title: Splenic architecture disruption and parasite-induced splenocyte activation and anergy in Plasmodium falciparum-infected Saimiri sciureus monkeys.
abstract: BACKGROUND
  The understanding of the mechanisms of immunity in malaria is crucial for the rational development of interventions such as vaccines. During blood stage infection, the spleen is considered to play critical roles in both immunity and immunopathology of Plasmodium falciparum infections.
  
  
  METHODS
  Saimiri sciureus monkeys were inoculated with blood stages of P. falciparum (FUP strain) and spleens removed during acute disease (days 7 and 13 of infection) and during convalescence (15 days after start of chloroquine treatment). Cytokine (IFNγ, TNFα, IL2, IL6, IL10, and IL12) responses of splenocytes stimulated with P. falciparum-parasitized red blood cells were assessed by real-time PCR using specific Saimiri primers, and histological changes were evaluated using haematoxylin-eosin and Giemsa-stained slides.
  
  
  RESULTS
  Early during infection (day 7, 1-2% parasitaemia), spleens showed disruption of germinal centre architecture with heavy B-cell activation (centroblasts), and splenocytes showed increased expression of IFNγ, IL6 and IL12 upon in vitro stimuli by P. falciparum-parasitized red blood cells (pRBC). Conversely, 15 days after treatment of blood stage infection with chloroquine, splenocytes showed spontaneous in vitro expression of TNFα, IL2, IL6, IL10, and IL12, but not IFNγ, and stimulation with P. falciparum pRBC blocked the expression of all these cytokines. During the acute phase of infection, splenic disarray with disorganized germinal centres was observed. During convalescence, spleens of the chloroquine-treated animals showed white pulp hyperplasia with extensive lymphocyte activation and persistency of heavily haemozoin-laden macrophages throughout the red pulp.
  
  
  CONCLUSIONS
  Inability to eliminate haemozoin is likely involved in the persistent lymphocyte activation and in the anergic responses of Saimiri splenocytes to P. falciparum pRBC, with important negative impact in immune responses and implications for the design of malaria vaccine.
authors.affiliation: Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz (IOC), Fiocruz, Rio de Janeiro, Brazil. falves@ufpa.br.|Laboratório de Imunobiologia, Universidade Federal do Pará (UFPA), Belém, Brazil. falves@ufpa.br.
authors.forename: Francisco A
authors.initials: FA
authors.lastname: Alves
authors.affiliation: Laboratório de Patologia, Instituto Oswaldo Cruz (IOC), Fiocruz, Rio de Janeiro, Brazil. mpelajo@ioc.fiocruz.br.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Pelajo-Machado
authors.affiliation: Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz (IOC), Fiocruz, Rio de Janeiro, Brazil. prtotino@ioc.fiocruz.br.
authors.forename: Paulo R R
authors.initials: PR
authors.lastname: Totino
authors.affiliation: Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz (IOC), Fiocruz, Rio de Janeiro, Brazil. marianats@gmail.com.
authors.forename: Mariana T
authors.initials: MT
authors.lastname: Souza
authors.affiliation: Laboratório de Tecnologia Biomolecular, Universidade Federal do Pará (UFPA), Belém, Brazil. ecostag@ufpa.br.
authors.forename: Evonnildo C
authors.initials: EC
authors.lastname: Gonçalves
authors.affiliation: Laboratório de Polimorfismo de DNA, Universidade Federal do Pará (UFPA), Belém, Brazil. Paula@ufpa.br.
authors.forename: Maria Paula C
authors.initials: MP
authors.lastname: Schneider
authors.affiliation: Centro Nacional de Primatas (Cenp), SVS, Belém, Brazil. japcmuniz@gmail.com.
authors.forename: José A P C
authors.initials: JA
authors.lastname: Muniz
authors.affiliation: Instituto Carlos Chagas de Biologia Molecular, Curitiba, Brazil. mkrieger@fiocruz.br.
authors.forename: Marco A
authors.initials: MA
authors.lastname: Krieger
authors.affiliation: Serviço de Criação de Primatas Não-Humanos, CECAL-Fiocruz, Rio de Janeiro, Brazil. m_mulatta@hotmail.com.
authors.forename: Marcia C R
authors.initials: MC
authors.lastname: Andrade
authors.affiliation: Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz (IOC), Fiocruz, Rio de Janeiro, Brazil. ctdr@uol.com.br.
authors.forename: Cláudio Tadeu
authors.initials: CT
authors.lastname: Daniel-Ribeiro
authors.affiliation: Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz (IOC), Fiocruz, Rio de Janeiro, Brazil. leojmc@ioc.fiocruz.br.
authors.forename: Leonardo J M
authors.initials: LJ
authors.lastname: Carvalho
mesh_terms: D000818:Animals; D016207:Cytokines / Q000235:genetics* / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D004195:Disease Models, Animal; D004912:Erythrocytes / Q000166:cytology / Q000469:parasitology*; D006801:Humans; D016778:Malaria, Falciparum / Q000469:parasitology / Q000473:pathology*; D018512:Parasitemia / Q000469:parasitology / Q000473:pathology; D010963:Plasmodium falciparum / Q000276:immunology*; D060888:Real-Time Polymerase Chain Reaction; D012453:Saimiri; D013154:Spleen / Q000469:parasitology* / Q000473:pathology
chemical_list: D016207:Cytokines; D017931:DNA Primers