Naturally Acquired Immunity and Reduced Susceptibility to falciparum Malaria in Two Subpopulations of Endemic Eastern India

Abstract

This study was aimed to assess the prevalence of naturally acquired humoral immune responses and their association with reduced susceptibility to malaria in children and adults with differential clinical conditions from an Indian zone where malaria is endemic. The study was undertaken in an eastern province of India (Keonjhar, Orissa) in a group of 341 children (both younger and older) and 98 adults living in two different areas, Town area and Forest area. They were studied for their parasitological and immunological profiles. Sera from different age‐matched groups were screened by ELISA to measure IgG reactivities for characterizing humoral immune responses to the B‐cell epitopes of Plasmodium falciparum MSP1, AMA1, RAP1 and EBA175 peptides and P. falciparum‐infected erythrocyte lysate. In Town area, overall P. falciparum cases were 5.5%, whereas those in Forest area were 26.7%. We observed an age‐wise increasing trend of immunity in these two populations. It was also noticed that the frequency of responders to stage‐specific antigens was higher in individuals from the Town area where the frequency of malaria was lower. The naturally acquired humoral immune responses to different stage‐specific antigens of P. falciparum reflect the reduced risk of malaria in the study groups. The higher frequency of seroresponders showed correlation with lower risk of developing malaria.

Comparison of Biological Activity of Human Anti-Apical Membrane Antigen-1 Antibodies Induced by Natural Infection and Vaccination

“…The higher growth-inhibitory activity of the Malian total IgG is likely due to anti-malarial antibodies with specificities other than AMA1. The data suggest that Malians with high levels of anti-AMA1 antibodies are likely to have high levels of antibodies to other malarial antigens, as has been reported in other epidemiological studies (30, 31), and as a consequence, the total IgG with higher anti-AMA1 ELISA units showed higher growth-inhibitory activity in vitro.…”

Microsatellite analysis of chloroquine resistance associated alleles and neutral loci reveal genetic structure of Indian Plasmodium falciparum

“…For example, the presence of local parasite population structure has been suggested to be a factor of exposure-related immunity, identifiable through seroprevalence frequencies to various P. falciparum surface antigens. However, the evidence for this remains somewhat controversial, as populations located in close proximity were reported to be more related (Biswas et al, 2008), in contrast identical genetic structures were also found between two distant localities ( i.e ., eastern and northeastern India) (Joshi et al, 2007). Previous work has shown an association between genetic diversity of the pfcrt -haplotypes and variable transmission intensities throughout India (Mallick et al, 2012).…”

Joint modelling of time-to-clinical malaria and parasite count in a cohort in an endemic area

“…Children aged up to 15 years had higher risk for clinical malaria disease when compared to adults over 15 years. The higher risk of experiencing a clinical malaria episode among children is possibly be due to the naturally under-developed humoral immune responses to different stage-specific antigens of P. Falciparum otherwise acquired with age [29]. In this study in an endemic area, high cumulative parasite count was associated with lower risk of getting a new clinical malaria episode suggesting that increased exposure to malaria parasites with time may result into protective effect to future clinical malaria episodes.…”