| 21. |
- Portugal, Silvia, et al.
(författare)
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B cell analysis of ethnic groups in Mali with differential susceptibility to malaria
- 2012
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Ingår i: Malaria Journal. - : Springer Science and Business Media LLC. - 1475-2875 .- 1475-2875. ; 11, s. 162-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Several studies indicate that people of the Fulani ethnic group are less susceptible to malaria compared to those of other ethnic groups living sympatrically in Africa, including the Dogon ethnic group. Although the mechanisms of this protection remain unclear, the Fulani are known to have higher levels of Plasmodium falciparum-specific antibodies of all Ig classes as compared to the Dogon. However, the proportions of B cell subsets in the Fulani and Dogon that may account for differences in the levels of Ig have not been characterized. Methods: In this cross-sectional study, venous blood was collected from asymptomatic Fulani (n = 25) and Dogon (n = 25) adults in Mali during the malaria season, and from P. falciparum-naive adults in the U. S. (n = 8). At the time of the blood collection, P. falciparum infection was detected by blood-smear in 16% of the Fulani and 36% of the Dogon volunteers. Thawed lymphocytes were analysed by flow cytometry to quantify B cell subsets, including immature and naive B cells; plasma cells; and classical, activated, and atypical memory B cells (MBCs). Results: The overall distribution of B cell subsets was similar between Fulani and Dogon adults, although the percentage of activated MBCs was higher in the Fulani group (Fulani: 11.07% [95% CI: 9.317 - 12.82]; Dogon: 8.31% [95% CI: 6.378 - 10.23]; P = 0.016). The percentage of atypical MBCs was similar between Fulani and Dogon adults (Fulani: 28.3% [95% CI: 22.73 - 34.88]; Dogon: 29.3% [95% CI: 25.06 - 33.55], but higher than U. S. adults (U. S.: 3.0% [95% CI: -0.21 - 6.164]; P < 0.001). Plasmodium falciparum infection was associated with a higher percentage of plasma cells among Fulani (Fulani infected: 3.3% [95% CI: 1.788 - 4.744]; Fulani uninfected: 1.71% [95% CI: 1.33 - 2.08]; P = 0.011), but not Dogon adults. Conclusion: These data show that the malaria-resistant Fulani have a higher percentage of activated MBCs compared to the Dogon, and that P. falciparum infection is associated with a higher percentage of plasma cells in the Fulani compared to the Dogon, findings that may account for the higher levels of P. falciparum antibodies in the Fulani.
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| 22. |
- Sanou, Guillaume S, et al.
(författare)
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Haematological parameters, natural regulatory CD4 + CD25 + FOXP3+ T cells and γδ T cells among two sympatric ethnic groups having different susceptibility to malaria in Burkina Faso.
- 2012
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Ingår i: BMC Research Notes. - : Springer Science and Business Media LLC. - 1756-0500 .- 1756-0500. ; 5, s. 76-(12 pp)
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Fulani ethnic group individuals are less susceptible than sympatric Mossi ethnic group, in term of malaria infection severity, and differ in antibody production against malaria antigens. The differences in susceptibility to malaria between Fulani and Mossi ethnic groups are thought to be regulated by different genetic backgrounds and offer the opportunity to compare haematological parameters, Tregs and γδT cell profiles in seasonal and stable malaria transmission settings in Burkina Faso. The study was conducted at two different time points i.e. during the high and low malaria transmission period.RESULTS: Two cross-sectional surveys were undertaken in adults above 20 years belonging either to the Fulani or the Mossi ethnic groups 1) at the peak of the malaria transmission season and 2) during the middle of the low malaria transmission season. Full blood counts, proportions of Tregs and γδ T cells were measured at both time-points.As previously shown the Fulani and Mossi ethnic groups showed a consistent difference in P. falciparum infection rates and parasite load. Differential white blood cell counts showed that the absolute lymphocyte counts were higher in the Mossi than in the Fulani ethnic group at both time points. While the proportion of CD4+CD25high was higher in the Fulani ethnic group at the peak of malaria transmission season (p = 0.03), no clear pattern emerged for T regulatory cells expressing FoxP3+ and CD127low. However CD3+γδ+ subpopulations were found to be higher in the Fulani compared to the Mossi ethnic group, and this difference was statistically significant at both time-points (p = 0.004 at low transmission season and p = 0.04 at peak of transmission).CONCLUSION: Our findings on regulatory T cell phenotypes suggest an interesting role for immune regulatory mechanisms in response to malaria. The study also suggests that TCRγδ + cells might contribute to the protection against malaria in the Fulani ethnic group involving their reported parasite inhibitory activities.
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| 23. |
- Shelton, Jennifer M. G., et al.
(författare)
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Genetic determinants of anti-malarial acquired immunity in a large multi-centre study
- 2015
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Ingår i: Malaria Journal. - : Springer Science and Business Media LLC. - 1475-2875 .- 1475-2875. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- Background: Many studies report associations between human genetic factors and immunity to malaria but few have been reliably replicated. These studies are usually country-specific, use small sample sizes and are not directly comparable due to differences in methodologies. This study brings together samples and data collected from multiple sites across Africa and Asia to use standardized methods to look for consistent genetic effects on anti-malarial antibody levels. Methods: Sera, DNA samples and clinical data were collected from 13,299 individuals from ten sites in Senegal, Mali, Burkina Faso, Sudan, Kenya, Tanzania, and Sri Lanka using standardized methods. DNA was extracted and typed for 202 Single Nucleotide Polymorphisms with known associations to malaria or antibody production, and antibody levels to four clinical grade malarial antigens [AMA1, MSP1, MSP2, and (NANP) 4] plus total IgE were measured by ELISA techniques. Regression models were used to investigate the associations of clinical and genetic factors with antibody levels. Results: Malaria infection increased levels of antibodies to malaria antigens and, as expected, stable predictors of anti-malarial antibody levels included age, seasonality, location, and ethnicity. Correlations between antibodies to blood-stage antigens AMA1, MSP1 and MSP2 were higher between themselves than with antibodies to the (NANP)(4) epitope of the pre-erythrocytic circumsporozoite protein, while there was little or no correlation with total IgE levels. Individuals with sickle cell trait had significantly lower antibody levels to all blood-stage antigens, and recessive homozygotes for CD36 (rs321198) had significantly lower anti-malarial antibody levels to MSP2. Conclusion: Although the most significant finding with a consistent effect across sites was for sickle cell trait, its effect is likely to be via reducing a microscopically positive parasitaemia rather than directly on antibody levels. However, this study does demonstrate a framework for the feasibility of combining data from sites with heterogeneous malaria transmission levels across Africa and Asia with which to explore genetic effects on anti-malarial immunity.
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| 24. |
- Vafa, Manijeh, et al.
(författare)
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Associations between the IL-4 -590 T allele and Plasmodium falciparum infection prevalence in asymptomatic Fulani of Mali
- 2007
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Ingår i: Microbes and infection. - : Elsevier BV. - 1286-4579 .- 1769-714X. ; 9:9, s. 1043-1048
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we compared the genotype and allele frequencies of the IL-10 -1087 A/G and IL-4 -590 C/T single nucleotide polymorphisms in asymptomatic subjects of two sympatric ethnic tribes differing in susceptibility to malaria, the Fulani and the Dogon in Mali. The genotype data was correlated with ethnicity and malariometric indexes. A statistically significant inter-ethnic difference in allele and genotype frequency for both loci was noted (P < 0.0001). Within the Fulani, the prevalence of Plasmodium falciparum infection, as detected by both microscopy and PCR, was associated with the IL-4 -590 T allele (P = 0.005 and P = 0.0005, respectively), whereas, no such associations were seen in the Dogon. Inter-ethnic differences in spleen rates, higher in the Fulani than the Dogon, were seen between T carriers (TT and CT) of both groups (P < 0.0001). Parasite densities and number of concurrent clones did not vary between IL-4 genotypes within any of the studied groups. These results suggest an association between the IL-4 -590 T allele and P. falciparum prevalence within the Fulani but not the Dogon. No associations between IL-10 genotypes and studied malariometric indexes were observed in any of the two communities.
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| 25. |
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| 26. |
- Vafa, Manijeh, et al.
(författare)
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Impact of the IL-4 -590 C/T transition on the levels of Plasmodium falciparum specific IgE, IgG, IgG subclasses and total IgE in two sympatric ethnic groups living in Mali.
- 2009
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Ingår i: Microbes and infection. - : Elsevier BV. - 1286-4579 .- 1769-714X. ; 11:8-9, s. 779-84
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Tidskriftsartikel (refereegranskat)abstract
- This study aimed to examine the effect of IL-4 -590 T/C polymorphism on the levels of malaria-specific IgE, IgG, IgG (1-4) subclasses as well as total IgE in the Fulani and their sympatric ethnic group, the Dogon, in Mali. Asymptomatic individuals, of the Fulani and the Dogon ethnic groups, were included in the study. IL-4 is involved in the regulation of IgE and IgG4 subclass. In line with this we found that within the Fulani, the T allele was associated with increased levels of total and anti-malarial IgE (P=0.02 and P=0.04, respectively). The Fulani T allele carriers had slightly higher levels of malarial specific IgG4 as compared to those with the CC genotype (P=0.08). No such differences were observed amongst the Dogon individuals. Taken together, these data indicate that the impact of IL-4 -590 variants on antibody levels may vary in different ethnic populations, and that this might affect the Ig-class and subclass distributions.
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| 27. |
- Vafa, Manijeh, et al.
(författare)
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Relationship between immunoglobulin isotype response to Plasmodium falciparum blood stage antigens and parasitological indexes as well as splenomegaly in sympatric ethnic groups living in Mali
- 2009
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Ingår i: Acta Tropica. - : Elsevier BV. - 0001-706X .- 1873-6254. ; 9:1, s. 12-16
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Tidskriftsartikel (refereegranskat)abstract
- This study aimed to assess correlations between anti-malarial antibody levels and differences in malariometric characteristics, seen between two sympatric ethnic groups, the Fulani and the Dogon, living in Mali. Plasma levels of anti-malarial IgE, IgG. IgG1-4 and total IgE were determined in asymptomatic individuals, of the above mentioned groups, and were correlated to malariometric indexes. Significantly higher levels of anti-malarial IgE, IgG, IgG1-3 and total IgE were detected in the Fulani individuals as compared to the Dogon. No difference in plasma levels of malaria specific IgG4 was noted between the two groups. Within the Fulani, an increase in total IgE levels was associated with the presence of infection. As the IgG4 level increased, the number of clones decreased in the Fulani individuals. A positive correlation between elevated levels of anti-malarial IgG and IgG3 and splenomegaly was noted only within the Fulani group. No other correlations between antibody levels and parasite prevalence, clone numbers or spleen rates were observed in any of the communities. These results suggest that the magnitude of antibody response against Plasmodium falciparum may not be as important as it is believed to be. Instead, the fine specificity or function of the response might be more critical in protection against malaria disease.
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