Immune response to a synthetic peptide corresponding to an epitope of a parasitophorous vacuole membrane antigen from Plasmodium falciparum

The parasitophorous vacuole membrane antigen QF 116 from Plasmodium falciparum contains a defined epitope, DNNLVSGP, proximal to the carboxyl-terminus which binds to the inhibitory monoclonal antibody 8E7/55. A synthetic peptide containing this epitope was constructed and coupled to diphtheria toxoid as carrier. Mice and rabbits were inoculated with this conjugate using CFA, SAF-1, or aluminum phosphate as adjuvants. The peptide conjugate was highly immunogenic in both animal species, giving rise to polyclonal antibodies with a similar epitope specificity as the original mAb. Antibody titers were dependent on the route of immunization. Rabbit antibodies produced in sufficient quantity for biologic assays inhibited parasite growth in vitro. This synthetic peptide thus shows promise as an immunogen for use in synthetic vaccine design.     

Amber suppression coupled with inducible surface display identifies cells with high recombinant protein productivity

Cell line development (CLD) for biotherapeutics is a time- and resource-intensive process requiring the isolation and screening of large numbers of clones to identify high producers. Novel methods aimed at enhancing cell line screening efficiency using markers predictive of productivity early in the CLD process are needed to reliably generate high-yielding cell lines. To enable efficient and selective isolation of antibody expressing Chinese hamster ovary cells by fluorescence-activated cell sorting, we developed a strategy for the expression of antibodies containing a switchable membrane-associated domain to anchor an antibody to the membrane of the expressing cell. The switchable nature of the membrane domain is governed by the function of an orthogonal aminoacyl transfer RNA synthetase/tRNApyl pair, which directs a nonnatural amino acid (nnAA) to an amber codon encoded between the antibody and the membrane anchor. The process is “switchable” in response to nnAA in the medium, enabling a rapid transition between the surface display and secretion. We demonstrate that the level of cell surface display correlates with productivity and provides a method for enriching phenotypically stable high-producer cells. The strategy provides a means for selecting high-producing cells with potential applications to multiple biotherapeutic protein formats.     

Genetical genomic determinants of alcohol consumption in rats and humans

Background

We have used a genetical genomic approach, in conjunction with phenotypic analysis of alcohol consumption, to identify candidate genes that predispose to varying levels of alcohol intake by HXB/BXH recombinant inbred rat strains. In addition, in two populations of humans, we assessed genetic polymorphisms associated with alcohol consumption using a custom genotyping array for 1,350 single nucleotide polymorphisms (SNPs). Our goal was to ascertain whether our approach, which relies on statistical and informatics techniques, and non-human animal models of alcohol drinking behavior, could inform interpretation of genetic association studies with human populations.

Results

In the HXB/BXH recombinant inbred (RI) rats, correlation analysis of brain gene expression levels with alcohol consumption in a two-bottle choice paradigm, and filtering based on behavioral and gene expression quantitative trait locus (QTL) analyses, generated a list of candidate genes. A literature-based, functional analysis of the interactions of the products of these candidate genes defined pathways linked to presynaptic GABA release, activation of dopamine neurons, and postsynaptic GABA receptor trafficking, in brain regions including the hypothalamus, ventral tegmentum and amygdala. The analysis also implicated energy metabolism and caloric intake control as potential influences on alcohol consumption by the recombinant inbred rats. In the human populations, polymorphisms in genes associated with GABA synthesis and GABA receptors, as well as genes related to dopaminergic transmission, were associated with alcohol consumption.

Conclusion

Our results emphasize the importance of the signaling pathways identified using the non-human animal models, rather than single gene products, in identifying factors responsible for complex traits such as alcohol consumption. The results suggest cross-species similarities in pathways that influence predisposition to consume alcohol by rats and humans. The importance of a well-defined phenotype is also illustrated. Our results also suggest that different genetic factors predispose alcohol dependence versus the phenotype of alcohol consumption.     

Effect of Incubation Temperature on Isolation of Campylobacter jejuni Genotypes from Foodstuffs Enriched in Preston Broth

Preston broth and agar incubated at either 37 or 42°C have been widely used to isolate campylobacters from foodstuffs. The consequences of using either incubation temperature were investigated. Retail packs of raw chicken (n = 24) and raw lamb liver (n = 30) were purchased. Samples were incubated in Preston broth at 37 and 42°C and then streaked onto Preston agar and incubated as before. Two Campylobacter isolates per treatment were characterized. Poultry isolates were genotyped by random amplification of polymorphic DNA (RAPD), pulsed-field gel electrophoresis (PFGE), and flagellin PCR-restriction fragment length polymorphism, and lamb isolates were genotyped by RAPD only. In total, 96% of the poultry and 73% of the lamb samples yielded campylobacters. The lamb isolates were all Campylobacter jejuni, as were 96% of the poultry isolates, with the remainder being Campylobacter lari. The incubation temperature had no significant effect on the number of positive samples or on the species isolated. However, genotyping of the C. jejuni isolates revealed profound differences in the types obtained. Overall (from poultry and lamb), the use of a single incubation temperature, 37°C, gave 56% of the total number of RAPD C. jejuni genotypes, and hence, 44% remained undetected. The effect was especially marked in the poultry samples, where incubation at 37°C gave 47% of the PFGE genotypes but 53% were exclusively recovered after incubation at 42°C. Thus, the incubation temperature of Preston media selects for certain genotypes of C. jejuni, and to detect the widest range, samples should be incubated at both 37 and 42°C. Conversely, genotyping results arising from the use of a single incubation temperature should be interpreted with caution.     

Design and development of a series of borocycles as selective,covalent kallikrein 5 inhibitors

The connection between Netherton syndrome and overactivation of epidermal/dermal proteases, particularly Kallikrein 5 (KLK5) has been well established and it is expected that a KLK5 inhibitor would improve the dermal barrier and also reduce the pain and itch that afflict Netherton syndrome patients. One of the challenges of covalent protease inhibitors has been achieving selectivity over closely related targets. In this paper we describe the use of structural insight to design and develop a selective and highly potent reversibly covalent KLK5 inhibitor from an initial weakly binding fragment.     

Insulin-like growth factor I stimulates recovery of bone lost after a period of skeletal unloading.

IGF-I stimulates osteoblast proliferation, bone formation, and increases bone volume in normal weight-bearing animals. During skeletal unloading or loss of weight bearing, bone becomes unresponsive to the anabolic effects of insulin-like growth factor I (IGF-I). To determine whether skeletal reloading after a period of unloading increases bone responsiveness to IGF-I, we examined bone structure and formation in response to IGF-I under different loading conditions. Twelve-week-old rats were divided into six groups: loaded (4 wk), unloaded (4 wk), and unloaded/reloaded (2/2 wk), and treated with IGF-I (2.5 mg x kg(-1) x day(-1)) or vehicle during the final 2 wk. Cortical bone formation rate (BFR), cancellous bone volume and architecture in the secondary spongiosa (tibia and vertebrae), and total volume and calcified volume in the primary spongiosa (tibia) were assessed. Periosteal BFR decreased during unloading, remained low during reloading in the vehicle-treated group, but was dramatically increased in IGF-I-treated animals. Cancellous bone volume decreased with unloading and increased with reloading, but the effect was exaggerated in the tibia of IGF-I-treated animals. Total and calcified volumes in the primary spongiosa decreased during unloading in the vehicle-treated animals. IGF-I treatment prevented the loss in volume. These data show that reloading after a period of skeletal unloading increases bone responsiveness to IGF-I, and they suggest that IGF-I may be of therapeutic use in patients who have lost bone as a consequence of prolonged skeletal disuse.     

Contributions of different mosquito species to the transmission of lymphatic filariasis in central Nigeria: implications for monitoring infection by PCR in mosquito pools

Background

Monitoring and evaluation are essential to the successful implementation of mass drug administration programmes for LF elimination. Monitoring transmission when it is low requires both large numbers of mosquito vectors and sensitive methods for detecting Wuchereria bancrofti infections in them. PCR-based methods are preferred over classical dissections but the best protocol so far achieved detection of one L₃ Wuchereria bancrofti larva in a pool of 35–50 Anopheles mosquitoes. It also lacks consistency and remains still a costly tool. Hence we decided to improve upon this to achieve detection in a pool of 100 or more by enhancing the quality of the template DNA. Prior to this we also evaluated three vector sampling methods in the context of numbers for monitoring.

Methods

Human landing, pyrethrium spray and light traps catches were conducted concurrently at sites in an LF endemic district in Ghana and the numbers obtained compared. Two DNA extraction methods; Bender buffer and phenol/chloroform purification, and DNAeasy Tissue kit (Quaigen Inc) were used on pools of 25, 50, 75 100 and 150 mosquitoes each seeded with one L₃ or its quivalent amount of DNA. Then another set of extracted DNA by the two methods was subjected to Dynal bead purification method (using capture oligonucleotide primers). These were used as template DNA in PCR to amplify W. bancrofti sequences. The best PCR result was then evaluated in the field at five sites by comparing its results (infections per 1000 mosquitoes) with that of dissection of roughly equal samples sizes.

Results

The largest numbers of mosquitoes were obtained with the human landing catches at all the sites sampled. Although PCR detection of one L₃ in pools of 25, 50 and 75 mosquitoes was consistent irrespective of the extraction method, that of one L₃ in 100 was only achieved with the kit-extracted DNA/Dynal bead purification method. Infections were found at only two sites by both dissection and pool-screening being 14.3 and 19 versus 13.4 and 20.1 per 1000 Anopheles mosquitoes respectively, which were not statistically significant

Discussion and conclusion

HLC still remains the best option for sampling for the large numbers of mosquitoes required for monitoring transmission during MDA programmes, when vector population densities are high and classical indices of transmission are required. One – in – 100 detection is an improvement on previous PCR pool-screening methods, which in our opinion was a result of the introduction of the extra step of parasite DNA capture using Dynal/beads. As pool sizes increase the insects DNA will swamp parasite DNA making the latter less available for an efficient PCR, therefore we propose either additional steps of parasite DNA capture or real-time PCR to improve further the pool screening method. The study also attests also to the applicability of Katholi et al's algorithm developed for determining onchocerciasis prevalence in LF studies.     

Resolvin E2 formation and impact in inflammation resolution

Acute inflammation and its resolution are essential processes for tissue protection and homeostasis. In this context, specialized proresolving mediators derived from polyunsaturated fatty acids are of interest. In this study, we report that resolvin E2 (RvE2) from eicosapentaenoic acid is endogenously produced during self-limited murine peritonitis in both the initiation and resolution phases. RvE2 (1-10 nM) carries potent leukocyte-directed actions that include: 1) regulating chemotaxis of human neutrophils; and 2) enhancing phagocytosis and anti-inflammatory cytokine production. These actions appear to be mediated by leukocyte G-protein-coupled receptors as preparation of labeled RvE2 gave direct evidence for specific binding of radiolabeled RvE2 to neutrophils (K(d) 24.7 ± 10.1 nM) and resolvin E1 activation of recombinant G-protein-coupled receptors was assessed. In addition to the murine inflammatory milieu, RvE2 was also identified in plasma from healthy human subjects. RvE2 rapidly downregulated surface expression of human leukocyte integrins in whole blood and dampened responses to platelet-activating factor. Together, these results indicate that RvE2 can stimulate host-protective actions throughout initiation and resolution in the innate inflammatory responses.