Myeloperoxidase Attenuates Pathogen Clearance during Plasmodium yoelii Nonlethal Infection.

Myeloperoxidase (MPO), a leukocyte-derived enzyme mainly secreted by activated neutrophils, is known to be involved in the immune response during bacterial and fungal infection and inflammatory diseases. Nevertheless, the role of MPO in a parasitic disease like malaria is unknown. We hypothesized that MPO contributes to parasite clearance. To address this hypothesis, we used Plasmodium yoelii nonlethal infection in wild-type and MPO-deficient mice as a murine malaria model. We detected high MPO plasma levels in wild-type mice with Plasmodium yoelii infection. Unexpectedly, infected MPO-deficient mice did not show increased parasite loads but were able to clear the infection more rapidly than wild-type mice. Additionally, the presence of neutrophils at the onset of infection seemed not to be essential for the control of the parasitemia. The effect of decreased parasite levels in MPO-deficient mice was absent from animals lacking mature T and B cells, indicating that this effect is most likely dependent on adaptive immune response mechanisms. Indeed, we observed increased gamma interferon and tumor necrosis factor alpha production by T cells in infected MPO-deficient mice. Together, these results suggest that MPO modulates the adaptive immune response during malaria infection, leading to an attenuated parasite clearance.

Correlation of interleukin-4 levels with Plasmodium falciparum malaria parasitaemia in Sudanese children.

OBJECTIVES: This study aimed to measure the level of interleukin-4 (IL-4) in the serum of children patients with falciparum malaria and to correlate the production of this cytokine with the severity of malaria parasitaemia. METHODS: One hundred ten patients with malaria participated in this study (53 males and 57 females) and their results were compared with that of 60 healthy control subjects. Their ages ranged between 6 months and 15 years. For the detection of parasitaemia, a calibrated thick-smear technique was used with standard Giemsa staining. For designation of the relative parasite count, a simple code from one to four crosses is used according to the criteria mentioned by Gilles and Warrell. The blood samples were assessed for IL-4 using enzyme-linked immunosorbent assay (ELISA) technique. RESULTS: Thirty-three malaria patients (30.27%) had one cross (+) parasitaemia, 13 patients (11.93%) had (++) parasitaemia, 24 patients (22.02%) had (+++) parasitaemia and 39 patients (35.78%) had (++++) parasitaemia. There was a significant difference (P<0.009) in the concentration of IL-4 between malaria patients (160.74±25.5 pg/ml) and control group (62.136±18.16 pg/ml). Uncomplicated malaria patients showed the highest record of IL-4 level followed by cerebral malaria (CM) group and then severe malaria anaemia group (SMA) (255.8±54.13, 102.7±34.88 and 90.95±20.90 pg/ml respectively, P>0.0001). CONCLUSION: It was concluded that elevation of serum IL-4 in Sudanese children suffering from Plasmodium falciparum malaria is correlated with the severity of malaria hyperparasitaemia rather than with the severity of the disease.

Diagnóstico microbiológico de la malaria importada / Microbiological diagnosis of imported malaria

El diagnóstico actual de la malaria se basa en el uso combinado y secuencial de los tests rápidos de detección de antígenos de Plasmodium y la visualización posterior del parásito teñido con solución de Giemsa en un frotis y una gota gruesa en muestras de sangre total capilar o venosa. Si no se dispone de un microscopista experto debe realizarse siempre un test rápido de detección de antígenos muy sensible para descartar la infección por Plasmodium falciparum, emitir inmediatamente el resultado y preparar gotas gruesas (secadas al aire) y extensiones finas (fijadas con metanol) para su posterior tinción y revisión por un microscopista experto del propio laboratorio o de un laboratorio de referencia. Los tests rápidos de detección de antígenos deben utilizarse como prueba inicial de cribado, pero no deben sustituir a las técnicas de microscopia, las cuales deben hacerse en paralelo. El diagnóstico de la malaria debe ser realizado inmediatamente tras la sospecha clínica. El retraso en el diagnóstico de laboratorio (demora mayor de 3 h) no debe impedir el inicio de tratamiento antimalárico empírico si la probabilidad de malaria es alta. Si el primer examen microscópico y el test rápido de detección de antígenos son negativos, estos deben repetirse diariamente en pacientes con alta sospecha. Si esta sospecha permanece tras 3 resultados negativos debe solicitarse la opinión de un experto en enfermedades tropicales. Los métodos de amplificación genómica (reacción en cadena de la polimerasa) son útiles como confirmación del diagnóstico microscópico, para caracterizar infecciones mixtas no detectables por otros métodos y para caracterizar infecciones asintomáticas por debajo del nivel de detección microscópica

Current diagnosis of malaria is based on the combined and sequential use of rapid antigen detection tests (RDT) of Plasmodium and subsequent visualization of the parasite stained with Giemsa solution in a thin and thick blood smears. If an expert microscopist is not available, should always be a sensitive RDT to rule out infection by Plasmodium falciparum, output the result immediately and prepare thick smears (air dried) and thin extensions (fixed with methanol) for subsequent staining and review by an expert microscopist. The RDT should be used as an initial screening test, but should not replace microscopy techniques, which should be done in parallel. The diagnosis of malaria should be performed immediately after clinical suspicion. The delay in laboratory diagnosis (greater than 3 hours) should not prevent the initiation of empirical antimalarial treatment if the probability of malaria is high. If the first microscopic examination and RDT are negative, they must be repeated daily in patients with high suspicion. If suspicion remains after three negative results must be sought the opinion of an tropical diseases expert. Genomic amplification methods (PCR) are useful as confirmation of microscopic diagnosis, to characterize mixed infections undetectable by other methods, and to diagnose asymptomatic infections with submicroscopic parasitaemia

Diagnóstico y tratamiento de la malaria importada en España: recomendaciones del Grupo de Trabajo de Malaria de la Sociedad Española de Medicina Tropical y Salud Internacional (SEMTSI) / Diagnosis and treatment of imported malaria in Spain: recommendations from the Malaria Working Group of the Spanish Scoiety of Tropical Medicine and International Health (SEMTSI)

La malaria es una de las enfermedades tropicales importadas que con más frecuencia se diagnostican en nuestro país. La mortalidad en viajeros que adquieren la enfermedad oscila alrededor del 2-3%, siendo el principal factor asociado al mal pronóstico el retraso diagnóstico y del inicio del tratamiento antiparasitario. Los casos de malaria importada suelen presentarse con fiebre, cefalea y artromialgias, aunque pueden aparecer otros síntomas. El diagnóstico se debe realizar de forma urgente, a través de gota gruesa o pruebas de diagnóstico rápido, y extensión sanguínea. El tratamiento debe ser instaurado lo antes posible. En los casos de malaria grave, el uso de artemisininas intravenosas ha demostrado ser superior al uso de quinina intravenosa. En este documento se detallan las recomendaciones del grupo de expertos de la Sociedad Española de Medicina Tropical y Salud Internacional (SEMTSI) para el diagnóstico y tratamiento de la malaria importada

Malaria is a common parasitic disease diagnosed in the returned traveler. Mortality in travelers with imported malaria is around 2-3%, and one of the main factors associated with poor prognosis is the delay in the diagnosis and treatment. Imported malaria cases usually present with fever, headache and myalgia, but other symptoms may appear. The diagnosis should be performed as soon as possible, using thick smear or rapid diagnostic tests, and a blood smear. Treatment should be initiated urgently. In cases of severe malaria, the use of intravenous artemisinins has proved to be superior to intravenous quinine. This document reviews the recommendations of the expert group of the Spanish Society of Tropical Medicine and International Health (SEMTSI) for the diagnosis and treatment of imported malaria in Spain

Toxoplasma gondii upregulates interleukin-12 to prevent Plasmodium berghei-induced experimental cerebral malaria.

A chronic infection with the parasite Toxoplasma gondii has previously been shown to protect mice against subsequent viral, bacterial, or protozoal infections. Here we have shown that a chronic T. gondii infection can prevent Plasmodium berghei ANKA-induced experimental cerebral malaria (ECM) in C57BL/6 mice. Treatment with soluble T. gondii antigens (STAg) reduced parasite sequestration and T cell infiltration in the brains of P. berghei-infected mice. Administration of STAg also preserved blood-brain barrier function, reduced ECM symptoms, and significantly decreased mortality. STAg treatment 24 h post-P. berghei infection led to a rapid increase in serum levels of interleukin 12 (IL-12) and gamma interferon (IFN-γ). By 5 days after P. berghei infection, STAg-treated mice had reduced IFN-γ levels compared to those of mock-treated mice, suggesting that reductions in IFN-γ at the time of ECM onset protected against lethality. Using IL-10- and IL-12ßR-deficient mice, we found that STAg-induced protection from ECM is IL-10 independent but IL-12 dependent. Treatment of P. berghei-infected mice with recombinant IL-12 significantly decreased parasitemia and mortality. These data suggest that IL-12, either induced by STAg or injected as a recombinant protein, mediates protection from ECM-associated pathology potentially through early induction of IFN-γ and reduction in parasitemia. These results highlight the importance of early IL-12 induction in protection against ECM.

Use of poly(amidoamine) drug conjugates for the delivery of antimalarials to Plasmodium.

Current malaria therapeutics demands strategies able to selectively deliver drugs to Plasmodium-infected red blood cells (pRBCs) in order to limit the appearance of parasite resistance. Here, the poly(amidoamines) AGMA1 and ISA23 have been explored for the delivery of antimalarial drugs to pRBCs. AGMA1 has antimalarial activity per se as shown by its inhibition of the in vitro growth of Plasmodium falciparum, with an IC50 of 13.7 µM. Fluorescence-assisted cell sorting data and confocal fluorescence microscopy and transmission electron microscopy images indicate that both polymers exhibit preferential binding to and internalization into pRBCs versus RBCs, and subcellular targeting to the parasite itself in widely diverging species such as P. falciparum and Plasmodium yoelii, infecting humans and mice, respectively. AGMA1 and ISA23 polymers with hydrodynamic radii around 7 nm show a high loading capacity for the antimalarial drugs primaquine and chloroquine, with the final conjugate containing from 14.2% to 32.9% (w/w) active principle. Intraperitoneal administration of 0.8 mg/kg chloroquine as either AGMA1 or ISA23 salts cured P. yoelii-infected mice, whereas control animals treated with twice as much free drug did not survive. These polymers combining into a single chemical structure drug carrying capacity, low unspecific toxicity, high biodegradability and selective internalization into pRBCs, but not in healthy erythrocytes for human and rodent malarias, may be regarded as promising candidates deserving to enter the antimalarial therapeutic arena.

Co-infection of human parvovirus B19 with Plasmodium falciparum contributes to malaria disease severity in Gabonese patients.

BACKGROUND: High seroprevalence of parvovirus B19 (B19V) coinfection with Plasmodium falciparum has been previously reported. However, the impact of B19V-infection on the clinical course of malaria is still elusive. In this study, we investigated the prevalence and clinical significance of B19V co-infection in Gabonese children with malaria. METHODS: B19V prevalence was analyzed in serum samples of 197 Gabonese children with P. falciparum malaria and 85 healthy controls using polymerase chain reaction (PCR), enzyme-linked immunosorbent assay (ELISA), and direct DNA-sequencing. RESULTS: B19V was detected in 29/282 (10.28%) of Gabonese children. B19V was observed more frequently in P. falciparum malaria patients (14.21%) in comparison to healthy individuals (1.17%) (P<0.001). Notably, the mild-malaria group revealed significantly lower hematocrit levels in B19V/P. falciparum co-infection than in P. falciparum mono-infection (P<0.05). Genetic analysis revealed a predominance of B19V genotype-1 (71.43%) in the studied population. However, B19V-genotype 2 was observed significantly more often in children with severe-malaria than in mild-malaria (P=0.04). CONCLUSION: Our findings reveal that B19V-infection is frequent in Gabonese children with P. falciparum malaria and signifies a possible contribution of B19V on the clinical course of malaria in a genotype-dependent manner. B19V co-infection should be considered as a additional diagnostic measure in malaria patients with life threatening anemia.

A longitudinal study on anaemia in children with Plasmodium falciparum infection in the Mount Cameroon region: prevalence, risk factors and perceptions by caregivers.

BACKGROUND: In heavily endemic malaria areas, it is almost inevitable that malarial infection will be associated with anaemia, although malaria may not be the prime cause of it. Anaemia is a major public health problem in Cameroon. We hypothesized that, factors other than falciparum malaria account for anaemia in the study area. METHODS: A longitudinal study was conducted among 351 Plasmodium falciparum positive children to determine the prevalence, risk factors and the perception of anaemia by the caregivers in a semi-rural community. The investigative methods included the use of a structured questionnaire, clinical evaluation and laboratory investigations. RESULTS: At enrolment the overall prevalence of anaemia as assessed by Hb concentration (Hb < 11 g/dl) was 80.3% (282). Following treatment the prevalence of persistent anaemia was 6% and 46.2% of the children achieved haematological recovery by day 42. Exploratory multiple linear regression analysis showed the following; parasitaemia density (P < 0.01), enlarged spleen (P < 0.05), duration of fever > 2 days (P < 0.01), high white blood cell count (P < 0.001), sex (P < 0.05), iron status indicators (ferritin and transferrin) (P < 0.001), level of education of the caregiver (P < 0.05), management of onset of malaria by caregiver (P < 0.005) and wasting (P < 0.05) to be risk factors for anaemia in children with falciparum infection. Approximately 75.5% (265) of the caregivers had some knowledge about anaemia. CONCLUSION: The identified risk factors revealed the important contributors to the pathogenesis of anaemia in the Mount Cameroon region. Control efforts should therefore be directed towards proper health education emphasizing on proper health seeking behaviour and attitudes of the population.

Antimalarial plant remedies from Burkina Faso: their potential for prophylactic use.

ETHNOPHARMACOLOGICAL RELEVANCE: Saye, a combination remedy prepared from Cochlospermum planchonii Hook.f. (Cochlospermaceae), Cassia alata L. (Fabaceae) and Phyllanthus amarus Schumach. et Thonn. (Euphorbiaceae), N'Dribala, a Cochlospermum planchonii root decoction, and a fruit preparation of Azadirachta indica A. Juss. (Meliaceae) are plant remedies of the folk medicine in Burkina Faso and are commonly used by traditional healers for the treatment of malaria. AIM OF THE STUDY: This study aimed at validating the antiplasmodial activity of the preparations and at estimating their potential for prophylaxis, using the murine malaria system Plasmodium berghei/Anopheles stephensi. MATERIALS AND METHODS: Aqueous extracts were orally administered to mice (6 animals per treatment group) at a daily dose of 200mg/kg body weight for nine days, applying protocols that mimic as much as possible traditional recipes and treatment schemes. RESULTS: Saye, N'Dribala and Azadirachta indica preparations revealed prophylactic activity, reducing parasitaemia in treated mice, with respect to controls, by 52.0% (CI(95) 46.1-57.9), 45.5% (CI(95) 44.5-46.5) and 45.0% (CI(95) 41.1-48.9), respectively. No evidence of transmission blocking effects was detected with any of the tested remedies. CONCLUSIONS: This study confirms, in the murine malaria system, the antiplasmodial properties of the examined remedies on the Plasmodium stages developing in the vertebrate host, thus encouraging studies aiming at identifying the active fractions and compounds responsible for the described activity and to develop standardized prophylactic remedies.

Stearoyl-CoA desaturase is an essential enzyme for the parasitic protist Trypanosoma brucei.

Trypanosoma brucei, the etiologic agent of sleeping sickness, is exposed to important changes in nutrients and temperature during its life cycle. To adapt to these changes, the fluidity of its membranes plays a crucial role. This fluidity, mediated by the fatty-acid composition, is regulated by enzymes named desaturases. We have previously shown that the oleoyl desaturase is essential for Trypanosoma cruzi and T. brucei. In this work, we present experimental support for the relevance of stearoyl-CoA desaturase (SCD) for T. brucei's survival, in both its insect or procyclic-form (PCF) and bloodstream-form (BSF) stages. We evaluated this essentiality in two different ways: by generating a SCD knocked-down parasite line using RNA interference, and by chemical inhibition of the enzyme with two compounds, Isoxyl and a thiastearate with the sulfur atom at position 10 (10-TS). The effective concentration for 50% growth inhibition (EC(50)) of PCF was 1.0 ± 0.2 µM for Isoxyl and 5 ± 2 µM for 10-TS, whereas BSF appeared more susceptible with EC(50) values 0.10 ± 0.03 µM (Isoxyl) and 1.0 ± 0.6 µM (10-TS). RNA interference showed to be deleterious for both stages of the parasite. In addition, T. brucei-infected mice were fed with Isoxyl, causing a reduction of the parasitemia and an increase of the rodents' survival.

Cytokines and cell adhesion receptors in the regulation of immunity to Trypanosoma cruzi.

Pathophysiology of Chagas' disease is not completely defined, although innate and adaptative immune responses are crucial. In acute infection some parasite antigens can activate macrophages, and this may result in pro-inflammatory cytokine production, nitric oxide synthesis, and consequent control of parasitemia and mortality. Cell-mediated immunity in Trypanosoma cruzi infection is also modulated by cytokines, but in addition to parasite-specific responses, autoimmunity can be also triggered. Importantly, cytokines may also play a role in the cell-mediated immunity of infected subjects. Finally, leukocyte influx towards target tissues is regulated by cytokines, chemokines, and extracellular matrix components which may represent potential therapeutic targets in infected patients. Here we will discuss recent findings on the role of cytokines, chemokines and extracellular matrix components in the regulation of innate and adaptive immunity during T. cruzi infection.

Transovarial transmission efficiency of Babesia bovis tick stages acquired by Rhipicephalus (Boophilus) microplus during acute infection.

The protozoan parasite Babesia bovis, a reemerging threat to U.S. cattle, is acquired by adult female ticks of the subgenus Boophilus and is transovarially transmitted as the kinete stage to developing larval offspring. Sporozoites develop within larvae and are transmitted during larval feeding on a bovine host. This study evaluated the efficiency of B. bovis infection within Rhipicephalus (Boophilus) microplus following acquisition feeding on acutely parasitemic cattle. Parasite levels were quantified in blood from experimentally infected cattle and within hemolymph and larvae derived from acquisition-fed female B. microplus. There was a positive correlation between blood parasite levels in acutely parasitemic cattle and kinete levels in the hemolymph of adult female Boophilus ticks following acquisition feeding; however, there was no relationship between kinete levels in females and infection rates of larval progeny. Boophilus microplus females that acquisition fed produced larval progeny with infection rates of 12% to 48%. Importantly, larvae derived from replete females with very low levels of kinete infection, as demonstrated by microscopy and PCR, had infection rates of 22% to 30% and transmitted B. bovis during transmission feeding. These data demonstrate that although hemolymph infection may be undetectable, transmission to larval progeny occurs at a level which ensures transmission to the bovine host.

[Diseases produced by Borrelia]. / Enfermedades producidas por Borrelia.

Lyme borreliosis, caused by Borrelia burgdorferi sensu lato, is a multi-organ infection with dermatological, rheumatological, neurological, and cardiac manifestations. The main characteristic is a skin lesion, named erythema migrans. Relapsing fever, caused by numerous species of Borrelia, is characterized by a periodic cycle of acute and afebrile episodes. The serological diagnosis of these infections has limited value in sensitivity, specificity and predictive values. Lyme borreliosis is usually diagnosed by recognition of a characteristic clinical picture with serological confirmation, and the diagnosis of relapsing fever relies on direct observation of spirochetes in peripherical blood. The elected treatment is almost always tetracycline for the young or for adults but not for pregnant women, although betalactamic (such as penicillin or 3rd generation cephalosporin for the central nervous system) or macrolides are indicated in several situations. The prognosis, with adequate treatment, is good. In the majority of Spanish regions, due to the low incidence of these diseases, the prophylactic antimicrobial treatment after a tick bite is not indicated.

Ehrlichia platys (Anaplasma platys) in dogs from Maracaibo, Venezuela: an ultrastructural study of experimental and natural infections.

Since 1982 Ehrlichia platys, now emended as Anaplasma platys, has been diagnosed in dogs from Maracaibo, Venezuela, using buffy coat smears stained with Dip Quick. Three dogs were inoculated with an A. platys strain. When parasitemia reached 60-97%, blood samples obtained from the inoculated dogs and from two naturally infected dogs were centrifuged to obtain platelet-rich plasma, which was mixed with 0.1% glutaraldehyde at 37 C for 10 minutes. Platelet pellets were fixed in 3% glutaraldehyde for 72 hours and processed for conventional transmission electron microscopy. Platelets contained pleomorphic organisms with a distinct double membrane that was not observed when the bodies were in a determinate developmental stage. There were 1-15 individual bodies included in a host cell vacuole. The organisms had an electron-lucent inner area, whereas the internal surface of their inner plasma membranes exhibited an electron-dense rough substance. In naturally infected dogs, organisms with different ultrastructural features were found inside the same platelet. Some organisms contained central dense material surrounded by a pale zone, which was in turn surrounded by a moderately dense peripheral area. Other organisms contained an eccentrically electron-dense material. The intravacuolar space appeared fully electron-lucent. Each organism usually exhibited inner fine strands. Empty structures displaying junctions with the vacuolar membrane were observed. Our results indicate that distinct ultrastructural characteristics are associated with different stages of A. platys development and may differ among A. platys strains.

Diagnostic criteria and risk factors for Plasmodium ovale malaria.

Plasmodium ovale is a common malaria parasite in Africa, but the epidemiology of P. ovale malaria is poorly known. Exposure to malaria, parasitemia, and morbidity were monitored for 6 years among the residents of a village in Senegal. The relationship between the level of P. ovale parasitemia and fever risk were analyzed, and diagnostic criteria for clinical P. ovale malaria were established. Then the relationships between the occurrence of P. ovale clinical malaria and a series of entomological, epidemiological, and genetic factors were investigated. There was no increased risk of fever when the P. ovale parasite count was <800 parasites/microL of blood. Of 6621 episodes of illness, 114 (1.7%) were attributable to P. ovale. Although most clinical episodes occurred during early childhood, a low incidence of the disease persisted among adults. Sickle cell trait carriers had increased susceptibility to the disease.

The blood parasites of anurans from Costa Rica with reflections on the taxonomy of their trypanosomes.

During May 1997, specimens of 7 species of anurans, that included 5 Phrynohyas venulosa Laurenti, 5 Rana forreri Boulenger, 7 Rana vaillanti Brucchi, 6 Eleutherodactylus fitzingeri Schimdt, 4 Smilisca baudinii Duméril and Bibron, 1 Leptodactylus melanonotus, and 3 Bufo marinus Linneaus, from the Guanacaste Conservation Area, Costa Rica were examined for blood parasites. Their hematozoan fauna included intraerythrocytic and intraleukocytic icosahedral viruses, a rickettsia (Aegyptianella sp.), 2 species of Hepatozoon, Lankesterella minima, 2 unknown species of apicomplexans, 9 morphologically distinct types of trypanosomes, and 2 species of microfilariae. Rana vaillanti, the most aquatic species of frog, harbored the most species of parasites. Recent evidence indicates that morphological changes in the highly pleomorphic trypanosomes of anurans from different geographical regions have not kept pace with biochemical (isozyme) and molecular (DNA sequence) changes. Describing new species based solely on bloodstream trypomastigotes is discouraged. Additional criteria described herein should be applied when naming new species of anuran trypanosomes.