Browsing by Author "Kariuki, Simon"

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    Innate immune activation restricts priming and protective efficacy of the radiation-attenuated PfSPZ malaria vaccine
    (American Society for Clinical Investigation, 2024-04-30) Senkpeil, Leetah; Bhardwaj, Jyoti; Little, Morgan R.; Holla, Prasida; Upadhye, Aditi; Fusco, Elizabeth M.; Swanson, Phillip A., II; Wiegand, Ryan E.; Macklin, Michael D.; Bi, Kevin; Flynn, Barbara J.; Yamamoto, Ayako; Gaskin, Erik L.; Sather, D. Noah; Oblak, Adrian L.; Simpson, Edward; Gao, Hongyu; Haining, W. Nicholas; Yates, Kathleen B.; Liu, Xiaowen; Murshedkar, Tooba; Richie, Thomas L.; Sim, B. Kim Lee; Otieno, Kephas; Kariuki, Simon; Xuei, Xiaoling; Liu, Yunlong; Polidoro, Rafael B.; Hoffman, Stephen L.; Oneko, Martina; Steinhardt, Laura C.; Schmidt, Nathan W.; Seder, Robert A.; Tran, Tuan M.; Medicine, School of Medicine
    A systems analysis was conducted to determine the potential molecular mechanisms underlying differential immunogenicity and protective efficacy results of a clinical trial of the radiation-attenuated whole-sporozoite PfSPZ vaccine in African infants. Innate immune activation and myeloid signatures at prevaccination baseline correlated with protection from P. falciparum parasitemia in placebo controls. These same signatures were associated with susceptibility to parasitemia among infants who received the highest and most protective PfSPZ vaccine dose. Machine learning identified spliceosome, proteosome, and resting DC signatures as prevaccination features predictive of protection after highest-dose PfSPZ vaccination, whereas baseline circumsporozoite protein-specific (CSP-specific) IgG predicted nonprotection. Prevaccination innate inflammatory and myeloid signatures were associated with higher sporozoite-specific IgG Ab response but undetectable PfSPZ-specific CD8+ T cell responses after vaccination. Consistent with these human data, innate stimulation in vivo conferred protection against infection by sporozoite injection in malaria-naive mice while diminishing the CD8+ T cell response to radiation-attenuated sporozoites. These data suggest a dichotomous role of innate stimulation for malaria protection and induction of protective immunity by whole-sporozoite malaria vaccines. The uncoupling of vaccine-induced protective immunity achieved by Abs from more protective CD8+ T cell responses suggests that PfSPZ vaccine efficacy in malaria-endemic settings may be constrained by opposing antigen presentation pathways.
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    Malaria Chemoprevention in the Postdischarge Management of Severe Anemia
    (Massachusetts Medical Society, 2020-12-03) Kwambai, Titus K.; Dhabangi, Aggrey; Idro, Richard; Opoka, Robert; Watson, Victoria; Kariuki, Simon; Onyango, Eric D.; Otieno, Kephas; Samuels, Aaron M.; Desai, Meghna R.; Boele van Hensbroek, Michael; Wang, Duolao; John, Chandy C.; Robberstad, Bjarne; Phiri, Kamija S.; Ter Kuile, Feiko O.; Pediatrics, School of Medicine
    BACKGROUND: Children who have been hospitalized with severe anemia in areas of Africa in which malaria is endemic have a high risk of readmission and death within 6 months after discharge. No prevention strategy specifically addresses this period. METHODS: We conducted a multicenter, two-group, randomized, placebo-controlled trial in nine hospitals in Kenya and Uganda to determine whether 3 months of malaria chemoprevention could reduce morbidity and mortality after hospital discharge in children younger than 5 years of age who had been admitted with severe anemia. All children received standard in-hospital care for severe anemia and a 3-day course of artemether-lumefantrine at discharge. Two weeks after discharge, children were randomly assigned to receive dihydroartemisinin-piperaquine (chemoprevention group) or placebo, administered as 3-day courses at 2, 6, and 10 weeks after discharge. Children were followed for 26 weeks after discharge. The primary outcome was one or more hospital readmissions for any reason or death from the time of randomization to 6 months after discharge. Conditional risk-set modeling for recurrent events was used to calculate hazard ratios with the use of the Prentice-Williams-Peterson total-time approach. RESULTS: From May 2016 through May 2018, a total of 1049 children underwent randomization; 524 were assigned to the chemoprevention group and 525 to the placebo group. From week 3 through week 26, a total of 184 events of readmission or death occurred in the chemoprevention group and 316 occurred in the placebo group (hazard ratio, 0.65; 95% confidence interval [CI], 0.54 to 0.78; P<0.001). The lower incidence of readmission or death in the chemoprevention group than in the placebo group was restricted to the intervention period (week 3 through week 14) (hazard ratio, 0.30; 95% CI, 0.22 to 0.42) and was not sustained after that time (week 15 through week 26) (hazard ratio, 1.13; 95% CI, 0.87 to 1.47). No serious adverse events were attributed to dihydroartemisinin-piperaquine. CONCLUSIONS: In areas with intense malaria transmission, 3 months of postdischarge malaria chemoprevention with monthly dihydroartemisinin-piperaquine in children who had recently received treatment for severe anemia prevented more deaths or readmissions for any reason after discharge than placebo. (Funded by the Research Council of Norway and the Centers for Disease Control and Prevention; ClinicalTrials.gov number, NCT02671175.).
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    Malaria chemoprevention with monthly dihydroartemisinin-piperaquine for the post-discharge management of severe anaemia in children aged less than 5 years in Uganda and Kenya: study protocol for a multi-centre, two-arm, randomised, placebo-controlled, superiority trial
    (BMC, 2018-11-06) Kwambai, Titus K.; Dhabangi, Aggrey; Idro, Richard; Opoka, Robert; Kariuki, Simon; Samuels, Aaron M.; Desai, Meghna; van Hensbroek, Michael Boele; John, Chandy C.; Robberstad, Bjarne; Wang, Duolao; Phiri, Kamija; Ter Kuile, Feiko O.; Pediatrics, School of Medicine
    BACKGROUND: Children hospitalised with severe anaemia in malaria endemic areas in Africa are at high risk of readmission or death within 6 months post-discharge. Currently, no strategy specifically addresses this period. In Malawi, 3 months of post-discharge malaria chemoprevention (PMC) with monthly treatment courses of artemether-lumefantrine given at discharge and at 1 and 2 months prevented 30% of all-cause readmissions by 6 months post-discharge. Another efficacy trial is needed before a policy of malaria chemoprevention can be considered for the post-discharge management of severe anaemia in children under 5 years of age living in malaria endemic areas. OBJECTIVE: We aim to determine if 3 months of PMC with monthly 3-day treatment courses of dihydroartemisinin-piperaquine is safe and superior to a single 3-day treatment course with artemether-lumefantrine provided as part of standard in-hospital care in reducing all-cause readmissions and deaths (composite primary endpoint) by 6 months in the post-discharge management of children less than 5 years of age admitted with severe anaemia of any or undetermined cause. METHODS/DESIGN: This is a multi-centre, two-arm, placebo-controlled, individually randomised trial in children under 5 years of age recently discharged following management for severe anaemia. Children in both arms will receive standard in-hospital care for severe anaemia and a 3-day course of artemether-lumefantrine at discharge. At 2 weeks after discharge, surviving children will be randomised to receive either 3-day courses of dihydroartemisinin-piperaquine at 2, 6 and 10 weeks or an identical placebo and followed for 26 weeks through passive case detection. The trial will be conducted in hospitals in malaria endemic areas in Kenya and Uganda. The study is designed to detect a 25% reduction in the incidence of all-cause readmissions or death (composite primary outcome) from 1152 to 864 per 1000 child years (power 80%, α = 0.05) and requires 520 children per arm (1040 total children). RESULTS: Participant recruitment started in May 2016 and is ongoing.