Specific immunization using keyhole limpet hemocyanin-ganglioside conjugates

Chemical synthesis and immunological evaluation of entirely carbohydrate conjugate Globo H-PS A1

An anticancer, entirely carbohydrate conjugate, Globo H-polysaccharide A1 (Globo H-PS A1), was chemically prepared and immunologically evaluated in C57BL/6 mice. Tumor associated carbohydrate antigen Globo H hexasaccharide was synthesized in an overall 7.8% yield employing a convergent [3 + 3] strategy that revealed an anomeric aminooxy group used for conjugation to oxidized PS A1 via an oxime linkage. Globo H-PS A1, formulated with adjuvants monophosphoryl lipid A and TiterMax® Gold. After immunization an antigen specific immune response was observed in ELISA with anti-Globo H IgG/IgM antibodies. Specificity of the corresponding antibodies was determined by FACS showing cell surface binding to Globo H-positive cancer cell lines MCF-7 and OVCAR-5. The anti-Globo H antibodies also exhibited complement-dependent cellular cytotoxicity against MCF-7 and OVCAR-5 cells.

Evolution of carbohydrate antigens--microbial forces shaping host glycomes?

Many glycans show remarkably discontinuous distribution across evolutionary lineages. These differences play major roles when organisms belonging to different lineages interact as host-pathogen or host-symbiont. Certain lineage-specific glycans have become important signals for multicellular host organisms, which use them as molecular signatures of their pathogens and symbionts through recognition by a toolkit of innate defense molecules. In turn, pathogens have evolved to exploit host lineage-specific glycans and are constantly shaping the glycomes of their hosts. These interactions take place in the face of numerous critical endogenous functions played by glycans within host organisms. Whether due to simple evolutionary divergence or adaptive changes under natural selection resulting from endogenous functional requirements, once different lineages elaborate on differential glycomes these mutual differences provide opportunities for host exploitation and/or pathogen defense between lineages. Such phylogenetic molecular recognition mechanisms will augment and likely contribute to the maintenance of lineage-specific differences in glycan repertoires.

Development and immunochemical evaluation of antibodies Y for the poorly immunogenic polypeptide prothymosin alpha

Since conserved mammalian polypeptides are believed to exhibit enhanced immunogenicity in avian species, hens were immunized against the poorly immunogenic, highly conserved mammalian polypeptide prothymosin alpha (ProTalpha), i.e. against either non-conjugated ProTalpha (isolated from bovine thymus) or ProTalpha conjugated to keyhole limpet hemocyanin (ProTalpha/KLH). The antibodies Y were isolated from the egg yolk and evaluated through suitable dot-blot and ELISA systems in parallel with antibodies G isolated from the antiserum of rabbits immunized against the same immunogens. As revealed, antibodies Y and G of low titer and/or affinity were obtained against non-conjugated ProTalpha, while antibodies Y against ProTalpha/KLH had a better apparent titer, could better discriminate between ProTalpha and the closely related bioactive peptide thymosin alpha 1, and were obtained at much larger quantities than the corresponding antibodies G.

The structure of a functional unit from the wall of a gastropod hemocyanin offers a possible mechanism for cooperativity

Structure-function relationships in a molluscan hemocyanin have been investigated by determining the crystal structure of the Rapana thomasiana (gastropod) hemocyanin functional unit RtH2e in deoxygenated form at 3.38 A resolution. This is the first X-ray structure of an unit from the wall of the molluscan hemocyanin cylinder. The crystal structure of RtH2e demonstrates molecular self-assembly of six identical molecules forming a regular hexameric cylinder. This suggests how the functional units are ordered in the wall of the native molluscan hemocyanins. The molecular arrangement is stabilized by specific protomer-to-protomer interactions, which are probably typical for the functional units building the wall of the cylinders. A molecular mechanism for cooperative dioxygen binding in molluscan hemocyanins is proposed on the basis of the molecular interactions between the protomers. In particular, the deoxygenated RtH2e structure reveals a tunnel leading from two opposite sides of the molecule to the active site. The tunnel represents a possible entrance pathway for dioxygen molecules. No such tunnels have been observed in the crystal structure of the oxy-Odg, a functional unit from the Octopus dofleini (cephalopod) hemocyanin in oxygenated form.

Tolerance to self gangliosides is the major factor restricting the antibody response to lipopolysaccharide core oligosaccharides in Campylobacter jejuni strains associated with Guillain-Barré syndrome

Guillain-Barré syndrome following Campylobacter jejuni infection is frequently associated with anti-ganglioside autoantibodies mediated by molecular mimicry with ganglioside-like oligosaccharides on bacterial lipopolysaccharide (LPS). The regulation of antibody responses to these T-cell-independent antigens is poorly understood, and only a minority of Campylobacter-infected individuals develop anti-ganglioside antibodies. This study investigates the response to gangliosides and LPS in strains of mice by using a range of immunization strategies. In normal mice following intraperitoneal immunization, antibody responses to gangliosides and LPS are low level but can be enhanced by the antigen format or coadministration of protein to recruit T-cell help. Class switching from the predominant immunoglobulin M (IgM) response to IgG3 occurs at low levels, suggesting B1-cell involvement. Systemic immunization results in poor responses. In GalNAc transferase knockout mice that lack all complex gangliosides and instead express high levels of GM3 and GD3, generation of anti-ganglioside antibodies upon immunization with either complex gangliosides or ganglioside-mimicking LPS is greatly enhanced and exhibits class switching to T-cell-dependent IgG isotypes and immunological memory, indicating that tolerance to self gangliosides is a major regulatory factor. Responses to GD3 are suppressed in knockout mice compared with wild-type mice, in which responses to GD3 are induced specifically by GD3 and as a result of polyclonal B-cell activation by LPS. The anti-ganglioside response generated in response to LPS is also dependent on the epitope density of the ganglioside mimicked and can be further manipulated by providing secondary signals via lipid A and CD40 ligation.

Antitumor effect of the idiotypic cascade induced by an antibody encapsulated in poly(d,l-lactide-co-glycolide) microspheres

A major difficulty encountered during development of antibody vaccines is their weak immunogenicity. In this study, a monoclonal antibody CS20.5 to human breast cancer antigen CA15.3 was coencapsulated in poly(d,l-lactide-co-glycolide) microspheres with monophosphoryl lipid A. The antitumor effect of this formulation was investigated in a murine model. The induced Ab2 biologically mimics antigen as it competed with CA15.3 for the same idiotope on Ab1. Ab3 induction was also observed. After five sequential administrations of encapsulated antibody, mice showed statistically significant tumor regression. These results indicate that this formulation may serve as a potential treatment for breast cancer.

Keyhole limpet hemocyanin (KLH): a biomedical review

In this review we present a broad survey of fundamental scientific and medically applied studies on keyhole limpet hemocyanin (KLH). Commencing with the biochemistry of KLH, information on the biosynthesis and biological role of this copper-containing respiratory protein in the marine gastropod Megathura crenulata is provided. The established methods for the purification of the two isoforms of KLH (KLH1 and KLH2) are then covered, followed by detailed accounts of the molecular mass determination, functional unit (FU) structure, carbohydrate content, immunological analysis and recent aspects of the molecular genetics of KLH. The transmission electron microscope (TEM) has contributed significantly to the understanding of KLH structure, primarily from negatively stained images. We give a brief account of TEM studies on the native KLH oligomers, the experimental manipulation of the oligomeric states, together with immunolabelling data and studies on subunit reassociation. The field of cellular immunology has provided much relevant biomedical information on KLH and has led to the expansion of use of KLH in experimental immunology and clinically as an immunotherapeutic agent; this area is presented in some detail. The major clinical use of KLH is specifically for the treatment of bladder carcinoma, with efficacy probably due to a cross-reacting carbohydrate epitope. KLH also has considerable possibilities for the treatment of other carcinomas, in particular the epithelially derived adenocarciomas, when used as a carrier for carcinoma ganglioside and mucin-like epitopes. The widespread use of KLH as a hapten carrier and generalised vaccine component represent other major on-going aspects of KLH research, together with its use for the diagnosis of Schistosomiasis, drug assay and the treatment of drug addiction. Immune competence testing, assessment of stress and the understanding of inflammatory conditions are other areas where KLH is also making a useful contribution to medical research.

Basidiolipids from Agaricus are novel immune adjuvants

The primary aim of the present study was to compare the immune adjuvanticity of two different groups of glycolipids, i.e., the newly discovered basidiolipids from Basidiomycete mushrooms (Bl-1, Bl-2, Bl-3, and Bl-4), and saponin fractions from Quillaja saponaria. The basidiolipids, though with differential effectiveness of the Bl-components, stimulated the expression of serum immune globulins in mice that recognized co-injected antigens, bovine serum albumin (BSA) or a keyhole-limpet hemocyanin-ganglioside Gfpt1 conjugate (KLH-Gfpt1), respectively. The immune adjuvanticity of the basidiolipids was comparable to that of acidic (QAS2, QAS5, QAS10), and novel neutral (QNS1, QNS2, QNS3) saponin compounds isolated and purified from Quillaja saponaria bark bulk material. Basidiolipids, as well as, the Q. saponin fractions were only marginally antigenic. MPL-A, by contrast, a comparable immune adjuvant, stimulated the expression of specific antibodies that recognized this glycophospholipid. Different from the Q. saponins with restricted toxicity, the basidiolipids displayed no toxic or hemolytic properties.

Mass determination, subunit organization and control of oligomerization states of keyhole limpet hemocyanin (KLH)

Analytical dark-field scanning transmission electron microscopy (STEM) of freeze-dried unstained specimens of keyhole limpet hemocyanin (KLH; from Megathura crenulata, a prosobranch gastropod) gave a molecular mass of 400 kDa for the subunit of KLH1 and of 345 kDa for the subunit of KLH2, which confirms our published values from SDS/PAGE. Within the 400-kDa KLH1 subunit we identified, by limited proteolysis, isolation of fragments and N-terminal sequencing, eight distinct 45-60 kDa functional domains (termed 1a through 1h) and determined their sequential arrangement. The KLH1 domains differ biochemically and immunologically from each other and from the previously characterized seven domains of KLH2 (termed 2a through 2g). Our partial amino acid sequences suggest that a domain, equivalent to the C-terminal domain 1h, is missing in KLH2. This deficiency is believed to be genuine and not an artifact of the subunit preparation procedure, since STEM measurements of the native didecamers yielded a mass difference of about 800 kDa between KLH1 and KLH2 (8.3 MDa versus 7.5 MDa), correlating with 20 copies of a functional 1h domain. It was also shown that the KLH1 didecamer can be rapidly split (minutes) into an almost homogeneous population of stable decamers by increasing the pH of the Tris/saline stabilizing buffer (routinely pH 7.4), which contains 5 mM CaCl2 and 5 mM MgCl2, to pH 8.5. Reformation of the didecamers occurred more slowly (days) upon dialysis against the pH 7.4 stabilizing buffer. Addition of 100 mM calcium and 100 mM magnesium ions to the pH 7.4 stabilizing buffer leads to the more rapid (overnight) formation of didecamers together with a significant number of previously unobserved KLH1 multidecamers, which could be structurally distinguished from the established multidecamers of KLH2.

Amino-terminal oxygen-binding functional unit of the Rapana thomasiana grosse (gastropod) hemocyanin: carbohydrate content, monosaccharide composition and amino acid sequence studies

The amino-terminal oxygen-binding unit Rta of the Rapana thomasiana hemocyanin is a glycoprotein with a carbohydrate content of 4.8% (w/w). Sugar analysis revealed as monosaccharide constituents xylose, fucose, 3-O-methylgalactose, mannose, galactose, N-acetylgalactosamine and N-acetylglucosamine residues. On subtracting the carbohydrate contribution from the molecular mass of 49,698 Da, determined by laser desorption mass spectrometry for Rta, an M(r) value of 47,318 Da was determined for the polypeptide part of the functional unit. The Rapana hemocyanin oxygen-binding unit Rta contains 400 residues in a single polypeptide chain. The nearly complete amino acid sequence (about 90%) is determined. This is the first report on a sequence of a marine gastropod oxygen-binding unit and also on a molluscan hemocyanin amino-terminal unit. Comparison of the Rta sequence with those of other molluscan hemocyanin units, localized in the C-terminus or in the middle of the respective multidomain polypeptide chains, revealed 42-46% homology (52-55%, including isofunctional residues). Probably, all molluscan oxygen-binding units evolved from a common ancestral gene.

Keyhole limpet hemocyanin (KLH), I: Reassociation from Immucothel followed by separation of KLH1 and KLH2

Studies of keyhole limpet hemocyanin (KLH) normally require purification of functional complexes directly from living animals. An alternative procedure is described wherein a commercial preparation of KLH which is fully dissociated into its subunits (Immucothel, biosyn Arzneimittel GmbH) is reassociated in the presence of a high concentration of calcium and magnesium. The reassociation products, when observed by electron microscopy, consist of didecamers, multidecamers and flexible tubules of varying length. The two forms of KLH described previously and designated KLH1 and KLH2, are present in the reassociated mixture as homo-oligomers/polymers and can be separated by selective dissociation of the KLH2 by treatment with 1% ammonium molybdate-0.2% PEG at pH 5.7, followed by gel filtration chromatography in this solution. In addition to discrete elution peaks containing didecameric KLH1 and dissociated subunits of KLH2, a leading peak contains a tubular/polymeric form of KLH1, not previously described. Under negative staining in conditions designed specifically for the creation of 2-dimensional crystals on mica (the negative staining-carbon film procedure), this tubular form of KLH1 can be transformed into a larger diameter multidecameric form, again not previously described for KLH1. The purified KLH2 peak is indistinguishable from subunit material prepared from living animals. This, Immucothel appears to provide a standardized source of subunits suitable for biochemical and structural studies on the two types of KLH.

Rapana thomasiana grosse (gastropoda) haemocyanin: spectroscopic studies of the structure in solution and the conformational stability of the native protein and its structural subunits

1. The stability towards pH changes, thermal and chemical (guanidine hydrochloride) denaturation of the oxy- and apo-forms of the native Rapana thomasiana haemocyanin and its structural subunits, RHSS1 and RHSS2, has been investigated using fluorescence and CD spectroscopy. The association of the subunits into haemocyanin aggregates increases considerably the melting temperature and the free energy of stabilization in water. The guanidine hydrochloride denaturation of the aggregated oxygen-transporting protein depends slightly on the protein concentration. The denaturation of the individual subunits is concentration-independent. Rapana haemocyanin is 5.9-7.5 kJ/mol more stable than the constituent polypeptide chains. 2. Upon excitation of the native haemocyanin and the subunits at 295 or 280 nm the fluorescence emission is determined by tryptophyl residues 'buried' deeply in the hydrophobic interior of the protein globules. This is confirmed by quenching experiments with acrylamide, caesium and iodide ions. The efficiency of the radiationless energy transfer between the phenol (donor) and indole (acceptor) fluorophores in the three species, native haemocyanin, RHSS1 and RHSS2, has been determined. An efficient 'interchain' energy transfer between tyrosyl and tryptophyl residues from different polypeptide chains occurs in the non-dissociated form of the haemocyanin. 3. The tryptophan emission of the oxyhaemocyanin, oxy-RHSS1 and oxy-RHSS 2 is strongly quenched by the copper-dioxygen complex at the active site and the respective quantum yields of fluorescence of the oxygenated species are 4-7 times lower than those of the apo-forms. Protonated imidazole groups quench the fluorescence of neighbouring exited indole rings, probably by charge-transfer complex formation.

Neutral glycolipids of Schistosoma mansoni as feasible antigens in the detection of schistosomiasis

The neutral glycolipid fraction from mouse-propagated, Schistosoma mansoni adult worms has been investigated as to its chromatographic and antigenic properties, and whether it fulfills the serodiagnostic antigen requirements of sensitivity and specificity in the detection of schistosomiasis. Serological analyses were performed by thin-layer chromatography immunostaining and ELISA. In the acute-phase form of mouse schistosomiasis, the kinetics of development of neutral glycolipid-specific antibody levels was correlated with the intensity of the initial infection and the response was dominated by IgG, as represented by the subclass IgG1. With the experimental animal helminthiases screened, glycolipid antigenicity fulfilled the fundamental traits for a serodiagnostic reagent. In the chronic-phase form of human schistosomiasis mansoni, neutral glycolipid-specific antibody levels were not correlated with the intensity of infection, as estimated from the faecal content of parasite eggs, whilst the isotypic response was dominated by IgM and IgG, the latter represented primarily by IgG1 and secondarily by IgG3. With other human helminthiases, glycolipid antigenicity was incomplete, in that, the specificity was only partially fulfilled. The reason for this incomplete specificity has been clarified, in part, by the detection of cryptic schistosomiasis infections in the cohorts of African patient sera examined.