Skin-draining lymph node priming is sufficient to induce sterile immunity against pre-erythrocytic malaria.
Bottom Line: However, it has recently been demonstrated that priming also occurs in the skin.We wished to establish if sterile protection could be obtained in the absence of priming by infected hepatocytes.We then compared and contrasted the patterns of priming with those obtained by intradermal immunization, where priming occurs in the liver.
Affiliation: Inserm, UMR-S 945, Paris, France. firstname.lastname@example.orgShow MeSH
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Mentions: In order to provide unequivocal evidence that the priming leading to sterile protection can be solely due to antigens present in the immunizing sporozoite, in vitro-generated DC were co-cultured with γ-spz for 90 min, after which the CD11c+-DC were FACS sorted and injected into recipient naïve mice. One week later, the recipient mice were challenged with 5 × 103 PyWT i.v. None of the recipient mice developed a blood stage infection, i.e. the transfer of CD11c+-DC primed with γ-spz was sufficient to confer sterile protection against a sporozoite challenge (Fig 4A). Given the observations on extra-hepatic development of exo-erythrocytic forms (EEFs), we analysed the presence of EEFs in DC by a double immunofluorescence staining with anti-CSP and anti-HSP70 (two parasites markers). None were detected in the purified DC co-cultured with γ-spz that were maintained for 0, 24 or 48 h (Fig 4B). Additional confirmation was obtained by RT-nPCR assays on samples collected at the same time intervals, which also proved negative (Fig 4C). In order to demonstrate that the γ-spz batch employed in these experiments was capable of developing into EEFs, the co-culture and incubations were conducted in parallel using primary mouse hepatocytes (Fig 4B) or HepG2-A16-CD81 cells (Fig 4C). These were invaded by γ-spz, which then developed into recognizable and PCR-detectable EEFs (Fig 4B and C). Finally, when DC incubated with PyWT sporozoites were FACS-purified and inoculated into mice, these did not develop a blood stage parasitemia, demonstrating that viable sporozoites are unlikely to be retained with the FACS-purified DC.
Affiliation: Inserm, UMR-S 945, Paris, France. email@example.com