Global selective sweep of a highly inbred genome of the cattle parasite Neospora caninum.

Neospora caninum, a cyst-forming apicomplexan parasite, is a leading cause of neuromuscular diseases in dogs as well as fetal abortion in cattle worldwide. The importance of the domestic and sylvatic life cycles of Neospora, and the role of vertical transmission in the expansion and transmission of infection in cattle, is not sufficiently understood. To elucidate the population genomics of Neospora, we genotyped 50 isolates collected worldwide from a wide range of hosts using 19 linked and unlinked genetic markers. Phylogenetic analysis and genetic distance indices resolved a single genotype of N. caninum Whole-genome sequencing of 7 isolates from 2 different continents identified high linkage disequilibrium, significant structural variation, but only limited polymorphism genome-wide, with only 5,766 biallelic single nucleotide polymorphisms (SNPs) total. Greater than half of these SNPs (∼3,000) clustered into 6 distinct haploblocks and each block possessed limited allelic diversity (with only 4 to 6 haplotypes resolved at each cluster). Importantly, the alleles at each haploblock had independently segregated across the strains sequenced, supporting a unisexual expansion model that is mosaic at 6 genomic blocks. Integrating seroprevalence data from African cattle, our data support a global selective sweep of a highly inbred livestock pathogen that originated within European dairy stock and expanded transcontinentally via unisexual mating and vertical transmission very recently, likely the result of human activities, including recurrent migration, domestication, and breed development of bovid and canid hosts within similar proximities.

High Levels of IL-10 and CD4+CD25hi+ Treg Cells in Endemic Burkitt's Lymphoma Patients.

BACKGROUND: The interplay between Epstein-Barr virus infection, malaria, and endemic Burkitt's Lymphoma is not well understood. Reports show diminished EBV-specific Th1 responses in children living in malaria endemic areas and deficiency of EBNA1-specific IFN-γ T cell responses in children with endemic Burkitt's Lymphoma (eBL). This study, therefore, examined some factors involved in the loss of EBNA-1-specific T cell responses in eBL. METHODS: T-cell subset frequencies, activation, and IFN-γ- or IL-4-specific responses were analyzed by flow-cytometry. Plasma cytokine levels were measured by ELISA. RESULTS: CD4+ and CD8+ cells in age- and sex-matched healthy controls (n = 3) expressed more IFN-γ in response to all immunostimulants than in pediatric endemic BL (eBL) patients (n = 4). In healthy controls, IFN-γ expression was higher than IL-4 expression, whereas in eBL patients the expression of IL-4 by CD4+ cells to EBNA-1 was slightly higher than IFN-γ. Moreover, the blood levels of TNF-α was significantly lower (p = 0.004) while IL-10 was significantly higher (p = 0.038), in eBL patients (n = 21) compared to controls (n = 16). Additionally, the frequency of CD4+CD25hi+ T cells was higher in both age-matched acute uncomplicated malaria (n = 26) and eBL (n = 14) patients compared to healthy controls (n = 19; p = 0.000 and p = 0.027, respectively). CONCLUSION: The data suggest that reduced Th1 response in eBL might be due to increased levels of IL-10 and T reg cells.

Insights into deregulated TNF and IL-10 production in malaria: implications for understanding severe malarial anaemia.

BACKGROUND: Severe malarial anaemia (SMA) is a major life-threatening complication of paediatric malaria. Protracted production of pro-inflammatory cytokines promoting erythrophagocytosis and depressing erythropoiesis is thought to play an important role in SMA, which is characterized by a high TNF/IL-10 ratio. Whether this TNF/IL-10 imbalance results from an intrinsic incapacity of SMA patients to produce IL-10 or from an IL-10 unresponsiveness to infection is unknown. Monocytes and T cells are recognized as the main sources of TNF and IL-10 in vivo, but little is known about the activation status of those cells in SMA patients. METHODS: The IL-10 and TNF production capacity and the activation phenotype of monocytes and T cells were compared in samples collected from 332 Ghanaian children with non-overlapping SMA (n = 108), cerebral malaria (CM) (n = 144) or uncomplicated malaria (UM) (n = 80) syndromes. Activation status of monocytes and T cells was ascertained by measuring HLA-DR+ and/or CD69+ surface expression by flow cytometry. The TNF and IL-10 production was assessed in a whole-blood assay after or not stimulation with lipopolysaccharide (LPS) or phytohaemaglutinin (PHA) used as surrogate of unspecific monocyte and T cell stimulant. The number of circulating pigmented monocytes was also determined. RESULTS: Monocytes and T cells from SMA and CM patients showed similar activation profiles with a comparable decreased HLA-DR expression on monocytes and increased frequency of CD69+ and HLA-DR+ T cells. In contrast, the acute-phase IL-10 production was markedly decreased in SMA compared to CM (P = .003) and UM (P = .004). Although in SMA the IL-10 response to LPS-stimulation was larger in amplitude than in CM (P = .0082), the absolute levels of IL-10 reached were lower (P = .013). Both the amplitude and levels of TNF produced in response to LPS-stimulation were larger in SMA than CM (P = .019). In response to PHA-stimulation, absolute levels of IL-10 produced in SMA were lower than in CM (P = .005) contrasting with TNF levels, which were higher (P = .001). CONCLUSIONS: These data reveal that SMA patients have the potential to mount efficient IL-10 responses and that the TNF/IL-10 imbalance may reflect a specific monocyte and T cell programming/polarization pattern in response to infection.

Human leukocyte antigen class I polymorphisms influence the mild clinical manifestation of Plasmodium falciparum infection in Ghanaian children.

A prospective study that included 429 children for active detection of mild malaria was conducted in a coastal region of Ghana to reveal whether the incidence of malaria is affected by human leukocyte antigen (HLA) polymorphism. During 12 months of follow-up, 85 episodes of mild clinical malaria in 74 individuals were observed, and 34 episodes among them were accompanied with significant parasitemia at >5000 infected red blood cells per cubic millimeter. Attributable and relative risks conferred by genetic factors in the HLA region were evaluated by comparison of the incidence in children, stratified by carrier status, of a given allele of HLA-A, -B, -DRB1 and TNFA promoter polymorphism. HLA-B*35:01 reduced the incidence by 0.178 events per person per year (0.060 versus 0.239 for B*35:01-positive and -negative subpopulations, respectively), and a relative risk of 0.25, which remained statistically significant after Bonferroni's correction for multiple testing (p(c) = 8.2 × 10(-5)). Further, HLA-B*35:01 and -B*53:01 exhibited opposite effects on the incidence of malaria with significant parasitemia. When parasite densities in different HLA carriers status were compared, HLA-A*01 conferred an increase in parasite load (p = 6.0 × 10(-7)). In addition, we found a novel DRB1 allele that appears to have emerged from DRB1*03:02 by single nucleotide substitution.

Levels of soluble CD163 and severity of malaria in children in Ghana.

CD163 is an acute-phase-regulated monocyte/macrophage membrane receptor expressed late in inflammation. It is involved in the haptoglobin-mediated removal of free hemoglobin from plasma, has been identified as a naturally soluble plasma glycoprotein with potential anti-inflammatory properties, and is possibly linked to an individual's haptoglobin phenotype. High levels of soluble CD163 (sCD163) in a malaria episode may therefore downregulate inflammation and curb disease severity. In order to verify this, the relationships between sCD163 levels, malaria severity, and selected inflammatory mediators (tumor necrosis factor alpha [TNF-alpha], interleukin-6 [IL-6], and IL-10) were assessed by enzyme-linked immunosorbent assay using plasma samples obtained from pediatric malaria patients with uncomplicated malaria (UM [n = 38]), cerebral malaria (CM [n = 52]), and severe malarial anemia (SA [n = 55]) during two consecutive malaria transmission seasons (2002 and 2003). Median sCD163 levels were higher in UM (11.9 microg/ml) patients than in SA (7.7 microg/ml; P = 0.010) and CM (8.0 microg/ml; P = 0.031) patients. Levels of sCD163 were also higher in all patient groups than in a group of 81 age-matched healthy controls. The higher sCD163/TNF-alpha ratio in UM patients, coupled with the fact that sCD163 levels correlated with TNF-alpha levels in UM patients but not in CM and SA patients, suggests inflammatory dysregulation in the complicated cases. The study showed that sCD163 levels are elevated during acute malaria. High sCD163 levels in UM patients may be due to the induction of higher-level anti-inflammatory responses, enabling them to avoid disease complications. It is also possible that UM patients simply lost their CD163 receptors from macrophages in inflammatory sites while complicated-malaria patients still had their receptors attached to activated macrophages, reflecting ongoing and higher-level inflammation associated with complicated malaria.

Selective activation of TCR-gammadelta+ cells in endemic Burkitt's lymphoma.

BACKGROUND: The overlap in geographical distribution of Plasmodium falciparum malaria and endemic Burkitt's lymphoma (eBL)--an aggressive Epstein-Barr virus (EBV)-associated B-cell tumour occurring almost exclusively in the tropics--strongly suggests a link between the two diseases. It is suspected that the polyclonal B-cell activation in P. falciparum malaria may precipitate a breakdown in homeostatic T-cell control of EBV-immortalized B-cell proliferation. Previous studies have suggested that a particular T-cell subset, characterized by expression of Vdelta1+ gammadelta T-cell receptors, is important for maintaining B-cell homeostasis, both in P. falciparum- exposed populations and in individuals subject to polyclonal B-cell activation of other aetiology. The objective of the present study was, therefore, to characterize lymphocyte phenotypes and to investigate possible differences in T-cell subset composition and activation status in P. falciparum-exposed Ghanaian children with and without eBL. METHODS: Venous blood samples in heparin from 21 eBL patients (mean age: 7.0 years; range: 3-11 years), referred to the Burkitt's Tumour Centre at Korle-Bu Teaching Hospital, Accra and 15 healthy, age and sex matched children, were stained with fluorescein isothiocyanate (FITC)-, phycoerythrin (PE)-, R-phycoerythrin (RPE)- and RPE-Cy5-conjugated antibodies (CD3, CD4, CD8, CD25, CD69, CD95, HLA-DR, TCR-gammadelta, Vdelta1, Vdelta3, Vgamma9 and B-cells) and acquired on a flow cytometer. RESULTS: A reduction in the proportion of CD3+ cells in eBL patients, due mainly to perturbations among TCR-gammadelta+ cells was observed. In contrast, the proportions of CD4+ or CD8+ cells were relatively unaffected, as were the mean numbers of peripheral blood mononuclear cells. CONCLUSION: Selective changes in numbers and activation status of TCR-gammadelta+ cells occurs in Ghanaian children with eBL, a pattern which is similar to P. falciparum-induced changes. The data supports the hypothesis of a regulatory role for Vdelta1+ TcR-gammadelta T-cells in maintaining B-cell homeostasis and provides insights into the pathogenesis of eBL.

Increased levels of inflammatory mediators in children with severe Plasmodium falciparum malaria with respiratory distress.

BACKGROUND: Respiratory distress (RD), a symptom of underlying metabolic acidosis, has been identified as a major risk factor for mortality in children with severe malaria in Africa, yet the molecular mediators involved in the pathogenesis of RD have not been identified. METHODS: We studied circulating levels of mediators of inflammation--including the cytokines tumor necrosis factor (TNF)- alpha and interleukin (IL)-10; the chemokines macrophage inflammatory protein (MIP)-1 alpha , MIP-1 beta , and IL-8; and the immune activation marker neopterin--in children with RD, severe malarial anemia (SMA), cerebral malaria (CM), and uncomplicated malaria (UM). RESULTS: Children with RD had significantly higher plasma levels of TNF- alpha , IL-10, and neopterin and a significantly higher TNF- alpha : IL-10 ratio than those without RD. In addition, the results demonstrated that, relative to UM, CM was associated with increased levels of TNF- alpha and decreased levels of MIP-1 alpha , whereas SMA was associated with decreased levels of IL-10. Circulating levels of neopterin were inversely correlated with hemoglobin, whereas levels of MIP-1 beta were positively correlated with parasitemia. CONCLUSIONS: We conclude that distinct clinical presentations of severe malaria are associated with specific patterns of inflammatory mediators. In particular, we show, to our knowledge for the first time, that patients with malaria and RD have a strong and unbalanced proinflammatory response that may be involved in the pathogenesis of the underlying metabolic acidosis.

Bone marrow suppression and severe anaemia associated with persistent Plasmodium falciparum infection in African children with microscopically undetectable parasitaemia.

BACKGROUND: Severe anaemia can develop in the aftermath of Plasmodium falciparum malaria because of protracted bone marrow suppression, possibly due to residual subpatent parasites. MATERIALS AND METHODS: Blood was collected from patients with recent malaria and negative malaria microscopy. Detection of the Plasmodium antigens, lactate dehydrogenase (Optimal), aldolase and histidine rich protein 2 (Now malaria) were used to differentiate between patients with (1) no malaria, (2) recent cleared malaria, (3) persistent P. falciparum infection. Red cell distribution width (RDW), plasma levels of soluble transferrin receptor (sTfR) and erythropoietin (EPO) were measured as markers of erythropoiesis. Interleukin (IL) 10 and tumour necrosis factor (TNF)alpha were used as inflammation markers. RESULTS: EPO was correlated with haemoglobin, irrespective of malaria (R = -0.36, P < 0.001). Persistent P. falciparum infection, but not recent malaria without residual parasites, was associated with bone marrow suppression i.e., low RDW (P < 0.001 vs. P = 0.56) and sTfR (P = 0.02 vs. P = 0.36). TNF-alpha and IL-10 levels were not associated with bone marrow suppression. CONCLUSION: In the treatment of malaria, complete eradication of parasites may prevent subsequent development of anaemia. Severely anaemic children may benefit from antimalarial treatment if antigen tests are positive, even when no parasites can be demonstrated by microscopy.

Increased levels of soluble CD30 in plasma of patients with Plasmodium falciparum malaria.

Levels of soluble CD30 (sCD30) in serum were elevated in patients with Plasmodium falciparum malaria but showed decline following treatment. The levels of sCD30 in serum were correlated significantly with the expression of gamma interferon by peripheral T cells. These data suggest that CD30(+) cells are upregulated during a malaria attack and that they may play a regulating role at the site of inflammation.

Acute P. falciparum malaria induces a loss of CD28- T IFN-gamma producing cells.

P. falciparum malaria is associated with increased activation among peripheral lymphocytes. In the present study, we investigated markers of susceptibility to apoptosis and expression of IFN-gamma and IL-4 by CD28-and CD28+T cells in West African children with acute P. falciparum malaria. The study showed increased susceptibility to apoptosis and cytokine production among T lymphocytes during acute malaria but also that T cells, in particular IFN-gamma producing CD28-T cells, were substantially reduced. These results are in line with previous studies suggesting that certain T cell subsets are sequestered away from the peripheral blood during P. falciparum malaria.