Genetic determinants of anti-malarial acquired immunity in a large multi-centre study.

BACKGROUND: Many studies report associations between human genetic factors and immunity to malaria but few have been reliably replicated. These studies are usually country-specific, use small sample sizes and are not directly comparable due to differences in methodologies. This study brings together samples and data collected from multiple sites across Africa and Asia to use standardized methods to look for consistent genetic effects on anti-malarial antibody levels. METHODS: Sera, DNA samples and clinical data were collected from 13,299 individuals from ten sites in Senegal, Mali, Burkina Faso, Sudan, Kenya, Tanzania, and Sri Lanka using standardized methods. DNA was extracted and typed for 202 Single Nucleotide Polymorphisms with known associations to malaria or antibody production, and antibody levels to four clinical grade malarial antigens [AMA1, MSP1, MSP2, and (NANP)4] plus total IgE were measured by ELISA techniques. Regression models were used to investigate the associations of clinical and genetic factors with antibody levels. RESULTS: Malaria infection increased levels of antibodies to malaria antigens and, as expected, stable predictors of anti-malarial antibody levels included age, seasonality, location, and ethnicity. Correlations between antibodies to blood-stage antigens AMA1, MSP1 and MSP2 were higher between themselves than with antibodies to the (NANP)4 epitope of the pre-erythrocytic circumsporozoite protein, while there was little or no correlation with total IgE levels. Individuals with sickle cell trait had significantly lower antibody levels to all blood-stage antigens, and recessive homozygotes for CD36 (rs321198) had significantly lower anti-malarial antibody levels to MSP2. CONCLUSION: Although the most significant finding with a consistent effect across sites was for sickle cell trait, its effect is likely to be via reducing a microscopically positive parasitaemia rather than directly on antibody levels. However, this study does demonstrate a framework for the feasibility of combining data from sites with heterogeneous malaria transmission levels across Africa and Asia with which to explore genetic effects on anti-malarial immunity.

Knowledge, attitudes, and practices (KAP) during the malaria elimination phase: A household-based cross-sectional survey.

Malaria is a major health problem in Southwestern Saudi Arabia. This study aimed to measure the level of community understanding of malaria transmission, protection, and treatment. A questionnaire-based cross-sectional study enrolled 1070 participants from 2 districts with different malaria prevalence rates in Jazan Province. The response rate was 97.27%. Of the 1070 total; 754 (70.5%) had heard about malaria. Sixty-seven percentage know that fever was the main symptom. Approximately 59.8% did not know that stagnant water is one of the most important locations for mosquito breeding. Nevertheless, we found that 50% of the participants knew that mosquitoes bite at night and 96.9% confirmed that mosquitoes did not bite during the day. The most effective sources of information were distributed leaflets (41.8%) and video awareness (31.9%). The most significant factors affecting participants knowledge were gender, residence, family members, income, and education (P < .05). Knowledge levels were satisfactory in this study, and the majority of participants exhibited adequate attitudes and practices related to malaria prevention. However, knowledge differences were observed with regard to the place of residence. Greater emphasis should be directed towards education programs in malaria-endemic areas to ensure complete eradication of malaria.

Variation of antibody responses to Plasmodium falciparum MSP1-19 antigen with parasitaemia and IL4vntr polymorphism in Khartoum state, Sudan.

A hospital-based cross-sectional study was conducted at Khartoum state to investigate the variation of antibody responses to Plasmodium falciparum 19-kDa C-terminal region of merozoite surface protein 1 antigen and the variation of human IL4 polymorphism with parasitaemia. Measurements of natural acquisition of anti-Plasmodium falciparum MSP1-19 IgG, IgG1 and IgG3 antibodies were performed using ELISA. Molecular characterization of IL4vntr polymorphism was achieved. We were able to detect a statistically significant negative correlation between parasitaemia and different age groups (r = - 0.262 and p value = 0.043) and with anti-P.fMSP1-19 IgG1 (r = - 0.418, p value = 0.047). Anti-P.fMSP1-19 IgG showed a significant difference among age groups (p < 0.001). Only anti-P.fMSP1-19 IgG showed a significant association with general appearance (p value < 0.001). The mean for total anti-P.fMSP1-19 IgG3 was statistically significantly higher in females compared to males (p value < 0.001). There was no significant difference in the distribution of human IL4 vntr genotypic and allelic frequencies between cases and control group as well as among different clinical manifestation.We concluded that IgG1 levels to MSP1-19 were found to be negatively correlated with parasitaemia and anti-PfMSP1-19 IgG was significantly increased in ill and severely ill with age considered as a cofactor. Further studies are needed to ascertain the role of IgG and IgG1 in protection and to investigate the IgG and subclasses' response against other antigenic markers. These findings are valuable for advancing vaccine development by providing evidence supporting merozoite antigens as targets of protective immunity in humans.

Loss of balancing selection in the betaS globin locus.

BACKGROUND: Probably the best example of the rise and maintenance of balancing selection as an evolutionary trend is the role of S-haemoglobin (HbS - rs334) in protecting from malaria. Yet, the dynamics of such a process remains poorly understood, particularly in relation to different malaria transmission rates and the genetic background of the affected populations. METHODS: We investigated the association of haemoglobin HbS in protection from clinical episodes of malaria in two populations/villages where malaria is endemic, but mostly presenting in mild clinical forms. Five-hundred and forty-six individuals comprising 65 and 82 families from the Hausa and Massalit villages respectively were genotyped for HbS. Allele and genotype frequencies as well as departure from Hardy-Weinberg Equilibrium were estimated from four-hundred and seventy independent genotypes across different age groups. Age-group frequencies were used to calculate the coefficient-of-fitness and to simulate the expected frequencies in future generations. RESULTS: Genotype frequencies were within Hardy-Weinberg expectations in Hausa and Massalit in the total sample set but not within the different age groups. There was a trend for a decrease of the HbS allele frequency in Hausa and an increase of frequency in Massalit. Although the HbS allele was able to confer significant protection from the clinical episodes of malaria in the two populations, as suggested by the odds ratios, the overall relative fitness of the HbS allele seems to have declined in Hausa. CONCLUSIONS: Such loss of balancing selection could be due to a combined effect of preponderance of non-clinical malaria in Hausa, and the deleterious effect of the homozygous HbS under circumstances of endogamy.

The spatial-temporal clustering of Plasmodium falciparum infection over eleven years in Gezira State, The Sudan.

BACKGROUND: Malaria infection and disease exhibit microgeographic heterogeneity which if predictable could have implications for designing small-area intervention. Here, the space-time clustering of Plasmodium falciparum infections using data from repeat cross-sectional surveys in Gezira State, a low transmission area in northern Sudan, is investigated. METHODS: Data from cross-sectional surveys undertaken in January each year from 1999-2009 in 88 villages in the Gezira state were assembled. During each survey, about a 100 children between the ages two to ten years were sampled to examine the presence of P. falciparum parasites. In 2009, all the villages were mapped using global positioning systems. Cluster level data were analysed for spatial-only and space-time clustering using the Bernoulli model and the significance of clusters were tested using the Kulldorff scan statistic. RESULTS: Over the study period, 96,022 malaria slide examinations were undertaken and the P. falciparum prevalence was 8.6% in 1999 and by 2009 this had reduced to 1.6%. The cluster analysis showed the presence of one significant spatial-only cluster in each survey year and one significant space-time cluster over the whole study period. The primary spatial-only clusters in 10/11 years were either contained within or overlapped with the primary space-time cluster. CONCLUSION: The results of the study confirm the generally low malaria transmission in the state of Gezira and the presence of spatial and space-time clusters concentrated around a specific area in the south of the state. Improved surveillance data that allows for the analysis of seasonality, age and other risk factors need to be collected to design effective small area interventions as Gezira state targets malaria elimination.

Chloroquine-resistant Plasmodium vivax malaria in Debre Zeit, Ethiopia.

BACKGROUND: Plasmodium vivax accounts for about 40% of all malaria infection in Ethiopia. Chloroquine (CQ) is the first line treatment for confirmed P. vivax malaria in the country. The first report of CQ treatment failure in P. vivax was from Debre Zeit, which suggested the presence of chloroquine resistance. METHODS: An in vivo drug efficacy study was conducted in Debre Zeit from June to August 2006. Eighty-seven patients with microscopically confirmed P. vivax malaria, aged between 8 months and 52 years, were recruited and treated under supervision with CQ (25 mg/kg over three days). Clinical and parasitological parameters were assessed during the 28 day follow-up period. CQ and desethylchloroquine (DCQ) blood and serum concentrations were determined with high performance liquid chromatography (HPLC) in patients who showed recurrent parasitaemia. RESULTS: Of the 87 patients recruited in the study, one was lost to follow-up and three were excluded due to P. falciparum infection during follow-up. A total of 83 (95%) of the study participants completed the follow-up. On enrolment, 39.8% had documented fever and 60.2% had a history of fever. The geometric mean parasite density of the patients was 7045 parasites/microl. Among these, four patients had recurrent parasitaemia on Day 28. The blood CQ plus DCQ concentrations of these four patients were all above the minimal effective concentration (> 100 ng/ml). CONCLUSION: Chloroquine-resistant P. vivax parasites are emerging in Debre Zeit, Ethiopia. A multi-centre national survey is needed to better understand the extent of P. vivax resistance to CQ in Ethiopia.

Hyper-reactive Malarial Splenomegaly (HMS) in malaria endemic area in Eastern Sudan.

Hyper-reactive Malarial Splenomegaly (HMS) is massive enlargement of the spleen resulting from abnormal immune response to repeated attacks of malaria. The present study was carried out in Kassala city, Eastern Sudan where HMS is considered as highly prevalent. The objectives of this study were to determine the incidence of HMS in Eastern Sudan, and to identify basic laboratory and clinical characteristics of this condition in Sudanese patients. In the period between January and March 2004, a cross-sectional study was carried out in four health centers in Kassala city. In the current study 114 out 1010 (11%) medical cases examined were found to have enlarged spleens, 87 (9%) of them were diagnosed as HMS. Sixty-three percent of HMS cases were males and the rest were females. The mean age of HMS patients was 28 years. Clinical investigations showed that all cases suffered from abdominal pain in the upper left quadrant and all had a palpable firm spleen (10-26cm) below the costal margin. Laboratory examinations showed that 74% of the cases were anaemic and the mean white blood count for all cases was 4237cell/mL(3). Serum concentration of IgM in all subjects was above the threshold of the mean value plus 2 S.D. for 35 asymptomatic controls. In more than 70% of the HMS patients (53 individuals) the spleens were impalpable after the third month of the treatment. Our data indicate that HMS is one of the major causes of tropical splenomegaly in Eastern Sudan.

Seroepidemiology of Toxoplasma gondii amongst Pregnant Women in Jazan Province, Saudi Arabia.

Background. Toxoplasma gondii (T. gondii) is an obligate intracellular protozoan parasite of worldwide distribution. There is limited information about the seroprevalence of toxoplasmosis in the southern area of Saudi Arabia. The current study was carried out to determine the prevalence of T. gondii in pregnant women in Jazan province. Materials and Methods. The study was conducted between January and June 2013 and included 195 pregnant women, data on sociodemographic and predisposing factors were collected from each participant. Venous blood samples were collected following standard operating procedures. Serological analysis for latent toxoplasmosis (levels of IgG) and active toxoplasmosis (IgM) was done using Enzyme Linked Immunosorbent Assay (ELISA). Results. The overall seroprevalence of T. gondii in the study area was 24.1%. The seroprevalence of anti-Toxoplasma IgG was 20% (39 out of 195), whereas IgM seropositivity was 6.2% (12 out of 195). Only 4 pregnant women tested positive for both IgG and IgM. The highest IgG and IgM seroprevalence was among the study participants aged 35 to 39 years (13.5% and 35.1%, resp.). The seropositivity rate of T. gondii-specific antibodies was higher among pregnant women from the urban areas than those from rural communities (7.4% versus 0% and 21% versus 15.4% for IgM and IgG, resp.). Conclusions. The seroprevalence of T. gondii was high in pregnant woman in Jazan. The prevalence of toxoplasmosis increases with increase of age. Awareness health education program in Jazan needs to be maintained and developed to targeted pregnant women.

Immunological characteristics of hyperreactive malarial splenomegaly syndrome in sudanese patients.

Hyperreactive Malarial Splenomegaly (HMS) is defined as a massive enlargement of the spleen resulting from abnormal immune responses after repeated exposure to the malaria parasites. This study was carried out in Khartoum, Sudan. Sudan is considered to be one of the countries where HMS is quite prevalent. The objective of the study was to determine the incidence of HMS in patients who reported to the Omdurman Tropical Diseases Hospital (OMTDH) in Sudan and to investigate the basic laboratory and immunological characteristics of this condition in these patients. A cross-sectional study was carried out in OMTDH, and all patients with enlarged spleens were included in the study. Thirty-one out of 335 (9.3%) patients were diagnosed as having the HMS condition using international criteria for HMS diagnosis. The mean serum immunoglobulin M (IgM) levels in HMS patient groups were 14.3 ± 5 g/L, and this was significantly higher compared with geographically matched controls (P < 0.001). Immunoglobulin G (IgG) C anticircumsporozoite (CSP) antibody levels were higher in the HMS patients although the difference was not statistically significant, when compared with a group of patients with mild malaria. In comparison with naïve European controls, both the HMS and the mild malaria groups had significantly higher antimalarial antibody levels P < 0.001 and P < 0.01, respectively. Plasma levels of interleukin 10 (IL10) and interferon gamma (IFN γ ) were significantly increased in the HMS patients compared with the healthy control donors (P < 0.05 and P < 0.01) for IL10 and IFN γ , respectively. The findings of this study suggest that HMS is one of the significant causes of tropical splenomegaly in Sudan. HMS is associated with significant elevations of circulating IgM and antimalarial IgG antibodies as well as IL10 and IFN γ .

Pattern of malaria transmission along the Rahad River basin, Eastern Sudan.

BACKGROUND: Understanding malaria vector mosquitoes and their infectivity dynamics is of importance in setting up intervention and control programmes. Patterns of malaria transmission have been shown to differ between non-irrigated and irrigated semi-arid areas of eastern Sudan. However, very little information is available regarding malaria transmission dynamics along the seasonal river's basin. Such information is required for the design of effective vector control strategies. METHODS: A longitudinal study for mosquito sampling using pyrethrum spray catch (PSC) was conducted in two villages (Koka & Um Salala) along the Rahad River basin from December 2005 to October 2006. The Plasmodium falciparum circumsporozoite (CSP) and human blood index (HBI) were detected by ELISA. Three seasons were considered and the surveys represented cool dry, hot dry and rainy seasons were November - February, March - June, July - October, respectively. The CSP was compared between the seasons and populations using Chi-square test. The differences between the seasons and the populations in the other entomological indices, including Entomological Inoculation Rates (EIR), were measured using Tukey-Kramer HSD and Student T-test, respectively. The association between An. arabiensis density and monthly total rainfall was examined using regression analysis. RESULTS: A total of 1,402 adult female anopheline mosquitoes were sampled, of which 98% were An. gambiae complex; the rest were An. rufipes. All specimens of An. gambiae complex identified by the PCR were An. arabiensis. Bimodal annual peaks of An. arabiensis densities were observed following the peak of rainfall and recess of the Rahad River after a time- lag of two months (Koka r = 0.79, d.f. = 1, P = 0.05; Um Salala, r = 0.88, d.f. = 1, P = 0.02). The CSP differed significantly among the seasons only in Koka (P = 0.0009) where the mean was nine times higher than in Um Salala (P = 0.0014). Active transmission was observed in Koka during the hot, dry season (CSP = 6.25%) and the EIR was observed to be 0.01 ib/p/n during this time. The EIR peaked to 0.71 ib/p/n during the rainy season and decreased to 0.18 ib/p/n during the minor peak of the cool dry season (P = 0.54). The combined annual average of the EIR for both populations was 55.48 ib/p/y and, typically, it would take approximately 192.7 days for an individual to receive an infective bite from An. arabiensis. CONCLUSION: The bimodal annual peaks and the active transmission observed during the hot dry season suggested low to moderate perennial malaria transmission pattern. Infectivity and transmission rates increased with proximity to the river following the peak of rainfall and the subsequent recession in the flow of the Rahad River. Current vector interventions can be integrated with larval control and should be formatted in accordance with targeted according to the time and space.

Immunity against HIV/AIDS, malaria, and tuberculosis during co-infections with neglected infectious diseases: recommendations for the European Union research priorities.

Infectious diseases remain a major health and socioeconomic problem in many low-income countries, particularly in sub-Saharan Africa. For many years, the three most devastating diseases, HIV/AIDS, malaria, and tuberculosis (TB) have received most of the world's attention. However, in rural and impoverished urban areas, a number of infectious diseases remain neglected and cause massive suffering. It has been calculated that a group of 13 neglected infectious diseases affects over one billion people, corresponding to a sixth of the world's population. These diseases include infections with different types of worms and parasites, cholera, and sleeping sickness, and can cause significant mortality and severe disabilities in low-income countries. For most of these diseases, vaccines are either not available, poorly effective, or too expensive. Moreover, these neglected diseases often occur in individuals who are also affected by HIV/AIDS, malaria, or TB, making the problem even more serious and indicating that co-infections are the rule rather than the exception in many geographical areas. To address the importance of combating co-infections, scientists from 14 different countries in Africa and Europe met in Addis Ababa, Ethiopia, on September 9-11, 2007. The message coming from these scientists is that the only possibility for winning the fight against infections in low-income countries is by studying, in the most global way possible, the complex interaction between different infections and conditions of malnourishment. The new scientific and technical tools of the post-genomic era can allow us to reach this goal. However, a concomitant effort in improving education and social conditions will be needed to make the scientific findings effective.

The outcome of children with acute myeloid leukemia (AML) post-allogeneic stem cell transplantation (SCT) is not improved by the addition of etoposide to the conditioning regimen.

BACKGROUND: Relapse remains a concern for children with AML undergoing allogeneic SCT, so in an effort to reduce the risk of relapse in these patients, we intensified our pre-SCT preparation by adding etoposide to the standard busulfan and cyclophosphamide regimen. PROCEDURE: We retrospectively analyzed the collected data and compared the two groups; Group A (n = 18) included patients who received busulfan 16 mg/kg plus cyclophosphamide 200 mg/kg (Bu/Cy), and Group B (n = 48) included patients who received busulfan 12 mg/kg, cyclophosphamide 90 mg/kg in addition to etoposide 60 mg/kg (Bu/Cy/VP). The patients' characteristics were similar in the two groups. RESULTS: No significant difference in the overall outcome was noted; the 5-year overall survival was 50% and 53.3% for Groups A and B, respectively (P = 0.9). Similarly, the 5-year probability of relapse was 64.1% and 46.1% for Groups A and B, respectively (P = 0.38). The use of etoposide was not associated with increased toxicity. CONCLUSION: The addition of etoposide to the Bu/Cy regimen was well tolerated, but did not appear to improve the outcome.

In vivo switching between variant surface antigens in human Plasmodium falciparum infection.

A semi-immune individual was retrospectively found to have maintained an apparently monoclonal and genotypically stable asymptomatic infection for months after clinical cure of a Plasmodium falciparum malaria episode. Before the attack, the individual had no antibodies to variant surface antigens (VSAs) expressed by an isolate (isolate A) obtained at the time of the episode or by a genotypically identical isolate (isolate B) obtained from the same individual 3 months later. Six weeks after the attack, a strong isolate A-specific VSA antibody response had developed in the complete absence of isolate B-specific antibodies. In contrast, plasma obtained 7 months after the attack contained high levels of VSA antibodies recognizing both isolates. This is the first direct evidence of in vivo switching between VSAs in human P. falciparum infection. Our results suggest that VSA switching is an important survival strategy of P. falciparum, enabling the parasite to persist despite protective, parasite-specific immune responses.