IgG responses to Anopheles gambiae salivary antigen gSG6 detect variation in exposure to malaria vectors and disease risk

Assessment of exposure to malaria vectors is important to our understanding of spatial and temporal variations in disease transmission and facilitates the targeting and evaluation of control efforts. Recently, an immunogenic Anopheles gambiae salivary protein (gSG6) was identified and proposed as the basis of an immuno-assay determining exposure to Afrotropical malaria vectors. In the present study, IgG responses to gSG6 and 6 malaria antigens (CSP, AMA-1, MSP-1, MSP-3, GLURP R1, and GLURP R2) were compared to Anopheles exposure and malaria incidence in a cohort of children from Korogwe district, Tanzania, an area of moderate and heterogeneous malaria transmission. Anti-gSG6 responses above the threshold for seropositivity were detected in 15% (96/636) of the children, and were positively associated with geographical variations in Anopheles exposure (OR 1.25, CI 1.01-1.54, p?=?0.04). Additionally, IgG responses to gSG6 in individual children showed a strong positive association with household level mosquito exposure. IgG levels for all antigens except AMA-1 were associated with the frequency of malaria episodes following sampling. gSG6 seropositivity was strongly positively associated with subsequent malaria incidence (test for trend p?=?0.004), comparable to malaria antigens MSP-1 and GLURP R2. Our results show that the gSG6 assay is sensitive to micro-epidemiological variations in exposure to Anopheles mosquitoes, and provides a correlate of malaria risk that is unrelated to immune protection. While the technique requires further evaluation in a range of malaria endemic settings, our findings suggest that the gSG6 assay may have a role in the evaluation and planning of targeted and preventative anti-malaria interventions.     

MHC-correlated odour preferences in humans and the use of oral contraceptives

Previous studies in animals and humans show that genes in the major histocompatibility complex (MHC) influence individual odours and that females often prefer odour of MHC-dissimilar males, perhaps to increase offspring heterozygosity or reduce inbreeding. Women using oral hormonal contraceptives have been reported to have the opposite preference, raising the possibility that oral contraceptives alter female preference towards MHC similarity, with possible fertility costs. Here we test directly whether contraceptive pill use alters odour preferences using a longitudinal design in which women were tested before and after initiating pill use; a control group of non-users were tested with a comparable interval between test sessions. In contrast to some previous studies, there was no significant difference in ratings between odours of MHC-dissimilar and MHC-similar men among women during the follicular cycle phase. However, single women preferred odours of MHC-similar men, while women in relationships preferred odours of MHC-dissimilar men, a result consistent with studies in other species, suggesting that paired females may seek to improve offspring quality through extra-pair partnerships. Across tests, we found a significant preference shift towards MHC similarity associated with pill use, which was not evident in the control group. If odour plays a role in human mate choice, our results suggest that contraceptive pill use could disrupt disassortative mate preferences.     

Automatically extracting functionally equivalent proteins from SwissProt

Background  

There is a frequent need to obtain sets of functionally equivalent homologous proteins (FEPs) from different species. While it is usually the case that orthology implies functional equivalence, this is not always true; therefore datasets of orthologous proteins are not appropriate. The information relevant to extracting FEPs is contained in databanks such as UniProtKB/Swiss-Prot and a manual analysis of these data allow FEPs to be extracted on a one-off basis. However there has been no resource allowing the easy, automatic extraction of groups of FEPs – for example, all instances of protein C.     

Improved genome assembly and evidence-based global gene model set for the chordate Ciona intestinalis: new insight into intron and operon populations

Background

The draft genome sequence of the ascidian Ciona intestinalis, along with associated gene models, has been a valuable research resource. However, recently accumulated expressed sequence tag (EST)/cDNA data have revealed numerous inconsistencies with the gene models due in part to intrinsic limitations in gene prediction programs and in part to the fragmented nature of the assembly.

Results

We have prepared a less-fragmented assembly on the basis of scaffold-joining guided by paired-end EST and bacterial artificial chromosome (BAC) sequences, and BAC chromosomal in situ hybridization data. The new assembly (115.2 Mb) is similar in length to the initial assembly (116.7 Mb) but contains 1,272 (approximately 50%) fewer scaffolds. The largest scaffold in the new assembly incorporates 95 initial-assembly scaffolds. In conjunction with the new assembly, we have prepared a greatly improved global gene model set strictly correlated with the extensive currently available EST data. The total gene number (15,254) is similar to that of the initial set (15,582), but the new set includes 3,330 models at genomic sites where none were present in the initial set, and 1,779 models that represent fusions of multiple previously incomplete models. In approximately half, 5'-ends were precisely mapped using 5'-full-length ESTs, an important refinement even in otherwise unchanged models.

Conclusion

Using these new resources, we identify a population of non-canonical (non-GT-AG) introns and also find that approximately 20% of Ciona genes reside in operons and that operons contain a high proportion of single-exon genes. Thus, the present dataset provides an opportunity to analyze the Ciona genome much more precisely than ever.     

Monitoring of residues of ochratoxin A in blood and kidney of chicken using HPLC-FLD

Detoxification of ochratoxin A can be achieved by chemical or enzymatic hydrolyzation, the products of such reactions are ochratoxin α and phenylalanine. Ochratoxin α like ochratoxin A, is a fluorescing molecule, therefore sensitive analysis is possible at very low concentration levels. Methods have been established that make it possible to look for residues of ochratoxin A and its main metabolite ochratoxin α in blood and tissues at very low concentration levels. Plasma is extracted by the use of small amounts of chloroform; the extract is cleaned with water and afterwards evaporated to dryness]. The residue is re-dissolved and analysed by HPLC-FLD. Using this method a limit of detection of 0.5μg/l for both ochratoxin A and ochratoxin α can be reached.     

Scent-marking by male mice under the risk of predation

The use by predators of scent marks made by potential prey isa largely unexplored potential cost of olfactory signaling.Here we investigate how animals that differ in their investmentin scent-marking respond to simulated predation risk, by comparingthe willingness to approach and counter-mark the scent marksof a competitor in the presence or absence of predator odor.We aimed to test whether animals that invest heavily in scent-marking,and which may thus be more vulnerable to eavesdropping predators,will either (1) take greater risks to counter-mark the competitor'sscent or (2) reduce or abandon scent-marking. Using outbredmale laboratory mice, Mus musculus, we show that, in the absenceof predators, individuals which initially scent-mark at highfrequency (high markers) approach the competitor's scent marksmore quickly and spend more time in counter-marking than thosewhich initially invest relatively little (low markers). Ina sib-sib experimental design, simulated presence of predationrisk (urine of ferrets, Mustela putorius furo) caused bothkinds of individual to approach the competitor's marks moreslowly, but high markers approached more quickly than low markersand spent more time in the vicinity of the competitor's marks.Only high markers significantly reduced their overmarking ofthe competitor's scent. These results suggest (1) that thereis a unique danger inherent to scent-marking at high frequenciesand (2) that high-marking males were prepared to accept increasedcosts of intrasexual competition in order to reduce the riskof predation. Further tests using the scent of naked mole-rats, Heterocephalus glaber, showed that these effects were not elicited simply by an unfamiliar odor. We discuss reasons for the observeddifference in response to predation risk between the groups,and the implications of these results for counter-selectionon scent-marking strategies.