Browsing by Author "Kironde, Fred"

Now showing 1 - 9 of 9

Development of Plasmodium falciparum specific naïve, atypical, memory and plasma B cells during infancy and in adults in an endemic area
(Bio Med Central, 2017) Lugaajju, A; Reddy, S. B.; Wahlgren, M; Kironde, Fred; Persson, K. E. M.
Background: B-cells are essential in immunity against malaria, but which sub-sets of B-cells specifically recognize Plasmodium falciparum and when they appear is still largely unknown. Results: Using the flow cytometry technique for detection of P. falciparum specific (Pf+) B-cells, this study for the first time measured the development of Pf+ B cell (CD19+) phenotypes in Ugandan babies from birth up to nine months, and in their mothers. The babies showed increases in Pf+ IgG memory B-cells (MBCs), atypical MBCs, and plasma cells/blasts over time, but the proportion of these cells were still lower than in the mothers who displayed stable levels (5, 18, and 3%, respectively). Pf+ non-IgG+ MBCs and naïve B-cells binding to P. falciparum antigens were higher in the babies compared to the mothers (12 and 50%). In ELISA there was an increase in IgG and IgM antibodies over time in babies, and stable levels in mothers. At baby delivery, multigravidae mothers had a higher proportion of Pf+ IgG MBCs and less Pf+ naïve B-cells than primigravidae mothers. Conclusions: In newborns, naïve B-cells are a major player in recognizing P. falciparum. In adults, the high proportion of Pf+ atypical MBCs suggests a major role for these cells. Both in infants and adults, non-IgG+ MBCs were higher than IgG MBCs, indicating that these cells deserve more focus in future.
Differences in affinity of monoclonal and naturally acquired polyclonal antibodies against Plasmodium falciparum merozoite antigens
(2015) Reddy, S. B.; Anders, R. F.; Cross, N; Mueller, I; Senn, N; Stanisic, D. I.; Siba, P. M.; Wahlgren, M; Kironde, Fred; Beeson, J. G.; Persson, K. E. M
Background: Malaria is a major global cause of deaths and a vaccine is urgently needed. Results: We have employed the P. falciparum merozoite antigens MSP2-3D7/FC27 and AMA1, used them in ELISA, and coupled them in different ways using surface plasmon resonance (SPR) and estimated affinity (measured as kd) of monoclonal as well as naturally-acquired polyclonal antibodies in human plasma. There were major differences in kd depending on how the antigens were immobilized and where the His-tag was placed. For AMA1 we could see correlations with invasion inhibition. Using different immobilizations of proteins in SPR, we could see only moderate correlations with levels of antibodies in ELISA, indicating that in ELISA the proteins were not uniformly bound and that antibodies with many specificities exist in natural immunisation. The correlations between ELISA and SPR were enhanced when only parasite positive samples were included, which may indicate that high affinity antibodies are difficult to maintain over long periods of time. We found higher kd values for MSP2 (indicating lower affinity) compared to AMA1, which might be partly explained by MSP2 being an intrinsically disordered protein, while AMA1 is globular. Conclusions: For future vaccine studies and for understanding immunity, it is important to consider how to present proteins to the immune system to achieve highest antibody affinities.
Family Planning Utilization among PLWHIV Attending TASO Masaka: Evidence from a Cross-Sectional Study
(AIJR Publisher, 2021-07-31) Kizito, Benjamin Birungi; Ayebare, Angella Arigye; Namubiru, Sophia; Nabukeera, Swalha Kabogo; Kafeero, Mukasa Hussein; Kironde, Fred
People living with HIV (PLWHIV) need family planning (FP) services to avert the spread of HIV and eliminate mother to child transmission (MTCT). Besides, family planning services greatly reduce the incidence of vertical transmission reducing new cases of pediatric infections.Â The aim of this study was to establish the factors influencing the utilization of FP services among PLWHIV affiliated to The AIDS Service Organization (TASO) Masaka responsible for the unmet need for FP utilization. A cross-sectional study with quantitative data analysis was used.Â A structured questionnaire was used to collect data in line with the set objectives. Categorical data were presented as frequency percent and continuous data as a mean Â±standard deviation. The data were analyzed with the statistical software called Medcalc software v. 19.5.6. Analysis was done using the test of proportion at 95% confidence interval and a P<0.05 was considered statistically significant. The study had significantly more females, married, and of low education level (p<0.05).Â Medium parity of 1-3, a spouse being comfortable with a partner using FP, knowledge about FP were significantly associated with FP use (P<0.05). The Majority of the participants were using FP methods (P<0.05) with injections being the most used method (P<0.05). The Majority of the clients would encourage others to use FP (P<0.05) and HIV had no effect on FP use (P<0.05). Culture and society beliefs did not affect FP utilization (P<0.05). Being close to the service provider, hospitality of the service provider, information about the benefits and risks associated with FP use were significantly associated with utilization of FP methods (P<0.05). However, the overall utilization of FP was low (58.9%) and was largely affected by personal factors other than community or service delivery factors. Future research should focus on the putative personal factors that may prevent the utilization of FP methods.
Frequency of RANTES gene polymorphisms and their association with incidence of malaria: a longitudinal study on children in Iganga district, Uganda
(Bio Med Central, 2015) Lwanira, C. N.; Mukasa, M. K; Swedberg, G; Kironde, Fred
Background: The severity and outcome of malaria is influenced by host immunity in which chemokines such as Regulated upon Activation, Normal T cell Expressed and Secreted (RANTES) play an important role. Previous studies show that variations in the RANTES gene affect RANTES protein production, hence altering host immunity. In this study, the relationship between presence of mutations in RANTES and incidence of malaria in a cohort of children living in a malaria-endemic area of Uganda was determined. Methods: This was a longitudinal study comprising of 423 children aged between 6 months and 9 years, who were actively followed up for 1 year. Malaria episodes occurring in the cohort children were detected and the affected children treated with national policy drug regimen. Mutations in the RANTES gene were determined by PCR–RFLP method and their frequencies were calculated. A multivariate negative binomial regression model was used to estimate the impact of RANTES mutations on malaria incidence. In all statistical tests, a P-value of <0.05 was considered as significant. Results: The frequencies of the −403A and In1.1C allele were 53.7 and 19.2 %, respectively. No mutations were found at the −28 locus. After adjustment of incidence rates for age, blood group, insecticide-treated bed net (ITN) use, malaria history and the sickle cell trait, 1n1.1T/C heterozygotes and homozygotes showed a non-significant trend towards higher incidence rates compared to wild-type individuals (IRR = 1.10; P = 0.55 and IRR = 1.25; P = 0.60, respectively). Similarly, there was no significant difference in malaria incidence rates between RANTES −403G/A heterozygotes or homozygotes and those without mutations (IRR = 1.09; P = 0.66 and IRR = 1.16; P = 0.50, respectively). No relation was seen between RANTES polymorphisms, baseline parasite densities and the time to first re-infection after administration of anti-malaria drugs. Conclusions: This study showed that the −403A mutation occurs in nearly half of the study population and the In1.1C allele occurs in one in every four children. Despite the high frequency of these mutations, there was no clear association with malaria incidence. Other studies evaluating more markers, that could potentially modulate RANTES gene transcription alongside other genetic modifiers of malaria susceptibility, may provide further explanations to these less dramatic findings.
Malariometric indices from Iganga, Uganda: baseline characterization in preparation of GMZ2 vaccine trial
(2014) Kaddumukasa, M; Buwembo, W; Sekikubo, M; Naiwumbwe, H; Namusoke, F; Kiwuwa, S; Oketch, B; Noor, R; Chilengi, R; Mworozi, E; Kironde, Fred
Background: Malaria still remains the leading cause of childhood morbidity and mortality in Uganda. Interventions like malaria vaccines which reduce the malaria burden are needed in malaria endemic communities. There is need to establish baseline characteristics in vaccine trial study sites. This study determined the following baseline malariometric indices: spleen rates, bed net use, malaria parasitaemia and malaria episodes in an inception cohort of children aged 12 – 60 months in Iganga district, Uganda. Methods: In a longitudinal cohort study, 748 children were enrolled with 397 in an active follow up arm and 351 in a passive arm. The children in the two arms were followed for 6 months to determine the incidence of malaria episodes. Results: The overall baseline spleen rate was 8.2% (61/748) among the study participants. Of the households surveyed, about 36% reported using bed nets and almost 30% of the users had insecticide-treated nets. 274 (36.6%) of the study participants had a history of fever in the past 24 hrs at the time of the baseline survey. All participants had a peripheral blood smear for malaria parasites done at enrollment with 76.8% having the asexual form of malaria parasites. The malaria episodes per child per year were 1.5 and 0.79 in the active and passive follow up arms respectively. Conclusions: There is a high prevalence of malaria asexual parasitaemia in children below five years. The bed net usage still remains low among this population. These baseline malariometric indices have important implication for malaria control interventions.
Novel flow cytometry technique for detection of Plasmodium falciparum specific B‑cells in humans: increased levels of specific B‑cells in ongoing infection
(Malaria Journal, 2015) Lugaajju, Allan; Sreenivasulu, Reddy. B; Rönnberg, Caroline; Wahlgren, Mats; Kironde, Fred; Persson, Kristina E. M.
Background: Malaria caused by Plasmodium falciparum is still a major health threat in endemic areas especially for children below 5 years of age. While it is recognized that antibody immunity plays an important role in controlling the disease, knowledge of the mechanisms of sustenance and natural boosting of immunity is very limited. Before, it has not been possible to investigate malaria specific B-cells directly in flow cytometry, making it difficult to know how much of a B cell response is due to malaria, or how much is due to other immunological stimulators. Methods: This study developed a technique using quantum dots and schizont extract made from ghosts of infected erythrocytes, to be able to investigate P. falciparum specific B-cells, something that has never been done before. Results: Major differences in P. falciparum specific B-cells were found between samples from immune (22.3 %) and non-immune (1.7 %) individuals. Samples from parasite positive individuals had the highest proportions of specific B-cells (27.9 %). Conclusion: The study showed increased levels of P. falciparum-specific B-cells in immune individuals, with the highest levels in active malaria infections, using a new technique that opens up new possibilities to study how these cells are sustained in vivo after natural infections. It will also be useful in vaccine studies. Keywords: Plasmodium falciparum, Quantum dots, Ghost infected red blood cells, Malaria, B-cells
Parasite Specific Antibody Increase Induced by an Episode of Acute P. falciparum Uncomplicated Malaria
(2015) Kaddumukasa, M; Lwanira, C; Lugaajju, A; Katabira, E; Persson, K. E. M.; Wahlgren, M; Kironde, Fred
Introduction There is no approved vaccine for malaria, and precisely how human antibody responses to malaria parasite components and potential vaccine molecules are developed and maintained remains poorly defined. In this study, antibody anamnestic or memory response elicited by a single episode of P. falciparum infection was investigated. Methods This study involved 362 malaria patients aged between 6 months to 60 years, of whom 19% were early-diagnosed people living with HIV/AIDS (PLWHA). On the day malaria was diagnosed and 42 days later, blood specimens were collected. Parasite density, CD4+ cells, and antibodies specific to synthetic peptides representing antigenic regions of the P. falciparum proteins GLURP, MSP3 and HRPII were measured. Results On the day of malaria diagnosis, Immunoglobulin (IgG) antibodies against GLURP, MSP3 and HRP II peptides were present in the blood of 75%, 41% and 60% of patients, respectively. 42 days later, the majority of patients had boosted their serum IgG antibody more than 1.2 fold. The increase in level of IgG antibody against the peptides was not affected by parasite density at diagnosis. The median CD4+ cell counts of PLWHAs and HIV negative individuals were not statistically different, and median post-infection increases in anti-peptide IgG were similar in both groups of patients. Conclusion In the majority (70%) of individuals, an infection of P. falciparum elicits at least 20% increase in level of anti-parasite IgG. This boost in anti-P. falciparum IgG is not affected by parasite density on the day of malaria diagnosis, or by HIV status.
Polymorphisms in Plasmodium falciparum Chloroquine Resistance Transporter and Multidrug Resistance 1 Genes: Parasite Risk Factors that Affect Treatment Outcomes for P. falciparum Malaria after Artemether-Lumefantrine and Artesunate-Amodiaquine
(2014) Venkatesan, M; Gadalla, N. B.; Stepniewska, K; Kironde, Fred
Adequate clinical and parasitologic cure by artemisinin combination therapies relies on the artemisinin component and the partner drug. Polymorphisms in the Plasmodium falciparum chloroquine resistance transporter ( pfcrt) and P. falciparummultidrug resistance1(pfmdr1) genes are associated with decreased sensitivity to amodiaquine and lumefantrine, but effects of these polymorphisms on therapeutic responses to artesunate-amodiaquine (ASAQ) and artemetherlumefantrine (AL) have not been clearly defined. Individual patient data from 31 clinical trials were harmonized and pooled by using standardized methods from the WorldWide Antimalarial Resistance Network. Data for more than 7,000 patients were analyzed to assess relationships between parasite polymorphisms in pfcrt and pfmdr1 and clinically relevant outcomes after treatment with AL or ASAQ. Presence of the pfmdr1 gene N86 (adjusted hazards ratio = 4.74, 95% confidence interval = 2.29 – 9.78, P < 0.001) and increased pfmdr1 copy number (adjusted hazards ratio = 6.52, 95% confidence interval = 2.36–17.97, P < 0.001) were significant independent risk factors for recrudescence in patients treated with AL. AL and ASAQ exerted opposing selective effects on single-nucleotide polymorphisms in pfcrt and pfmdr1. Monitoring selection and responding to emerging signs of drug resistance are critical tools for preserving efficacy of artemisinin combination therapies; determination of the prevalence of at least pfcrt K76T and pfmdr1 N86Y should now be routine.
Prevalence of glucose-6-phosphate dehydrogenase deficiency and its association with Plasmodium falciparum infection among children in Iganga distric in Uganda
(Biomed central, 2014) Bwayo, Denis; Kaddumukasa, Mark; Ddungu, Henry; Kironde, Fred
Background: Glucose-6-phosphate dehydrogenase (G6PD) is a metabolic enzyme involved in the pentose phosphate pathway, its especially important in red blood cell metabolism. Glucose-6-phosphate dehydrogenase deficiency is an X-linked recessive hereditary disease characterised by abnormally low levels of G6PD. About 400 million people worldwide have a deficiency of this enzyme. The remarkable geographic correlation of G6PD deficiency distribution with historical endemicity patterns of malaria has led to suggestions that the two could be linked. Some studies have concluded that G6PD deficiency confers resistance to malaria. Objective: To determine the prevalence of G6PD deficiency, and determine its relationship with prevalence and incidence of P. falciparum infection among children in Uganda. Methods: This was longitudinal study involving 245 children, 135 were actively followed up for 12 months. G6PD status was assessed for using PCR-RFLP method. A thick smear was done to determine presence of plasmodium trophozoites and parasite densities. Results: A total of 245 children between 6 months and 9 years were recruited. Of these 46.5% were males. Overall prevalence for the X-linked G6PD A- mutation was; 79.59% wild type, 12.65% heterozygous and 7.76% homozygous or hemizygous. Among the males 14% were hemizygous. At baseline, 40.8% had asymptomatic P falciparum infection. There was no statistically significant difference in prevalence and incidence rates of malaria infection among the different G6PD genotypes with prevalence among heterozygous, homozygous, and wild type being 29%, 42.6% and 43% respectively (p = 0.11) and incidence among heterozygous and wild type being 0.56 and 0.52 episodes/year (p = 0.5). The heterozygous G6PD A- females had a lower parasite density compared to the wild type (2505 vs 941 parasites/μL; P = 0.024). Conclusions: This study showed that 20.41% of the population in this part of Uganda carry the G6PD A-mutation, within the range of 15-32% seen in other parts of Africa. P. falciparum infection incidence and prevalence rates are similar among the G6PD genotypes though, once infected, P. falciparum parasite densities are lowest among G6PD A- heterozygous females. This suggests differences in P. falciparum infection rates and severity of disease could be mediated by differences in parasite densities among the different G6PD genotypes.