Abstract
New tools are required to expedite the development of an effective vaccine against the blood-stage infection with the human malaria parasite Plasmodium falciparum. This work describes the assessment of the ADRB assay in a mouse model, characterizing the functional interaction between antimalarial serum antibodies and FcRs upon neutrophils. We describe a reproducible, antigen-specific assay, dependent on functional FcR signaling, and show that ADRB activity is induced equally by IgG1 and IgG2a isotypes and is modulated by blocking FcR function. However, following immunization of mice with the blood-stage vaccine candidate antigen MSP142, no measurable ADRB activity was induced against PEMS and neither was vaccine efficacy modulated against Plasmodium yoelii blood-stage challenge in γ(-/-) mice compared with WT mice. In contrast, following a primary, nonlethal P. yoelii parasite challenge, serum from vaccinated mice and nonimmunized controls showed anti-PEMS ADRB activity. Upon secondary challenge, nonimmunized γ(-/-) mice showed a reduced ability to control blood-stage parasitemia compared with immunized γ(-/-) mice; however, WT mice, depleted of their neutrophils, did not lose their ability to control infection. Thus, whereas neutrophil-induced ADRB against PEMS does not appear to play a role in protection against P. yoelii rodent malaria, induction of ADRB activity after challenge suggests that antigen targets of anti-PEMS ADRB activity remain to be established, as well as further supporting the observation that ADRB activity to P. falciparum arises following repeated natural exposure.
Highlights
Throughout the 20th century, vaccination has proved to be the most successful and cost-effective strategy for fighting disease; highly efficacious vaccines against major global health threats, such as malaria, remain elusive [1]
Neutrophil respiratory burst activity (NADPH oxidase activation), induced by mouse sera, was assessed initially using neutrophils enriched from mouse bone marrow and recombinant protein coated onto a plate, according to published methodologies [19, 43]
Sera from BALB/c mice, immunized with Ad-M PfMSP1, were used, which were known to be reactive against PfMSP119-GST protein [29]
Summary
Throughout the 20th century, vaccination has proved to be the most successful and cost-effective strategy for fighting disease; highly efficacious vaccines against major global health threats, such as malaria, remain elusive [1]. Subunit vaccines against the blood stage of the malaria lifecycle, whereby the parasite undergoes multiple rounds of invasion into the host’s erythrocytes, followed by asexual replication, have been a significant focus of preclinical vaccine-development efforts. The vast majority of work has focused on two candidate antigens from the invasive Mz form of the parasite: MSP1 and AMA1; the progression of these candidates into clinical trials has provided largely disappointing. Facultad de Ciencias Químicas, Universidad Autónoma de Chihuahua, Chihuahua, México.
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