Lack of interspecies barriers in anti-Id stimulated antibody production against Echinococcus granulosus antigens

Nanoparticle-Based Delivery Systems for Vaccines

Vaccination is still the most cost-effective way to combat infectious illnesses. Conventional vaccinations may have low immunogenicity and, in most situations, only provide partial protection. A new class of nanoparticle-based vaccinations has shown considerable promise in addressing the majority of the shortcomings of traditional and subunit vaccines. This is due to recent breakthroughs in chemical and biological engineering, which allow for the exact regulation of nanoparticle size, shape, functionality, and surface characteristics, resulting in improved antigen presentation and robust immunogenicity. A blend of physicochemical, immunological, and toxicological experiments can be used to accurately characterize nanovaccines. This narrative review will provide an overview of the current scenario of the nanovaccine.

Vaccine delivery using nanoparticles

Vaccination has had a major impact on the control of infectious diseases. However, there are still many infectious diseases for which the development of an effective vaccine has been elusive. In many cases the failure to devise vaccines is a consequence of the inability of vaccine candidates to evoke appropriate immune responses. This is especially true where cellular immunity is required for protective immunity and this problem is compounded by the move toward devising sub-unit vaccines. Over the past decade nanoscale size (<1000 nm) materials such as virus-like particles, liposomes, ISCOMs, polymeric, and non-degradable nanospheres have received attention as potential delivery vehicles for vaccine antigens which can both stabilize vaccine antigens and act as adjuvants. Importantly, some of these nanoparticles (NPs) are able to enter antigen-presenting cells by different pathways, thereby modulating the immune response to the antigen. This may be critical for the induction of protective Th1-type immune responses to intracellular pathogens. Their properties also make them suitable for the delivery of antigens at mucosal surfaces and for intradermal administration. In this review we compare the utilities of different NP systems for the delivery of sub-unit vaccines and evaluate the potential of these delivery systems for the development of new vaccines against a range of pathogens.

Cytokine response and outcome of infection depends on the infective dose of parasites in experimental infection by Echinococcus granulosus

We here analysed whether the cytokine responses in early and late experimental infection with Echinococcus granulosus depend on the dose of parasites to which the host is exposed. To this purpose Balb/c mice were inoculated intraperitoneally (i.p.) with either 500 or 2000 protoscoleces. Splenocytes of mice were obtained at days 3, 7, 14 and 21 and also on week 37 post-infection and cultured in vitro with protoscolex antigens. Type-1 and type-2 cytokines were analysed in supernatants by ELISA. Results showed that the inoculation of 500 protoscoleces induced an early type-0 and a late type-2 cytokine response, whereas the inoculation of 2000 protoscoleces induced an early type-2 and a late type-0 cytokine response. Parasite growth was lower in the group inoculated with the low infective dose. These results indicate that the cytokine response during the infection by the helminth E. granulosus depends on the dose of parasites to which the host has been exposed.

O-glycosylation in Echinococcus granulosus: identification and characterization of the carcinoma-associated Tn antigen

In the present work we demonstrate that the cancer-associated O-glycosylated Tn antigen (GalNAc-O-Ser/Thr) is expressed by the cestode Echinococcus granulosus. This antigen was detected in both larval and adult worm extracts, with the highest specific activity observed in the adult excretion/secretion preparation. Histochemical analysis showed that Tn is preferentially expressed in the parenchyma in both parasite stages and the external part of tegument in adult worms. A similar pattern was observed for sialyl-Tn, a related O-linked antigen. Tn glycoproteins from protoscoleces were resolved by SDS-PAGE in two main components of 43 and 49 kDa. After purification, this material was reactive with lectins which bind GlcNAc/sialic acid, GalNAc, and T antigen. In a preliminary evaluation, high levels of Tn antigen were detected in serum samples from patients with hydatid cyst, suggesting that the measure of Tn in serum could be a biomarker of this disease, although extensive work is necessary in order to determine the clinical usefulness of this assay. The results reported here, the first evidence of O-glycosylation pathways in E. granulosus and the presence of Tn antigen in cestodes, suggest that the evaluation of O-glycosylated antigens might give new insights in the host-parasite relationship.

Characterization and optimization of bovine Echinococcus granulosus cyst fluid to be used in immunodiagnosis of hydatid disease by ELISA

The aim of this work was to assess the influence in the diagnostic value for human hydatid disease of the composition of bovine hydatid cyst fluid (BHCF) obtained from fertile (FC) and non-fertile cysts (NFC). Eight batches from FC and 5 from NFC were prepared and analysed with respect to chemical composition: total protein, host-derived protein, carbohydrate and lipid contents. No differences were observed in the first two parameters but carbohydrate and lipid contents were shown to be higher in batches from FC than in those from NFC. Bands of 38 and 116 kD in SDS-PAGE profiles were observed to be present in BHCF from FC only. Two pools were prepared from BHCF batches obtained from FC (PFC) and NFC (PNFC), respectively. Antigen recognition patterns were analysed by immunoblot. Physicochemical conditions for adsorption of antigens to the polystyrene surface (ELISA plates) were optimized. The diagnostic value of both types of BHCF as well as the diagnostic relevance of oxidation of their carbohydrate moieties with periodate were assessed by ELISA using 42 serum samples from hydatid patients, 41 from patients with other disorders, and 15 from healthy donors. Reactivity of all sera against native antigen were tested with and without free phosphorylcholine. The best diagnostic efficiency was observed using BHCF from periodate-treated PFC using glycine buffer with strong ionic strength to coat ELISA plates.

Structural characterization of the N-glycans from Echinococcus granulosus hydatid cyst membrane and protoscoleces

Infection by the tapeworm Echinococcus granulosus in the intermediate host results in the development of a hydatid cyst which contains the protoscoleces within a fluid-filled cavity enclosed by the bilayered cyst membrane. N-glycans were enzymatically released from crude extracts of homogenates of hydatid cyst membranes and protoscoleces and their structures were defined by high sensitivity fast atom bombardment mass spectrometry in conjunction with sequential exoglycosidase digestions. The major N-glycans from the cyst membrane were found to be non-charged structures having complex-type antennae and core fucosylation. The antennae are either truncated at the first N-acetylglucosamine or are extended with beta-galactose to form N-acetyllactosamine (lacNAc). A significant proportion of the lacNAc backbones are capped by alpha-galactose. The resulting Gal alpha-Gal beta-terminal structures may account for the earlier observation that antibodies against the blood group P1 epitope recognise components of hydatid cyst extracts. The complex-type N-glycans identified in the protoscoleces extracts were the same as the neutral structures found in the cyst membrane but a small proportion of high mannose structures and truncated di- and trimannosyl core structures were also identified. Sialylated N-glycans were identified as minor constituents of the cyst membrane preparation but were not observed in protoscoleces extracts. Whether the sialylated glycans are host derived or endogenously synthesized by the parasite remains to be established. This is the first reported structural analysis of N-glycans from cestodes and provides new insights into protein glycosylation in helminths.

Induction of protective immunity against murine secondary hydatidosis

Significant protective immunity against secondary hydatidosis in mice was achieved by immunization with a preparation of surface molecules of E. granulosus protoscoleces with Freund's incomplete adjuvant (PSEx-IFA). Study of PSEx-IFA immunogenicity demonstrates that glucidic epitopes evoked mainly IgM responses while peptidic epitopes evoke mainly IgG responses; however both types of epitopes elicit both types of responses. Analysis of the possible association between susceptibility or resistance to infection and antibody responses after challenge was also performed. Cyst fluid antigen (CFAg) specific antibody titres on month eight after challenge correlated with number and size of cysts. On the other hand no correlation was observed between protection and PSEx specific IgG titres either on the day of challenge or one month later. Nonetheless, immunoblot analysis revealed that some PSEx molecules were recognized on day 30 after challenge only by sera from immunized mice.

High performance latex reagent for hydatid serology using an Echinococcus granulosus lipoprotein antigen fraction purified from cyst fluid in one step

A lipoprotein fraction from fertile bovine hydatid cyst fluid (FBHCF) was isolated by affinity chromatography on acrylic-heparin. The heparin-binding lipoprotein fraction (HBLF) was proved to be free from host immunoglobulins and albumin. Immunoblotting with confirmed human hydatid sera showed that the major relevant diagnostic bands in FBHCF were also present in HBLF. HBLF or FBHCF were used to sensitize polystyrene latex particles. HBLF-latex showed both higher reactivity with positive hydatid human sera and higher batch-to-batch reproducibility than FBHCF-latex. Titration of sera from 119 surgically confirmed hydatid patients, 48 with other parasitic diseases, 6 with unrelated diseases and 37 healthy subjects was performed using HBLF-latex and conventional ELISA (using FBHCF). Sensitivity and specificity were 83 and 87% for ELISA and 87 and 88% for HBLF-latex. These results indicate that, while being simpler and faster to perform, the HBLF-latex has a similar diagnostic value to that of the conventional ELISA test.

Metalloproteinases in the larvae of Echinococcus granulosus

Proteolytic activity in hydatid cyst fluid, cyst membranes and protoscoleces of E. granulosus was analyzed by electrophoresis in gelatin-containing polyacrylamide gels, including characterization with a set of protease inhibitors. All contained metalloproteinases in the range 60-120 kDa, with neutral/alkaline pH optima. Major activity was observed in hydatid fluid and the membranes (five bands) with both exhibiting similar electrophoretic patterns. The samples prepared from protoscoleces shared only some of these bands.

Induction of an immune response to the porin of Haemophilus influenzae type b by monoclonal anti-idiotypic antibodies

Monoclonal anti-idiotypes were generated against monoclonal antibody (mAb) Hb-2 which recognized a highly conserved epitope on the outer membrane porin protein from Haemophilus influenzae type b (Hib). Four hybridomas reacting with F(ab') 2 fragments of Hb-2 were selected and characterized. Inhibition studies using syngeneic anti-anti-idiotypic antisera suggested that at least three different antigenic determinants on Hb-2 were recognized by these monoclonal anti-idiotypes. The binding of each anti-idiotype to Hb-2 was inhibited by Hb-2 whereas the reaction was not affected by any other anti-Hib mAb. Complete inhibition of the binding of anti-idiotype to the idiotype could be achieved with 10 micrograms of total outer membrane protein (OMP) from Hib suggesting that the anti-idiotypes might be directed against paratope-associated idiotypes. Outer membrane antigens not recognized by mAb Hb-2 did not inhibit the reaction. Furthermore, the pre-incubation of Hb-2 with each anti-idiotype specifically prevented the reaction of Hb-2 with its antigen. Antibodies with specificity for the porin were generated in guinea pigs immunized with anti-idiotypes AHb-22 and AHb-23. This study indicates that these particular monoclonal anti-idiotypes may be used as an antigen substitute for the porin of Hib in a xenogeneic species.