title: Plasmodium vivax sporozoite challenge in malaria-naïve and semi-immune Colombian volunteers.
abstract: BACKGROUND
  Significant progress has been recently achieved in the development of Plasmodium vivax challenge infections in humans, which are essential for vaccine and drug testing. With the goal of accelerating clinical development of malaria vaccines, the outcome of infections experimentally induced in naïve and semi-immune volunteers by infected mosquito bites was compared.
  
  
  METHODS
  Seven malaria-naïve and nine semi-immune Colombian adults (n = 16) were subjected to the bites of 2-4 P. vivax sporozoite-infected Anopheles mosquitoes. Parasitemia levels, malaria clinical manifestations, and immune responses were assessed and compared.
  
  
  RESULTS
  All volunteers developed infections as confirmed by microscopy and RT-qPCR. No significant difference in the pre-patent period (mean 12.5 and 12.8 days for malaria-naïve and malaria-exposed, respectively) was observed but naïve volunteers developed classical malaria signs and symptoms, while semi-immune volunteers displayed minor or no symptoms at the day of diagnosis. A malaria-naïve volunteer developed a transient low submicroscopic parasitemia that cured spontaneously. Infection induced an increase in specific antibody levels in both groups.
  
  
  CONCLUSIONS
  Sporozoite infectious challenge was safe and reproducible in semi-immune and naïve volunteers. This model will provide information for simultaneous comparison of the protective efficacy of P. vivax vaccines in naïve and semi-immune volunteers under controlled conditions and would accelerate P. vivax vaccine development.
  
  
  BACKGROUND
  clinicaltrials.gov NCT01585077.
authors: Malaria Vaccine and Drug Development Center (MVDC), Cali, Colombia; School of Health, Universidad del Valle, Cali, Colombia.
authors: Myriam
authors: M
authors: Arévalo-Herrera
authors: Malaria Vaccine and Drug Development Center (MVDC), Cali, Colombia; Caucaseco Scientific Research Center (CSRC), Cali, Colombia.
authors: David A
authors: DA
authors: Forero-Peña
authors: Malaria Vaccine and Drug Development Center (MVDC), Cali, Colombia; Caucaseco Scientific Research Center (CSRC), Cali, Colombia.
authors: Kelly
authors: K
authors: Rubiano
authors: Malaria Vaccine and Drug Development Center (MVDC), Cali, Colombia; Caucaseco Scientific Research Center (CSRC), Cali, Colombia.
authors: José
authors: J
authors: Gómez-Hincapie
authors: Malaria Vaccine and Drug Development Center (MVDC), Cali, Colombia; Caucaseco Scientific Research Center (CSRC), Cali, Colombia.
authors: Nora L
authors: NL
authors: Martínez
authors: Malaria Vaccine and Drug Development Center (MVDC), Cali, Colombia; Caucaseco Scientific Research Center (CSRC), Cali, Colombia.
authors: Mary
authors: M
authors: Lopez-Perez
authors: Malaria Vaccine and Drug Development Center (MVDC), Cali, Colombia; Caucaseco Scientific Research Center (CSRC), Cali, Colombia.
authors: Angélica
authors: A
authors: Castellanos
authors: Malaria Vaccine and Drug Development Center (MVDC), Cali, Colombia; School of Health, Universidad del Valle, Cali, Colombia; Caucaseco Scientific Research Center (CSRC), Cali, Colombia.
authors: Nora
authors: N
authors: Céspedes
authors: Meridional R&D, São Paulo, Brazil.
authors: Ricardo
authors: R
authors: Palacios
authors: Centro Médico Imbanaco, Cali, Colombia.
authors: José Millán
authors: JM
authors: Oñate
authors: Malaria Vaccine and Drug Development Center (MVDC), Cali, Colombia; Caucaseco Scientific Research Center (CSRC), Cali, Colombia.
authors: Sócrates
authors: S
authors: Herrera
mesh_terms: D000328:Adult; D000818:Animals; D000852:Anopheles / Q000469:parasitology; D003105:Colombia; D005260:Female; D006801:Humans; D055256:Infectious Disease Incubation Period; D008288:Malaria / Q000276:immunology*; D017780:Malaria Vaccines; D008297:Male; D018512:Parasitemia; D010966:Plasmodium vivax / Q000276:immunology*; D013997:Time Factors
chemical_list: D017780:Malaria Vaccines