A Pfs48/45-based vaccine to block Plasmodium falciparum transmission: phase 1, open-label, clinical trial

BACKGROUND

The stalling global progress in malaria control highlights the need for novel tools for malaria elimination, including transmission-blocking vaccines. Transmission-blocking vaccines aim to induce human antibodies that block parasite development in the mosquito and mosquitoes becoming infectious. The Pfs48/45 protein is a leading Plasmodium falciparum transmission-blocking vaccine candidate. The R0.6C fusion protein, consisting of Pfs48/45 domain 3 (6C) and the N-terminal region of P. falciparum glutamate-rich protein (R0), has previously been produced in Lactococcus lactis and elicited functional antibodies in rodents. Here, we assess the safety and transmission-reducing efficacy of R0.6C adsorbed to aluminium hydroxide with and without Matrix-M™ adjuvant in humans.

METHODS

In this first-in-human, open-label clinical trial, malaria-naïve adults, aged 18-55 years, were recruited at the Radboudumc in Nijmegen, the Netherlands. Participants received four intramuscular vaccinations on days 0, 28, 56 and 168 with either 30 µg or 100 µg of R0.6C and were randomised for the allocation of one of the two different adjuvant combinations: aluminium hydroxide alone, or aluminium hydroxide combined with Matrix-M1™ adjuvant. Adverse events were recorded from inclusion until 84 days after the fourth vaccination. Anti-R0.6C and anti-6C IgG titres were measured by enzyme-linked immunosorbent assay. Transmission-reducing activity of participants' serum and purified vaccine-specific immunoglobulin G was assessed by standard membrane feeding assays using laboratory-reared Anopheles stephensi mosquitoes and cultured P. falciparum gametocytes.

RESULTS

Thirty-one participants completed four vaccinations and were included in the analysis. Administration of all doses was safe and well-tolerated, with one related grade 3 adverse event (transient fever) and no serious adverse events occurring. Anti-R0.6C and anti-6C IgG titres were similar between the 30 and 100 µg R0.6C arms, but higher in Matrix-M1™ arms. Neat participant sera did not induce significant transmission-reducing activity in mosquito feeding experiments, but concentrated vaccine-specific IgGs purified from sera collected two weeks after the fourth vaccination achieved up to 99% transmission-reducing activity.

CONCLUSIONS

R0.6C/aluminium hydroxide with or without Matrix-M1™ is safe, immunogenic and induces functional Pfs48/45-specific transmission-blocking antibodies, albeit at insufficient serum concentrations to result in transmission reduction by neat serum. Future work should focus on identifying alternative vaccine formulations or regimens that enhance functional antibody responses.

TRIAL REGISTRATION

The trial is registered with ClinicalTrials.gov under identifier NCT04862416.

Pionic hydrogen and deuterium

The strong-interaction effects both in pionic hydrogen and deuterium atoms have been re-determined with improved precision. The hadronic shift and width in pionic hydrogen together with the hadronic shift in pionic deuterium constitute a one-fold constraint for the two independent pion-nucleon scattering lengths. Furthermore, the hadronic width in pionic deuterium measures the transition strength of s-wave pions on an isoscalar nucleon-nucleon pair which is an independent quantity not related to the pion-nucleon scattering lengths. The experiment was performed at the Paul Scherrer Institute by stopping a high-intensity low-energy pion beam in gaseous targets using the cyclotron trap. The X-rays emitted by the πH and πD atoms were analysed with a high resolution Bragg spectrometer equipped with spherically bent crystals. The pion-nucleon scattering lengths and other physical quantities extracted from the atom data are in good agreement with the results obtained from pionnucleon and nucleon-nucleon scattering experiments and confirm that a consistent picture is achieved for the low-energy pion-nucleon sector with respect to the expectations of chiral perturbation theory.

Natural antibody responses to Plasmodium falciparum MSP3 and GLURP(R0) antigens are associated with low parasite densities in malaria patients living in the Central Region of Ghana

Background

Plasmodium falciparum genetic diversity and multiplicity of infection (MOI) are parasite features that have been suggested to influence the acquisition of protective immunity against malaria. This study sought to assess the relationship between MOI and parasite density (PD) in malaria patients living in the Central Region of Ghana and to determine whether naturally occurring antibody levels against P. falciparum GLURP (PF3D7_1035300) and MSP3 (PF3D7_1035400) antigens are associated with decreased parasite load.

Methods

Dried filter paper blood blots were obtained from children and adults diagnosed with uncomplicated P. falciparum malaria. Microscopy was used to estimate P. falciparum parasite density and polymerase chain reaction (PCR) amplification of the polymorphic regions of msp1 (PF3D7_0930300) and msp2 (PF3D7_0206800) was used for parasite genotyping and MOI determination. ELISA was used to measure the serum IgG concentration of R0 fragment of GLURP (GLURP(R0)) and MSP3 antibodies.

Results

All 115 samples were positive for P. falciparum by PCR using either the msp1 or msp2 genotyping primer sets. The most prevalent msp1 and msp2 alleles were KI and 3D7, respectively. The geometric mean (GM) for MOI determined by both msp1 and msp2 genotyping was 1.3 for the entire population and was generally higher in children than in adults. Seropositivity was estimated at 67 and 63% for GLURP(R0) and MSP3 antibodies, respectively, and antibody titers were negatively correlated with parasite density.

Conclusions

The negative correlation between naturally occurring GLURP(R0) and MSP3 antibody levels and parasite density observed in this study suggest that augmenting the antibody response with the GMZ2 vaccine could enhance protection in the Central Region of Ghana.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-2338-7) contains supplementary material, which is available to authorized users.

FcγRIIa polymorphism and anti-malaria-specific IgG and IgG subclass responses in populations differing in susceptibility to malaria in Burkina Faso

FcγRIIa is known to be polymorphic; and certain variants are associated with different susceptibilities to malaria. Studies involving the Fulani ethnic group reported an ethnic difference in FcγRIIa-R131H genotype frequencies between the Fulani and other sympatric groups. No previous studies have addressed these questions in Burkina Faso. This study aimed to assess the influence of FcγRIIa-R131H polymorphism on anti-falciparum malaria IgG and IgG subclass responses in the Fulani and the Mossi ethnic groups living in Burkina Faso. Healthy adults more than 20 years old belonging to the Mossi or the Fulani ethnic groups were enrolled for the assessment of selected parasitological, immunological and genetic variables in relation to their susceptibility to malaria. The prevalence of the Plasmodium falciparum infection frequency was relatively low in the Fulani ethnic group compared to the Mossi ethnic group. For all tested antigens, the Fulani had higher antibody levels than the Mossi group. In both ethnic groups, a similar distribution of FcγRIIa R131H polymorphism was found. Individuals with the R allele of FcγRIIa had higher antibody levels than those with the H allele. This study confirmed that malaria infection affected less the Fulani group than the Mossi group. FcγRIIa-R131H allele distribution is similar in both ethnic groups, and higher antibody levels are associated with the FcγRIIa R allele compared to the H allele.

Do antibody responses to malaria vaccine candidates influenced by the level of malaria transmission protect from malaria?

OBJECTIVES

To examine whether the humoural response to malaria vaccine candidate antigens, Plasmodium falciparum [circumsporozoite repetitive sequence (NANP)(5) GLURP fragments (R0 and R2) and MSP3] varies with the level of malaria transmission and to determine whether the antibodies (IgG) present at the beginning of the malaria transmission season protect against clinical malaria.

METHODS

Cross-sectional surveys were conducted to measure antibody response before, at the peak and at the end of the transmission season in children aged 6 months to 10 years in two villages with different levels of malaria transmission. A cohort study was performed to estimate the incidence of clinical malaria.

RESULTS

Antibodies to these antigens showed different seasonal patterns. IgG concentrations to any of the four antigens were higher in the village with high entomological inoculation rate. Multivariate analysis of combined data from the two villages indicated that children who were classified as responders to the selected antigens were at lower risk of clinical malaria than children classified as non-responders [(NANP)(5) (incidence rate ratio (IRR) = 0.65, 95% CI: 0.46-0.92; P = 0.016), R0 (IRR = 0.69, 95% CI: 0.48-0.97; P = 0.032), R2 (IRR = 0.73, 95% CI: 0.50-1.06; P = 0.09), MSP3 (IRR = 0.52, 95% CI: 0.32-0.85; P = 0.009)]. Fitting a model with all four antibody responses showed that MSP3 looked the best malaria vaccine candidate (IRR = 0.63; 95% CI: 0.38-1.05; P = 0.08).

CONCLUSION

Antibody levels to the four antigens are affected by the intensity of malaria transmission and associated with protection against clinical malaria. It is worthwhile investing in the development of these antigens as potential malaria vaccine candidates.

Natural antibody response to Plasmodium falciparum Exp-1, MSP-3 and GLURP long synthetic peptides and association with protection

A longitudinal study was undertaken in Burkina Faso among 293 children aged 6 months to 9 years in order to determine the correlation between an antibody response to several individual malarial antigens and malarial infection. It was found that the presence of a positive antibody response at the beginning of the rainy season to three long synthetic peptides corresponding to Plasmodium falciparum Exp-1 101-162, MSP-3 154-249 and GLURP 801-920 but not to CSP 274-375 correlated with a statistically significant decrease in malarial infection during the ongoing transmission season. The simultaneous presence of an antibody response to more than one antigen is indicative of a lower frequency of malarial infection. This gives scientific credibility to the notion that a successful malaria vaccine should contain multiple antigens.

Immunization of Saimiri sciureus monkeys with Plasmodium falciparum merozoite surface protein-3 and glutamate-rich protein suggests that protection is related to antibody levels

The immunogenicity and protective efficacy of various antigen-adjuvant formulations derived either from the merozoite-surface protein-3 (MSP-3) or the glutamate-rich protein (GLURP) of Plasmodium falciparum were evaluated in Saimiri sciureus monkeys. These proteins were selected for immunogenicity studies based primarily on their capacity of inducing an antibody-dependent cellular inhibition effect on parasite growth. Some of the S. sciureus monkeys immunized with MSP-3(212-380)-AS02 or GLURP(27-500)-alum were able to fully or partially control parasitaemia upon an experimental P. falciparum [Falciparum Uganda Palo Alto (FUP-SP) strain] blood-stage infection, and this protection was related to the prechallenge antibody titres induced. The data are indicative that MSP-3 and GLURP can induce protective immunity against an experimental P. falciparum infection using adjuvants that are acceptable for human use and this should trigger further studies with those new antigens.

Humoral responses to defined malaria antigens in children living since birth under insecticide treated curtains in Burkina Faso

Insecticide treated materials (ITM) are considered a useful malaria control measure for endemic countries, but whether they also delay the acquisition of immunity to malaria remains unclear. This study investigates plasma antibody levels in 160 children aged 3-6 years from five villages protected by insecticide treated curtains (ITC) over 6 years and in 184 children of the same age group from five villages in the same area never covered by ITC. The antigens to which antibodies were investigated were: the Plasmodium falciparum circumsporozoite protein (CSP) repetitive sequence (NANP)5; the C-terminal domain of the P. falciparum exported protein 1 (Cter-PfExp1); three fragments of the glutamate rich protein (GLURP), referred to as R0, R1 and R2; the merozoite surface protein 3 (MSP3). The level of antibodies was lower in children from the ITC area than in children from the non-ITC area for (NANP)5, R0, R2 and MSP3. Prevalence and intensity of P. falciparum infection were similar in the two groups of children. These findings suggest that reducing the level of malaria transmission over a long period may affect the level of antibodies in children to both sporozoite and blood stage malaria antigens.

Effect of combining nicotinamide as a PARS-inhibitor with selective iNOS blockade during porcine endotoxemia

OBJECTIVE

To investigate the effects of combined selective inducible nitric oxide synthase (iNOS) inhibition using 1400 W with nicotinamide (NAD) as a PARS-inhibitor on hepato-splanchnic hemodynamics, O(2) kinetics, and energy metabolism during hyperdynamic porcine endotoxemia.

DESIGN

Prospective, randomized, controlled, interventional experiment.

SETTING

Animal research laboratory.

SUBJECTS

Seventeen domestic pigs.

INTERVENTIONS

After 12 h of continuous i.v. endotoxin (LPS) infusion 17 pigs received either no drug (CON, n=9) or 1400 W, titrated to maintain mean arterial pressure (MAP) at pre-endotoxin level, plus 10 mg.kg.h NAD ( n=8;). Measurements were obtained before, 12 h, 18 h, and 24 h after starting LPS infusion.

MEASUREMENTS AND RESULTS

In addition to systemic and pulmonary hemodynamics and gas exchange, we measured hepatic arterial and portal venous blood flow, liver and portal venous drained viscera O(2) exchange, ileal mucosal-arterial PCO(2) gap, and portal as well as hepatic venous lactate/pyruvate ratios. Expired NO and plasma nitrate levels were assessed as a parameter of NO production. Without affecting cardiac output, therapy maintained MAP and blunted the LPS-induced rise in expired NO levels, attenuated the progressive fall in liver lactate clearance, and blunted the impairment of hepato-splanchnic redox state. The rise of ileal mucosal-arterial PCO(2) gap was not influenced.

CONCLUSIONS

Combining selective iNOS inhibition with NAD as a PARS blocker may prevent circulatory failure and attenuate the detrimental consequences of LPS in intestinal and hepatocellular energy metabolism. Given the potential hepatotoxicity of high-dose NAD treatment, more potent PARS blockers with higher selectivity might further enhance the benefit of this therapeutic approach.

Hydroxylated human homotrimeric collagen I in Agrobacterium tumefaciens-mediated transient expression and in transgenic tobacco plant

Potential contamination of animal-derived collagen with pathogens has led to the demand for safe recombinant sources of this complex molecule. In continuation of our previous work [Ruggiero et al. (2000) FEBS Lett. 469, 132-136], here we show that it is possible to produce recombinant hydroxylated homotrimeric collagen in tobacco plants that are co-transformed with a human type I collagen and a chimeric proline-4-hydroxylase (P4H). This is to our knowledge the first time that transient expression in tobacco was used to improve the quality of a recombinant protein produced in plants through co-expression with an animal cell-derived modifying enzyme. We demonstrated the functionality of the new chimeric P4H and thus improved the thermal stability of recombinant collagen I from plants to 37 degrees C.

In situ deprotection: a method for covalent immobilization of peptides with well-defined orientation for use in solid phase immunoassays such as enzyme-linked immunosorbent assay

The orientation of an immobilized antigen is important for recognition by, e.g., an antibody. When noncovalent passive adsorption is used for immobilization, the number of ways that the antigen can attach to the surface is numerous and control of how the antigen orientates on the surface is limited. Covalent immobilization restricts the number of the ways that the antigen can be immobilized to the number of reactive groups on the antigen and, hence, the orientation of the immobilized antigen is more predictable. Peptide antigens were synthesized and purified with protection groups on the lysine and cysteine side chains. These peptides, which have only one good nucleophilic group (the N-terminal alpha-amino group), were immobilized covalently in microtiter plates supplied with tresyl groups on the surface and the protection groups were cleaved off in situ after immobilization. The controlled orientation of these peptides resulted in enhanced recognition by antibodies in general. An enzyme-linked immunosorbent assay for detection of antibodies against a peptide derived from outer surface protein C from Borrelia burgdorferi, found in Lyme borreliosis patients, was established using this strategy. Lyme borreliosis suspect patient sera showed up to a 10-fold increase in the signal when the orientation of the peptide antigen was controlled by the in situ deprotection strategy.

Unhydroxylated triple helical collagen I produced in transgenic plants provides new clues on the role of hydroxyproline in collagen folding and fibril formation

Human unhydroxylated homotrimeric triple-helical collagen I produced in transgenic plants was used as an experimental model to provide insights into the role of hydroxyproline in molecular folding and fibril formation. By using chemically cross-linked molecules, we show here that the absence of hydroxyproline residues does not prevent correct folding of the recombinant collagen although it markedly slows down the propagation rate compared with bovine fully hydroxylated homotrimeric collagen I. Relatively slow cis-trans-isomerization in the absence of hydroxyproline likely represents the rate-limiting factor in the propagation of the unhydroxylated collagen helix. Because of the lack of hydroxylation, recombinant collagen molecules showed increased flexibility as well as a reduced melting temperature compared with native homotrimers and heterotrimers, whereas the distribution of charged amino acids was unchanged. However, unlike with bovine collagen I, the recombinant collagen did not self-assemble into banded fibrils in physiological ionic strength buffer at 20 degrees C. Striated fibrils were only obtained with low ionic strength buffer. We propose that, under physiological ionic strength conditions, the hydroxyl groups in the native molecule retain water more efficiently thus favoring correct fibril formation. The importance of hydroxyproline in collagen self-assembly suggested by others from the crystal structures of collagen model peptides is thus confirmed experimentally on the entire collagen molecule.

Effects of selective iNOS inhibition on gut and liver O2-exchange and energy metabolism during hyperdynamic porcine endotoxemia

We have previously demonstrated that non-selective nitric oxide synthase (NOS) inhibition did not reverse the LPS-induced deterioration of hepato-splanchnic energy status in porcine endotoxic shock. Therefore, this study investigated the effect of selective inducible NOS (iNOS) inhibition using 1400 W on intestinal and liver perfusion, O2 kinetics, and energy metabolism during hyperdynamic porcine endotoxemia. Intravenous E. Coli LPS was continuously infused over 24 h concomitant with fluid resuscitation. After 12 h of endotoxemia, continuous intravenous infusion of 1400 W was started until the end of the experiment and was titrated to maintain mean blood pressure (MAP) at baseline levels. Twelve, 18, and 24 h after starting LPS, we measured hepatic arterial and portal venous blood flow, ileal mucosal-arterial PCO2 gap, portal as well as hepatic venous lactate/pyruvate ratios, and endogenous glucose production rate. Expired NO and plasma nitrate levels were assessed as a measure of NO production. 1400 W decreased LPS-induced increase in expired NO and allowed for the maintenance of MAP without modification of cardiac output. Despite unchanged regional macrocirculation, 1400 W prevented the progressive rise of ileal mucosal-arterial PCO2 gap, significantly improved the LPS-induced impairment of hepato-splanchnic redox state, and blunted the decline in liver lactate clearance. Increased glucose production rate was not influenced. Thus, the selective iNOS inhibition with 1400 W prevented circulatory failure and largely attenuated otherwise progressive LPS-induced deterioration of intestinal and hepatocellular energy metabolism.

Selection of glutamate-rich protein long synthetic peptides for vaccine development: antigenicity and relationship with clinical protection and immunogenicity

Antibodies against three long synthetic peptides (LSPs) derived from the glutamate-rich protein (GLURP) of Plasmodium falciparum were analyzed in three cohorts from Liberia, Ghana, and Senegal. Two overlapping LSPs, LR67 and LR68, are derived from the relatively conserved N-terminal nonrepeat region (R0), and the third, LR70, is derived from the R2 repeat region. A high prevalence of antibody responses to each LSP was observed in all three areas of endemic infection. Levels of cytophilic immunoglobulin G (IgG) antibodies against both GLURP regions were significantly correlated with protection from clinical P. falciparum malaria. Protected children from the Ghana cohort possessed predominantly IgG1 antibodies against the nonrepeat epitope and IgG3 antibodies against the repeat epitope. T-cell proliferation responses, studied in the cohort from Senegal, revealed that T-helper-cell epitopes were confined to the nonrepeat region. When used as immunogens, the LR67 and LR68 peptides elicited strong IgG responses in outbred mice and LR67 also induced antibodies in mice of different H-2 haplotypes, confirming the presence of T-helper-cell epitopes in these constructs. Mouse antipeptide antisera recognized parasite proteins as determined by immunofluorescence and immunoblotting. This indicates that synthetic peptides derived from relatively conserved epitopes of GLURP might serve as useful immunogens for vaccination against P. falciparum malaria.

Effects of combined selective iNOS inhibition and peroxynitrite blockade during endotoxemia in pigs

We investigated the effect of mercaptoethylguanidine (MEG, 3 mg kg(-1)h(-1)), a combined selective inducible nitric oxide synthase (iNOS) inhibitor, a peroxynitrite and oxygen free radical scavenger with cyclooxygenase-inhibitor properties on intestinal and hepatic perfusion, O2 exchange, and metabolism during long-term hyperdynamic porcine endotoxemia. MEG was started 12 h after onset of endotoxemia. At baseline and after 12, 18, and 24 h of endotoxemia, hepatic arterial and portal venous blood flow, ileal mucosal-arterial PCO2 gap, portal and hepatic venous lactate/pyruvate ratio, free glutathione (GSH), and 8-isoprostanes were measured. Expired NO and plasma nitrate levels were assessed as well. MEG blunted the endotoxin-induced increase in expired NO and prevented the progressive fall in blood pressure without affecting cardiac output. It attenuated both systemic and regional venous acidosis without influencing the impairment of hepatosplanchnic metabolism nor counteracting the increase in GSH levels. In our model MEG failed to beneficially affect variables of oxidative stress.

N-glycosylation potential of maize: the human lactoferrin used as a model

In order to determine the N-glycosylation potential of maize, a monocotyledon expression system for the production of recombinant glycoproteins, human lactoferrin was used as a model. The human lactoferrin coding sequence was inserted into the pUC18 plasmid under control of the wheat glutenin promoter. Maize was stably transformed and recombinant lactoferrin was purified from the fourth generation seeds. Glycosylation was analysed by gas chromatography, lectin detection, glycosidase digestions and mass spectrometry. The results indicated that both N-glycosylation sites of recombinant lactoferrin are mainly substituted by typical plant paucimannose-type glycans, with beta1,2-xylose and alpha1,3-linked fucose at the proximal N-acetylglucosamine, and that complex-type glycans with Lewis(a) determinants are not present in maize recombinant lactoferrin.

Increased ileal-mucosal-arterial PCO2 gap is associated with impaired villus microcirculation in endotoxic pigs

OBJECTIVE

To investigate whether an increased ileal-mucosal-arterial PCO2 gap (delta PCO2) during hyperdynamic porcine endotoxemia is associated with impaired villus microcirculation.

DESIGN

Prospective, randomized, controlled, experimental study.

SETTING

Animal research laboratory.

ANIMALS

Twenty-two domestic pigs.

INTERVENTIONS

After baseline measurements, anesthetized and ventilated pigs received continuous i.v. endotoxin (ETX, n = 12) for 24 h or placebo (SHAM, n = 10).

MEASUREMENTS AND RESULTS

Before, as well as 12 and 24 h after, the start of endotoxin or saline portal venous blood flow (QPV, ultrasound flow probe) and lactate/pyruvate ratios (L/P), the ileal-mucosal-arterial delta PCO2 (fiberoptic sensor) and bowel-wall capillary hemoglobin O2 saturation (%Hb-O2-cap, remission spectrophotometry) were assessed together with intravital video records of the ileal-mucosal microcirculation (number of perfused/heterogeneously perfused/unperfused villi) using orthogonal polarization spectral imaging (CYTOSCAN A/R) via an ileostomy. At 12 and 24 h endotoxin infusion, about half of the evaluated villi were heterogeneously or unperfused which was paralleled by a progressive significant increase of the ileal-mucosal-arterial delta PCO2 and portal venous L/P ratios, whereas QPV as well as both the mean %Hb-O2-cap and the %Hb-O2-cap frequency distributions remained unchanged. By contrast, in the SHAM-group, mucosal microcirculation was well-preserved, and none of the other parameters were influenced.

CONCLUSIONS

We conclude that an increased ileal-mucosal-arterial delta PCO2 during porcine endotoxemia is related to impaired villus microcirculation. A putative contribution of disturbed cellular oxygen utilization resulting from "cytopathic hypoxia" may also assume importance.

Effects of nicotinamide, an inhibitor of PARS activity, on gut and liver O2 exchange and energy metabolism during hyperdynamic porcine endotoxemia

OBJECTIVE

To investigate the effects of nicotinamide (NIC), an inhibitor of poly(ADP-ribose) synthetase (PARS), on intestinal and liver perfusion, O2 kinetics, and energy metabolism over 24 h of hyperdynamic porcine endotoxemia.

DESIGN

Prospective, randomized, controlled experimental study with repeated measures.

SETTING

Animal laboratory in a university hospital.

SUBJECTS

Sixteen pigs, divided into two groups: nine endotoxemic animals without therapy (CON); seven animals treated with NIC.

INTERVENTIONS

Pigs were anesthetized, mechanically ventilated, and instrumented. Intravenous E. Coli LPS was continuously infused over 24 h concomitant with fluid resuscitation. After 12 h of endotoxemia continuous i.v. infusion of NIC (10 mg/kg per hour) was administered until the end of the experiment.

MEASUREMENTS AND RESULTS

All animals developed hyperdynamic circulation with sustained increase in cardiac output and progressive fall in mean arterial pressure. NIC maintained blood pressure without affecting CO. Hepato-splanchnic macrocirculation was not modified by the treatment. Nevertheless, although NIC attenuated the progressive rise of ileal mucosal-arterial PCO2 gap, it failed to improve portal venous L/P ratio, a marker of the overall energy state of the portal venous drained viscera. Similarly, neither the increased hepatic venous L/P ratio nor the simultaneous drop in hepatic lactate uptake were influenced by NIC.

CONCLUSIONS

Although NIC maintained hemodynamic stabilization during long-term endotoxemia, it was unable to improve LPS-induced deterioration of the hepato-splanchnic energy metabolism. More potent and selective PARS inhibitors are needed to elucidate the role of a PARS-dependent pathway in a clinically relevant models of sepsis.

Conservation and heterogeneity of the glutamate-rich protein (GLURP) among field isolates and laboratory lines of Plasmodium falciparum

Genetic variation of the glutamate-rich protein (GLURP) of Plasmodium falciparum was analysed in 29 field isolates and 15 laboratory lines of diverse geographical origin, by DNA sequencing of the non-repetitive 5'-region (R0) of the glurp gene. Polymorphism with respect to the length of the GLURP R2 repeat region was also analysed by a polymerase chain reaction method. As reference, the nucleotide sequence of the highly polymorphic 3'-region of the circumsporozoite protein gene was determined in the same isolates. It was found that even in the presence of variations in the GLURP R2 repeat region, immunodominant parts of the GLURP R0 region are surprisingly well conserved and the conservation is most pronounced in isolates from locations with very high malaria transmission. This might indicate that the R0 structure plays an important role in the parasite.

Identification of a major B-cell epitope of the Plasmodium falciparum glutamate-rich protein (GLURP), targeted by human antibodies mediating parasite killing

The antigenicity of the glutamate-rich protein (GLURP) of Plasmodium falciparum was comprehensively evaluated in epitope-mapping studies utilizing a phage display library, synthetic peptides and anti-GLURP IgG preparations previously shown to promote strong antibody-dependent cellular inhibition (ADCI) effects. We identified six major B-cell epitopes within the nonrepetitive region R0, corresponding to amino acid residues 173 to 187 (P1), 193 to 207 (P3), 216 to 229 (P4), 264 to 288 (P11), 343 to 357 (P10), and 407 to 434 (S3). Of these, four (P1, P3, P4, and S3) were frequently recognized by high-titered IgG antibodies in plasma samples from immune Liberian adults (prevalence: 29.1-45.0%). The three epitopes P1, P3, and P4 contained a common motif (seven out of nine positions are identical) and may thus constitute a family of structurally related epitopes. This leaves two distinct epitopes, one (P3) representing this new epitope family and S3 as targets for biologically active antibodies. Human IgG antibodies from single plasma samples were affinity-purified against these peptides. P3-specific IgG preparations were consistently more effective in ADCI than S3-specific IgG. Among the different GLURP epitopes, we therefore suggest that the P3 epitope is potentially the most important epitope in GLURP for the development of clinical immunity to malaria in man.

Determination of metal additives and bromine in recycled thermoplasts from electronic waste by TXRF analysis

A new method for analysis of metal additives in recycled thermoplasts from electronic waste was developed, based on dissolving the samples in an organic solvent and subsequent analysis of the corresponding solutions or suspensions by total-reflection X-ray fluorescence spectroscopy (TXRF). The procedure proved to be considerably less time consuming than the conventional digestion of the polymer matrix. Additives containing Ti, Zn, Br, Cd, Sn, Sb, and Pb were analyzed in a hundred randomly selected samples from recycling, which provided an overview of the range of elemental concentrations in thermoplasts utilized for consumer electronics. The results were validated independently by instrumental neutron activation analysis (INAA), subsequent regression analysis confirmed the trueness of the chosen approach.

Ligand-presenting assembly: a method for C- and N-terminal antigen presentation

Achiral dicarboxylic acids were coupled with 2 eq. of the free alpha-amino groups of two fully side-chain protected peptide chains while these were still attached to a synthesis resin. Cleavage from the resin with simultaneous side-chain deprotection afforded two assembled peptide chains with free C-terminals. Suitable functionalization of the achiral dicarboxylic acid alternatively permitted continued peptide synthesis in a C to N orientation leading to a final peptide assembly which, after cleavage from the resin, may have multiple N to C and C to N presentation of one or more epitopes.

Analysis of the cellular localization of Bdr paralogs in Borrelia burgdorferi, a causative agent of lyme disease: evidence for functional diversity

The bdr (Borrelia direct repeat) gene family of the genus Borrelia encodes a polymorphic group of proteins that carry a central repeat motif region containing putative phosphorylation sites and a hydrophobic carboxyl-terminal domain. It has been postulated that the Bdr proteins may anchor to the inner membrane via the C-terminal domain. In this study, we used cellular fractionation methodologies, salt and detergent treatments, and immunoblot analyses to assess the association of the Bdr proteins with the cellular infrastructure in both Borrelia burgdorferi (a Lyme disease spirochete) and B. turicatae (a relapsing fever spirochete). Triton X-114 extraction and partitioning experiments demonstrated that most Bdr paralogs are associated with the inner membrane-peptidoglycan complex. Analyses of cells treated with the highly chaotropic bile salt detergent deoxycholic acid demonstrated that some Bdr paralogs may also interact with the peptidoglycan, as evidenced by their tight association with the insoluble cellular matrix. In addition, immunoprecipitation (IP) experiments revealed an enhanced IP of all Bdr paralogs when the cell lysates were boiled prior to addition of the precipitating antibody. Furthermore, some Bdr paralogs were accessible to antibody in the IP experiments only in the boiled cell lysates. These observations suggest that different Bdr paralogs may carry out different structural-functional roles. Demonstration of the inner membrane localization of the Bdr proteins and of the differences in nature of the interaction of individual Bdr paralogs with the cell infrastructure is an important step toward defining the functional role of this unique protein family in the genus Borrelia.

Antigenic equivalence of human T-cell responses to Mycobacterium tuberculosis-specific RD1-encoded protein antigens ESAT-6 and culture filtrate protein 10 and to mixtures of synthetic peptides

The early secreted antigenic target 6-kDa protein (ESAT-6) and culture filtrate protein 10 (CFP-10) are promising antigens for reliable immunodiagnosis of tuberculosis. Both antigens are encoded by RD1, a genomic region present in all strains of Mycobacterium tuberculosis and M. bovis but lacking in all M. bovis bacillus Calmette-Guérin vaccine strains. Production and purification of recombinant antigens are laborious and costly, precluding rapid and large-scale testing. Aiming to develop alternative diagnostic reagents, we have investigated whether recombinant ESAT-6 (rESAT-6) and recombinant CFP-10 (rCFP-10) can be replaced with corresponding mixtures of overlapping peptides spanning the complete amino acid sequence of each antigen. Proliferation of M. tuberculosis-specific human T-cell lines in response to rESAT-6 and rCFP-10 and that in response to the corresponding peptide mixtures were almost completely correlated (r = 0.96, P < 0.0001 for ESAT-6; r = 0.98, P < 0.0001 for CFP-10). More importantly, the same was found when gamma interferon production by peripheral blood mononuclear cells in response to these stimuli was analyzed (r = 0.89, P < 0.0001 for ESAT-6; r = 0.89, P < 0.0001 for CFP-10). Whole protein antigens and the peptide mixtures resulted in identical sensitivity and specificity for detection of infection with M. tuberculosis. The peptides in each mixture contributing to the overall response varied between individuals with different HLA-DR types. Interestingly, responses to CFP-10 were significantly higher in the presence of HLA-DR15, which is the major subtype of DR2. These results show that mixtures of synthetic overlapping peptides have potency equivalent to that of whole ESAT-6 and CFP-10 for sensitive and specific detection of infection with M. tuberculosis, and peptides have the advantage of faster production at lower cost.

Cytophilic immunoglobulin responses to Plasmodium falciparum glutamate-rich protein are correlated with protection against clinical malaria in Dielmo, Senegal

The goal of this study was to analyze antibody responses to Plasmodium falciparum glutamate-rich protein (GLURP) using clinical data and plasma samples obtained from villagers of Dielmo, Senegal. This molecule was chosen because it is targeted by human antibodies which induce parasite growth inhibition in antibody-dependent cellular inhibition (ADCI) assays. The results showed a strong correlation between protection against malaria attacks and levels of immunoglobulin G2 (IgG2) and IgG3 against GLURP(94-489) (R0) and IgG3 against GLURP(705-1178) (R2) when corrected for the confounding effect of age-related exposure to malaria. Thus, GLURP may play a role in the induction of protective immunity against P. falciparum malaria.

Molecular and immunological analyses of the Borrelia turicatae Bdr protein family

Here, we describe the molecular and immunological characterization of the bdr gene family of Borrelia turicatae, a relapsing-fever spirochete. Nine bdr alleles belonging to two different subfamilies were sequenced and localized to linear plasmids. Anti-Bdr antiserum was generated and used to analyze Bdr expression in pre- and postinfection isogenic populations. The analyses presented here provide a detailed characterization of the Bdr proteins in a relapsing-fever spirochete species, enhancing our understanding of these proteins at the genus-wide level.

Triple helix assembly and processing of human collagen produced in transgenic tobacco plants

The use of tobacco plants as a novel expression system for the production of human homotrimeric collagen I is presented in this report. Constructs were engineered from cDNA encoding the human proalpha1(I) chain to generate transgenic tobacco plants expressing collagen I. The recombinant proalpha1(I) chains were expressed as disulfide-bonded trimers and were shown to fold into a stable homotrimeric triple helix. Moreover, the recombinant procollagen was subsequently processed to collagen as it occurs in animals. Large amounts of recombinant collagen were purified from field grown plant material. The data suggest that plants are a valuable alternative for the recombinant production of collagen for various medical and scientific purposes.

Naturally acquired antibodies to the glutamate-rich protein are associated with protection against Plasmodium falciparum malaria

The development of effective malaria vaccines depends on the identification of targets of well-defined protective immune responses. Data and samples from a longitudinal study of a cohort of children from coastal Ghana were used to investigate the role of antibody responses to 3 regions of the Plasmodium falciparum glutamate-rich protein (GLURP). The data show that levels of the GLURP-specific IgG that occurs in the nonrepeat region of the antigen are significantly correlated with clinical protection from P. falciparum malaria, after correction for the confounding effect of age. Furthermore, levels of cytophilic antibodies were found to be of particular importance for protection, lending support to the hypothesis that antibody-dependent cellular inhibition is the important element in GLURP-specific protective immunity.

Combination of asymmetric flow field-flow fractionation (AF4) and total-reflexion X-ray fluorescence analysis (TXRF) for determination of heavy metals associated with colloidal humic substances

To assess the structural variability of colloidal humic substances and the associated heavy metals an off-line coupling of asymmetric flow field-flow fractionation (AF4) with total-reflection X-ray fluorescence analysis (TXRF) is presented. AF4 allows a rather gentle separation of colloids with a minimum of interference and artifacts as no shear forces, drying, or interactions with a stationary phase are involved. After a calibration with suitable polymer particles of known molecular weight, the molecular weight distribution of colloidal humic substances between 1 and 10(3) kDa can be assessed with AF4. The combination with TXRF permits a simultaneous multielement analysis after preconcentration of samples on the AF4 channel using an optimized buffer. The analysis of seepage and sewage water sample and a sewage sludge sample yielded continuous distributions of the molecular weight and the associated heavy metals. The potential of AF4-TXRF coupling for the study of metal ion exchange equilibria with colloids was demonstrated by spiking seepage water with various heavy metals and subsequent AF4-TXRF analysis of the heavy metals bound to the colloidal fraction (Cu, Cr, Zn, Ni, Co).

The bdr gene families of the Lyme disease and relapsing fever spirochetes: potential influence on biology, pathogenesis, and evolution

Species of the genus Borrelia cause human and animal infections, including Lyme disease, relapsing fever, and epizootic bovine abortion. The borrelial genome is unique among bacterial genomes in that it is composed of a linear chromosome and a series of linear and circular plasmids. The plasmids exhibit significant genetic redundancy and carry 175 paralogous gene families, most of unknown function. Homologous alleles on different plasmids could influence the organization and evolution of the Borrelia genome by serving as foci for interplasmid homologous recombination. The plasmid-carried Borrelia direct repeat (bdr) gene family encodes polymorphic, acidic proteins with putative phosphorylation sites and transmembrane domains. These proteins may play regulatory roles in Borrelia. We describe recent progress in the characterization of the Borrelia bdr genes and discuss the possible influence of this gene family on the biology, pathogenesis, and evolution of the Borrelia genome.

[When should a patient with severe acute respiratory distress syndrome (ARDS) be transferred to a specialized hospital?]

The mortality rate for the advanced adult respiratory distress syndrome is still high. Nevertheless there are recent publications showing decreasing incidence and an improving survival rate. This is due to early diagnosis as well as differentiated treatment concepts. The use of special therapy methods including extracorporal gas exchange is only possible at specialized centres. This raises the question as to the right timing of the transfer of those ARDS-patients, whose lungs cannot be cured by the therapy standards practiced locally. In a prospective study, all requests for transfer were noted over a period of 36 months (1992 to 1994) and analyzed by a hospital with a special ward for ARDS. In a total of 469 patients the most prominent predisposing diseases were community-acquired pneumonia (26.3%), followed by multiple trauma (24.4%), the postoperative conditions of systemic inflammatory response syndrome (SIRS) or sepsis (21.3%), bronchopulmonary aspiration (5.8%), and status asthmaticus (2.6%). With a mean preventilation time of 9.5 +/- 9 days and a mean ventilatory peak pressure of 39 +/- 8 cm H2O there was a mean oxygenation index (Horrowitz Index) of 95 (+/- 40) mm Hg. The mean Smith and Gordon Ventilator Score was 82.3 (+/- 12.8) and the mean PIF rate (Benzer Score) 12 (+/- 8.6), 121 out of 469 patients were transferred for further specialized therapy. 75 patients were treated on a conventional basis and 46 patients had to be treated with extracorporal lung assistance (ELA) because conventional treatment failed. The mortality rate was 22.3% altogether, in the group with the conventional treatment 16.0% and 32.6% in the group with ELA. As there are no generally accepted guidelines for the transfer of patients with ARDS to specialized centres, an indication for such a transfer must be established taking into consideration the individual patient history. Very early contact with the specialized centre of choice is recommended.

IgG reactivities against recombinant Rhoptry-Associated Protein-1 (rRAP-1) are associated with mixed Plasmodium infections and protection against disease in Tanzanian children

A cross-sectional sero-epidemiological study was performed in Magoda, Tanzania, an area where malaria is holoendemic. Blood samples were collected from children (1-4 years) and tested for IgG antibody reactivity against 2 recombinant protein fragments of Plasmodium falciparum Rhoptry-Associated Protein-1 (rRAP-1). The data were related to the prevalence of malarial disease and single P. falciparum or mixed Plasmodium infections. Fever (> or = 37.5 degrees C) in combination with parasite densities > 5000/microliter were used to distinguish between children with asymptomatic malaria infections and those with acute clinical disease. Furthermore, C-reactive protein (CRP) was applied as a surrogate marker of malaria morbidity. The prevalence of Plasmodium infections was 96.0%. Eleven children were defined as clinical malaria cases, all with single P. falciparum infections. The density of P. falciparum was significantly lower in children with mixed Plasmodium infections compared to those with single P. falciparum infections. Children with asymptomatic P. falciparum infections had higher IgG reactivities to rRAP-1, compared to IgG reactivities of children with malarial disease. Children with mixed Plasmodium infections generally showed elevated IgG reactivity to rRAP-1, when compared to children with single P. falciparum infections. The possible relationship between mixed species infections, clinical outcome of the disease and antibody responses to RAP-1 is discussed.

Production of recombinant blood factors in transgenic plants

The production of recombinant proteins for therapeutic use in transgenic plants has become an alternative to the isolation of these molecules from natural or other recombinant sources. Plant bioreactors offer the possibility of an inexpensive large scale production of high volumes of recombinant proteins with increased safety concerning contaminations with human pathogens. Several laboratories are involved in the commercial production of the first recombinant products, such as antibodies or recombinant human hemoglobin, from transgenic plants.

Peptide-based OspC enzyme-linked immunosorbent assay for serodiagnosis of Lyme borreliosis

Sera from 210 patients with Lyme borreliosis (LB) were studied by an enzyme-linked immunosorbent assay (ELISA) based on a synthetic peptide (pepC10) comprising the C-terminal 10-amino-acid residues of OspC of Borrelia burgdorferi. We found that 36.3 and 45.0% of the serum samples from patients with erythema migrans (EM) and neuroborreliosis (NB), respectively, displayed immunoglobulin M (IgM) anti-pepC10 reactivities, while these samples rarely (</=8%) displayed IgG antibody reactivities. Sera from patients with acrodermatitis chronica atrophicans did not contain anti-pepC10 antibodies. The diagnostic performance of this newly developed peptide ELISA was compared with those of an ELISA based on the full-length recombinant OspC protein (rOspC) and a commercially available ELISA based on the B. burgdorferi flagellum (Fla). The sensitivity of the IgM pepC10 ELISA was slightly lower (P < 0.04) than that of the rOspC ELISA for EM patients (36.3 versus 43.8%), while there was no difference for NB patients (45.0 versus 48.0%). However, the optical density values obtained by the pepC10 ELISA were generally higher than those obtained by the rOspC ELISA, leading to a significantly better quantitative discrimination between seropositive patients with NB and controls (P < 0.008). The specificity of the pepC10 ELISA was similar to those of the rOspC ELISA and the Fla ELISA for relevant controls including patients with syphilis and mononucleosis. Although the overall diagnostic sensitivity of the Fla ELISA was superior, 8.8 and 12.0% of the EM and NB patients, respectively, were antibody positive only by the pepC10 ELISA. Thus, use of a diagnostic test for LB based on the detection of IgM antibodies to pepC10 and Fla has increased sensitivity for the diagnosis of early LB.

The dominant epitope of Borrelia garinii outer surface protein C recognized by sera from patients with neuroborreliosis has a surface-exposed conserved structural motif

Epitope mapping of outer surface protein C (OspC) by using sera from patients with neuroborreliosis led to the identification of one single major immunodominant epitope within the C-terminal 10 amino acid residues. Peptide binding studies and alanine replacement scanning of the C-terminal decapeptide, PVVAESPKKP, revealed a critical role for the PKKP sequence and its terminal carboxyl group for the binding of immunoglobulin M (IgM) antibodies from patients with Lyme borreliosis. Electron microscopy of antibody-labeled spirochetes indicated that the C-terminal region is exposed on the surface of the spirochete. Based on homology to proteins of known function, this region most probably adopts a polyproline II-like helix, which is found in surface-exposed structures involved in protein-protein interactions. This structural motif is highly conserved in Borrelia species causing Lyme borreliosis and subjected to purifying selection. We suggest that the abundance of the C-terminal region of OspC on the surface of B. burgdorferi allows a multimeric high-avidity interaction between the spirochete and surface Igs on B cells. The resulting cross-linking of surface Igs on B cells may induce a T-cell-independent B-cell activation without IgM-to-IgG switching, thus explaining the lack of IgG antibodies to OspC in neuroborreliosis.

Production of human lactoferrin in transgenic tobacco plants

Production and characterization of human lactoferrin (hLf) in transgenic tobacco is reported. We have engineered two constructs containing either the native signal peptide from human lactoferrin or the signal peptide from sweet potato sporamin fused to human lactoferrin encoding cDNA. N-terminal sequences of rhLf purified from tobacco were identical to Lf from human milk for both constructs. The tobacco rhLf presents a molecular mass closely identical to native protein. Overall sugar composition shows the presence of plant specific xylose while sialic acid is absent. Binding parameters of the recombinant molecule to both Jurkat lymphoblastic T-cells or HT29-18-C1 enterocytes are similar to those of human lactoferrin isolated from milk.

Identification and characterization of a 29-kilodalton protein from Mycobacterium tuberculosis culture filtrate recognized by mouse memory effector cells

Culture filtrate proteins from Mycobacterium tuberculosis induce protective immunity in various animal models of tuberculosis. Two molecular mass regions (6 to 10 kDa and 24 to 36 kDa) of short-term culture filtrate are preferentially recognized by Th1 cells in animal models as well as by patients with minimal disease. In the present study, the 24- to 36-kDa region has been studied, and the T-cell reactivity has been mapped in detail. Monoclonal antibodies were generated, and one monoclonal antibody, HYB 71-2, with reactivity against a 29-kDa antigen located in the highly reactive region below the antigen 85 complex was selected. The 29-kDa antigen (CFP29) was purified from M. tuberculosis short-term culture filtrate by thiophilic adsorption chromatography, anion-exchange chromatography, and gel filtration. In its native form, CFP29 forms a polymer with a high molecular mass. CFP29 was mapped in two-dimensional electrophoresis gels as three distinct spots just below the antigen 85 complex component MPT59. CFP29 is present in both culture filtrate and the membrane fraction from M. tuberculosis, suggesting that this antigen is released from the envelope to culture filtrate during growth. Determination of the N-terminal amino acid sequence allowed cloning and sequencing of the cfp29 gene. The nucleotide sequence showed 62% identity to the bacteriocin Linocin from Brevibacterium linens. Purified recombinant histidine-tagged CFP29 and native CFP29 had similar T-cell stimulatory properties, and they both elicited the release of high levels of gamma interferon from mouse memory effector cells isolated during the recall of protective immunity to tuberculosis. Interspecies analysis by immunoblotting and PCR demonstrated that CFP29 is widely distributed in mycobacterial species.

Inflammatory reactions in placental blood of Plasmodium falciparum-infected women and high concentrations of soluble E-selectin and a circulating P. falciparum protein in the cord sera

To better understand reasons for increased susceptibility to malaria in pregnancy; and the interrelationships between maternal malaria, local immune reactions and the development of the fetus, concentrations of soluble interleukin-10 (IL-10), cytokine receptors, adhesion molecules, a Plasmodium falciparum protein, glutamate-rich protein (GLURP) and antibodies to P. falciparum rhoptry-associated protein-1 were measured among 105 Gambian women and their neonates. Peripheral blood concentrations of IL-10, soluble cytokine receptors and soluble adhesion molecules were found to be different from those concentrations measured in the placenta. Markers of inflammatory reactions: IL-10, sIL-2R, sIL-4R, and soluble tumour necrosis factor receptor I (sTNF-RI) were found in high concentrations in the placenta, indicating that inflammatory reactions take place in the placenta which has been regarded as an immunoprivileged site. Concentrations of soluble vascular cell adhesion molecule-1 (sVCAM-1) and soluble intracellular adhesion molecule-1 (sICAM-1), potential adhesion receptors for malaria parasites, were associated with an active P. falciparum infection in the placenta although the associations did not reach significance. P. falciparum exoantigen, GLURP, was detected in cord blood indicating transplacental passage of malarial antigens. Concentrations of E-selectin were higher in cord blood samples compared with peripheral blood samples. This appeared to be associated with development of cord endothelial cells and not with P. falciparum infection.

The glutamate-rich protein (GLURP) of Plasmodium falciparum is a target for antibody-dependent monocyte-mediated inhibition of parasite growth in vitro

Monocyte-dependent as well as direct inhibitory effects of antimalarial antibodies point toward antigens accessible at the time of merozoite release as targets for biologically active antibodies capable of mediating protection against Plasmodium falciparum. The glutamate-rich protein (GLURP), being an antigen associated with mature schizont-infected erythrocytes, was therefore the object of the present investigation, in which we analyzed whether anti-GLURP antibodies can either interfere directly with merozoite invasion or act indirectly by promoting a monocyte-dependent growth inhibition, antibody-dependent cellular inhibition. GLURP-specific human immunoglobulin G (IgG) antibodies, from pooled IgG of healthy Liberian adults who were clinically immune to malaria, were purified by affinity chromatography on columns containing R0 (N-terminal nonrepetitive region of GLURP) or R2 (C-terminal repetitive region of GLURP) recombinant protein or synthetic peptides as ligands. Analysis of the pattern of reactivity of highly purified anti-GLURP antibodies led to the definition of at least four B-cell epitopes. One epitope was specific for R0, two were specific for R2, and the fourth displayed cross-reactivity between R0 and R2. None of the purified IgG antibodies had direct invasion-inhibitory effects, even at high concentrations. In contrast, when allowed to cooperate with monocytes, all anti-GLURP IgG preparations mediated a strong monocyte-dependent parasite growth inhibition in a dose-dependent manner.

Proteolytical processing of mutated human amyloid precursor protein in transgenic mice

The evidence that betaA4 is central to the pathology of Alzheimer's disease (AD) came from the identification of several missense mutations in the amyloid precursor protein (APP) gene co-segregating with familial AD (FAD). In an attempt to study the proteolytical processing of mutated human APP in vivo, we have created transgenic mice expressing the human APP695 isoform with four FAD-linked mutations. Expression of the transgene was controlled by the promoter of the HMG-CR gene. Human APP is expressed in the brain of transgenic mice as shown by Western blot and immunohistology. The proteolytic processing of human APP in the transgenic mice leads to the generation of C-terminal APP fragments as well as to the release of betaA4. Despite substantial amounts of betaA4 detected in the brain of the transgenic mice, neither signs of Alzheimer's disease-related pathology nor related behavioural deficits could be demonstrated.

Analysis of the human antibody response to outer surface protein C (OspC) of Borrelia burgdorferi sensu stricto, B. garinii, and B. afzelii

The aim of this study was to determine by Western blotting (WB) the prevalence of anti-outer surface protein C (OspC) IgM and IgG antibodies in patients with Lyme borreliosis according to each of the three genospecies of Borrelia burgdorferi sensu lato. Strains of B. burgdorferi sensu stricto (MUL), B. garinii (DK 6), and B. afzelii (DK 26) served as antigen, all of which expressed abundant OspC. We examined sera from 117 patients with untreated early and late Lyme borreliosis, as well as from 100 blood donors and 29 patients with syphilis. WB results were compared with the B. burgdorferi flagellum enzyme-linked immunosorbent assay (ELISA) data. OspC from B. burgdorferi sensu stricto showed the lowest diagnostic sensitivity. OspC from B. garinii and B. afzelii performed almost identically in erythema migrans, with an IgM positive rate of 36% versus 34%, whereas OspC from B. garinii performed best in neuroborreliosis (60% versus 44%). The anti-OspC IgG response was less prominent than the IgM response and was infrequent in the late stages of the disease (0-20%). The benefit of combining the evaluation of anti-OspC responses with all three species was limited. The overall diagnostic sensitivity of WB anti-B. garinii OspC evaluation was, in the early stages of the disease, comparable to the results obtained using the flagellum ELISA. In erythema migrans and neuroborreliosis, the addition of anti-OspC IgM to the flagellum ELISA increased the sensitivity by 15% and 10%, respectively. It can, therefore, be concluded that OspC from B. garinii is a suitable OspC test antigen, and that supplementary use of OspC from other species adds little to the overall diagnostic sensitivity. An ELISA based on B. garinii OspC and native flagella seems currently the most promising concept for a future antibody test in early Lyme borreliosis.

Molecular cloning and characterization of nlpH, encoding a novel, surface-exposed, polymorphic, plasmid-encoded 33-kilodalton lipoprotein of Borrelia afzelii

Borrelia burgdorferi sensu lato organisms, comprising B. burgdorferi sensu stricto, Borrelia afzelii, and Borrelia garinii, are tick-borne pathogens causing Lyme borreliosis in humans. To identify putative virulence determinants, a B. afzelii DNA library was screened for Congo red dye binding, a property associated with virulence in pathogenic bacteria. One clone was found to carry a 663-nucleotide-long open reading frame encoding a Congo red dye-binding protein with a calculated molecular mass of 25,660 Da. The amino acid sequence deduced from its nucleotide sequence was found to include a consensus bacterial lipidation site present at residues 15 to 18 (Leu-Ser-Gly-Cys). The lipoprotein nature was demonstrated by incorporation of radioactive palmitate; hence, this protein has been termed NlpH, for new lipoprotein H. NlpH is located on the surface of B. afzelii, and the nlpH gene is found on a circular plasmid. The nlpH gene is also found in B. burgdorferi sensu stricto and B. garinii. Immediately upstream of nlpH is located a smaller reading frame encoding a polypeptide containing the casein kinase II phosphorylation recognition sequence, (Ser/Thr)-X-Y-(Glu/Asp), repeated 10 times.