RESUMO
INTRODUCTION: Heritability in type 2 diabetes mellitus (T2DM) is observed but not well understood. METHODS: In this study, family history and clinical/biochemical data from 789 Bahrainis (418 T2DM, 371 controls) was analyzed. Fasting blood glucose (FBG) and HbA1c were measured and angiotensin-converting enzyme (ACE) and methylene tetrahydrofolate reductase (MTHFR) polymorphisms (SNPs) were analyzed. RESULTS: Patients compared to controls have higher proportions of diabetic mothers (50.2% vs. 32.7%, p=0.005), fathers (35.2% vs. 12.1%, p<0.001) and siblings (56% vs. 15.3%, p<0.001). The proportions of diabetic mothers was higher than the proportions of diabetic fathers among the patients (50.2% vs. 35.2%, p<0.001) and the controls (32.7% vs. 12.1%, p<0.001). Patients born to diabetic mothers compared to the other patients were smaller in age at the time of enrollment in this study (p=0.005), and at onset of T2DM (p<0.001), and also had higher FBG (p=0.033). Interestingly, the prevalence of T1DM was highest amongst the siblings of the controls compared to patients (p=0.04). Finally, the heterozygote I/D genotype of the ACE gene was over expressed in patients born to diabetic mothers when compared to patients born to diabetic fathers, p=0.007. CONCLUSIONS: there was strong clustering of T2DM in families, with significant dominant maternal role in transmission of T2DM and associated severity markers. Patients (T2DM) born to diabetic mothers were genetically and phenotypically different from the other patients.
Assuntos
Diabetes Mellitus Tipo 2/genética , Padrões de Herança/genética , Peptidil Dipeptidase A/genética , Idoso , Barein , Estudos de Casos e Controles , Feminino , Predisposição Genética para Doença , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
A malaria vaccine targeting Plasmodium falciparum remains a strategic goal for malaria control. If a polyvalent vaccine is to be developed, its subunits would probably be chosen based on immunogenicity (concentration of elicited antibodies) and associations of selected antigens with protection. We propose an additional possible selection criterion for the inclusion of subunit antigens; that is, coordination between elicited antibodies. For the quantitative estimation of this coordination, we developed a malaria serological map (MSM). Construction of the MSM was based on three categories of variables: (i) malaria antigens, (ii) total IgG and IgG subclasses, (iii) different sources of plasma. To validate the MSM, in this study, we used four malaria antigens (AMA1, MSP2-3D7, MSP2-FC27 and Pf332-C231) and re-grouped the plasma samples into five pairs of subsets based on age, gender, residence, HbAS and malaria morbidity in 9 years. The plasma total IgG and IgG subclasses to the test antigens were measured, and the whole material was used for the MSM construction. Most of the variables in the MSM were previously tested and their associations with malaria morbidity are known. The coordination of response to each antigens pair in the MSM was quantified as the correlation rate (CR = overall number of significant correlations/total number of correlations × 100 %). Unexpectedly, the results showed that low CRs were mostly associated with variables linked with malaria protection and the antigen eliciting the least CRs was the one associated with protection. The MSM is, thus, of potential value for vaccine design and understanding of malaria natural immunity.
Assuntos
Anticorpos Antiprotozoários/sangue , Variação Antigênica , Antígenos de Protozoários/imunologia , Técnicas Imunológicas/métodos , Malária Falciparum/imunologia , Plasmodium falciparum/imunologia , Adolescente , Adulto , Idoso , Criança , Feminino , Humanos , Imunoglobulina G/sangue , Vacinas Antimaláricas/imunologia , Masculino , Pessoa de Meia-Idade , Adulto JovemRESUMO
The anti-malarial IgG immune response during the lengthy and dry season in areas of low malaria transmission as in Eastern Sudan is largely unknown. In this study, ELISA was used for the measurement of pre-existing total IgG and IgG subclasses to a panel of malaria antigens, MSP2-3D7, MSP2-FC27, AMA-1 and Pf332-C231. The results showed that the antibody responses were predominantly age dependent, antigen specific, and their lifespan was at least 5-6 month long. Generally, the IgG3 was most abundant IgG subclass, and the most recognized antigen was Pf332-C231. Furthermore, the correlation between the levels of IgG subclasses was strongest between IgG1 and IgG3, which were more predictive to the total IgG levels. Finally, the response pattern of each of the IgG subclasses to the different test antigens that were spanning the dry season and the correlation between these responses were described in details for the first time.
Assuntos
Anticorpos Antiprotozoários/sangue , Antígenos de Protozoários/imunologia , Imunoglobulina G/sangue , Malária/imunologia , Proteínas de Membrana/imunologia , Proteínas de Protozoários/imunologia , Adolescente , Adulto , Idoso , Anticorpos Antiprotozoários/imunologia , Criança , Ensaio de Imunoadsorção Enzimática , Feminino , Humanos , Imunoglobulina G/imunologia , Masculino , Pessoa de Meia-Idade , Plasmodium falciparum/imunologia , Reação em Cadeia da Polimerase , Estações do Ano , SudãoRESUMO
Presumptive malaria treatment (PMT) is a common strategy in many areas of the world, especially in settings where the facilities for diagnosis are limited. The subjects of a recent study in central Sudan, in an area with a low level of Plasmodium falciparum transmission, were 322 individuals who had each presented at one of seven suburban health facilities, complaining of repeated febrile episodes. Although all were found bloodsmear-negative for malarial parasites, all were presumptively diagnosed as cases of malaria and prescribed artemisinin-based combination therapy. When pretreatment samples of blood were, however, checked for P. falciparum histidine-rich protein 2, using a rapid diagnostic test (RDT), and for Plasmodium DNA, using a PCR-based assay, only one (0.03%) of the cases was found RDT-positive and none was found PCR-positive. Although more studies are needed, in different areas and seasons, to see if these results mirror the general situation, it appears that the wide use of PMT in central Sudan, among patients who are bloodsmear-negative, is unjustified, of little, if any, benefit, and a waste of resources that are already limited. An international consortium for the revision of the conceptual aspects of malaria diagnosis and PMT is suggested.
Assuntos
Antimaláricos/uso terapêutico , Artemisininas/uso terapêutico , Febre , Malária , Plasmodium falciparum/isolamento & purificação , Antígenos de Protozoários/imunologia , Feminino , Febre/tratamento farmacológico , Febre/etiologia , Humanos , Malária/diagnóstico , Malária/tratamento farmacológico , Malária Falciparum/diagnóstico , Masculino , Plasmodium falciparum/imunologia , Reação em Cadeia da Polimerase , SudãoRESUMO
An interpretation of historical, clinical, and laboratory data was made to identify the correlates of and the diversity between cerebral malaria (CM) and severe malarial anemia (SMA) in a setting of low, seasonal, and unstable malaria transmission in eastern Sudan. Hemoglobin (Hb), random blood glucose (RBG), and anti-MSP antibodies were measured. Results showed that SMA and CM were significantly different with regard to age, malaria history, fever duration, convulsions, and hepatosplenomegaly. The MSP Ab response was inversely correlated with the number of previous malaria episodes but not with fever duration in the current attack. The spleen size was significantly inversely correlated with Hb level while hepatomegaly was significantly associated with low RBG. Furthermore, two malaria patients presented with neuropsychiatric upset. Finally, the correlates of SMA and CM fit perfectly with an adopted severity numeric scoring.
Assuntos
Anemia/patologia , Malária Cerebral/patologia , Malária/complicações , Malária/patologia , Índice de Gravidade de Doença , Anticorpos Antiprotozoários/sangue , Criança , Pré-Escolar , Feminino , Hemoglobinas/análise , Hepatomegalia , Humanos , Fígado/patologia , Masculino , Baço/patologia , Esplenomegalia , SudãoRESUMO
Estimation of the prevalence of the molecular markers of sulfadoxine/pyrimethamine (SP) and chloroquine (CQ) resistance and validation of the association of mutations with resistance in different settings is needed for local policy guidance and for contributing to a global map for anti-malarial drug resistance. In this study, malaria patients treated with SP alone (60) and SP with CQ (194) had a total treatment failure (TF) of 35.4%, with no difference between the two arms. The polymerase chain reaction-enzyme-linked immunosorbent assay (PCR-ELISA) method was used to identify polymorphisms in 15 loci in the dhfr, dhps and pfcrt genes in a subset of 168 infections. The results revealed a similar frequency of all single nucleotide polymorphisms (SNPs) in the two arms, except dhps 581G, which was over-represented in infections that failed to respond to SP alone (TF). In all infections, a high frequency of dhfr CICNI haplotype (51I and 108N) was found, but without discrimination between the adequate clinical and parasitological response (ACPR, 75.6%) and TF (82.9%). Similarly, the dhps SGEAA haplotype (437G and 540E) (ACPR, 60.5%; TF, 65.9%) and the combined CICNI/SGEAA haplotype (ACPR, 50%; TF 55%) were not associated with TF. In contrast to other studies in Africa, the triple 51I/59R/108N mutation was rare (0.6%). In addition, the pfcrt CVIET haplotype (93%) was found to be associated with the CICNI/SGEAA haplotype. Finally, these data represent a baseline for SP resistance molecular markers needed before the deployment of SP/artesunate combination therapy in the Sudan.
Assuntos
Antimaláricos/farmacologia , Plasmodium falciparum/efeitos dos fármacos , Animais , Cloroquina/farmacologia , Combinação de Medicamentos , Resistência a Medicamentos , Humanos , Mutação , Plasmodium falciparum/classificação , Plasmodium falciparum/genética , Pirimetamina/farmacologia , Sudão , Sulfadoxina/farmacologiaRESUMO
In a prospective clinical study in New Halfa Teaching Hospital, the possible association between FcgammaRIIa-R/H131 polymorphism and anti-malarial antibody responses with clinical outcome of Plasmodium falciparum malaria among Sudanese patients was investigated. A total of 256 individuals were consecutively enrolled, comprising 115 patients with severe malaria, 85 with mild malaria and 56 malaria-free controls. Genotyping of FcgammaRIIa-R/H131 dimorphism was performed using gene-specific polymerase chain reaction (PCR) amplification with allele-specific restriction enzyme digestion of the PCR product. The antibody responses to asexual blood-stage antigens were assessed by an enzyme-linked immunosorbent assay. The frequency of the FcgammaRIIa-R/R131 genotype was significantly higher in those with severe malaria when compared with patients with mild malaria, while the FcgammaRIIa-H/H131 genotype showed a significant association with mild malaria. A reduced risk of severe malaria with IgG3 antibodies in combination with the H/H131 genotype was observed. Furthermore, low levels of IgG2 antibodies reactive with the Pf332-C231 antigen were also associated with lower risk of severe malaria in individuals carrying the H131 allele. The levels of IgG1 and IgG3 antibodies were statistically significantly higher in the mild malaria patients when compared with the severe malaria patients. Taken together, our study revealed that the FcgammaRIIa-R/R131 genotype is associated with the development of severe malaria, while the H/H131 genotype is more likely to be associated with mild malaria. Our results also revealed that the natural acquisition of immunity against clinical malaria appeared to be more associated with IgG1 and IgG3 antibodies, signifying their roles in parasite-neutralizing immune mechanisms.
Assuntos
Anticorpos Antiprotozoários/sangue , Antígenos de Protozoários/imunologia , Malária Falciparum/genética , Plasmodium falciparum/imunologia , Polimorfismo Genético , Receptores de IgG/genética , Adolescente , Adulto , Fatores Etários , Animais , Anticorpos Antiprotozoários/imunologia , Criança , Pré-Escolar , Ensaio de Imunoadsorção Enzimática , Feminino , Frequência do Gene , Predisposição Genética para Doença , Genótipo , Humanos , Imunoglobulina G/sangue , Imunoglobulina G/imunologia , Malária Falciparum/sangue , Malária Falciparum/imunologia , Masculino , Pessoa de Meia-Idade , Reação em Cadeia da Polimerase , SudãoRESUMO
The variant surface antigens (VSA) of infected erythrocytes are important pathogenic markers, a set of variants (VSA(SM)), were assumed to be associated with severe malaria (SM), while SM constitutes clinically diverse forms, such as, severe malarial anemia (SMA) and cerebral malaria (CM). This study was conducted in Eastern Sudan, an area of seasonal and unstable malaria transmission. Parasites and plasma were obtained from patients with different clinical grades of malaria, and flow cytometry was used for analysis of VSA antibody (Ab) response. We found that individuals recognized a broader range of isolates had a higher level of VSA Ab against the recognized isolates (correlation coefficient, 0.727, P<0.001). Unexpectedly, at the time of malaria diagnosis, plasma from patients with CM recognized a significantly larger number of isolates than did the plasma from patients with SMA (P<0.001). Parasites obtained from patients with SMA or from children were better recognized than isolates obtained from patients with uncomplicated malaria or from adults, P<0.001, P=0.021, respectively. Taken together, the above findings suggest that the limitations in the VSA immunoglobulin G repertoire were most probably contributing to the pathogenesis of SMA but not to that of CM.
Assuntos
Antígenos de Protozoários/biossíntese , Malária Falciparum/imunologia , Malária Falciparum/parasitologia , Plasmodium falciparum/isolamento & purificação , Adolescente , Fatores Etários , Anemia/imunologia , Anemia/parasitologia , Animais , Anticorpos Antiprotozoários/sangue , Formação de Anticorpos , Especificidade de Anticorpos , Reações Antígeno-Anticorpo , Antígenos de Superfície/metabolismo , Criança , Pré-Escolar , Transmissão de Doença Infecciosa , Humanos , Malária Cerebral/imunologia , Malária Cerebral/parasitologiaRESUMO
A hospital-based study was carried out in Gedarif town, eastern Sudan, an area of markedly unstable malaria transmission. Among the 2488 diagnosed malaria patients, 4.4% fulfilled the WHO criteria for severe malaria, and seven died of cerebral malaria. The predominant complication was severe malarial anemia (45.4%), followed by convulsions (21%), cerebral malaria (16. 4%) and hypotension (11.8%). Severe malaria was recognized in all age groups, but 44.5% of patients were aged 2 to 4 years. The mean ages of patients with severe anemia (5.6 years) and convulsions (5.9 years) were significantly lower than the mean ages of patients with cerebral malaria (14.1 years) or hypotension (35.2 years). Patients with convulsions and cerebral malaria had significantly higher mean parasite count (69972 and 56110 parasites/microL, respectively) than patients with severe anemia (24637 parasites/microL) or hypotension (13667 parasites/microL). The mean blood glucose level was higher in patients with cerebral malaria than in patients with anemia, and higher in patients who died than in patients who survived. In this setting, the clinico-epidemiological pattern of severe malaria varies considerably from that of hyperendemic regions in sub-Saharan Africa, and there is considerable variation between the individual complications of severe malaria.
Assuntos
Malária Falciparum/epidemiologia , Estações do Ano , Doença Aguda , Adolescente , Adulto , Distribuição por Idade , Anemia/epidemiologia , Anemia/etiologia , Criança , Pré-Escolar , Doenças Endêmicas , Feminino , Humanos , Hipotensão/epidemiologia , Hipotensão/etiologia , Lactente , Malária Cerebral/epidemiologia , Malária Cerebral/etiologia , Malária Falciparum/complicações , Malária Falciparum/mortalidade , Masculino , Convulsões/epidemiologia , Convulsões/etiologia , Índice de Gravidade de Doença , Sudão/epidemiologiaRESUMO
An analysis is presented of continuous data collected over 11 years based on 1,902,600 person/days of observation on the malaria experience of the people of Daraweesh, a village in eastern Sudan. Malaria transmission is hypo-endemic: the acquisition of clinical immunity with age is not as obvious as in more holo-endemic areas and malaria remained a problem in all age groups throughout the study. However, this population, who are of Fulani origin, showed a distinctly variable level of disease susceptibility. Thirty-two percent of the village never reported malaria symptoms or required malaria treatment while others experienced up to 8 clinical episodes over the 11 years of observation. Malaria incidence was clearly influenced by drought but much less obviously by rainfall. To what extent outbreak patterns are explicable in terms of anopheline factors, and to human immune factors, remains an interesting question for malaria modelling in this, and in other low transmission zones, such as the burgeoning urban areas of modern Africa.
Assuntos
Suscetibilidade a Doenças/parasitologia , Malária Falciparum/epidemiologia , Plasmodium falciparum/crescimento & desenvolvimento , Adolescente , Adulto , Animais , Criança , Pré-Escolar , Clima , Estudos de Coortes , Feminino , Humanos , Lactente , Estudos Longitudinais , Malária Falciparum/tratamento farmacológico , Malária Falciparum/parasitologia , Malária Falciparum/transmissão , Masculino , Pessoa de Meia-Idade , Gravidez , Prevalência , População Rural , Estações do Ano , Sudão/epidemiologiaRESUMO
Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) is a variant antigen expressed on the surface of infected erythrocytes. Each parasite genome contains about 40 PfEMP1 genes, but only 1 PfEMP1 gene is expressed at a given time. PfEMP1 serves as a parasite-sequestering ligand to endothelial cells and enables the parasites to avoid splenic passage. PfEMP1 antibodies may protect from disease by inhibiting sequestration, thus facilitating the destruction of infected erythrocytes in the spleen. In this study, we have measured antibodies in Ghanaian children to a conserved region of PfEMP1 by enzyme-linked immunosorbent assay and antibodies to variant molecules on erythrocytes infected with field isolates of P. falciparum by flow cytometry. Based on close clinical monitoring, the children were grouped into those who did (susceptible) and those who did not (protected) have malaria during the season. The prevalences of antibodies to both the conserved PfEMP1 peptide and the variant epitopes were greater than 50%, and the levels of immunoglobulin G (IgG) correlated with age. The levels of antibodies to both the conserved peptide and the variant epitopes were higher in protected than in susceptible children. After correcting for the effect of age, the levels of IgG to variant antigens on a Sudanese and a Ghanaian parasite isolate remained significantly higher in protected than in susceptible children. Thus, the levels of IgG to variant antigens expressed on the surface of infected erythrocytes correlated with protection from clinical malaria. In contrast, the levels of IgG to a peptide derived from a conserved part of PfEMP1 did not correlate with protection from malaria.
Assuntos
Anticorpos Antiprotozoários/sangue , Eritrócitos/imunologia , Malária Falciparum/prevenção & controle , Plasmodium falciparum/imunologia , Proteínas de Protozoários/imunologia , Adolescente , Animais , Anticorpos Antiprotozoários/imunologia , Criança , Pré-Escolar , Eritrócitos/metabolismo , Eritrócitos/parasitologia , Gana , Humanos , Malária Falciparum/imunologia , Proteínas de Protozoários/metabolismoRESUMO
In areas of unstable transmission malaria affects all age groups, but the malaria incidence is lower in adults compared to children and teenagers. Under such conditions subclinical Plasmodium falciparum infections are common and some infections are controlled, because blood parasitaemia is maintained at low densities. Here, we test the hypothesis that the presence or absence of antibodies against variant antigens on the surface of P. falciparum-infected erythrocytes protect individuals against some infectious challenges and render them susceptible to others. Plasma collected in Daraweesh, eastern Sudan, before and after the malaria season from individuals who had (susceptible) or did not have malaria (protected) during the season, were tested for reactivity against variant antigens on the surface of nine parasite isolates by flow cytometry. Both protected and susceptible individuals acquired antibodies to variant antigens during the malaria season. The presence of antibody to a Ghanaian isolate before the season was statistically significantly associated with protection against malaria. When considering all nine isolates, the patterns of antibody acquisition differed between susceptible and protected individuals. Together, the results indicate that pre-existing anti-PfEMP1 antibodies can reduce the risk of contracting clinical malaria when challenged by novel parasite clones expressing homologous, but not heterologous variable surface antigens. The results also confirm that antibodies to variant antigens are induced by both clinical and subclinical infections, and that antibodies against several var sero-types are induced during an infection.
Assuntos
Anticorpos Antiprotozoários/sangue , Membrana Eritrocítica/parasitologia , Malária Falciparum/imunologia , Malária Falciparum/parasitologia , Plasmodium falciparum/imunologia , Adolescente , Adulto , Fatores Etários , Animais , Antígenos de Protozoários , Criança , Pré-Escolar , Membrana Eritrocítica/imunologia , Feminino , Humanos , Malária Falciparum/sangue , Masculino , Proteínas de Membrana/imunologia , Pessoa de Meia-Idade , Parasitemia/sangue , Parasitemia/imunologia , Parasitemia/parasitologia , Proteínas de Protozoários/imunologia , Estações do Ano , SudãoRESUMO
This study investigated the epidemiology of uncomplicated falciparum malaria in an area of unstable and seasonal transmission in eastern Sudan. About 90% of malaria morbidity in this region occurs in the months of September to November, and very few malaria cases occur during the intensely arid Sudanese dry season and during years of drought. The malaria situation in the study site, the village of Daraweesh, was analysed during 3 consecutive malaria seasons in 1993-95 during which the 457 inhabitants suffered at total of 436 episodes of falciparum malaria. Using an Andersen-Gill proportional hazard model for recurrent events stratified by family, we have calculated the relative hazard for clinical malaria episodes by age, sex, haemoglobin genotype, blood type and infection in the previous season. The malaria risk was significantly lower in individuals aged 20-88 years than in the 5-19 years age-group. The relative protection due to adulthood varied between seasons (relative risk, RR, 0x34 to 0x67). Serological data were not consistent with the hypothesis that the age difference in incidence was due to differences in exposure. During the 1993 season the malaria incidence in males was lower than in females (RR = 0x75), during the 1994 season the incidences were comparable, whereas males had an increased risk of malaria in 1995 (RR = 1x87). The relative risk in individuals carrying the haemoglobin AS genotype compared to homozygous AA individuals was 0x57.
Assuntos
Febre/epidemiologia , Malária Falciparum/epidemiologia , Estações do Ano , Adolescente , Adulto , Distribuição por Idade , Anticorpos Antiprotozoários/análise , Criança , Pré-Escolar , Feminino , Febre/sangue , Febre/imunologia , Genótipo , Hemoglobinas/química , Humanos , Malária Falciparum/sangue , Malária Falciparum/imunologia , Masculino , Prevalência , Fatores de Risco , Distribuição por Sexo , Sudão/epidemiologiaRESUMO
Antibodies against variable antigens expressed on the surface of Plasmodium falciparum-infected erythrocytes are believed to be important for protection against malaria. A target for these antibodies is the P. falciparum erythrocyte membrane protein 1, PfEMP1, which is encoded by around 50 var genes and undergoes clonal variation. Using agglutination and mixed agglutination tests and flow cytometry to analyse the recognition of variant antigens on parasitized erythrocytes by plasma antibodies from individuals living in Daraweesh in eastern Sudan, an area of seasonal and unstable malaria transmission, we show that these antibodies recognize different variant antigens expressed by parasites of different genotype. Comparing the levels and acquisition of antibody to variant antigens in pairs of parasite isolates expressing different variant types, there is a correlation between the acquisition of antibodies to some combinations of variant antigens but not to others. These results indicate that (1) a single infection will induce the production of antibodies recognizing several variants of surface-expressed antigens, (2) the repertoire of variable antigens expressed by different parasites is overlapping and the degree of overlap differs between isolates, and (3) the expression of at least some variant antigens is genetically linked.
Assuntos
Variação Antigênica , Antígenos de Protozoários/imunologia , Membrana Eritrocítica/imunologia , Eritrócitos/parasitologia , Malária Falciparum/imunologia , Proteínas de Protozoários/imunologia , Anticorpos Antiprotozoários/sangue , Especificidade de Anticorpos , Antígenos de Protozoários/genética , Membrana Eritrocítica/genética , Citometria de Fluxo , Genótipo , Testes de Hemaglutinação , Humanos , Estudos Longitudinais , Malária Falciparum/sangue , Malária Falciparum/epidemiologia , Proteínas de Protozoários/genética , População Rural , Estações do Ano , Sudão/epidemiologiaRESUMO
PfEMP1 is an antigenically variable molecule which mediates the adhesion of parasitized erythrocytes to a variety of cell types and which is believed to constitute an important target for naturally acquired protective immune responses in malaria. For 9 years we have monitored individuals living in an area of low-intensity, seasonal, and unstable malaria transmission in eastern Sudan, and we have used this database to study the acquisition, specificity, and duration of the antibody response to variant parasitized erythrocyte surface antigens. Both the levels and the spectrum of reactivity of these antibodies varied considerably among individuals, ranging from low levels of antibodies recognizing only few parasitized erythrocyte surface antigens to high levels of broad-specificity antibodies. In general, episodes of clinical malaria were associated with increases in the levels of parasitized erythrocyte surface-specific antibodies that subsided within months of the attack. This response was often, but not always, specific for the antigenic variants expressed by the parasite isolate causing disease. Our study provides evidence that Palciparum falciparum malaria is associated with a short-lived, variant-specific antibody response to PfEMP1-like antigens exposed on the surface of parasitized erythrocytes. Furthermore, our data suggest that the antigenic repertoires of variant antigens expressed by different parasite isolates show considerable overlapping, at least under Sahelian conditions of low-intensity, seasonal, and unstable malaria transmission. Finally, we demonstrate the existence of persistent differences among individuals in the capacity to mount antibody responses to variant surface antigens.
Assuntos
Anticorpos Antiprotozoários/sangue , Antígenos de Protozoários/imunologia , Membrana Eritrocítica/parasitologia , Plasmodium falciparum/imunologia , Proteínas de Protozoários/imunologia , Adolescente , Adulto , Animais , Especificidade de Anticorpos , Criança , Feminino , Humanos , Estudos Longitudinais , Masculino , Proteínas de Membrana/imunologia , Pessoa de Meia-IdadeRESUMO
BACKGROUND: Naturally induced antibodies binding to surface antigens of Plasmodium falciparum-infected erythrocytes can be detected by direct agglutination of infected erythrocytes or by indirect immunofluorescence on intact, unfixed, infected erythrocytes. Agglutinating antibodies have previously been shown to recognise Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1). This protein is inserted by the parasite into the host cell membrane and mediates the adhesion to the venular endothelium of the host organism in vivo. METHODS: Erythrocytes infected at high parasitaemias with ethidium-bromide-labelled mature forms of P. falciparum parasites were sequentially exposed to immune plasma, goat anti-human immunoglobulin (Ig) G, and fluorescein-isothiocyanate-conjugated rabbit anti-goat Ig. Plasma antibodies recognising antigens exposed on the surface of parasitised erythrocytes were subsequently detected by two-colour flow cytometry. RESULTS: Binding of human antibodies to the surface of erythrocytes infected with adhesive strains of Plasmodium falciparum can be measured by the two-colour flow cytometry (FCM) assay described. In addition, we demonstrate that the adhesive capacity of a parasite isolate correlates with the capacity of human immune plasmas to label the isolate as detected by FCM. We also show that the antigens recognised by the labelling antibodies are strain specific and that their molecular weights are in the range previously described for PfEMP1 antigens. CONCLUSIONS: Our FCM assay predominantly detects antibodies that recognise PfEMP1 and thus constitutes a convenient assay for the analysis of acquisition, maintenance, and diversity of anti-PfEMP1-specific antibodies and for the examination of class and subclass characteristics.
Assuntos
Anticorpos Antiprotozoários/imunologia , Antígenos de Protozoários/imunologia , Eritrócitos/imunologia , Citometria de Fluxo/métodos , Plasmodium falciparum/imunologia , Adulto , Animais , Eritrócitos/parasitologia , Humanos , CoelhosRESUMO
Residents of Daraweesh village in Sudan were monitored for Plasmodium falciparum infection and malaria morbidity in 3 malaria seasons from 1993 to 1996. Malaria parasites were detected microscopically and by polymerase chain reaction (PCR) in a series of cross-sectional surveys. PCR revealed submicroscopical infections during the dry season, particularly among individuals who had recovered from a malaria episode following successful drug treatment. Clinical and subclinical infections were contrasted by assaying for allelic polymorphism at 2 gene loci, MSP-1 and GLURP and 2 hypotheses examined with reference to these data: that clinical malaria is associated with infection with novel parasite genotypes not previously detected in that host, or alternatively, that clinical malaria episodes are associated with an increased number of clones in an infection. We detected more mixed infections among clinical isolates, but people carrying parasites during the dry season were not found to have an increased risk of disease in the following malaria season. There was a clear association of disease with the appearance of novel parasite genotypes.
Assuntos
Malária Falciparum/epidemiologia , Plasmodium falciparum/isolamento & purificação , Adolescente , Adulto , Animais , Criança , Estudos de Coortes , Genótipo , Humanos , Estudos Longitudinais , Malária Falciparum/sangue , Morbidade , Plasmodium falciparum/genética , Reação em Cadeia da Polimerase , Polimorfismo Genético , Estações do Ano , Sudão/epidemiologiaRESUMO
Merozoite surface protein-1 (MSP-1) of Plasmodium falciparum is a malaria vaccine candidate Ag. Immunity to MSP-1 has been implicated in protection against infection in animal models. However, MSP-1 is a polymorphic protein and its immune recognition by humans following infection is not well understood. We have compared the immunogenicity of conserved and polymorphic regions of MSP-1, the specificity of Ab responses to a polymorphic region of the Ag, and the duration of these responses in Sudanese villagers intermittently exposed to P. falciparum infections. Recombinant Ags representing the conserved N terminus (Block 1), the conserved C terminus, and the three main types of the major polymorphic region (Block 2) of MSP-1 were used to determine the specificity and longitudinal patterns of IgG Ab responses to MSP-1 in individuals. Abs from 52 donors were assessed before, during, and after malaria transmission seasons for 4 yr. Ags from the Block 1 region were rarely recognized by any donor. Responses to the C-terminal Ag occurred in the majority of acutely infected individuals and thus were a reliable indicator of recent clinical infection. Ags from the polymorphic Block 2 region of MSP-1 were recognized by many, although not all individuals after clinical malaria infections. Responses to Block 2 were type specific and correlated with PCR typing of parasites present at the time of infection. Responses to all of these Ags declined within a few months of drug treatment and parasite clearance, indicating that naturally induced human Ab responses to MSP-1 are short lived.
Assuntos
Anticorpos Antiprotozoários/biossíntese , Especificidade de Anticorpos , Malária Falciparum/imunologia , Plasmodium falciparum/genética , Plasmodium falciparum/imunologia , Precursores de Proteínas/imunologia , Proteínas de Protozoários/imunologia , Adolescente , Adulto , Animais , Anticorpos Antiprotozoários/sangue , Variação Antigênica/genética , Variação Antigênica/imunologia , Sequência Conservada , Feminino , Genótipo , Humanos , Estudos Longitudinais , Malária Falciparum/epidemiologia , Malária Falciparum/parasitologia , Masculino , Proteína 1 de Superfície de Merozoito , Dados de Sequência Molecular , Plasmodium falciparum/isolamento & purificação , Polimorfismo Genético , Sudão/epidemiologiaRESUMO
Agglutination and rosette formation are in vitro characteristics of Plasmodium falciparum-infected erythrocytes, which have been associated with host protective immune responses and also with parasite virulence. The present study was carried out in an area of seasonal and unstable malaria transmission in eastern Sudan. Plasma samples were obtained before, during, and after the transmission season from a volunteer cohort of 64 individuals seven years of age and older. These plasmas were assayed for their ability to agglutinate cultured parasitized erythrocytes originally obtained from acute malaria infection samples taken from five of the cohort members. Our data show that the capacity of donor plasma samples to agglutinate parasitized cells depended largely on the time of sampling relative to the transmission season, at least within this epidemiologic setting. Thus, although less than half of the pretransmission season samples could agglutinate any of the five lines of cultured parasites, all post-transmission season samples could agglutinate at least one of the parasite lines, with 74% agglutinating two or more lines. This increase in the agglutination capacity of individual plasma samples after the transmission season occurred essentially regardless of whether an individual had experienced a clinical malaria attack during the transmission season. The study thus confirms the acquisition of agglutinating antibodies following episodes of clinical malaria, but also demonstrates that such acquisition can take place in the absence of disease, presumably as a consequence of subclinical infection. This is the first demonstration of marked seasonal fluctuations in the capacity of individuals' sera to agglutinate parasitized red blood cells. Possible explanations for this effect include a decrease in the levels of agglutinating antibodies between seasons, or shifts in the antigens being recognized by such antibodies from one transmission season to the next. Finally, we showed the existence of marked seasonal fluctuation in the levels of agglutinating antibodies, either because levels of such antibodies are not sustained between seasons or because the antigens recognized change from one season to the next.
Assuntos
Eritrócitos/parasitologia , Malária Falciparum/imunologia , Plasmodium falciparum/imunologia , Adolescente , Adulto , Testes de Aglutinação , Alelos , Animais , Células Cultivadas , Criança , Estudos de Coortes , Eritrócitos/imunologia , Feminino , Genótipo , Humanos , Malária Falciparum/sangue , Masculino , Plasmodium falciparum/classificação , Plasmodium falciparum/genética , Reação em Cadeia da Polimerase , Estações do AnoRESUMO
The Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) family of protein antigens are involved in adhesion of P. falciparum infected erythrocytes to the capillary endothelium of the host. Antibodies to variable regions of these proteins, measured by agglutination, correlates with clinical protection against falciparum malaria. In this study we investigated the occurrence of antibodies to conserved sequences of these very variable proteins in a population living in an area endemic for falciparum malaria. Using the ELISA method, we were able to measure an antibody response to three synthetic peptides derived from conserved regions of PfEMP1. The antibody responses to these peptides increased with age and were higher in individuals with asymptomatic P. falciparum infection compared to individuals presenting with fever attributable to falciparum malaria. This indicates that antibodies recognising the conserved regions of PfEMP1 arise upon exposure to the parasite, and that these may be involved in the development of protection against malaria. Antibodies to the Pfalhesin peptide of the human aniontransporter, band3, were measured by the same method. The magnitude of this antibody response did not correlate with neither age nor clinical protection.