Characterisation of the immune response to the UK human anthrax vaccine

The UK human anthrax vaccine consists of the alum-precipitated culture supernatant of Bacillus anthracis Sterne. In addition to protective antigen (PA), the key immunogen, the vaccine also contains a number of other bacteria- and media-derived proteins. These proteins may contribute to the transient side effects experienced by some individuals and could influence the development of the PA-specific immune response. Bacterial cell-wall components have been shown to be potent immunomodulators. B. anthracis expresses two S-layer proteins, EA1 and Sap, which have been demonstrated to be immunogenic in animal studies. These are also immunogenic in man so that convalescent and post-immunisation sera contain specific antibodies to Ea1, and to a lesser extent, to Sap. To determine if these proteins are capable of modifying the protective immune response to PA, A/J mice were immunised with equivalent amounts of recombinant PA and S-layer proteins in the presence of alhydrogel. IgG isotype profiles were determined and the animals were subsequently challenged with spores of B. anthracis STI. The results suggest that there was no significant shift in IgG isotype profile and that the presence of the S-layer proteins did not adversely affect the protective immune response induced by PA.     

DNA prime-protein boost immunization in monkeys: efficacy of a novel construct containing functional domains of Plasmodium cynomolgi CS and TRAP

We report the efficacy of a bimodal immunization regimen that involved priming with naked DNA (multiple doses) followed by a booster with recombinant protein in rhesus monkeys with a chimeric construct containing the N-terminus of thrombospondin-related adhesive protein and the C-terminus of circumsporozoite protein of Plasmodium cynomolgi. The vaccinated animals developed high titer antibodies against the chimeric antigen, the two components of the hybrid and the native proteins of sporozoites. The peripheral blood mononuclear cells isolated from the vaccinated animals had significant in vitro T cell proliferation activity when stimulated with the recombinant chimeric protein. Furthermore, following challenge with 1000 P. cynomolgi sporozoites, the peak and total parasitemia were significantly lower in vaccinated animals than in the control animals.     

Modulation of lymphocyte proliferative responses by a canine Lyme disease vaccine of recombinant outer surface protein A (OspA)

The modulation of human lymphocyte proliferative responses was demonstrated with a recombinant outer surface protein A (OspA) vaccine preparation for the prevention of Borrelia burgdorferi infection. After exposure to either the unaltered vaccine preparation or OspA prepared in saline, normal lymphocyte responses to the mitogens concanavalin A, phytohemagglutinin-M or pokeweed mitogen, or the antigen BCG were consistently reduced. Whole cell extracts of B. burgdorferi also modulated immune responses but required a much greater quantity of protein than needed for the OspA preparation. The magnitude of modulation was directly dependent on the quantity of OspA. OspA interferes with the response of lymphocytes to proliferative stimuli including a blocking of cell cycle phase progression. Future studies designed to delete the particular region or component of the OspA molecule responsible for this effect may lead to improved vaccine preparations.     

Correlation between the immune response elicited in rabbits by env-recombinant avipox vaccines and the inhibition of HIV-1-specific functions

The fine immunoreactivity of the rabbit humoral response elicited by four env-recombinant avipoxviruses and their ability to stimulate a memory T-cell response and a protective immunity have been studied. The antibody specificity was compared with the serum neutralizing activity and virus-specific T-cell proliferative response. Resistance to challenge by cell-associated HIV-1 was monitored by PCR. Canarypox (CP) and fowlpox (FP) constructs, containing the complete env gene (IS(+)) from the HIV-1(SF2) strain, induced a higher profile of epitope recognition than their counterparts expressing the env gene deleted of the putative immunosuppressive region (IS(-)). Serum neutralizing activity was in agreement with fusion inhibition and lymphoproliferative response in rabbits immunized with CPIS(+), and only partially with FPIS(+). Rabbits failed to be infected, but anti- p55 gag-specific antibodies could be demonstrated by Western blot. This study confirms the ability of these non-replicative live recombinant viruses to elicit a complete immune response, capable of inhibiting specific HIV-1 functions.     

Glycosylations versus conformational preferences of cancer associated mucin core

Synthetic oligosaccharide vaccines based on core STn (sialyl 2-6 GalNAc) carbohydrate epitopes are being evaluated by a number of biopharmaceutical firms as potential immunotherapeutics in the treatment of mucin-expressing adenocarcinomas. The STn carbohydrate epitopes exist as discontinuous clusters, O-linked to proximal serine and threonine residues within the mucin sequence. In an effort to probe the structure and dynamics of STn carbohydrate clusters as they may exist on the cancer-associated mucin, we have used NMR spectroscopy and MD simulations to study the effect of O-glycosylation of adjacent serine residues in a repeating (Ser)n sequence. Three model peptides/glyco-peptides were studied: a serine trimer containing no carbohydrate groups ((Ser)₃ trimer); a serine trimer containing three Tn (GalNAc) carbohydrates -linked to the hydroxyls of adjacent serine sidechains ((Ser.Tn)₃ trimer); and a serine trimer containing three STn carbohydrates -linked to the hydroxyls of adjacent serine sidechains ((Ser.STn)₃ trimer). Our results demonstrate that clustering of carbohydrates shifts the conformational equilibrium of the underlying peptide backbone into a more extended and rigid state, an arrangement that could function to optimally present the clustered carbohydrate antigen to the immune system. Steric effects appear to drive these changes since an increase in the size of the attached carbohydrate (STn versus Tn) is accompanied by a stronger shift in the equilibrium toward the extended state. In addition, NMR evidence points to the formation of hydrogen bonds between the peptide backbone NH protons and the proximal GalNAc groups in the (Ser.Tn)₃ and (Ser.STn)₃ trimers. The putative peptide-sugar hydrogen bonds may also play a role in influencing the conformation of the underlying peptide backbone, as well as the orientation of the O-linked carbohydrate. The significance of these results will be discussed within the framework of developing clustered STn-based vaccines, capable of targeting the clustered STn epitopes on the cancer-associated mucin.     

Phase I clinical trial of a recombinant canarypoxvirus (ALVAC) vaccine expressing human carcinoembryonic antigen and the B7.1 co-stimulatory molecule

 The generation of cytotoxic effector T cells requires delivery of two signals, one derived from a specific antigenic epitope and one from a costimulatory molecule. A phase I clinical trial was conducted with a non-replicating canarypoxvirus (ALVAC) constructed to express both human carcinoembryonic antigen (CEA) and the B7.1 costimulatory molecule. This was the first study in cancer patients to determine if the delivery of costimulation with a tumor vaccine was feasible and improved immune responses. Three cohorts of six patients, each with advanced CEA-expressing adenocarcinomas, were treated with increasing doses of an ALVAC-CEA-B7.1 vaccine (4.5 × 10⁶, 4.5 × 10⁷, and 4.5 × 10⁸ plaque-forming units, PFU). Patients were vaccinated by intramuscular injection every 4 weeks for 3 months and monitored for side-effects, tumor growth and anti-CEA immune responses. ALVAC-CEA- B7.1 at doses up to 4.5 × 10⁸ PFU was given without evidence of significant toxicity or autoimmune reactions. Three patients experienced clinically stable disease that correlated with increasing CEA-specific precursor T cells, as shown by in vitro interferon-γ enzyme-linked immunoassay spot tests (ELISPOT). These three patients underwent repeated vaccination resulting in augmented CEA-specific T cell responses. This study represents the first use of costimulation to enhance antitumor vaccines in cancer patients. This approach resulted in CEA-specific immunity associated with stable diseases in three patients. This study also demonstrated that CEA-specific T cell responses could be sustained by repeated vaccinations. Although the number of patients was small, the addition of B7.1 to virus-based vaccines may improve immunological and stable diseases to vaccination against tumor-associated antigens with tolerable toxicity. Received: 6 May 2000 / Accepted: 13 July 2000     

Oral immunization of mice with transgenic tomato fruit expressing respiratory syncytial virus-F protein induces a systemic immune response

Respiratory syncytial virus (RSV) is one of the most important pathogens of infancy and early childhood. Here a fruit-based edible subunit vaccine against RSV was developed by expressing the RSV fusion (F) protein gene in transgenic tomato plants. The F-gene was expressed in ripening tomato fruit under the control of the fruit-specific E8 promoter. Oral immunization of mice with ripe transgenic tomato fruits led to the induction of both serum and mucosal RSV-F specific antibodies. The ratio of immunoglobulin subclasses produced in response to immunization suggested that a type 1 T-helper cell immune response was preferentially induced. Serum antibodies showed an increased titer when the immunized mice were exposed to inactivated RSV antigen.     

Vaccines, coming of age after 200 years

An overview on the short, only 200 years, past history and future expectations in the field of vaccines is presented. The focus is on development trends and potential rather than individual vaccines. While the first vaccines were a result of keen observation, the further development has been tightly dependent on the development of microbiology to provide both the knowledge basis and the technology for new vaccines for new purposes. The post-genomic era just starting therefore promises an exponential increase of vaccine research and new vaccines, both improved vaccines with a greater efficacy and less adverse effects to replace old ones and vaccines for prevention of diseases for which no vaccines exist. Furthermore, fully new applications to prevention or treatment of chronic diseases not traditionally associated with infections are expected.     

培养基除菌过滤在百日咳菌苗生产中的应用

经一系列试验证实百日咳菌大罐培养浓度的下降与培养基中不耐热营养因子不足有关,将培养基的高压灭菌方式改为除菌过滤,保留热不稳定营养因子,可以提高百日咳菌大罐培养浓度;优化酸沉淀条件后,提高了菌苗回收率,从而节省了大量培养基,缩短了生产时间,获得了良好的经济效益。