Cytotoxic Markers Associate With Protection Against Malaria in Human Volunteers Immunized With Plasmodium falciparum Sporozoites

• Published in: The Journal of infectious diseases Vol. 210; no. 10; pp. 1605 - 1615
• Main Authors: Bijker, Else M., Teirlinck, Anne C., Schats, Remko, van Gemert, Geert-Jan, van de Vegte-Bolmer, Marga, van Lieshout, Lisette, IntHout, Joanna, Hermsen, Cornelus C., Scholzen, Anja, Visser, Leo G., Sauerwein, Robert W.
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 15.11.2014
• Subjects: Adolescent; Adult; Biological and medical sciences; Biomarkers; Bites and stings; CD4-Positive T-Lymphocytes - immunology; CD8-Positive T-Lymphocytes - immunology; Female; Flow Cytometry; Fundamental and applied biological sciences. Psychology; Healthy Volunteers; Hepatocytes; Human protozoal diseases; Humans; Immunization; Infections; Infectious diseases; Leukocytes, Mononuclear - immunology; Life cycle. Host-agent relationship. Pathogenesis; Major and Brief Reports; Malaria; Malaria vaccines; Malaria Vaccines - administration & dosage; Malaria Vaccines - immunology; Malaria, Falciparum - immunology; Malaria, Falciparum - prevention & control; Male; Medical sciences; Microbiology; Parasites; Parasitic diseases; Plasmodium falciparum; Plasmodium falciparum - immunology; Protozoa; Protozoal diseases; Sporozoites; Sporozoites - immunology; T lymphocytes; T-Lymphocytes, Cytotoxic - immunology; Treatment Outcome; Volunteerism; Young Adult; Human; Infection; Protozoa; Plasmodium falciparum; Apicomplexa; Protozoal disease; Immunization; Malaria; Parasitosis; chloroquine; Plasmodium; granzyme B; immunization; protection; degranulation; immunity; T cells; malaria; cytotoxicity
• ISSN: 0022-1899; 1537-6613; 1537-6613
• DOI: 10.1093/infdis/jiu293

Background. Immunization of healthy volunteers by bites from Plasmodium falciparum-infected mosquitoes during chloroquine chemoprophylaxis (hereafter, chemoprophylaxis and sporozoites [CPS] immunization) induces sterile protection against malaria. CPS-induced protection is mediated by immunity against pre-erythrocytic stages, presumably at least partially by cytotoxic cellular responses. We therefore aimed to investigate the association of CPS-induced cytotoxic T-cell markers with protection. Methods. In a double-blind randomized controlled trial, we performed dose titration of CPS immunization followed by homologous challenge infection in 29 subjects. Immune responses were assessed by in vitro restimulation of peripheral blood mononuclear cells and flow cytometry. Results. Dose-dependent complete protection was obtained in 4 of 5 volunteers after immunization with bites from 45 P. falciparum-infected mosquitoes, in 8 of 9 volunteers with bites from 30, and in 5 of 10 volunteers with bites from 15 (odds ratio [OR], 5.0; 95% confidence interval [CI], 1.5-17). Completely protected subjects had significantly higher proportions of CD4 T cells expressing the degranulation marker CD107a (OR, 8.4; 95% CI, 1.5-123; P = .011) and CD8 cells producing granzyme B (OR, 11; 95% CI, 1.9-212; P = .004) after P. falciparum restimulation. Conclusions. These data underline the efficiency of CPS immunization to induce sterile protection and support a possible role for cytotoxic CD4 and CD8 T-cell responses in pre-erythrocytic immunity. Clinical Trials Registration. NCT01218893.