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BACKGROUND: Substantial evidence indicates that cytophilic IgG responses to Plasmodium falciparum merozoite antigens play a role in protection from malaria. The specific targets mediating immunity remain unclear. Evaluating antibody responses in infants naturally-exposed to malaria will allow to better understand the establishment of anti-malarial immunity and to contribute to a vaccine development by identifying the most appropriate merozoite candidate antigens.METHODS: The study was based on parasitological and clinical active follow-up of infants from birth to 18 months of age conducted in the Tori Bossito area of southern Benin. For 399 infants, plasma levels of cytophilic IgG antibodies with specificity for five asexual stage malaria vaccine candidate antigens were determined by ELISA in infants' peripheral blood at 6, 9, 12 and 15 months of age. Multivariate mixed logistic model was used to investigate the association between antibody levels and anti-malarial protection in the trimester following the IgG quantification. Moreover, the concentrations of merozoite antigen-specific IgG were compared between a group of infants apparently able to control asymptomatic malaria infection (CAIG) and a group of infants with no control of malaria infection (Control group (NCIG)). Protective effect of antibodies was also assessed after 15 months of malaria exposure with a Cox regression model adjusted on environmental risk.RESULTS: Cytophilic IgG responses to AMA1, MSP1, MSP2-3D7, MSP2-FC27, MSP3 and GLURP R2 were associated with increasing malarial infection risk in univariate analysis. The multivariate mixed model showed that IgG1 and IgG3 to AMA1 were associated with an increased risk of malarial infection. However infants from CAIG (n = 53) had significantly higher AMA1-, MSP2-FC27-, MSP3-specific IgG1 and AMA1-, MSP1-, MSP2-FC27-, MSP3 and GLURP-R2-specific IgG3 than those from NCIG (n = 183). The latter IgG responses were not associated with protection against clinical malaria in the whole cohort when protective effect is assessed after 15 months of malaria exposition.CONCLUSION: In this cohort, merozoite antigen-specific cytophilic IgG levels represent a marker of malaria exposure in infants from 6 to 18 months of age. However, infants with resolution of asymptomatic infection (CAIG) seem to have acquired naturally immunity against P. falciparum. This observation is encouraging in the context of the development of multitarget P. falciparum vaccines.

Background Evaluation of local Plasmodium falciparum malaria transmission has been investigated previously using the reversible catalytic model based on prevalence of antibody responses to single antigen to estimate seroconversion rates. High correlations were observed between seroconversion rates and entomological inoculation rates (EIR). However, in this model, the effects of malaria control interventions and clinical episodes on serological measurements were not assessed. This study monitors the use of antibody responses to P. falciparum crude extracts for assessing malaria transmission, compares seroconversion rates estimated from longitudinal data to those derived from cross-sectional surveys and investigates the effects of malaria control interventions on these measures in an area of declining malaria transmission. In addition, the validity of this model was evaluated by comparison with the alternative model. Methods Five cross-sectional surveys were carried out at the end of the wet season in Dielmo, a malaria-endemic Senegalese rural area in 2000, 2002, 2008, 2010 and 2012. Antibodies against schizonts crude extract of a local P. falciparum strain adapted to culture (Pf 07/03) were measured by ELISA. Age-specific seroprevalence model was used both for cross-sectional surveys and longitudinal data (combined data of all surveys). Results A total of 1504 plasma samples obtained through several years follow-up of 350 subjects was used in this study. Seroconversion rates based on P. falciparum schizonts crude extract were estimated for each cross-sectional survey and were found strongly correlated with EIR. High variability between SCRs from cross-sectional and longitudinal surveys was observed. In longitudinal studies, the alternative catalytic reversible model adjusted better with serological data than the catalytic model. Clinical malaria attacks and malaria control interventions were found to have significant effect on seroconversion. Discussion The results of the study suggested that crude extract was a good serological tool that could be used to assess the level of malaria exposure in areas where malaria transmission is declining. However, additional parameters such as clinical malaria and malaria control interventions must be taken into account for determining serological measurements for more accuracy in transmission assessment. Electronic supplementary material The online version of this article (doi:10.1186/s12936-017-2052-0) contains supplementary material, which is available to authorized users.

Background The three members of the ring-infected erythrocyte surface antigen (RESA) proteins family share high sequence homologies, which impair the detection and assignment to one or another protein of some pathogenic processes inherent to Plasmodium falciparum malaria. The present study was intended to determine if the antibody and inflammatory responses of children living in a malaria-endemic area varied depending on the RESA-1, RESA-2 or RESA-3 proteins and the severity of the disease, two groups of severe and uncomplicated malaria cases being considered. Methods Two synthetic peptides representing predicted B cell epitopes were designed per RESA protein, all located outside of the 3′ and 5′ repetition blocks, in order to allow an antibody detection specific of each member of the family. Recombinant rRESA-1B and rRESA-3B proteins were also engineered. Two groups of Beninese children admitted to hospital in 2009 for either uncomplicated or severe malaria were compared for their plasma levels of IgG specifically recognizing each recombinant RESA protein or synthetic peptide, and for their plasma inflammatory cytokine levels (IFN-γ, TNF-α and IL-10), taking into account host and parasite genetic factors. Results The absence of IgG cross-reactivity between rRESA proteins and their protein carrier as well as between each RESA peptide and a non-epitopic RESA control peptide validated the use of the engineered recombinant proteins and peptides for the measurement of plasma IgG. Taking into account age, fever duration and parasitaemia, a multiple logistic regression performed on children clustered according to their antibody responses’ profiles concluded to an increased risk of severe malaria for P2 (representative of RESA-1) responders (P = 0.007). Increased IL-10 plasma levels were found in children harbouring multiclonal P. falciparum infections on the basis of the T1526G resa2 gene polymorphism (P = 0.004). Conclusions This study provided novel tools to dissect the seroreactivity against the three members of the RESA protein family and to describe its relation to protection against malaria. It suggested the measurement of plasma antibodies raised against specific peptides to serve as predictive immunologic markers for disease severity. Lastly, it reinforced previous observations linking the T1526G resa2 gene mutation to severe malaria. Electronic supplementary material The online version of this article (doi:10.1186/s12936-015-0799-8) contains supplementary material, which is available to authorized users.

BACKGROUND: The antenatal diagnosis of congenital toxoplasmosis rests in Tunisia on ultrasonography coupled with biological explorations. Among these explorations the search of Toxoplasma gondii by means of real time PCR in amniotic fluid is the examination of choice. AIM: We report the results of 33 parturients for which the biological examinations allowed to retain the notion of perigravidic or pergravidic toxoplasmic infection. METHODS: They were 13 patients having a seroconversion during the pregnancy, 19 having anti-toxoplasmic IgM with a low or intermediate index of avidity and a patient having presented a symptomatic anteconceptional primary infection. The ADN was extracted by means of the Kit (Qiagen). Genic amplification by PCR TaqMan targeted a portion of 71 pairs of bases of the B 1 gene. RESULTS: The PCR was positive among 9 patients (27.3%). They were a patient having presented a symptomatic toxoplasmosis during the pregnancy, 4 patients having consulted only in the 2nd quarter and for which the index of avidity was intermediate and 4 patients having presented seoconversions of 1st (n=1) of 2nd (n=2) or 3rd trimester. Among these patients, 2 had a medical interruption of pregnancy. The 7 others were put under pyrimethamine sulfadiazine. The neonatal assessment practised at 5 new-born babies was negative in all the cases. The PCR was negative for 24 patients. 18 pregnancies were followed. The neonatal serology was negative. The follow-up of 13 newborn child showed the disappearance of the antitoxoplasmic IgG between the 6th and 12th month.

International audience; Toxoplasma antibodies prevalence was studied in the north of Tunisia where a mild climate prevails. Two groups of individuals were investigated: 857 living in rural area and 564 living in urb town. Sera were analysed by ELISA and indirect immunofluorescence. The overall prevalence was 58.4%. It roses from 24.5% at ten years to 52.1% at 20 years of age. A maximum level, around 70%, was reached by about 30 years. The risk of acute infection after this age seemed low as judging by the proportion of high antibodies titers observed in this group (14.2% before 30 years vs 3.7% after). A significantly higher prevalence was detected in urban residents (67% vs 52.8%). In this group, the rate of seroconversion seems the highest between ten and 20 years of age and the majority of women are infected before reaching childbearing age. In the rural area, the seropositivity is lower between ten-20 years and many women at childbearing age still susceptible to toxoplasmosis. The risk of acute infection seems higher in the youngest ones as showed by the proportion of high antibodies titers observed in the 18-30 age group (9.2%) compared to the one observed after 30 years (1.9%).; La prévalence de la toxoplasmose a été étudiée dans le nord de la Tunisie chez 857 individus d'origine rurale et 564 individus d'origine urbaine. Les anticorps anti-toxoplasmiques ont été recherchés par immunofluorescence indirecte (IFI) et par ELISA. La prévalence de la toxoplasmose dans la population générale était de 58,4 %. Elle a significativement varié avec l'âge, passant de 24,5 % à dix ans à 52, I % à 20 ans, pour atteindre un maximum autour de 70 % vers l'âge de 30 ans. A partir de cet âge, les séroconversions semblent rares à en juger par la faible proportion des sérums à titres élevés en IFI (14,2 % avant 30 ans vs 3,7 % après 30 ans). La prévalence était significativement plus élevée en milieu urbain (67 % vs 52,8 %). Dans ce milieu, c'est entre dix et vingt ans, que les séroconversions semblent les plus fréquentes, la majorité des femmes étant alors immunisées à l'âge de la procréation. En milieu rural, l'immunisation, moins intense entre dix et 20 ans, fait que le nombre de femmes réceptives à la toxoplasmose à l'âge légal du mariage (18 ans) est plus important. Ce sont donc les femmes jeunes de ce milieu qui sont les plus exposées au risque d'infection toxoplasmique comme en témoigne la proportion élevée de sérum fortement positifs dans cette population (9,2 % pour les 18-30 ans vs 1,9 % pour les 30- 48 ans).

A serological survey on tropical theileriosis was conducted on sample of 54 farms in a region within the semi-arid bioclimatic zone of Tunisia. Screening of cattle sera at a dilution of 1/160 using the indirect immunofluorescent antibody test with the schizont antigen of Theileria annulata ,revealed the presence of animals with positive sera in 92.15% of the sampled farms. The exposure of calves to infection in the first season was shown to be significantly lower than in older cattle. Three endemic situations were identified based on the serological profiles of herds and the incidence and age distribution of disease cases. Endemic stability was obsered in farms showing a sero-prevalence of 100% in calves at first disease season. Low endemic instability was recognised by a sero-prevalence of 100% in cattle of four theileriosis seasons or more and by the incidence of the highest disease levels in cattle at their second and third theileriosis season. High endemic instability was identified on the basis of low-prevalencerates and the occurrence of the highest disease incidence in cattle at fourth theileriosis season or more.

International audience; The immunofluorescent antibody test (IFAT) using schizont and piroplasm antigens was compared with the microscopic examination of Giemsa-stained blood smears for the diagnosis of Theileria annulata infection in experimentally and naturally infected cattle. The results obtained on 100 naive cattle showed that non-specific fluorescence disappeared at serum dilution levels of 1/40 and 1/160 for the piroplasm and schizont antigens, respectively. These levels were therefore retained as the starting dilutions for this study. On day 30 post-infection, 16 experimentally infected calves were shown to be serologically positive for schizont and piroplasm IFAT, while 13 of them were positive for blood smears. A total of 109 cattle from an endemic region of tropical theileriosis were sampled before the onset of the disease season in April and later in September. Globally the IFAT results revealed more cattle exposed to T annulata infection than the blood smear examination. The piroplasm IFAT and the blood smears were less reliable than the schizont IFAT. The latter appeared to be the best test for detecting exposure to T annulata.; Résumé : Diagnostic de l’infection des bovins par Theileria annulata. Étude comparative de la sérologie et de l’examen de frottis sanguins. Le test d’immunofluorescence indirecte (7F/! utilisant l’antigène schizonte (IFI schizonte) et l’antigène piroplasme (IFI piroplasmes) a été comparé à l’examen microscopique de frottis sanguins pour le dépistage d’infections expérimentales et naturelles de bovins par Theileria annulata. Les résultats obtenus sur 100 bovins indemnes ont montré la disparition de la fluorescence non spécifique aux dilutions sérologiques de 1/40e et de 11160e respectivement pour l’IFI schizonte et l’IFI piroplasme. Ces dilutions ont de ce fait été retenues comme dilutions test pour le diagnostic sérologique. Un groupe de i6 veaux infectés expérimentalement ont tous présenté une sérologie positive au 30e jour de l’infection alors que seuls 13 d’entre eux ont montré un frottis sanguin positif. Des prélèvements obtenus avant et après la saison de theilériose sur un échantillon de i09 bovins en zone d’endémie de theilériose ont permis de constater que /’/FI était globalement plus sensible que l'examen de frottis de sang pour le dépistage à l'infection par T annulata. Par ailleurs l'IFI schizonte apparaît comme la technique de dépistage la plus fiable par comparaison à l'IFI piroplasme et au frottis de sang