| 1. |
- Algady, Walid, et al.
(author)
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The Malaria-Protective Human Glycophorin Structural Variant DUP4 Shows Somatic Mosaicism and Association with Hemoglobin Levels
- 2018
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In: American Journal of Human Genetics. - : Elsevier BV. - 0002-9297 .- 1537-6605. ; 103:5, s. 769-776
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Journal article (peer-reviewed)abstract
- Glycophorin A and glycophorin B are red blood cell surface proteins and are both receptors for the parasite Plasmodium falciparum, which is the principal cause of malaria in sub-Saharan Africa. DUP4 is a complex structural genomic variant that carries extra copies of a glycophorin A-glycophorin B fusion gene and has a dramatic effect on malaria risk by reducing the risk of severe malaria by up to 40%. Using fiber-FISH and Illumina sequencing, we validate the structural arrangement of the glycophorin locus in the DUP4 variant and reveal somatic variation in copy number of the glycophorin B-glycophorin A fusion gene. By developing a simple, specific, PCR-based assay for DUP4, we show that the DUP4 variant reaches a frequency of 13% in the population of a malaria-endemic village in southeastern Tanzania. We genotype a substantial proportion of that village and demonstrate an association of DUP4 genotype with hemoglobin levels, a phenotype related to malaria, using a family-based association test. Taken together, we show that DUP4 is a complex structural variant that may be susceptible to somatic variation and show that DUP4 is associated with a malarial-related phenotype in a longitudinally followed population.
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| 2. |
- Jahnmatz, Peter, et al.
(author)
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An antigen-specific, four-color, B-cell FluoroSpot assay utilizing tagged antigens for detection
- 2016
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In: JIM - Journal of Immunological Methods. - : Elsevier BV. - 0022-1759 .- 1872-7905. ; 433, s. 23-30
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Journal article (peer-reviewed)abstract
- The FluoroSpot assay, a variant of ELISpot utilizing fluorescent detection, has so far been used primarily for assessment of T cells, where simultaneous detection of several cytokines has allowed a more qualitative analysis of functionally distinct T cells. The potential to measure multiple analytes also presents several advantages when analyzing B cells. Our aim was to develop a B-cell FluoroSpot assay adaptable to studies of a variety of antigens. The assay utilizes anti-IgG antibodies immobilized in 96-well filter membrane plates. During cell culture, IgG antibodies secreted by antibody-secreting cells (ASCs) are captured in the vicinity of each of these cells and the specificity of single ASCs is defined using antigens for detection. The antigens were labeled with biotin or peptide tags enabling secondary detection with fluorophore-conjugated streptavidin or tag-specific antibodies. The assay, utilizing up to four different tag systems and fluorophores simultaneously, was evaluated using hybridomas and immunized splenocytes as ASCs. Assay variants were developed that could: i) identify multiple ASCs with different antigen specificities; ii) detect ASCs showing cross-reactivity with different but related antigens; and iii) define the antigen-specificity and, by including anti-IgG subclass detection reagents, simultaneously determine the IgG subclass of antibodies secreted by ASCs. As demonstrated here, the B-cell FluoroSpot assay using tag-based detection systems provides a versatile and powerful tool to investigate antibody responses by individual cells that can be readily adapted to studies of a variety of antigen-specific ASCs.
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| 3. |
- Naucler, Pontus, et al.
(author)
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HAI-Proactive : Development of an Automated Surveillance System for Healthcare-Associated Infections in Sweden
- 2020
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In: Infection control and hospital epidemiology. - : Cambridge University Press. - 0899-823X .- 1559-6834. ; 41, s. S39-S39
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Journal article (other academic/artistic)abstract
- Background: Healthcare-associated infection (HAI) surveillance is essential for most infection prevention programs and continuous epidemiological data can be used to inform healthcare personal, allocate resources, and evaluate interventions to prevent HAIs. Many HAI surveillance systems today are based on time-consuming and resource-intensive manual reviews of patient records. The objective of HAI-proactive, a Swedish triple-helix innovation project, is to develop and implement a fully automated HAI surveillance system based on electronic health record data. Furthermore, the project aims to develop machine-learning–based screening algorithms for early prediction of HAI at the individual patient level. Methods: The project is performed with support from Sweden’s Innovation Agency in collaboration among academic, health, and industry partners. Development of rule-based and machine-learning algorithms is performed within a research database, which consists of all electronic health record data from patients admitted to the Karolinska University Hospital. Natural language processing is used for processing free-text medical notes. To validate algorithm performance, manual annotation was performed based on international HAI definitions from the European Center for Disease Prevention and Control, Centers for Disease Control and Prevention, and Sepsis-3 criteria. Currently, the project is building a platform for real-time data access to implement the algorithms within Region Stockholm. Results: The project has developed a rule-based surveillance algorithm for sepsis that continuously monitors patients admitted to the hospital, with a sensitivity of 0.89 (95% CI, 0.85–0.93), a specificity of 0.99 (0.98–0.99), a positive predictive value of 0.88 (0.83–0.93), and a negative predictive value of 0.99 (0.98–0.99). The healthcare-associated urinary tract infection surveillance algorithm, which is based on free-text analysis and negations to define symptoms, had a sensitivity of 0.73 (0.66–0.80) and a positive predictive value of 0.68 (0.61–0.75). The sensitivity and positive predictive value of an algorithm based on significant bacterial growth in urine culture only was 0.99 (0.97–1.00) and 0.39 (0.34–0.44), respectively. The surveillance system detected differences in incidences between hospital wards and over time. Development of surveillance algorithms for pneumonia, catheter-related infections and Clostridioides difficile infections, as well as machine-learning–based models for early prediction, is ongoing. We intend to present results from all algorithms. Conclusions: With access to electronic health record data, we have shown that it is feasible to develop a fully automated HAI surveillance system based on algorithms using both structured data and free text for the main healthcare-associated infections.Funding: Sweden’s Innovation Agency and Stockholm County CouncilDisclosures: None
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| 4. |
- Reddy, Sreenivasulu B., et al.
(author)
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High Affinity Antibodies to Plasmodium falciparum Merozoite Antigens Are Associated with Protection from Malaria
- 2012
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In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:2
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Journal article (peer-reviewed)abstract
- Background: Malaria kills almost 1 million people every year, but the mechanisms behind protective immunity against the disease are still largely unknown. Methodology/Principal Findings: In this study, surface plasmon resonance technology was used to evaluate the affinity (measured as kd) of naturally acquired antibodies to the Plasmodium falciparum antigens MSP2 and AMA1. Antibodies in serum samples from residents in endemic areas bound with higher affinities to AMA1 than to MSP2, and with higher affinities to the 3D7 allele of MSP2-3D7 than to the FC27 allele. The affinities against AMA1 and MSP2-3D7 increased with age, and were usually within similar range as the affinities for the monoclonal antibodies also examined in this study. The finding of MSP2-3D7 type parasites in the blood was associated with a tendency for higher affinity antibodies to both forms of MSP2 and AMA1, but this was significant only when analyzing antibodies against MSP2-FC27, and individuals infected with both allelic forms of MSP2 at the same time showed the highest affinities. Individuals with the highest antibody affinities for MSP2-3D7 at baseline had a prolonged time to clinical malaria during 40 weeks of follow-up, and among individuals who were parasite positive at baseline higher antibody affinities to all antigens were seen in the individuals that did not experience febrile malaria during follow up. Conclusions/Significance: This study contributes important information for understanding how immunity against malaria arises. The findings suggest that antibody affinity plays an important role in protection against disease, and differs between antigens. In light of this information, antibody affinity measurements would be a key assessment in future evaluation of malaria vaccine formulations.
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| 5. |
- Sundling, Christopher, et al.
(author)
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B cell profiling in malaria reveals expansion and remodeling of CD11c+ B cell subsets
- 2019
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In: JCI Insight. - : American Society for Clinical Investigation. - 2379-3708. ; 4:9
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Journal article (peer-reviewed)abstract
- Humoral immunity is important in limiting clinical disease in malaria, yet the longitudinal B cell response to infection remains unclear. We performed a 1-year prospective study in patients treated for acute Plasmodium fakiporum malaria for the first time or with previous exposure to the disease. Using an unbiased exploratory approach with mass cytometry, followed by targeted flow cytometry, we found that approximately 80% of mature B cells that proliferated in response to acute infection expressed CD11c. Only approximately 40% of CD11c+ B cells displayed an atypical B cell phenotype, with the remaining cells primarily made up of activated and resting memory B cells. The CD11c+ B cells expanded rapidly following infection, with previous exposure to malaria resulting in a significantly larger increase compared with individuals with primary infection. This was attributed to an expansion of switched CD11c+ B cells that was absent in primary infected individuals. The rate of contraction of the CD11c+ B cell compartment was independent of previous exposure to malaria and displayed a slow decay, with a half-life of approximately 300 days. Collectively, these results identify CD11c as a marker of B cells responding to malaria and further highlight differences in primary and secondary B cell responses during infection.
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| 6. |
- Yman, Victor, et al.
(author)
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Persistent transmission of Plasmodium malariae and Plasmodium ovale species in an area of declining Plasmodium falciparum transmission in eastern Tanzania
- 2019
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In: PLoS Neglected Tropical Diseases. - : PUBLIC LIBRARY SCIENCE. - 1935-2727 .- 1935-2735. ; 13:5
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Journal article (peer-reviewed)abstract
- A reduction in the global burden of malaria over the past two decades has encouraged efforts for regional malaria elimination. Despite the need to target all Plasmodium species, current focus is mainly directed towards Plasmodium falciparum, and to a lesser extent P. vivax. There is a substantial lack of data on both global and local transmission patterns of the neglected malaria parasites P. malariae and P. ovale spp. We used a species-specific real-time PCR assay targeting the Plasmodium 18s rRNA gene to evaluate temporal trends in the prevalence of all human malaria parasites over a 22-year period in a rural village in Tanzania.We tested 2897 blood samples collected in five cross-sectional surveys conducted between 1994 and 2016. Infections with P. falciparum, P. malariae, and P. ovale spp. were detected throughout the study period, while P. vivax was not detected. Between 1994 and 2010, we found a more than 90% reduction in the odds of infection with all detected species. The odds of P. falciparum infection was further reduced in 2016, while the odds of P. malariae and P. ovale spp. infection increased 2- and 6-fold, respectively, compared to 2010. In 2016, non-falciparum species occurred more often as mono-infections. The results demonstrate the persistent transmission of P. ovale spp., and to a lesser extent P. malariae despite a continued decline in P. falciparum transmission. This illustrates that the transmission patterns of the non-falciparum species do not necessarily follow those of P. falciparum, stressing the need for attention towards non-falciparum malaria in Africa. Malaria elimination will require a better understanding of the epidemiology of P. malariae and P. ovale spp. and improved tools for monitoring the transmission of all Plasmodium species, with a particular focus towards identifying asymptomatic carriers of infection and designing appropriate interventions to enhance malaria control. Author summary The reduction in the global burden of malaria has encouraged efforts for elimination. Attempts to control and monitor transmission have mainly focused on the predominant malaria parasites Plasmodium falciparum and P. vivax. However, eliminating malaria requires the elimination of all human malaria parasites and limited interest has been directed towards estimating the disease burden attributable to the neglected malaria parasites P. ovale spp. and P. malariae. The authors used molecular methods to analyse 2897 blood samples collected in five cross-sectional surveys over a period of 22 years, and described the transmission patterns of all human malaria parasites in a Tanzanian village. They demonstrate a persistent transmission of P. malariae and P. ovale spp. despite a substantial reduction in transmission of P. falciparum, highlighting the need for more attention towards non-falciparum malaria. The authors discuss the implications of these findings in the context of current efforts for regional malaria elimination.
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