Comparative antibody responses against three antimalarial vaccine candidate antigens from urban and rural exposed individuals in Gabon

Abstract

The analysis of immune responses in diverse malaria endemic regions provides more information to understand the host’s immune response to Plasmodium falciparum. Several plasmodial antigens have been reported as targets of human immunity. PfAMA1 is one of most studied vaccine candidates; PfRH5 and Pf113 are new promising vaccine candidates. The aim of this study was to evaluate humoral response against these three antigens among children of Lastourville (rural area) and Franceville (urban area). Malaria was diagnosed using rapid diagnosis tests. Plasma samples were tested against these antigens by enzyme-linked immunosorbent assay (ELISA). We found that malaria prevalence was five times higher in the rural area than in the urban area (p < 0.0001). The anti-PfAMA1 and PfRh5 response levels were significantly higher in Lastourville than in Franceville (p < 0.0001; p = 0.005). The anti-AMA1 response was higher than the anti-Pf113 response, which in turn was higher than the anti-PfRh5 response in both sites. Anti-PfAMA1 levels were significantly higher in infected children than those in uninfected children (p = 0.001) in Franceville. Anti-Pf113 and anti-PfRh5 antibody levels were lowest in children presenting severe malarial anemia. These three antigens are targets of immunity in Gabon. Further studies on the role of Pf113 in antimalarial protection against severe anemia are needed.

Factors That Influence the Immune Response to Vaccination

“…Rural versus urban environment. Children living in rural areas have higher antibody responses to tetanus (351) and an experimental malaria vaccine (485,486). They have a Th1-skewed response (IL-5 production) to tetanus and TIV vaccination, while children living in semiurban areas have a Th2-skewed response (IFN-␥ production) (351,487).…”

IgG antibody response against Plasmodium falciparum aminopeptidase 1 antigen in Gabonese children living in Makokou and Franceville

“…Our previous studies, comparing the humoral response against plasmodial antigens among Gabonese children from urban and rural areas, support this idea by revealing high levels of immunoglobulin (Ig)G antibodies against Pf113 antigen in children from rural areas and more exposed to plasmodial infection. . Unlike IgG, IgM responses are not influenced by either clinical or parasitological status in malaria in Gabonese children .…”

High level of specific anti-plasmodium falciparum merozoite IgG1 antibodies in rural asymptomatic individuals of dienga, south-eastern Gabon

“…All of these peptides were diluted in 1× PBS buffer pH 7.4. A 2000-fold diluted mouse anti-human IgG (Fc specific) conjugated to peroxidase (Sigma, St. Louis, MO, USA) was used, and bound enzyme was detected with tetra methyl benzidine (TMB) substrate (Prod Thermo-Scientific, USA); the absorbance was read at 405 nm as previously described [ 34 , 38 ].…”

“…Bound enzyme was detected as described above. Reference positive (a pool+ of 10 plasmas from infected individuals with at least 40,000 parasites/µl of blood of each subject) and negative (a pool– of 10 plasmas from Caucasian individuals, all negative for Plasmodium infection) control plasmas were included in each plate, and results were expressed in arbitrary units as previously described (AU) [ 27 , 34 , 35 , 38 ].…”

“…Gabon, in Central Africa, is an area of high malaria transmission and one of the seven sub-Saharan countries where the third trial phase on the most advanced vaccine candidate RTS,S/AS01 was carried out [ 33 ]. However, only one study on humoral responses to PfRH5, Pf113, and PfAMA1 antigens has been conducted in the country [ 34 ].…”