1,721,044 research outputs found
Cohort study of the association of antibody levels to AMA1, MSP119, MSP3 and GLURP with protection from clinical malaria in Ghanaian children.
Get PDFBACKGROUND: Antigen-specific antibody-mediated immune responses play an important role in natural protection against clinical malaria, but conflicting estimates of this association have emerged from immuno-epidemiological studies in different geographical settings. This study was aimed at assessing in a standardized manner the relationship between the antibody responses to four malaria vaccine candidate antigens and protection from clinical malaria, in a cohort of Ghanaian children. METHODS: Standardized ELISA protocols were used to measure isotype and IgG subclass levels to Apical Membrane Antigen 1 (AMA1), Merozoite Surface Protein 1-19 (MSP119), Merozoite Surface Protein 3 (MSP3) and Glutamate Rich Protein (GLURP) antigens in plasma samples from 352 Ghanaian children, aged three to 10 years with subsequent malaria surveillance for nine months. This is one of a series of studies in different epidemiological settings using the same standardized ELISA protocols to permit comparisons of results from different laboratories. RESULTS: The incidence rate of malaria was 0.35 episodes per child per year. Isotype and IgG subclasses for all antigens investigated increased with age, while the risk of malaria decreased with age. After adjusting for age, higher levels of IgG to GLURP, MSP119, MSP3 and IgM to MSP119, MSP3 and AMA1 were associated with decreased malaria incidence. Of the IgG subclasses, only IgG1 to MSP119 was associated with reduced incidence of clinical malaria. A previous study in the same location failed to find an association of antibodies to MSP119 with clinical malaria. The disagreement may be due to differences in reagents, ELISA and analytical procedures used in the two studies. When IgG, IgM and IgG subclass levels for all four antigens were included in a combined model, only IgG1 [(0.80 (0.67-0.97), p = 0.018)] and IgM [(0.48 (0.32-0.72), p < 0.001)] to MSP119 were independently associated with protection from malaria. CONCLUSION: Using standardized procedures, the study has confirmed the importance of antibodies to MSP119 in reducing the risk of clinical malaria in Ghanaian children, thus substantiating its potential as a malaria vaccine candidate
Antibody levels to multiple malaria vaccine candidate antigens in relation to clinical malaria episodes in children in the Kasena-Nankana district of Northern Ghana.
Get PDFBACKGROUND: Considering the natural history of malaria of continued susceptibility to infection and episodes of illness that decline in frequency and severity over time, studies which attempt to relate immune response to protection must be longitudinal and have clearly specified definitions of immune status. Putative vaccines are expected to protect against infection, mild or severe disease or reduce transmission, but so far it has not been easy to clearly establish what constitutes protective immunity or how this develops naturally, especially among the affected target groups. The present study was done in under six year old children to identify malaria antigens which induce antibodies that correlate with protection from Plasmodium falciparum malaria. METHODS: In this longitudinal study, the multiplex assay was used to measure IgG antibody levels to 10 malaria antigens (GLURP R0, GLURP R2, MSP3 FVO, AMA1 FVO, AMA1 LR32, AMA1 3D7, MSP1 3D7, MSP1 FVO, LSA-1and EBA175RII) in 325 children aged 1 to 6 years in the Kassena Nankana district of northern Ghana. The antigen specific antibody levels were then related to the risk of clinical malaria over the ensuing year using a negative binomial regression model. RESULTS: IgG levels generally increased with age. The risk of clinical malaria decreased with increasing antibody levels. Except for FMPOII-LSA, (p = 0.05), higher IgG levels were associated with reduced risk of clinical malaria (defined as axillary temperature ≥37.5°C and parasitaemia of ≥5000 parasites/ul blood) in a univariate analysis, upon correcting for the confounding effect of age. However, in a combined multiple regression analysis, only IgG levels to MSP1-3D7 (Incidence rate ratio = 0.84, [95% C.I.= 0.73, 0.97, P = 0.02]) and AMA1 3D7 (IRR = 0.84 [95% C.I.= 0.74, 0.96, P = 0.01]) were associated with a reduced risk of clinical malaria over one year of morbidity surveillance. CONCLUSION: The data from this study support the view that a multivalent vaccine involving different antigens is most likely to be more effective than a monovalent one. Functional assays, like the parasite growth inhibition assay will be necessary to confirm if these associations reflect functional roles of antibodies to MSP1-3D7 and AMA1-3D7 in this population
Anopheles gambiae salivary proteins as a tool to evaluate spatial and temporal variation of human exposure to malaria vectors.
No full textSaliva of blood sucking arthropods, injected into host skin during feeding, evokes an antibody response that may be used as serological indicator of exposure to disease vectors. Studies on mosquito salivary repertoires highlighted that Anopheles saliva carries genus-specific proteins (i.e. not found in Aedes/Culex or in other blood feeders). These proteins, if immunogenic, may be ideal candidates as markers of exposure to anopheline vectors, a tool which would be very useful for malaria epidemiological studies.
Human plasma samples collected in an hyperendemic area of Burkina Faso (Ouagadougou) and in an area of moderate malaria endemicity in Tanzania (Korogwe) were used to evaluate by ELISA the IgG, IgG1 and IgG4 antibody responses to the anopheline-specific salivary proteins gSG6 and cE5 from the malaria vector Anopheles gambiae.
The anti-gSG6 IgG response varied according to transmission/rainy season and was positively associated with the level of Anopheles exposure. The cE5 protein was more immunogenic than gSG6, but no variation of the IgG response was found during the transmission season, most likely because of its longer lasting nature. Moreover, the anti-gSG6 IgG level decreased with age, suggesting the induction of tolerance mechanisms, which was not the case for the anti-cE5 IgG response. Finally, the analysis of IgG1 and IgG4 subclasses pointed out the differential responses evoked by these two salivary proteins in exposed individuals with (i) gSG6 triggering a short-lived response of the Th2-type, with high IgG4 levels and induction of tolerance and (ii) cE5 eliciting a longer-lived Th1-type response, with high IgG1 levels and no tolerance induction.
The Entomological Inoculation Rate, which measures the number of infectious bites/person/unit of time, is presently the gold standard for the assessment of malaria transmission intensity. However, its determination may be problematic or not fully reliable (logistic constraints, low vector density, micro heterogeneity, low infection level, sampling technique, etc.) and additional/alternative tools would be very helpful. Our studies provide clear evidence that the An. gambiae gSG6 salivary protein can be used in malaria transmission areas as a reliable marker to evaluate spatial and temporal variation of human exposure to Afrotropical vectors. The cE5 protein showed higher sensitivity and may be of use in conditions of low or transient exposure to Anopheles vectors (i.e. low vector density, travellers). In conclusion, since parasite antigens (AMA-1, MSP-1, CSP) are already in use for the serological assessment of malaria transmission, the addition of Anopheles salivary antigens for measuring vector exposure may allow for comprehensive epidemiological profiling using just serological techniques
Efficacy of artesunate plus chloroquine for treatment of uncomplicated malaria in Burkina Faso children: a double-blind randomised controlled trial
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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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