RESUMO
In malaria endemic regions, a fetus is often exposed in utero to Plasmodium falciparum blood-stage Ags. In some newborns, this can result in the induction of immune suppression. We have previously shown these modulated immune responses to persist postnatally, with a subsequent increase in a child's susceptibility to infection. To test the hypothesis that this immune suppression is partially mediated by malaria-specific regulatory T cells (T(regs)) in utero, cord blood mononuclear cells (CBMC) were obtained from 44 Kenyan newborns of women with and without malaria at delivery. CD4(+)CD25(lo) T cells and CD4(+)CD25(hi) FOXP3(+) cells (T(regs)) were enriched from CBMC. T(reg) frequency and HLA-DR expression on T(regs) were significantly greater for Kenyan as compared with North American CBMC (p < 0.01). CBMC/CD4(+) T cells cultured with P. falciparum blood-stage Ags induced production of IFN-γ, IL-13, IL-10, and/or IL-5 in 50% of samples. Partial depletion of CD25(hi) cells augmented the Ag-driven IFN-γ production in 69% of subjects with malaria-specific responses and revealed additional Ag-reactive lymphocytes in previously unresponsive individuals (n = 3). Addition of T(regs) to CD4(+)CD25(lo) cells suppressed spontaneous and malaria Ag-driven production of IFN-γ in a dose-dependent fashion, until production was completely inhibited in most subjects. In contrast, T(regs) only partially suppressed malaria-induced Th2 cytokines. IL-10 or TGF-ß did not mediate this suppression. Thus, prenatal exposure to malaria blood-stage Ags induces T(regs) that primarily suppress Th1-type recall responses to P. falciparum blood-stage Ags. Persistence of these T(regs) postnatally could modify a child's susceptibility to malaria infection and disease.
Assuntos
Sangue Fetal/imunologia , Tolerância Imunológica , Subunidade alfa de Receptor de Interleucina-2/biossíntese , Proteína 1 de Superfície de Merozoito/sangue , Plasmodium falciparum/imunologia , Proteínas Ribossômicas/sangue , Linfócitos T Reguladores/imunologia , Linfócitos T Reguladores/parasitologia , Sequência de Aminoácidos , Células Cultivadas , Relação Dose-Resposta Imunológica , Feminino , Sangue Fetal/citologia , Sangue Fetal/parasitologia , Humanos , Memória Imunológica , Recém-Nascido , Subunidade alfa de Receptor de Interleucina-2/sangue , Malária/sangue , Malária/imunologia , Malária/patologia , Dados de Sequência Molecular , Linfócitos T Reguladores/metabolismoRESUMO
Late benefits of remote antischistosomal therapy were estimated among long-term residents of an area with high transmission of Schistosoma haematobium (Msambweni, Kenya) by comparing infection and disease prevalence in two local adult cohorts. We compared 132 formerly treated adults (given treatment in childhood or adolescence > or = 10 years previously) compared with 132 age- and sex-matched adults from the same villages who had not received prior treatment. The prevalence of current infection, hematuria, and ultrasound bladder abnormalities were significantly lower among the previously treated group, who were found to be free of severe bladder disease. Nevertheless, heavy infection was equally prevalent (2-3%) in both study groups, and present rates of hydronephrosis were not significantly different. Therapy given in childhood or adolescence appears to improve risk for some but not all manifestations of S. haematobium infection in later adult life. Future prospective studies of continued treatment into adulthood will better define means to obtain optimal, community-based control of S. haematobium-related disease in high-risk locations.
Assuntos
Anti-Helmínticos/uso terapêutico , Esquistossomose Urinária/tratamento farmacológico , Esquistossomose Urinária/fisiopatologia , Adulto , Animais , Anti-Helmínticos/administração & dosagem , Feminino , Seguimentos , Hematúria/epidemiologia , Humanos , Quênia/epidemiologia , Nefropatias/epidemiologia , Masculino , Prevalência , Schistosoma haematobium/efeitos dos fármacos , Esquistossomose Urinária/epidemiologia , Esquistossomose Urinária/parasitologia , Fatores de Tempo , Resultado do Tratamento , Doenças da Bexiga Urinária/epidemiologiaRESUMO
Levels of prepatent Schistosoma haematobium infection were monitored in intermediate host snails (Bulinus nasutus) collected from transmission sites in coastal Kenya, using a polymerase chain reaction (PCR) assay amplifying the Dra I repeated sequence of S. haematobium. The timing and number of prepatent and patent infections were determined for each site and, where the time of first appearance was clear, the minimal prepatent period was estimated to be five weeks. High, persistent, prepatency rates (range = 28-54%), indicated a significant degree of repeated area contamination with parasite ova. In contrast, rates of cercarial shedding proved locally variable, and were either low (range = 0.14-3.4%) or altogether absent, indicating that only a small proportion of infected snails reach the stage of cercarial shedding. Given the apparently strong focal effects of environmental conditions, implications of these new data are discussed regarding the estimation of local force of transmission and the design of control activities.
Assuntos
Bulinus/parasitologia , DNA de Protozoário/análise , Reação em Cadeia da Polimerase/métodos , Schistosoma haematobium/isolamento & purificação , Animais , Vetores de Doenças , Quênia , Schistosoma haematobium/genéticaRESUMO
At present, anthelmintic therapy with praziquantel at a dose of 40 mg/kg of body weight is the recommended treatment for control of urinary tract morbidity caused by Schistosoma haematobium. Although this standard regimen is effective, drug cost may represent a significant barrier to implementation of large-scale schistosomiasis control programs in developing areas. Previous comparison trials have established that low-dose (20-30 mg/kg) praziquantel regimens can effectively suppress the intensity of S. haematobium infection in endemic settings. However, the efficacy of these low-dose regimens in controlling infection-related morbidity has not been determined in a randomized field trial. The present random allocation study examined the relative efficacy of a 20 mg/kg dose versus a 40 mg/kg dose of praziquantel in control of hematuria and bladder and renal abnormalities associated with S. haematobium infection in an endemic area of Coast Province, Kenya. After a nine-month observation period, the results indicated an advantage to the standard 40 mg/kg praziquantel dose in terms of reduction of infection prevalence and hematuria after therapy (P < 0.01 and P < 0.005, respectively). However, the two treatment groups were equally effective in reducing structural urinary tract morbidity detected on ultrasound examination. We conclude that in certain settings, a 20 mg/kg dose of praziquantel may be sufficient in providing control of morbidity due to urinary schistosomiasis in population-based treatment programs.
Assuntos
Hematúria/etiologia , Praziquantel/uso terapêutico , Esquistossomose Urinária/tratamento farmacológico , Doenças Urológicas/parasitologia , Adolescente , Adulto , Animais , Anti-Helmínticos/efeitos adversos , Anti-Helmínticos/uso terapêutico , Criança , Pré-Escolar , Relação Dose-Resposta a Droga , Feminino , Seguimentos , Geografia , Hematúria/tratamento farmacológico , Humanos , Quênia , Masculino , Morbidade , Contagem de Ovos de Parasitas , Praziquantel/efeitos adversos , População Rural , Schistosoma haematobium , Fatores de Tempo , Resultado do Tratamento , Doenças Urológicas/epidemiologia , Doenças Urológicas/prevenção & controleRESUMO
To estimate their heritable component of risk for Schistosoma haematobium infection intensity and disease, we performed a community-based family study among an endemic population in coastal Kenya. Demography and family linkages were defined by house-to-house interviews, and infection prevalence and disease severity were assessed by standard parasitologic testing and by ultrasound. The total population was 4,408 among 912 households, with 241 identified pedigree-household groups. Although age- and sex-adjusted risk for greater infection intensity was clustered within households (odds ratio = 2.7), analysis of extended pedigree-household groups indicated a relatively low heritability score for this trait (h2 = 0.199), particularly after adjustment for common household exposure effects (adjusted h2 = 0.086). Statistical evidence was slightly stronger (h2 = 0.353) for familial clustering of bladder morbidity, with an adjusted h2 = 0.142 after accounting for household exposure factors. We conclude that among long-established populations of coastal Kenya, heritable variation in host susceptibility is low, and likely plays a minimal role in determining individual risk for infection or disease.
Assuntos
Doenças Endêmicas , Schistosoma haematobium/crescimento & desenvolvimento , Esquistossomose Urinária/genética , Infecções Urinárias/genética , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Animais , Criança , Pré-Escolar , Feminino , Predisposição Genética para Doença , Humanos , Quênia , Masculino , Pessoa de Meia-Idade , Contagem de Ovos de Parasitas , Prevalência , Esquistossomose Urinária/parasitologia , Infecções Urinárias/parasitologia , Urina/parasitologiaRESUMO
Cord blood T cells have been reported to respond to a variety of exogenous Ags, including environmental allergens and various viruses and parasites, as demonstrated by enhanced proliferation and cytokine secretion. This finding is evidence that Ags in the maternal environment transplacentally prime and result in fetal development of memory T cells. Some studies suggest these neonatal T cell responses may arise by nonspecific activation of T cells that express TCRs with low binding affinity, thus lacking fine lymphocyte specificity. To address this question, we examined malaria Ag stimulation of human cord and adult blood mononuclear cells in samples from residents of a malaria endemic area in Kenya. We constructed overlapping 18-mer peptides derived from sequences contained in dimorphic alleles of the C-terminal 33-kDa fragment of Plasmodium falciparum merozoite protein 1. This study identified a dominant T cell epitope for one MSP1(33) allele (MAD20) and two T cell epitopes for the second allele (K1); these epitopes were nonoverlapping and allele specific. In a given donor, peptide-specific proliferation and IFN-gamma secretion were highly concordant. However, IL-10 and IL-13 secretion were not correlated. Importantly, the fine specificity of lymphocyte proliferation and cytokine secretion in cord and adult blood mononuclear cells was similar. Cord blood cells obtained from malaria-infected pregnant women were 4-fold more likely to acquire a peptide-specific immune response. We conclude that the fetal malaria response functions in a fully adaptive manner and that this response may serve to help protect the infant from severe malaria during infancy.
Assuntos
Mapeamento de Epitopos , Epitopos de Linfócito T/sangue , Sangue Fetal/imunologia , Malária/imunologia , Proteína 1 de Superfície de Merozoito/sangue , Fragmentos de Peptídeos/sangue , Plasmodium falciparum/imunologia , Subpopulações de Linfócitos T/imunologia , Adulto , Alelos , Sequência de Aminoácidos , Animais , Mapeamento de Epitopos/métodos , Epitopos de Linfócito T/genética , Feminino , Sangue Fetal/citologia , Sangue Fetal/parasitologia , Humanos , Epitopos Imunodominantes/sangue , Epitopos Imunodominantes/genética , Recém-Nascido , Quênia/epidemiologia , Malária/epidemiologia , Malária/parasitologia , Malária/prevenção & controle , Proteína 1 de Superfície de Merozoito/genética , Proteína 1 de Superfície de Merozoito/imunologia , Dados de Sequência Molecular , Peso Molecular , Fragmentos de Peptídeos/genética , Fragmentos de Peptídeos/imunologia , Plasmodium falciparum/genética , Plasmodium falciparum/crescimento & desenvolvimento , Gravidez , Índice de Gravidade de Doença , Subpopulações de Linfócitos T/parasitologia , Subpopulações de Linfócitos T/patologiaRESUMO
The effect of oropharyngeal administration of insulin lente (BP, USP) on alloxan-induced diabetic rabbits was investigated. In mild cases of hyperglycaemia (below 500 mg/dl), a buccal dose of 100 IU was able to produce significant reduction in blood glucose levels over seven hours, as compared with diabetic animals during the same period. As much as 60% reduction in glucose level from the starting level could be achieved. However, at very high levels of hyperglycaemia (above 500 mg/dl), this regimen failed to produce normoglycaemia although it rendered the animal tolerant to high levels of glucose. This mode of administration of insulin did not produce hypoglycaemia in any of the animals: the blood levels in the mildly diabetic animals were reduced to normoglycaemia without progressing into the hypoglycaemic state. The administration of insulin to normoglycaemic rabbits by this route did not produce any reduction in glucose levels. This preliminary report suggests that a noninvasive oropharyngeal route may be an alternative for the clinical management of insulin and non-insulin dependent diabetes mellitus in man.
RESUMO
Direct biological activity of a 1,2,4-trioxolane derivative was assessed in vitro using bacteria and fungi causing common infections. The product was found to be uniformly active against all organisms tested. In addition, it is active against certain tumour cells and protozoa and is also an immunomodulator. These observations are discussed in the light of the product's potential use in the clinical management of conditions in which its use is indicated.
RESUMO
Little is known about the common antigens of the various strains of Leishmania in Kenya, and their possible role in immunity to disease. Kenyan isolates of Leishmania donovani, L. Major and L. tropica were cultured, crude antigens prepared and electrophoresced in sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Immunoblots by pooled sera from cutaneous and visceral leishmaniasis patients revealed common antigens within the 110-116kD, 70kD and the 63kD ranges. Only the 112-116kD antigens from L. major strains were reacted to by both cutaneous and visceral leishmaniasis patient sera. Sera from normal individuals living in an endemic area for leishmaniasis also showed reactivity to the 116kD antigen. We suggest that these common antigens may be of value in future vaccine studies
RESUMO
Exposure of Leishmania donovani culture promastigotes to ethyleneglycol-bis-((-aminoethyl ether) N,N,N(1),N(1),-tetraacetic acid (EGTA) concentrations of between 0.2 to 1.6 mg/ml significantly inhibited their growth, though the different concentrations did not significantly differ between themselves on their effect on promastigotes in cell free media. EGTA concentrations of between 0.05 and 0.1 mg/ml were non-toxic to mouse peritoneal macrophages in vitro. Treatment of L. donovani-infected macrophages with EGTA at concentrations of 0.05, 0.1 and 0.2 mg/ml contributed significantly to a decline in amastigote parasite-loads in the macrophages. The higher the chelator concentration within the acceptable toxic levels for macrophages, the greater was the rate at which parasites were cleared from the macrophages. It is speculated that EGTA chelates manganese from phosphoenol pyruvate (PEP) carboxykinase, a TCA-rate limiting enzyme in the metabolism of Leishmania parasites. A manganese-complex is also probably used by these parasites as a defense mechanism against oxygen-derived radicals. Chelation of manganese would destabilise PEP carboxykinase, and therefore severely interfere with the parasite metabolism. All these factors would render the Leishmania parasite susceptible to digestion in the lysosomal vacuoles of the macrophage, hence the observed significant reduction in parasite-loads of L. donovani-infected EGTA-treated macrophages in vitro. These results suggest an exciting future potential use of chelators in the experimental chemotherapy of visceral leishmaniasis.
RESUMO
Large forensic mtDNA databases which adhere to strict guidelines for generation and maintenance, are not available for many populations outside of the United States and western Europe. We have established a high quality mtDNA control region sequence database for urban Nairobi as both a reference database for forensic investigations, and as a tool to examine the genetic variation of Kenyan sequences in the context of known African variation. The Nairobi sequences exhibited high variation and a low random match probability, indicating utility for forensic testing. Haplogroup identification and frequencies were compared with those reported from other published studies on African, or African-origin populations from Mozambique, Sierra Leone, and the United States, and suggest significant differences in the mtDNA compositions of the various populations. The quality of the sequence data in our study was investigated and supported using phylogenetic measures. Our data demonstrate the diversity and distinctiveness of African populations, and underline the importance of establishing additional forensic mtDNA databases of indigenous African populations.
Assuntos
DNA Mitocondrial/genética , Bases de Dados de Ácidos Nucleicos , Variação Genética , Filogenia , População Negra , Impressões Digitais de DNA/normas , DNA Mitocondrial/sangue , DNA Mitocondrial/classificação , Medicina Legal , Haplótipos , Humanos , Quênia , Probabilidade , Controle de QualidadeRESUMO
T cell responses to a specific Leishmania antigens, 70kD and 116kD were investigated in individuals from an endemic area for leishmaniasis. Peripheral blood mononuclear cells were obtained from 38 individuals (24 test an d14 controls) and T cell responses to phytohaemaglutinin (PHA), Concanavalin A (ConA) and the specific Leishmania antigens were examined. PHA and Con A-induced responses were all positive in both the test and control groups. Eighteen out of 24 individuals with previous history of visceral leishmaniasis and 12 out of 14 normal individuals residing in the endemic areas responded to the 70kD antigen. In contrast, all the eight normal individuals all the eight normal individuals from a non-endemic area for leishmaniasis did not responded, indicating that cellular responses to the 70kD antigen are specific for Leishmanai spp. The 116kD antigen, on the other hand, exhibited poor specificity: about 30% of the individuals with a previous history of leishmaniasis did not respond to this antigen. A significant proportion of the population from an endemic area, but with no history of visceral leishmaniasis, responded to the 70kD antigen. This is an indicator of a prior exposure to Leishmania parasite and is consistent with previous studies which have shown that subclinical infections of visceral leishmaniasis do occur in such areas. Results from the present study suggest that the 70kD antigen is a strong candidate for vaccine development.
RESUMO
Infants born in areas of stable malaria transmission are relatively protected against severe morbidity and high density Plasmodium falciparum blood-stage infection. This protection may involve prenatal sensitization and immunologic reactivity to malaria surface ligands that participate in invasion of red cells. We examined cord blood T and B cell immunity to P. falciparum merozoite surface protein-1 (MSP-1) in infants born in an area of stable malaria transmission in Kenya. T cell cytokine responses to the C-terminal 19-kDa fragment of MSP-1 (MSP-1(19)) were detected in 24 of 92 (26%) newborns (4-192 IFN-gamma and 3-88 IL-4-secreting cells per 10(6)/cord blood lymphocytes). Peptide epitopes in the N-terminal block 3 region of MSP-1 also drove IFN-gamma and/or IL-13 production. There was no evidence of prenatal T cell sensitization to liver-stage Ag-1. A total of 5 of 86 (6%) newborns had cord blood anti-MSP-1(19) IgM Abs, an Ig isotype that does not cross the placenta and is therefore of fetal origin. The frequency of neonatal B cell sensitization was higher than that indicated by serology alone, as 5 of 27 (18%) cord blood samples contained B cells that produced IgG when stimulated with MSP-1(19) in vitro. Neonatal B cell IgG responses were restricted to the Q-KNG allele of MSP-1(19), the major variant in this endemic area, whereas T cells responded to all four MSP-1(19) alleles evaluated. In utero sensitization to MSP-1 correlated with the presence of malaria parasites in cord blood (chi(2) = 20, p < 0.0001). These data indicate that prenatal sensitization to blood-stage Ags occurs in infants born in malaria endemic areas.
Assuntos
Feto/imunologia , Imunidade Materno-Adquirida , Malária Falciparum/imunologia , Proteína 1 de Superfície de Merozoito/imunologia , Plasmodium falciparum/imunologia , Animais , Anticorpos Antiprotozoários/biossíntese , Antígenos de Protozoários/imunologia , Células Cultivadas , Citocinas/biossíntese , Feminino , Sangue Fetal/imunologia , Humanos , Imunoglobulina G/biossíntese , Proteína 1 de Superfície de Merozoito/genética , Mutação , Peptídeos/imunologia , Gravidez , Linfócitos T/imunologiaRESUMO
The course of Leishmania infection in pristane-primed BALB/c mice infected with either Leishmania major or Leishmania donovani was examined. Pristane-primed L. donovani infected mice had spleen parasite-loads that were 13 times less than controls. Likewise pristane-primed L. major infected animals had significantly smaller footpad lesion areas than controls. Pristane-primed mice had an atypical haematology compared to controls. To the best of our knowledge, this is the first report to demonstrate that pristane inhibits progression of disease in Leishmania-infected BALB/c mice.
RESUMO
Syrian hamsters and BALB/c mice were inoculated intraperitoneally with various doses of stationary phase Leishmania donovani promastigotes derived from primary, secondary and tertiary cultures. Axenic derived amastigotes from a tertiary culture and mass-culture derived promastigotes from primary, secondary, and tertiary cultures were also used. Animals were sacrificed after 30 days incubation period and parasite-loads quantified from Giemsa stained spleen smears. A primary inoculum dose of 1 x10(8) was found to be the most appropriate in effecting a visceral infection. This parasite dose resulted in a spleen parasite-load of 10-20 amastigotes per field of microscope view at x1,000 magnification. Those involved in candidate vaccine molecules or experimental drugs against kala-azar will find these results useful.
RESUMO
A total of 728 animals comprising of 633 rodents and 95 canids were examined for leishmanial parasites. Flagellates were isolated from 67 out of 111 (60.4%) Acomys subspinosus (spiny mouse), 12 out of 143 (8.4% ) Mastomys natalensis (multimammate rat), 2 out of 50 (4.0%) Lemniscomys striatus (striped mouse), 2 out of 6 (33.3%) Herpestes sanguineus (slender mongoose), 1 of 1 Helogale parvula (dwarf mongoose) and 1 out of 84 Canis familiaris (domestic dog). All isolates were characterized by Isoenzyme analysis using nine enzymes, namely, malate dehydrogenase (MDH), phosphoglucomutase (PGM), glucose phosphate isomerase (GPI), isocitrate dehydrogenase (ICD), nucleoside hydrolase (NH), glucose 6-phosphate dehydrogenase (G6PD), malic enzyme (ME), 6-phosphogluconate dehydrogenase (GPGD) and mannose phosphate isomerase (MPI). Enzyme profiles of these isolates were compared with those of five WHO Leishmania reference strains and five well characterized rodent trypanosomes of the subgenus Herpetosoma. The profiles of the isolates were found to be different from those of the Leishmania and Trypanosoma reference strains but the parasites were morphologically similar to rodent trypanosomes. These results suggest that Leishmania parasites were not among the isolates. The enzymes profiles of the three mongoose isolates were identical but differed from profiles of isolates from rodents and dog. This is the first time in Kenya that a high prevalence of nonpathogenic trypanosomes is reported in rodents and canids. From the epidemiological point of view, these trypanosomes must be differentiated from the pathogenic species of trypanosomes and Leishmania that infect man and other animals. The results of this study suggest that rodents do not seem to play a role as reservoirs of Leishmania parasites in Masinga Location, Kenya.
RESUMO
Leishmania donovani-infected Syrian hamsters were treated intraperitoneally with 0.23 mmoles/kg/day of EDTA, EGTA, HEEDTA and 100 mg/kg/day of Pentostam R. The control group received 0.1 ml of phosphate buffered saline. After 30 days of treatment, the animals were sacrificed. Of the Pentostam-treated animals, 5 out 6 had negative spleen cultures, while all the chelator and PBS-treated ones yielded parasites. While all the Pentostam-treated animals had negative bone marrow cultures, only 1 out of 6 HEEDTA-treated hamsters yielded parasites. Spleen, liver and bone marrow parasite- loads calculated from chelator-treated animals were consistently significantly higher than for Pentostam-treated animals. These results suggest that although metal ion chelators have some antileishmanial potential, their in vivo activity against L. donovani is low compared to Pentostam.
RESUMO
Identical impression smears of spleen, liver and bone marrow biopsy materials from Leishmania donovani-infected hamsters were stained using either acridine orange or Giemsa. Spleen parasite-loads calculated from the two stains for identical biopsy material were significantly different from each other. However, liver and bone marrow parasite- loads calculated from either Giemsa-stained or acridine orange-stained biopsies were not significantly different from each other. This study has shown that acridine orange, which is a quick and simple technique, has great potential in the diagnosis of kala-azar when liver and bone marrow biopsies are used.
RESUMO
Bladder and kidney disease, which affect approximately 25%-30% of subjects infected with Schistosoma haematobium, are mediated by T cell-dependent granulomatous responses to schistosome eggs. To determine why only some infected subjects develop disease, we examined the hypothesis that infected Kenyan subjects with ultrasound-detected urinary-tract morbidity (n=49) had dysregulated cytokine production leading to enhanced granulomatous responses, compared with subjects of similar age and intensity of infection without morbidity (n=100). Peripheral blood mononuclear cells from subjects with morbidity produced 8-fold greater levels of egg antigen-driven tumor necrosis factor (TNF)-alpha and had a 99-fold greater mean TNF-alpha:interleukin (IL)-10 ratio, compared with subjects without disease. No differences in cytokine response to non-egg-derived schistosome antigens were observed between groups. Subjects with morbidity had increased TNF-alpha production in response to endotoxin, suggesting an innate hyperresponsiveness. These results indicate that increased TNF-alpha production, relative to that of IL-10, is associated with developing bladder-wall morbidity with S. haematobium infection.