Plasma cytokines, chemokines and cellular immune responses in pre-school Nigerian children infected with Plasmodium falciparum

Association between Plasmodium Infection and Nitric Oxide Levels: A Systematic Review and Meta-Analysis

Nitric oxide (NO) has been implicated in the pathology of malaria. This systematic review and meta-analysis describe the association between NO levels and malaria. Embase, Ovid, PubMed, Scopus, and Google Scholar were searched to identify studies evaluating NO levels in malaria patients and uninfected controls. Meta-regression and subgroup analyses were conducted to discern differences in NO levels between the groups. Of the 4517 records identified, 21 studies were included in the systematic review and meta-analysis. The findings illustrated significant disparities in NO levels based on geographic location and study time frames. Despite the fluctuations, such as higher NO levels in adults compared to children, no significant differences in mean NO levels between patients and uninfected controls (p = 0.25, Hedge's g: 0.35, 95% confidence interval (CI): -0.25-0.96, I2: 97.39%) or between severe and non-severe malaria cases (p = 0.09, Hedge's g: 0.71, 95% CI: -0.11-1.54, I2: 96.07%) were detected. The systematic review and meta-analysis highlighted inconsistencies in NO levels in malaria patients. Given the high heterogeneity of the results, further studies using standardized metrics for NO measurements and focusing on biochemical pathways dictating NO responses in malaria are imperative to understand the association between NO and malaria.

Clinical features, immunological interactions and household determinants of visceral leishmaniasis and malaria coinfections in West Pokot, Kenya: protocol for an observational study

INTRODUCTION

Visceral leishmaniasis (VL) and malaria are two deadly parasitic diseases that coexist in West Pokot County, Kenya. The local population is at considerable risk of coinfection with VL and malaria; however, few studies have described the clinical implications of this comorbidity. Questions remain regarding the immune responses responsible for possible predisposing or protective effects. Moreover, characterisation of environmental and household risk factors for co-acquiring VL and malaria is warranted to increase awareness and guide implementation of targeted control strategies. This protocol intends to address these knowledge gaps concerning VL-malaria coinfections.

METHODS AND ANALYSIS

This observational research project will have a multimethod approach, starting with a cross-sectional study at Kacheliba Sub-County Hospital in West Pokot, Kenya. Patients with laboratory confirmation of a VL and/or malaria infection will be clinically assessed and symptomatology of monoinfections and coinfections will be compared. Second, a questionnaire will be addressed to all included patients and to healthy controls in local communities. This case-control study will aim to describe household and environmental determinants associated with VL-malaria coinfection. Lastly, blood samples will be collected from a small cohort of VL and malaria monoinfected and coinfected patients during treatment of their infection(s), and from healthy controls and asymptomatic VL and malaria cases recruited in local communities. These specimens will be used for serum cytokine measurements and molecular quantitation of Plasmodium and Leishmania. In this way, the immune response and parasite dynamics during VL-malaria coinfection will be characterised longitudinally and compared with those observed in clinical and asymptomatic monoinfections.

ETHICS AND DISSEMINATION

Ethical approval was obtained from the Ethics and Scientific Research Committee of Amref Health Africa. The study findings will be presented at international conferences and published in open-access, peer-reviewed journals.

TRIAL REGISTRATION NUMBER

ISRCTN Registry (ISRCTN15023306).

Immunological and anti-oxidant profiles of malarial children in Abuja, Nigeria

BACKGROUND

The clinical symptoms, cellular immune response, and serum cytokine homeostasis during falciparum malaria among children living in endemic regions depend on the parasite densities. This study aims to evaluate the CD4+ and CD8+ T cells, leucocytes subpopulations, IL-6, IL-10 and biomarkers of oxidative stress among children infected with varying grades of malaria attending the University of Abuja Teaching Hospital and National Hospital, Abuja, Nigeria.

MATERIALS AND METHODS

This case-control study involved blood samples collected from 165 children (between 5 and 12 years). This comprised 45 children with mild malaria, 40 each with moderate, severe malaria and apparently healthy (control). Serum cytokines, ferritin, malonaldehyde (MDA), ascorbate, α-tocopherol levels were determined by Enzyme-Linked ImmunoSorbent Assay (ELISA). Leucocytes differentials and CD4+/CD8+ T cells counts were enumerated by automated hematology analyzer and flow cytometry, respectively.

RESULTS

All malarial children had only Plasmodium falciparum. The male to female ratio of children with mild malaria was 1.5:1 (mean ± SD age of 8.5 ± 1.9 years). However, other groups had 1:1 male to female ratio and mean ages of 9.2 ± 2.3, 9.8 ± 2.2, 8.5 ± 1.5 for children with moderate, severe malaria and control, respectively. There was a positive but not significant association of neutrophils and monocytes with the 3 grades of malaria parasitemia (p>0.05). There was a negative and significant correlation between severe malaria and lymphocyte count (p = 0.048; r = -0.647). However, there was positive and significant correlation between eosinophil with moderate (p = 0.03; r = 0.994) and severe malaria (p = 0.006; r = 0.825). There was a significant decline in serum ascorbate with increased malaria density (p<0.0001). However, there was no difference in the serum α-tocopherol concentration within the 4 groups of children (p = 0.182). Serum ferritin and MDA significantly elevated with an increase in malaria density (p<0.0001). There was a significant decline in CD4+ T and CD8+ T cells counts with an increase in malaria densities (p<0.0001). Serum IL-10 and IL-6 significantly elevated with increased malaria density (p<0.0001).

CONCLUSION

Based on these findings, severe malaria was significantly associated with declined CD4+ and CD8+ T cell counts, upregulation of IL-6, and high serum levels of oxidative stress biomarkers.

Epidemiology of malaria among pregnant women during their first antenatal clinic visit in the middle belt of Ghana: a cross sectional study

Background

Malaria during pregnancy may result in unfavourable outcomes in both mothers and their foetuses. This study sought to document the current burden and factors associated with malaria and anaemia among pregnant women attending their first antenatal clinic visit in an area of Ghana with perennial malaria transmission.

Methods

A total of 1655 pregnant women aged 18 years and above with a gestational age of 13–22 weeks, who attended an antenatal care (ANC) clinic for the first time, were consented and enrolled into the study. A structured questionnaire was used to collect socio-demographic and obstetric data and information on use of malaria preventive measures. Venous blood (2 mL) was collected before sulfadoxine-pyrimethamine administration. Malaria parasitaemia and haemoglobin concentration were determined using microscopy and an automated haematology analyser, respectively. Data analysis was carried out using Stata 14.

Results

Mean age (SD) and gestational age (SD) of women at enrolment were 27.4 (6.2) years and 16.7 (4.3) weeks, respectively. Overall malaria parasite prevalence was 20.4% (95% CI 18.5–22.4%). Geometric mean parasite density was 442 parasites/µL (95% CI 380–515). Among women with parasitaemia, the proportion of very low (1–199 parasites/µL), low (200–999 parasites/µL), medium (1000–9999 parasites/µL) and high (≥ 10,000 parasites/µL) parasite density were 31.1, 47.0, 18.9, and 3.0%, respectively. Age ≥ 25 years (OR 0.57, 95% CI 0.41–0.79), multigravid (OR 0.50, 95% CI 0.33–0.74), educated to high school level or above (OR 0.53, 95% CI 0.33–0.83) and in household with higher socio-economic status (OR 0.34, 95% CI 0.21–0.54) were associated with a lower risk of malaria parasitaemia. The prevalence of anaemia (< 11.0 g/dL) was 56.0%, and the mean haemoglobin concentration in women with or without parasitaemia was 9.9 g/dL or 10.9 g/dL, respectively.

Conclusion

One out of five pregnant women attending their first ANC clinic visit in an area of perennial malaria transmission in the middle belt of Ghana had Plasmodium falciparum infection. Majority of the infections were below 1000 parasites/µL and with associated anaemia. There is a need to strengthen existing malaria prevention strategies to prevent unfavourable maternal and fetal birth outcomes in this population.

Chemokine, cytokine and haematological profiles in Sprague-Dawley rats co-infected with Plasmodium berghei ANKA and Trichinella zimbabwensis-A laboratory animal model for malaria and tissue-dwelling nematodes co-infection

Malaria remains a major cause of mortality and morbidity in sub-Saharan Africa (SSA) and tissue-dwelling helminth parasites (TDHPs) are also prevalent in this region presenting a geographical overlap in endemicity. There is paucity of information on the specific host immune responses elicited at different phases of the life cycle by the co-infecting helminth parasites. This study aimed at using a laboratory animal model to determine selected chemokine, cytokine and hematological profiles in Sprague-Dawley rats co-infected with Plasmodium berghei ANKA (Pb) and a tissue-dwelling nematode, Trichinella zimbabwensis (Tz). One-hundred-and-sixty-eight male Sprague-Dawley rats (90–150g) were randomly divided into four experimental groups; Control (n = 42), Pb-infected (n = 42), Tz-infected (n = 42) and Pb + Tz-infected group (n = 42). Trichinella zimbabwensis infection (3 muscle larvae/g body weight per os) was done on day 0 while intra-peritoneal Pb infection (10⁵ parasitised RBCs) was done at day 28 of the 42-day experimental study for the co-infection group which corresponded with day 0 of the Pb group on the protocol. Haematological parameters, cytokines (TNF-α, IL-10, IL-4, IL-6), chemokines (CXCL10, CCL5, CCL11) and burden of Tz adult worms and muscle larvae burden were determined as per need for each group. Results showed that Tz infection predisposed the co-infected animals towards rapid development of Pb parasitaemia during co-infection, reaching a higher peak percentage parasitaemia at day 7 post-infection than the Pb mono-infected group at day 6 post-infection. Animals in the co-infected group also exhibited severe anaemia, basophilia, neutrophilia, eosinophilia and lymphopenia at day 7 post Pb infection compared to the control groups. Significant elevation of Pb parasitaemia coincided with elevated pro-inflammatory cytokine TNF-α (P < 0.001), regulatory anti-inflammatory IL-10 (P < 0.001), and pro-inflammatory chemokines CXCL10 (P < 0.001) concentration in comparison to control group, at day 7 post Pb infection. Our results confirm that co-infection of Pb with Tz resulted in increased Pb parasitaemia compared to the control group in the early stages of infection and this might translate to severe malaria.

CD209 and Not CD28 or STAT6 Polymorphism Mediates Clinical Malaria and Parasitemia among Children from Nigeria

Malaria remains a significant disease, causing epic health problems and challenges all over the world, especially in sub-Saharan Africa. CD209 and CD28 genes act as co-stimulators and regulators of the immune system, while the STAT6 gene has been reported to mediate cytokine-induced responses. Single nucleotide polymorphisms of these genes might lead to differential disease susceptibility among populations at risk for malaria, due to alterations in the immune response. We aim to identify key drivers of the immune response to malaria infection among the three SNPs: CD209 (rs4804803), CD28 (rs35593994) and STAT6 (rs3024974). After approval and informed consent, we genotyped blood samples from a total of 531 children recruited from Nigeria using the Taqman SNP genotyping assay and performed comparative analysis of clinical covariates among malaria-infected children. Our results reveal the CD209 (rs4804803) polymorphism as a susceptibility factor for malaria infection, significantly increasing the risk of disease among children, but not CD28 (rs35593994) or STAT6 (rs3024974) polymorphisms. Specifically, individuals with the homozygous mutant allele (rs4804803G/G) for the CD209 gene have a significantly greater susceptibility to malaria, and presented with higher mean parasitemia. This observation may be due to a defective antigen presentation and priming, leading to an ineffective downstream adaptive immune response needed to combat infection, as well as the resultant higher parasitemia and disease manifestation. We conclude that the CD209 gene is a critical driver of the immune response during malaria infection, and can serve as a predictor of disease susceptibility or a biomarker for disease diagnosis.

NF90 regulation of immune factor expression in response to malaria antigens

Nuclear factor 90 (NF90) is a dual DNA- and RNA-binding protein expressed ubiquitously in mammalian cells, including monocytes. Here, to elucidate the function of NF90 in the immune response, we analyzed systematically its influence on gene expression programs in the human monocytic cell line THP-1 expressing normal or reduced NF90 levels. RNA sequencing analysis revealed many mRNAs showing differential abundance in NF90-silenced cells, many of them encoding proteins implicated in the response to immune stimuli and malaria infection. The transcription of some of them (e.g. TNF, LILRB1, and CCL2 mRNAs) was modulated by silencing NF90. Ribonucleoprotein immunoprecipitation (RIP) analysis further revealed that a subset of these mRNAs associated directly with NF90. To understand how NF90 influenced globally the immune response to malaria infection, lysates of red blood cells infected with Plasmodium falciparum (iRBC lysates) or uninfected/mock-infected (uRBC lysates) were used to treat THP-1 cells as a surrogate of malaria infection. NF90 affected the stability of a few target mRNAs, but influenced more generally the translation and secretion of the encoded cytokines after treatment with either uRBC or iRBC lysates. Taken together, these results indicate that NF90 contributes to repressing the immune response in cells responding to P. falciparum infection and suggest that NF90 can be a therapeutic target in malaria.

Initial effects of inflammation-related cytokines and signaling pathways on the pathogenesis of post-traumatic osteoarthritis

The main pathological change in post-traumatic osteoarthritis (PTOA) is cartilage degeneration, which is closely related to inflammation and oxidative stress. Inflammation can cause degeneration of articular cartilage. Cartilage degeneration can also stimulate the progression of inflammation. It has been found that inflammatory cytokines can participate in the pathological process of cartilage degeneration through multiple signaling pathways, mainly mitogen-activated protein kinase, nuclear transcription factor kappa B, and Wnt–β-catenin signal transduction pathways. This review aimed at exploring the relationship between PTOA and inflammation-related cytokines by introducing the role of proinflammatory cytokines in chondrocyte destruction and extracellular matrix degradation.

Plasmodium and intestinal parasite perturbations of the infected host's inflammatory responses: a systematic review

Co-infection of malaria and intestinal parasites is widespread in sub-Saharan Africa and causes severe disease especially among the poorest populations. It has been shown that an intestinal parasite (helminth), mixed intestinal helminth or Plasmodium parasite infection in a human induces a wide range of cytokine responses, including anti-inflammatory, pro-inflammatory as well as regulatory cytokines. Although immunological interactions have been suggested to occur during a concurrent infection of helminths and Plasmodium parasites, different conclusions have been drawn on the influence this co-infection has on cytokine production. This review briefly discusses patterns of selected cytokine (IL-6, IL-8, IL-10, TNF-α and INF-γ) responses associated with infections caused by Plasmodium, intestinal parasites as well as a Plasmodium-helminth co-infection.

Serum cytokine responses in Rickettsia felis infected febrile children, Ghana

The intracellular pathogen Rickettsia felis causes flea-borne spotted fever and is increasingly recognized as an emerging cause of febrile illness in Africa, where co-infection with Plasmodium falciparum is common. Rickettsiae invade endothelial cells. Little is known, however, about the early immune responses to infection. In this study, we characterize for the first time the cytokine profile in the acute phase of illness caused by R. felis infection, as well as in plasmodial co-infection, using serum from 23 febrile children < 15 years of age and 20 age-matched healthy controls from Ghana. Levels of IL-8 (interleukin-8), IP-10 (interferon-γ-induced protein-10), MCP-1 (monocyte chemotactic protein-1), MIP-1α (macrophage inflammatory protein-1α) and VEGF (vascular endothelial growth factor) were significantly elevated in R. felis mono-infection; however, IL-8 and VEGF elevation was not observed in plasmodial co-infections. These results have important implications in understanding the early immune responses to R. felis and suggest a complex interplay in co-infections.

Potential Role for Regulatory B Cells as a Major Source of Interleukin-10 in Spleen from Plasmodium chabaudi-Infected Mice

Interleukin-10 (IL-10)-producing regulatory B (Breg) cells were found to be induced in a variety of infectious diseases. However, its importance in the regulation of immune response to malaria is still unclear. Here, we investigated the dynamics, phenotype, and function of Breg cells using Plasmodium chabaudi chabaudi AS-infected C57BL/6 and BALB/c mice. BALB/c mice were more susceptible to infection and had a stronger IL-10 response in spleen than C57BL/6 mice. Analysis of the surface markers of IL-10-producing cells with flow cytometry showed that CD19⁺ B cells were one of the primary IL-10-producing populations in P. c. chabaudi AS-infected C57BL/6 and BALB/c mice, especially in the latter one. The Breg cells had a heterogeneous phenotype which shifted during infection. The well-established Breg subset, CD19⁺ CD5⁺ CD1d^hi cells, accounted for less than 20% of IL-10-producing B cells in both strains during the course of infection. Most Breg cells were IgG⁺ and CD138^- from day 0 to day 8 postinfection. Adoptive transfer of Breg cells to C57BL/6 mice infected with P. c. chabaudi AS led to a transient increase of parasitemia without an impact on survival rate. Our finding reveals that B cells play an active and important regulatory role in addition to mediating humoral immunity in immune response against malaria, which should be paid more attention in developing therapeutic or vaccine strategies against malaria involving stimulation of B cells.

MCP-1, KC-like and IL-8 as critical mediators of pathogenesis caused by Babesia canis

Canine babesiosis caused by the intraerythrocytic protozoan parasite Babesia canis is a tick-borne disease characterized by a host response that involves both cellular and humoral immunity. This study focuses on the secretion of cytokines Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF), Keratinocyte Chemotactic-like (KC-like), Interleukins (IL)-2, IL-7, IL-8, IL-10, IL-15, IL-18 and Monocyte Chemotactic Protein-1 (MCP-1) in babesiosis caused by Babesia canis upon treatment with Imizol®. We assessed time dependent changes in cytokine levels and tested whether these changes correlate with pathogenesis of the disease. Sixteen healthy dogs and 31 dogs infected with Babesia canis, of which 18 showed complications, were treated with Imizol®. One dog died during the study (3.2%). Longitudinal study was perfomed by monitoring dogs at the first day of presentation (day 1) and 6 days later (day 7). Our results show that higher MCP-1 levels on day 1 are positively associated with the occurrence of complications, (complicated vs. uncomplicated; p = 0.00016). A similar pattern was observed for KC-like on day 1 (p = 0.0326) and day 7 (p = 0.044). Moreover, babesiosis caused by B. canis produced a steady increase in IL-8 levels with a moderate to strong negative correlation with erythrocyte counts and hematocrit in uncomplicated diseased dogs only (Spearman's rank correlation coefficient rs = -0.582 and rs = -0.598 respectively). Like for MCP-1, KC-like levels also differed in complicated and uncomplicated diseased dogs on day 1 (p = 0.03236) and day 7 (p = 0.044). Furthermore, KC-like levels were strongly correlated with IL-8 levels (rs = 0.663-0.7) and non-segmented neutrophil counts (rs = 0.572-0.732) in both diseased groups. Analysis of ROC suggests the use of serum levels of MCP-1 and IL-7 as predictors of the occurrence of complications with an AUC of 0.906 and 0.896 respectively and linear combinations of MCP-1, KC-Like, IL-7 and GM-CSF with values up to AUC = 0.983. Cytokine cluster analysis presented in this study can contribute to a better understanding of the pathogenesis of babesiosis and serve as a prognostic tool for the early detection of cases with highest likelihood of developing complications. Overall, our studies show that infection by B. canis elicits a cytokine pattern that is distinct from that observed with B. rossi, and that some of the inflammatory mediators can be useful to predict complications. Our results also suggest targets for the development of novel therapeutic strategies in babesiosis caused by B. canis.

Both inflammatory and regulatory cytokine responses to malaria are blunted with increasing age in highly exposed children

Background

Young children are at greatest risk for malaria-associated morbidity and mortality. The immune response of young children differs in fundamental ways from that of adults, and these differences likely contribute to the increased susceptibility of children to severe malaria and to their delayed development of immunity. Elevated levels of pro-inflammatory cytokines and chemokines in the peripheral blood during acute infection contribute to the control of parasitaemia, but are also responsible for much of the immunopathology seen during symptomatic disease. Clinical immunity to malaria may depend upon the ability to regulate these pro-inflammatory responses, possibly through mechanisms of immunologic tolerance. In order to explore the effect of age on the immune response to malaria and the development of clinical immunity, cytokines and chemokines were measured in the plasma of children at day 0 of an acute malaria episode and during convalescence.

Results

Younger children presenting with acute malaria exhibited much higher levels of TNF, IL2, and IL6, as well as increased Th1 associated chemokines IP10, MIG, and MCP1, compared to older children with acute malaria. Additionally, the regulatory cytokines IL10 and TNFRI were dramatically elevated in younger children compared to older children during acute infection, indicating that regulatory as well as pro-inflammatory cytokine responses are dampened in later childhood.

Conclusions

Together these data suggest that there is a profound blunting of the cytokine and chemokine response to malaria among older children residing in endemic settings, which may be due to repeated malaria exposure, intrinsic age-based differences in the immune response, or both.

A novel in vitro model reveals distinctive modulatory roles of Plasmodium falciparum and Plasmodium vivax on naïve cell-mediated immunity

BACKGROUND

To date, human peripheral blood mononuclear cells (PBMCs) have been used mainly in immune stimulation assays and the interpretation of data can be influenced by the previous immunological history of donors and cross reactivity with other infectious agents. Resolving these limitations requires an alternative in vitro model to uncover the primary response profiles.

METHODS

A novel in vitro model of mononuclear cells (MNCs) generated from haematopoietic stem cells (HSCs) was developed and these cells were then co-cultured with various antigens from Plasmodium falciparum and Plasmodium vivax to investigate the response of naïve immune cells to malaria antigens by flow cytometry.

RESULTS

In vitro stimulation of naïve lymphocytes showed that CD4+ and CD8+ T lymphocytes were significantly reduced (P < 0.01) by exposure to lysates of infected erythrocytes or intact erythrocytes infected with P. falciparum. The depletion was associated with the expression of CD95 (Fas receptor) on the surface of T lymphocytes. Maturation of T lymphocytes was affected differently, showing elevated CD3+CD4+CD8+ and CD3+CD4-CD8- T lymphocytes after stimulation with cell lysates of P. falciparum and P. vivax, respectively. In addition, antigen presenting monocytes and dendritic cells derived from haematopoietic stem cells showed impaired HLA-DR expression as a consequence of exposure to different species of malaria parasites.

CONCLUSION

These results suggest that naïve mononuclear cells differentiated in vitro from HSCs could provide a valid model for the assessment of immunity. P. falciparum and P. vivax malaria parasites could modulate various populations of immune cells starting from newly differentiated mononuclear cells.

Tumour necrosis factor alpha promoter polymorphism, TNF-238 is associated with severe clinical outcome of falciparum malaria in Ibadan southwest Nigeria

Tumour necrosis factor (TNF) - α has been shown to play an important role in the pathogenesis of falciparum malaria. Two TNF promoter polymorphisms, TNF-308 and TNF-238 have been associated with differential activity and production of TNF. In order to investigate the association between TNF-308 and TNF-238 and the clinical outcome of malaria in a Nigerian population, the two TNF polymorphisms were analysed using Sequenom iPLEX Platform. A total of 782 children; 283 children with uncomplicated malaria, 255 children with severe malaria and 244 children with asymptomatic infection (controls) were studied. The distribution of TNF-308 and TNF-238 genotypes were consistent with the Hardy-Weinberg equilibrium. Distribution of both TNF polymorphisms differed significantly across all clinical groups (TNF-308: p=0.007; TNF-238: p=0.001). Further tests for association with severe malaria using genotype models controlling for age, parasitaemia and HbAS showed a significant association of the TNF-238 polymorphism with susceptibility to severe malaria (95% CI=1.43-6.02, OR=2.94, p=0.003237) The GG genotype of TNF-238 significantly increased the risk of developing cerebral malaria from asymptomatic malaria and uncomplicated malaria (95% CI=1.99-18.17, OR=6.02, p<0.001 and 95% CI=1.78-8.23, OR=3.84, p<0.001 respectively). No significant association was found between TNF-308 and malaria outcome. These results show thegenetic association of TNF-238 in the clinical outcome of malaria in Ibadan, southwest Nigeria. These findings add support to the role of TNF in the outcome of malaria infection. Further large scale studies across multiple malaria endemic populations will be required to determine the specific roles of TNF-308 and TNF-238 in the outcome of falciparum malaria infection.

Associations Between Helminth Infections, Plasmodium falciparum Parasite Carriage and Antibody Responses to Sexual and Asexual Stage Malarial Antigens

Infections with helminths and Plasmodium spp. overlap in their geographical distribution. It has been postulated that helminth infections may influence malarial transmission by altering Plasmodium falciparum gametocytogenesis. This cross-sectional study assessed the effect of helminth infections on P. falciparum gametocyte carriage and on humoral immune responses to sexual stage antigens in Gabon. Schistosoma haematobium and filarial infections as well as P. falciparum asexual forms and gametocyte carriage were determined. The antibody responses measured were to sexual (Pfs230, Pfs48/45) and asexual P. falciparum antigens (AMA1, MSP1, and GLURP). A total of 287 subjects were included. The prevalence of microscopically detectable P. falciparum asexual parasites was higher in S. haematobium-infected subjects in comparison to their uninfected counterparts (47% versus 26%, P = 0.003), but this was not different when filarial infections were considered. Plasmodium falciparum gametocyte carriage was similar between Schistosoma- or filaria-infected and uninfected subjects. We observed a significant decrease of Pfs48/45 immunoglobulin G titer in S. haematobium-infected subjects (P = 0.037), whereas no difference was seen for Pfs230 antibody titer, nor for antibodies to AMA1, MSP1, or GLURP. Our findings suggest an effect of S. haematobium on antibody responses to some P. falciparum gametocyte antigens that may have consequences for transmission-blocking immunity.

A STAT6 Intronic Single-Nucleotide Polymorphism is Associated with Clinical Malaria in Ghanaian Children

Malaria pathogenesis may be influenced by IgE responses and cytokine cross-regulation. Several mutations in the IL-4/STAT6 signaling pathway can alter cytokine cross-regulation and IgE responses during a Plasmodium falciparum malarial infection. This study investigated the relationship between a STAT6 intronic single-nucleotide polymorphism (rs3024974), total IgE, cytokines, and malaria severity in 238 Ghanaian children aged between 0.5 and 13 years. Total IgE and cytokine levels were measured by ELISA, while genotyping was done by polymerase chain reaction-restriction fragment length polymorphism (RFLP). Compared with healthy controls, heterozygosity protected against clinical malaria: uncomplicated malaria (odds ratios [OR] = 0.13, P < 0.001), severe malarial anemia (OR = 0.18, P < 0.001), and cerebral malaria (OR = 0.39, P = 0.022). Levels of total IgE significantly differed among malaria phenotypes (P = 0.044) and rs3024974 genotypes (P = 0.037). Neither cytokine levels nor IL-6/IL-10 ratios were associated with malaria phenotypes or rs3024974 genotypes. This study suggests a role for rs3024974 in malaria pathogenesis and offers further insights into an IL-4/STAT6 pathway mutation in malaria pathogenesis.

Excessive Pro-Inflammatory Serum Cytokine Concentrations in Virulent Canine Babesiosis

Babesia rossi infection causes a severe inflammatory response in the dog, which is the result of the balance between pro- and anti-inflammatory cytokine secretion. The aim of this study was to determine whether changes in cytokine concentrations were present in dogs with babesiosis and whether it was associated with disease outcome. Ninety-seven dogs naturally infected with B. rossi were studied and fifteen healthy dogs were included as controls. Diagnosis of babesiosis was confirmed by polymerase chain reaction and reverse line blot. Blood samples were collected from the jugular vein at admission, prior to any treatment. Cytokine concentrations were assessed using a canine-specific multiplex assay on an automated analyser. Serum concentrations of interleukin (IL)-2, IL-6, IL-8, IL-10, IL-18, granulocyte-macrophage colony stimulating factor (GM-CSF) and monocyte chemotactic protein-1 (MCP-1) were measured. Twelve of the Babesia-infected dogs died (12%) and 85 survived (88%). Babesia-infected dogs were also divided into those that presented within 48 hours from displaying clinical signs, and those that presented more than 48 hours after displaying clinical signs. Cytokine concentrations were compared between the different groups using the Mann-Whitney U test. IL-10 and MCP-1 concentrations were significantly elevated for the Babesia-infected dogs compared to the healthy controls. In contrast, the IL-8 concentration was significantly decreased in the Babesia-infected dogs compared to the controls. Concentrations of IL-6 and MCP-1 were significantly increased in the non-survivors compared to the survivors. Concentrations for IL-2, IL-6, IL-18 and GM-CSF were significantly higher in those cases that presented during the more acute stage of the disease. These findings suggest that a mixed cytokine response is present in dogs with babesiosis caused by B. rossi, and that an excessive pro-inflammatory response may result in a poor outcome.

Cytokine and chemokine profile of the innate and adaptive immune response of Schistosoma haematobium and Plasmodium falciparum single and co-infected school-aged children from an endemic area of Lambaréné, Gabon

BACKGROUND

Helminths and malaria are among the most prevalent infectious diseases in the world. They both occur in tropical area where they often affect the same populations. There are studies suggesting an effect of helminths on malariometric indices. For example, malaria attacks as well as disease severity has been shown to be influenced by a concurrent chronic helminth infection. However, there are also studies that show no effect of concurrent helminth infections on malarial outcomes. To start addressing this issue, the effect of chronic Schistosoma haematobium infection on both the innate and adaptive immune response of Plasmodium falciparum-infected subjects was assessed in an area endemic for both these infections in Gabon.

METHOD

Subjects infected with S. haematobium and or P. falciparum, as well as a control group with neither of these infections, were recruited. For innate immune response, heparinized blood was obtained and cultured for 24 hours with a panel of TLR ligands. For adaptive immune response, PBMC was isolated and stimulated with SEB for 72 hours. Cytokines and chemokines were measured in supernatants using a multiplex beads array immunoassay. Principal Component analysis was used to assess pattern of cytokine and chemokine responses representing the innate and adaptive components of the immune system.

RESULTS

Overall it was observed that the presence of P. falciparum infection was marked by an increase in innate and adaptive immune responsiveness while S. haematobium infection was characterized by an increased chemokine profile, with at the same time, lower pro inflammatory markers. When the study subjects were split into single infected and co-infected groups no effect of S. haematobium on the immune response of P. falciparum infected subjects was observed, neither for the innate nor for the adaptive component of the immune response.

CONCLUSION

This study provides original information on the cellular immune response of S. haematobium and/or P. falciparum in infected subjects. It rules out an effect of S. haematobium on the cytokine profile of subjects co-infected with P. falciparum.

Fatal cerebral malaria: a venous efflux problem

Most Plasmodium falciparum-infected children with cerebral malaria (CM) die from respiratory arrest, but the underlying pathology is unclear. Here we present a model in which the ultimate cause of death from CM is severe intracranial hypertension. Dynamic imaging of mice infected with P. berghei ANKA, an accepted model for experimental CM, revealed that leukocyte adhesion impairs the venous blood flow by reducing the functional lumen of postcapillary venules (PCV). The resulting increase in intracranial pressure (ICP) exacerbates cerebral edema formation, a hallmark of both murine and pediatric CM. We propose that two entirely different pathogenetic mechanisms-cytoadherence of P. falciparum-infected erythrocytes in pediatric CM and leukocyte arrest in murine CM-result in the same pathological outcome: a severe increase in ICP leading to brainstem herniation and death from respiratory arrest. The intracranial hypertension (IH) model unifies previous hypotheses, applies to human and experimental CM alike, eliminates the need to explain any selective recognition mechanism Plasmodium might use to target multiple sensitive sites in the brain, and explains how an intravascular parasite can cause so much neuronal dysfunction.

Intestinal parasites coinfection does not alter plasma cytokines profile elicited in acute malaria in subjects from endemic area of Brazil

In Brazil, malaria is prevalent in the Amazon region and these regions coincide with high prevalence of intestinal parasites but few studies explore the interaction between malaria and other parasites. Therefore, the present study evaluates changes in cytokine, chemokine, C-reactive protein, and nitric oxide (NO) concentrations in 264 individuals, comparing plasma from infected individuals with concurrent malaria and intestinal parasites to individuals with either malaria infection alone and uninfected. In the studied population 24% of the individuals were infected with Plasmodium and 18% coinfected with intestinal parasites. Protozoan parasites comprised the bulk of the intestinal parasites infections and subjects infected with intestinal parasites were more likely to have malaria. The use of principal component analysis and cluster analysis associated increased levels of IL-6, TNF-α, IL-10, and CRP and low levels of IL-17A predominantly with individuals with malaria alone and coinfected individuals. In contrast, low levels of almost all inflammatory mediators were associated predominantly with individuals uninfected while increased levels of IL-17A were associated predominantly with individuals with intestinal parasites only. In conclusion, our data suggest that, in our population, the infection with intestinal parasites (mainly protozoan) does not modify the pattern of cytokine production in individuals infected with P. falciparum and P. vivax.

Host matrix metalloproteinases in cerebral malaria: new kids on the block against blood-brain barrier integrity?

Cerebral malaria (CM) is a life-threatening complication of falciparum malaria, associated with high mortality rates, as well as neurological impairment in surviving patients. Despite disease severity, the etiology of CM remains elusive. Interestingly, although the Plasmodium parasite is sequestered in cerebral microvessels, it does not enter the brain parenchyma: so how does Plasmodium induce neuronal dysfunction? Several independent research groups have suggested a mechanism in which increased blood–brain barrier (BBB) permeability might allow toxic molecules from the parasite or the host to enter the brain. However, the reported severity of BBB damage in CM is variable depending on the model system, ranging from mild impairment to full BBB breakdown. Moreover, the factors responsible for increased BBB permeability are still unknown. Here we review the prevailing theories on CM pathophysiology and discuss new evidence from animal and human CM models implicating BBB damage. Finally, we will review the newly-described role of matrix metalloproteinases (MMPs) and BBB integrity. MMPs comprise a family of proteolytic enzymes involved in modulating inflammatory response, disrupting tight junctions, and degrading sub-endothelial basal lamina. As such, MMPs represent potential innovative drug targets for CM.