was applied to a Reverse Phase High Performance Liquid Chromatography (RP-HPLC)-C4 column, for further purification. The obtained recombinant Opc protein was refolded in vitro, by the addition of several compounds to the resuspended solution. Over time, the progress of renaturation was tested by immunoblot with the human monoclonal antibody LuNm03 against the meningococcal Opc protein. LuNm03 recognizes a conformational epitope on the native meningococcal Opc protein. Having established the optimal conditions of renaturation. Balb/c mice were immunized to study the humoral immune response. The human at immune response elicited in mice was measured by ELISA and immunoblot, while the functional activity of these antibodies was assayed in a bactericidal test. According to our results, it was possible to obtain a recombinant Opc protein folded in vitro, with a conformation suitable enough to generate functional antibodies in mice, capable of killing meningococci in the presence of human complement.

The major outer membrane protein, CD, extracted from Moraxella (Branhamella) catarrhalis is a potential vaccine antigen that induces bactericidal antibodies

The major outer membrane protein of Moraxella (Branhamella) catarrhalis, CD, was detergent-extracted from the bacterial cell wall and purified to homogeneity in high yields by a simple process. The purified protein appeared to exhibit immunogenic properties similar to those of native CD exposed on the surface of the bacterium. Antibodies to CD raised in mice specifically bound to intact B. catarrhalis, as determined by flow cytometry analysis. The IgG subclass distributions of anti-CD antibodies in sera from mice immunized with purified CD or with B. catarrhalis were also similar. CD was found to be antigenically conserved among a panel of B. catarrhalis isolates, as demonstrated by the consistent reactivities of mouse anti-CD antisera with a common 60 kDa protein on immunoblots. Furthermore, convalescent sera collected from patients with otitis media due to B. catarrhalis infection were found to be reactive with the CD protein by immunoblotting. Finally, the purified protein induced antibodies in guinea pigs and mice that exhibited in vitro bactericidal activity against the pathogen. Therefore, the native CD outer membrane protein represents a potentially useful antigen for inclusion in a vaccine against B. catarrhalis.

Serotypes of Streptococcus pneumoniae causing invasive childhood infections in Bangladesh, 1992 to 1995

One hundred sixty-five invasive Streptococcus pneumoniae strains were isolated from children under five at Dhaka Shishu (Children's) Hospital during the period 1992 to 1995. Ninety-four strains were from cerebrospinal fluid, and 71 were from blood. More than 91% of the strains were isolated from patients aged 24 months or less. Predominant serotypes were, in descending order 7F, 12F, 14, 15B, 18, 5, and 22A. These comprised 70% of all isolates. The marked differences in serotype distribution in different countries indicate the need for a sentinel surveillance study for the countries of South Asia, particularly Bangladesh, China, India, and Pakistan.

Immunization with bacterial antigens: yersiniosis

Yersinia ruckeri causes salmonid fish diseases called yersiniosis or enteric redmouth disease (ERM). Isolates include several serological varieties and disease outbreaks are frequently associated with stress or poor environmental factors. As a result, it is difficult to define clearly the significant virulence factors and pathogenic mechanisms of the bacterium, which introduces uncertainties about the appropriate formulation of bacterins for immunization. An enteric redmouth bacterin was the first commercially-produced fish vaccine, and the formalin-killed whole-cell product continues to be highly effective whether administered by immersion, spray, injection, or oral routes. Serovar 1, "Hagerman" strains are the basis for most commercial bacterins, and serovar 2 is not included, despite epizootics in chinook salmon and brook trout. Vaccination studies report different degrees of cross-protection between serogroups of Y. ruckeri, but the basis for the cross-protection is not clear. Lipopolysaccharide (LPS) of serovar 1 Y. ruckeri elicits negligible or weak antibody responses in fish and low cell-proliferation memory responses compared with serovar 2 strains. These observations raise fundamental questions about the kinds of immune responses that are involved in the highly effective vaccine-protection provided by commercial vaccines.

Immunization with bacterial antigens: furunculosis

Although the nature of the antigens and the immune responses they elicit to achieve immunity to furunculosis are still not well defined, the currently available vaccines comprising A. salmonicida bacterins emulsified in oil adjuvants and delivered by intraperitoneal injection provide remarkably high levels of long-lasting protection. Despite some concern over side-effects, these vaccines have been adopted by most Atlantic salmon farmers over the last four years, transforming a situation where furunculosis outbreaks were becoming catastrophic to one where losses from the disease are negligible. Present evidence indicates that antibody responses to the polysaccharide capsule and iron regulated outer membrane proteins are associated with protection. Furthermore, cell-mediated immune responses involving antigen-induced release of cytokines from lymphocytes and the resultant activation of macrophages with the ability to kill the pathogen are also considered important protective mechanisms. Vaccines comprising whole A. salmonicida cultures grown under iron-restricted conditions and delivered by injection in an oil adjuvant are expected to induce prolonged stimulation of all the above responses. While these vaccines are suitable and effective for administration to salmon smolts there is still a need for mass vaccination by immersion or oral routes for salmonid fry. Effective means of achieving this are still required.

[The effect of the processes of Klebsiella pneumoniae cultivation on the antigenic activity of vaccinal preparations for peroral use]

Whole-cell preparations, obtained from the microbial mass of K. pneumoniae grown by batch and continuous cultivation at a dilution rate of 0.24 and 0.41 hr-1 and used in animal experiments for oral administration, were shown to have different serological activity. The preparation obtained from biomass grown by continuous cultivation at a dilution rate of 0.41 hr-1 proved to be most active regarding the level of hemagglutinating antibodies to K. pneumoniae LPS. At the same time the 360-fold rise of the level of anti-LPS antibodies in rabbit immune sera was observed. On day 258 oral revaccination was made; after that the twofold rise of the level of anti-LPS antibodies in the sera of the animals was observed. These antibody levels exceeded 40-fold those registered before primary immunization, and sufficiently high antibody levels were retained for 4 more months (the term of observation).

Immunization with bacterial antigens: bacterial kidney disease

Bacterial kidney disease has consistently resisted attempts to control it by prophylactic immunisation. Although successful vaccines have been produced to a number of Gram-negative fish pathogens, the relatively simple method used in these cases have not been successful with Renibacterium salmoninarum. A more circumspect and thorough knowledge of the biological function of R. salmoninarum antigens must be obtained. Also required is a more precise understanding of the role of regional immunity in effective prophylaxis. Aspects of R. salmoninarum's biology provide a provocative challenge to the vaccinologist. Its residence in, and apparent commandeering of the macrophage, indicate that a vigorous cell-mediated response will probably be required to generate protective immunity. Its most biologically potent secreted product, p57, appears to be an aggressin. Further, p57 has the capability of frustrating immunoprophylaxis by either misdirecting the immune response, or by preventing its induction. Many immunization studies have used injection immunization and challenge protocols. It now appears that alternative routes of immunization which had been considered less protective (i.e. oral immunization) may not only be more efficacious, but may be the only route that does not lead to a misdirected and possibly pathological immune response. Also, the general reliance on serum antibodies as the only means to assess immunity is fraught with difficulties, particularly with pathogens such as R. salmoninarum. Recent advances in the analysis of cellular immunity will be a great aid in the design of future vaccines.

Immunization with bacterial antigens: Vibrio infections

Within the genus Vibrio, the species causing the most economically important diseases in marine culture are Vibrio anguillarum, V. ordalii, V. salmonicida and V. vulnificus biotype 2. For these bacterial fish pathogens host range, clinical importance, virulence mechanisms, the antigenic variants relevant to vaccination, the existence of genetic intraspecific diversity and the available vaccines including commercial or domestically produced will be described. Among the 10 serotypes described in V. anguillarum, only serotypes O1, O2 and O3 have been associated with mortality in a great variety of farmed and feral fish worldwide. Whereas serotype O1 is a very homogeneous group from the biochemical, serological and genetic stand-point, within serotype O2 and O3 two antigenic entities have been detected. Moreover these two serotypes present a remarkable genetic heterogeneity. However, many of the available commercial vibriosis vaccines include in their formulations only V. anguillarum serotype O1 in combination with V. ordalii (formerly V. anguillarum biotype 2). In addition no commercial vaccine provides information about the subgroup(s) used as representative of V. anguillarum O2. Recently, Vibrio species taxonomically related to V. anguillarum (VAR) have been isolated from diseased fishes. An extensive characterization of these VAR organisms allowed us to distribute them into at least seven O-serogroups. The inclusion of representative VAR strains in the vibriosis vaccines need to be discussed. V. ordalii, V. salmonicida and V. vulnificus are homogeneous species with respect to biochemical reactions, serology and degree of virulence, possess a narrow host range and seem to be restricted to some geographic areas. Although iron acquisition systems can be involved in the virulence mechanisms of these pathogens, only in V. anguillarum has it been clearly demonstrated that the ability to scavenge iron from the host is a crucial virulence determinant. The role of exotoxins and cell surface associated properties in the Vibrio infections remains to be elucidated.

An aroA mutant of Yersinia pestis is attenuated in guinea-pigs, but virulent in mice

This study describes a PCR-based approach for the production of a rationally attenuated mutant of Yersinia pestis. Degenerate primers were used to amplify a fragment encoding 91.45% of the aroA gene of Y. pestis MP6 which was cloned into pUC18. The remainder of the gene was isolated by inverse PCR. The gene was sequenced and a restriction map was generated. The Y. pestis aroA gene had 75.9% identity with the aroA gene of Yersinia enterocolitica. The cloned gene was inactivated in vitro and reintroduced into Y. pestis strain GB using the suicide vector pGP704. A stable aro-defective mutant. Y. pestis GB aroA, was isolated and its virulence was examined in vivo. The mutant was attenuated in guinea-pigs and capable of inducing a protective immune response against challenge with the virulent Y. pestis strain GB. Unusually for an aro-defective mutant, the Y. pestis aroA mutant was virulent in mice, with a median dose which induced morbidity of death similar to that of the wild-type, although time to death was significantly prolonged.

Identification of a second family of high-molecular-weight adhesion proteins expressed by non-typable Haemophilus influenzae

We previously reported that two surface-exposed high-molecular-weight proteins, HMW1 and HMW2, expressed by a prototypic strain of non-typable Haemophilus influenzae (NTHI), mediate attachment to human epithelial cells. These proteins are members of a family of highly immunogenic proteins common to 70-75% of NTHI strains. NTHI strains that lack HMW1/HMW2-like proteins remain capable of efficient attachment to cultured human epithelial cells, suggesting the existence of additional adhesion molecules. We reasoned that characterization of high-molecular-weight immunogenic proteins from an HMW1/HMW2-deficient strain might identify additional adhesion proteins. A genomic library was prepared in lambda EMBL3 with chromosomal DNA from non-typable Haemophilus strain 11, a strain that lacks HMW1/HMW2-like proteins. The library was screened immunologically with convalescent serum from a child naturally infected with strain 11, and phage clones expressing high-molecular-weight recombinant proteins were identified by Western blot analysis. One clone was identified that expressed a protein with an apparent molecular mass greater than 200 kDa. Transformation of non-adherent Escherichia coli strain DH5 alpha with plasmids containing the genetic locus encoding this protein gave rise to E. coli transformants that adhered avidly to Chang conjunctival cells. Subcloning and mutagenesis studies localized the DNA conferring the adherence phenotype to a 4.8 kbp fragment, and nucleotide sequence analysis further localized the gene encoding the adhesion protein to a 3.3 kbp open reading frame predicted to encode a protein of 114 kDa. The gene was designated hia for Haemophilus influenzae adhesin. Southern analysis revealed an hia homologue in 13 of 15 HMW1/HMW2-deficient non-typable H. influenzae strains. In contrast, the hia gene was not present in any of 23 non-typable H. influenzae strains which expressed HMW1/HMW2-like proteins. Identification of this second family of high-molecular-weight adhesion proteins suggests the possibility of developing vaccines based upon a combination of HMW1/HMW2-like proteins and Hia-like proteins which would be protective against disease caused by most or all non-typable H. influenzae.

[The use of a new strain of Vibrio cholerae O139 as a producer of an enteric chemical vaccine]

Conditions for the submerged cultivation of a strain of V. cholerae O139, were worked out. These conditions ensured a high yield of biomass, soluble O-antigen and exoenzymes (proteinase, phospholipase A) into the culture medium, which exceeded their production by strains of serovar O1, respectively, 2, 3, 4 and 8 times. The preparation, isolated from the culture fluid and lyophilized, contained up to 50% of O-antigen and exoenzymes. In experiments on white mice the preparation exhibited low toxicity (LD50 was equal, on the average, to 1.2 mg) and immunogenicity (ED50 was equal to 3-5 micrograms) with respect to V. cholerae O139, which corresponded to the protective potency of commercial vaccine against V. cholerae O1 infection.

Experimental immunization of hamsters with an EDTA extract of Leptospira interrogans, serovar icterohaemorrhagiae

The EDTA extract was prepared from the Leptospira interrogans serovar icterohaemorrhagiae. When inoculated subcutaneously in hamsters it conferred protection from challenge with virulent leptospires with a low dose (10 micrograms/ml) and low agglutinating antibody (40). The protection of animals obtained by the EDTA extract opens up the perspective of its use as a component of a vaccine for the control of leptospirosis.

Vaccination today and tomorrow

The vaccines against infectious diseases in use today are, with few exceptions, prepared from the causal agents themselves, either by inactivating them with a chemical such as formaldehyde or by attenuating them so that they grow and thus evoke an immune response in the natural host but cause no disease. These empirical approaches have produced many highly successful vaccines. Increasing knowledge at the molecular level of the agents and of the immune response to protein antigent is now providing us with the opportunity to design vaccines that will elicit protective responses without the need to use the agents themselves. The critical issue is to identify the immune responses that correlate with protection.

Immunogenicity and protective ability of corpuscular and soluble vaccines prepared from different Coxiella burnetii phase I strains

BALB/c mice immunized intraperitoneally (ip) with killed purified Coxiella burnetii phase I corpuscular vaccines or trichloroacetic acid (TCA) extracts from phase I corpuscles (soluble vaccines) were protected against ip challenge with both homologous and heterologous C. burnetii phase I strains. Though the degree of protection, namely the inhibition of C. burnetii multiplication in the mouse spleen slightly varied, in general, corpuscular vaccines provided better protection than soluble ones. Cross-protection was accompanied by comparable levels of cell-mediated immune response as evaluated by lymphocyte transformation test (LTT). However, higher stimulation indices of LTT were obtained with homologous than with heterologous strains. The values of antibody response as determined by enzyme-linked immunosorbent assay (ELISA) were higher with homologous strains too. On average, both antibody-inducing and antibody-binding capabilities of the strains Priscilla and S were lower than those of the Nine Mile and Luga strains, except for values obtained with the antigens from homologous strains.

Protective effect of the combined vaccine prepared from cell-free-antigen of Actinobacillus pleuropneumoniae serotypes 1, 2 and 5 in pigs

Cell-free-antigens prepared from a concentrated culture supernatant of Actinobacillus pleuropneumoniae (A. pleuropneumoniae) serotypes 1, 2 and 5 were mixed and emulsified with oil adjuvant. The combined vaccine of these 3 serotypes of A. pleuropneumoniae was tested for its ability to confer protection. Pigs immunized with the combined vaccine survived and showed no clinical signs against an intratracheal challenge with A. pleuropneumoniae. In contrast, control pigs inoculated with concentrated culture media emulsified with oil adjuvant developed typical symptoms of pleuropneumonia after challenge inoculation.

Prospects for a vaccine to prevent Lyme disease in humans

Vaccination with recombinant outer-surface protein A (OspA) preparations has been highly successful in protecting laboratory animals against challenge by strains of Borrelia burgdorferi closely related to the one from which the OspA was derived. Humoral immunity is sufficient for protection. Against natural infection introduced by ticks, the vaccine-induced immune response may begin to take effect in the tick itself--i.e., before the spirochete enters the host--and may extend to a broader spectrum of strains of B. burgdorferi than are represented in the vaccine. Single recombinant OspA vaccine preparations are currently being evaluated in two large-scale efficacy trials in adults in the United States. Greater heterogeneity among B. burgdorferi strains in Europe than among those in the United States will likely necessitate the development of a vaccine containing antigens from multiple strains; a multivalent vaccine may or may not be needed in the United States.

Beef allergy and the Persian Gulf syndrome

It is suggested that the Persian Gulf Syndrome (PGS) is caused by beef allergy. In the first symptomless phase, as a result of an energetic US Army immunizing program, using sera with adjuvants to produce detectable antibody levels, the subjects not only developed immunity to the targeted substances, but also became sensitized to one or more of the other substances in the immunizing sera, and specifically to beef protein. The subjects remained healthy while in the war zone on a restricted diet essentially free from beef, but developed PGS after they came home, and were again able to obtain steaks and hamburgers.

Prolonged survival of AVN Wistar rats with transplanted Yoshida sarcoma and increase of granular lymphocytes after administration of Bacillus firmus and their crude lipids

Bacillus firmus is a Gram-positive, aerobic, sporulating, nonpathogenic air contaminant which, according to earlier findings, is a strong polyclonal activator of B lymphocytes. The crude lipids of this microbe induced significant resistance of mice against listerial infection. The administration of bacterin, like that of crude lipids obtained by the extraction of cell suspension with chloroform-methanol to rats, strain AVN Wistar, transplanted later with Yoshida sarcoma, significantly prolonged the survival of the animals in comparison with the control group. At the same time the number of granular lymphocytes was increased. The destruction of tumor cells in the peritoneal exudate of immunostimulated rats was also determined.

Immunology of reactive arthritides

Reactive arthritis (ReA) and Lyme arthritis together comprise a pair of chronic inflammatory diseases of the joints. Although differing in detail, these relatively rare diseases are related in their immunopathology to the much commoner rheumatoid arthritis (RA), for which they serve as both model and control. The trigger for rheumatoid arthritis is unknown, but for these rarer diseases triggering occurs by certain well-defined bacterial infections. Arthritis is an uncommon outcome of these infections, for reasons unknown, and the development of chronic, as distinct from brief, arthritis is even rarer; again, the reasons are unknown. Not only does knowing the trigger greatly assist us in understanding these diseases, so also does knowing the contrasting pattern of Th1 versus Th2 cytokines observed in RA and ReA. ReA and Lyme arthritis are here considered in the wider setting of infections where chronic morbidity arises first from hypersensitivity, and perhaps finally from autoimmunity, such as occurs in some of the major tropical diseases. The immunology of ReA and Lyme disease is surveyed in detail, concentrating on T cells and including an update on the Lyme vaccine(s). Additional sections deal with the enigma of HLA B27, with epidemiological findings relevant to the chronicity of ReA and to the need for enlarged prospective studies of ReA in the setting of a developing country.

Reversible expression of motility and flagella in Clostridium chauvoei and their relationship to virulence

Clostridium chauvoei strain Okinawa produced spontaneous non-motile variants at an unusually high rate (approx. 10(-4) per generation) under normal conditions without mutagen. Revertants of non-motile variants were detected at a rate of approximately 10(-3). Biochemically, every variant corresponded well with the parental strain. By transmission electron microscopy, three of nine non-motile variants of strain Okinawa were found to be flagellate, while the other six were found to be aflagellate. These phenotypes were confirmed by Western blot analysis using monoclonal antibodies directed against the flagella of C. chauvoei. Moreover, the parental flagellate strain and non-motile flagellate variants were significantly more virulent in mice than non-motile, aflagellate variants. Our results demonstrated that phase variation in motility and flagellation occurs in C. chauvoei, and that the flagella are associated with the full expression of virulence.

Pulsed-field gel electrophoretic identification of Salmonella enterica serovar Typhimurium live vaccine strain Zoosaloral H

Salmonella enterica subsp. enterica serovar Typhimurium (Salm. Typhimurium) live vaccine strain Zoosaloral H was characterized by pulsed-field gel electrophoresis (PFGE). Each of the two suitable restriction enzymes, XbaI and SpeI, produced a unique restriction fragment pattern for this live vaccine strain which was not shared by field isolates of the same serovar. The characteristic fragment pattern proved to be stable during a 22 month observation period and was also not altered after animal passage of the vaccine strains. Thus PFGE analysis proved to be a helpful tool in the identification of Salm. Typhimurium live vaccine strain Zoosaloral H and its differentiation from wild-type isolates of the same serovar.