Interferon-γresponses toPlasmodium falciparumvaccine candidate antigens decrease in the absence of malaria transmission

Abstract

BackgroundMalaria elimination campaigns are planned or active in many countries. The effects of malaria elimination on immune responses such as antigen-specific IFN- γ responses are not well characterized.MethodsIFN- γ responses to the P. falciparum antigens circumsporozoite protein, liver stage antigen-1, thrombospondin-related adhesive protein, apical membrane antigen-1, MB2, and merozoite surface protein-1 were tested by ELISA in 243 individuals in highland Kenya in April 2008, October 2008, and April 2009, after a one-year period of interrupted malaria transmission from April 2007 to March 2008.ResultsWhile one individual (0.4%) tested positive for P. falciparum by PCR inOctober 2008 and another two (0.9%) tested positive in April 2009, no clinical malaria cases were detected during weekly visits. Levels of IFN-γ to all antigens decreased significantly from April 2008 to April 2009 (all P < 0.001).DiscussionNaturally acquired IFN- γ responses to P. falciparum antigensare short-lived in the absence of repeated P. falciparum infection. Even short periods of malaria interruption may significantly decrease IFN-γ responses to P. falciparum antigens.

Transdermal Immunization of Elastic Liposome-Laden Recombinant Chimeric Fusion Protein of P. falciparum (PfMSP-Fu24) Mounts Protective Immune Response

“…Recent studies, as earlier [ 73 , 74 ], has confirmed the requirement of IFN-γ responses to several pre-erythrocytic and blood-stage P. falciparum vaccine candidates as decrease was seen in the absence of malaria transmission. Therefore, human malaria infection is associated with protection rendered by IFN-γ [ 75 ]. Present study demonstrates that suppressed levels of protein level of endogenous IL4 allowed the higher production of IFN- γ .…”

Immunosuppression in Malaria: Do Plasmodium falciparum Parasites Hijack the Host?

“…Tolerance to malaria was observed to be a feature to inhabitants of Pf endemic areas and not only dependent on ethnicity [20,34]. This tolerance disappears without exposure to the parasite, which results in an overactivated immune system, symptomatology and complications upon new infections [20,[35][36][37]. Moreover, as seen during several studies, children and adults whose exposure to malaria is severely reduced by relocation to a geographical area with no or very low endemicity or by chemoprophylaxis, responded better to specific antigens, resolving in better maintenance and prolonged immune memory response, than those under constant exposure to the parasite [34,38,39].…”

Interferon-γ and Interleukin-10 Responses during Clinical Malaria Episodes in Infants Aged 0–2 Years Prenatally Exposed to Plasmodium falciparum: Tanzanian Birth Cohort

“…This suggests that in utero exposure to P. falciparum may modulate the development of fetal protective immune cells culminating into disruption in the balancing of T helper 1 (Th1) and T helper 2 (Th2) immune responses as reported elsewhere [ 8 ]. Interferon- γ (IFN- γ ) is a Th1 proinflammatory cytokine that has been demonstrated to have antiparasitic effect [ 9 , 10 ], while IL-10 is a Th2 cytokine that has been demonstrated to be an important immunoregulatory anti-inflammatory cytokine [ 11 ]. Although a number of studies have been carried out to explain the phenomenon of prenatal exposure to the parasite antigen and its subsequent effect on the development of protective immune responses, the findings remain inconclusive.…”