Molecular and genetic characterisation of the host-protective oncosphere antigens of taeniid cestode parasites

Highly effective recombinant vaccines have been developed against Taenia ovis infection in sheep, Taenia saginata infection in cattle, Taenia solium infection in pigs, Echinococcus granulosus and Echinococcus multilocularis infections in a variety of intermediate host species. These vaccines have been based on the identification and expression in Escherichia coli of antigens derived from the oncosphere life cycle stage, contained within the parasites' eggs. Investigation of the molecular aspects of these proteins and the genes encoding them have revealed a number of common features, including the presence of a predicted secretory signal sequence, and one or two copies of a fibronectin type III domain, each encoded by separate exons within the associated gene. Evidence has been obtained to confirm glycosylation of some of these antigens. Ongoing investigations will shed light on the biological roles played by the proteins within the parasites and the mechanism by which they make the parasites vulnerable to vaccine-induced immune responses.     

Adaptation of Borrelia burgdorferi in the tick and the mammalian host

Borrelia burgdorferi, the causative agent of Lyme disease, shows a great ability to adapt to different environments, including the arthropod vector, and the mammalian host. The success of these microorganisms to survive in nature and complete their enzootic cycle depends on the regulation of genes that are essential to their survival in the different environments. This review describes the current knowledge of gene expression by B. burgdorferi in the tick and the mammalian host. The functions of the differentially regulated gene products as well as the factors that influence their expression are discussed. A thorough understanding of the changes in gene expression and the function of the differentially expressed antigens during the life cycle of the spirochete will allow a better control of this prevalent infection and the design of new, second generation vaccines to prevent infection with the spirochete.     

Influence of adjuvants in inducing immune responses to different epitopes included in a multiepitope,multivalent, multistage Plasmodium falciparum candidate vaccine (FALVAC-1) in outbred mice

FALVAC-1, a vaccine against Plasmodium falciparum was developed by joining 21 epitopes from P. falciparum vaccine antigens and an universal T helper epitope from tetanus toxoid. Since adjuvants influence different aspects of immune responses, in this study we investigated the effect of four adjuvants aluminum hydroxide (alum), nonionic copolymer adjuvant P1005 (water-in-oil emulsion), CpG oligodeoxynucleotides (ODN), and QS-21 in eliciting immune responses in outbred mice. QS-21 and copolymer adjuvants were the best formulations in inducing higher and long-lasting antibody titers to the whole vaccine compared to alum and CpG. QS-21 was the only adjuvant to elicit predominantly IgG2a response and antibodies reactive with all epitopes incorporated in the vaccine construct. Vaccine elicited antibodies recognized sporozoites and asexual blood-stage parasites. FALVAC-1 immunized mice induced lymphoproliferative and IFN-gamma response to the vaccine. QS-21 and CpG adjuvants were able to elicit T proliferative responses to 20 of the 22 epitopes in the vaccine. In conclusion, this study demonstrated that with suitable adjuvant such as QS-21, it is possible to elicit immune responses to most of the epitopes included in the FALVAC-1 vaccine.     

A novel Helicobacter pylori cell-surface polysaccharide

Helicobacter pylori bacteria colonize the gastric mucosa of more than half of the world's human population and its infection may instigate a wide spectrum of gastric diseases in the host. At the moment, there is no vaccine against H. pylori, a microorganism recognized as a category 1 human carcinogen, and treatment is limited to antibiotic management. Pioneering antigenic studies carried out by Penner and co-workers, which employed homologous H. pylori antisera specific for cell-surface lipopolysaccharide (LPS), revealed the presence of six distinct H. pylori serotypes (O1 to O6). Subsequent studies have shown that H. pylori serotype O1 expressed LPS with lengthy O-chain polysaccharide (PS) composed of Lewis blood-group structures ('Lewis O-chains'), serotype O3 LPS produced 'Lewis O-chains' attached to a heptoglycan domain, serotype O4 LPS possessed LPS with glucosylated 'Lewis O-chains' and serotype O6 LPS expressed the heptoglycan domain capped by a short 'Lewis O-chain'. These LPSs were terminated at the reducing-end by a core oligosaccharide and lipid A of conserved structures. With the intent of formulating a multivalent H. pylori LPS-based vaccine, we are studying the structural variability of H. pylori cell-surface glycans. Here, we describe the novel LPS structure produced by H. pylori serotype O2 that differed markedly from the typical H. pylori 'Lewis O-chain' structures, in that its main component was an elongated PS composed of alternating 2-, and 3-monosubstituted alpha-D-Glcp residues [-->2)-alpha-D-Glcp-(1-->3)-alpha-D-Glcp-(1-->]n. These findings revealed the bio-molecular basis for the observed serospecificity of H. pylori serotype O2, and that this unique bacterial PS must be included in the formulation of a multivalent LPS H. pylori vaccine.     

Characterization and quantification of C-polysaccharide in Streptococcus pneumoniae capsular polysaccharide preparations

Purified capsular polysaccharide preparations from Streptococcus pneumoniae that are used for vaccine production typically contain residual levels of C-polysaccharide (C-Ps). Residual C-Ps is typically found in one of two forms, either chemically linked to the capsular polysaccharide (bound) or present by itself (free). Two analytical methods have been developed and applied to determine the relative percentages of the two C-Ps forms present in various capsular polysaccharide preparations. Both methods differentiate the two forms of C-Ps according to the difference of their hydrodynamic sizes. One method is based on labeling C-Ps with a fluorescent tag and separating the two forms of C-Ps by high-performance size exclusion chromatography with on-line refractive index and fluorescence detection, and the other method is based on measuring self-diffusion rates of the two forms of C-Ps by nuclear magnetic resonance (NMR) and quantifying each form with deconvolution. Both methods were evaluated for relative accuracy, precision, and ease of application, and they were found to provide comparable results for a large number of pneumococcal polysaccharide preparations. These analyses, combined with other quantitative NMR measurement of total C-Ps in the polysaccharide powder, provide a more refined means of evaluating the amount of each form of C-Ps in polysaccharide preparations targeted for vaccine production.     

Tularemia vaccine: past,present and future

Francisella tularensis is a Gram negative intracellular pathogen that causes the highly debilitating or fatal disease tularemia. F. tularensis can infect a wide range of animals and can be transmitted to humans in a variety of ways, the most common being by the bite of an infected insect or arthropod vector. The attenuated F. tularensis live vaccine strain (LVS) has been used previously under investigational new drug status to vaccinate at-risk individuals. However the history of the strain and lack of knowledge regarding the basis of attenuation has so far prevented its licensing. Therefore the focus of current research is on producing a new vaccine against tularemia that would be suitable for licensing.     

CELO病毒载体在人类和动物疾病控制上的应用

CELO病毒的DNA长43．8kb,具有末端倒转重复序列(ITR),基因结构与人腺病毒的比较,无可识别的E1、E3和E4区,但存在可替代的新读码框。2个fiber基因是病毒毒力基因,表达2个不同的蛋白,在病毒复制扩散中起作用,缺失fiberl导致柯萨奇病毒和腺病毒受体(CAR)的特异性转导作用消失,使CELO病毒只能感染禽类细胞,不能感染哺乳类动物细胞。在基因组的某些区段可以删除并插入外源基因不影响病毒复制。CELO病毒及其载体可在廉价的鸡胚中得到大量复制。CELO病毒的这些特性为其发展成新型基因工程载体提供了条件。插入表达外源基因制备疫苗成为可能,新型的无病毒基因的载体也可以应用ITR及一些调控元件、包装信号共同构建形成。CELO病毒与人腺病毒属于同一属,CELO病毒作为基因工程载体有同样的特性,并且具有种属特异性和安全性,在动物基因工程疫苗的研制方面有特殊而广阔的研究和应用前景。     

α-Tocopheryl succinate sensitizes established tumors to vaccination with nonmatured dendritic cells

Purpose: Dendritic cells (DCs) are considered potential candidates for cancer immunotherapy due to their ability to process and present antigens to T cells and stimulate immune responses. However, DC-based vaccines have exhibited minimal effectiveness against established tumors in mice and human cancer patients. The use of appropriate adjuvants can enhance the efficacy of DC-based cancer vaccines in treating established tumors. Methods: In this study we have employed -tocopheryl succinate (-TOS), a nontoxic esterified analogue of vitamin E, as an adjuvant to enhance the effectiveness of DC vaccines in treating established murine Lewis lung (3LL) carcinomas. Results: We demonstrate that locally or systemically administered -TOS in combination with nonmatured DCs injected intratumorally (i.t.) or subcutaneously (s.c.) significantly inhibits the growth of preestablished 10-day tumors (mean tumor volume of 77.5 ± 17.8 mm³ on day 30 post–tumor injection) as compared to -TOS alone (mean tumor volume of 471 ± 68 mm³ on day 30 post–tumor injection). Additionally, the adjuvant effect of -TOS was superior to that of cyclophosphamide (CTX). The mean tumor volume on day 28 post–tumor injection in mice treated with CTX+DCs was 611 ± 94 mm³ as compared to 105 ± 36 mm³ in mice treated with -TOS+DCs. Analysis of purified T lymphocytes from mice treated with -TOS+DC revealed significantly increased secretion of IFN- as compared to T cells from the various control groups. Conclusion: This study demonstrates the potential usefulness of -tocopheryl succinate, an agent nontoxic to normal cell types, as an adjuvant to augment the effectiveness of DC-based vaccines in treating established tumors.Abbreviations AO acridine orange - CTX cyclophosphamide - DC dendritic cell - dUTP deoxyuridine triphosphate - FACS fluorescence-activated cell sorter - FBS fetal bovine serum - FITC fluorescein isothiocyanate - GM-CSF granulocyte-macrophage colony-stimulating factor - IFN- interferon-gamma - IL-4 interleukin-4 - NaS sodium succinate - OCT optimal cutting temperature - PBS phosphate-buffered saline - PI propidium iodide - Tdt terminal deoxynucleotidyl transferase - TNF- tumor necrosis factor alpha - -TOS -tocopheryl succinateSupported by grants 1 RO1 CA94111-02 from the NIH and DAMD 17010126 from the DOD.     

Immunization with a novel HIV-1-Tat multiple-peptide conjugate induces effective immune response in mice

We report here a novel, highly immunogenic synthetic, multiple-peptide conjugate comprising functional domains Tat_21–40 and Tat_53–68 from HIV-1 group M plus Tat_9–20 from HIV-1 group O of the HIV-Tat protein (HIV-1-Tat-MPC). Vaccination of mice with HIV-1-Tat-MPC induced an effective immune response to all three functional domains. The anti-HIV-1-Tat-MPC antibodies efficiently inhibited Tat-induced viral activation in monocytes infected with HIV_Ba-L as well as with various clinical HIV-1 isolates, and reduced Tat-mediated cytopathicity in infected cells by 60–75%. Our results indicate that anti-HIV-1-Tat-MPC antibodies inhibit viral pathogenesis, possibly by blocking functional determinants of Tat and disrupting autocrine and paracrine actions of secreted Tat protein. This epitope-specific, synthetic Tat construct may, therefore, provide a subunit AIDS vaccine candidate for inducing an effective immunoprophylaxis response to reduce progression of HIV infection.