Strain specific protective immunity induced by pre-erythrocytic infection of toque monkeys with Plasmodium cynomolg

Abstract

Strain specific protective immunity (SSPI) was investigated using two strains of Plasmodium cynomolgi, Pc746 and PcCeylon, in toque monkey. Two groups of monkeys were immunized against either Pc746 (n=5) or PcCeylon (n=4), by giving bites with 2-4 sporozoiteinfected Anopheles tessellates mosquitoes per monkey. Primary blood infection was prevented by simultaneous chloroquine cover and secondary, hypnozoite-induced, blood infection was prevented by treating the monkeys one month later with primaquine. The two immunized groups and a group of unimmunized monkeys (n=4) were given a mixed-strain sporozoite challenge infection, 140 and 100 days respectively after immunization. Parasite DNA was collected for 5-8 consecutive days after parasitaemia reached 0.05% or above. The proportions of the two parasite strains in these samples were quantified using a Pyrosequencing TM assay based on SNPs in MSP1 and CSP genes. In subsequent blood infections in immunized monkeys the earliest recorded proportion of parasites of an immunizing strain was significantly lower than its proportion in monkeys immunized against a heterologous strain (P=0.014 and 0.027 for the two SNPs) and the proportions of an immunizing strain tended to decline during the period of sample collection. These results show that a parasite strain specific protective immunity to P. cynomolgi was indcued following a sporozoite induced pre-erythrocytic infection. This immunity may have been directed against the liver stages or against the blood stage parasites, or against both Acknowledgements

Baseline results of the first malaria indicator survey in Iran at the health facility level

“…Furthermore, data suggests striking differences in time interval between onset of symptoms and lab diagnosis/treatment of malaria patients across three surveyed provinces, which is consistent with the previous studies [11-15,19-21]. Interestingly, individuals in urban areas were more likely than those in rural areas to receive anti-malarial drugs or receive treatment promptly amongst the prior studies [11-15,19-21].…”

“…Interestingly, individuals in urban areas were more likely than those in rural areas to receive anti-malarial drugs or receive treatment promptly amongst the prior studies [11-15,19-21]. In contrast, malaria patients both uncomplicated and severe cases in rural areas were more likely to receive medical attention and take an anti-malarial drug within 24 to 48 hours of disease onset in the current study.…”

“…However, treatment was sought within 24 to 48 hours for two-third of uncomplicated and half of severe malaria cases which is far from the 80% target set by the RBM Partnership for 2010. Available documents from other parts of the world [11-15,19-21], with an exception for Morogoro Region (82.7%), have also shown that the proportion of patients receiving an appropriate anti-malarial timely and correctly-dosed were low and too far from the RBM targets for 2010.…”

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“…The survey questionnaires were both based on the MIS Household Questionnaire modified for the local conditions to include socio-economic factors [36] as has been described previously [37]. The questionnaire was translated and conducted in Amharic language and pilot-tested in a non-survey cluster to determine the validity of the pre-coded answers.…”

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“…Since then LLIN have become the recommended approach for malaria prevention with mosquito nets [4] and in some countries the proportion of all nets that are LLIN is already exceeding 90% [5]. …”