Immunology

Biography

Biography: Makhtar Niang

Abstract

Introduction: A better understanding of the impacts of malaria control interventions on Anopheles mosquito vector and Plasmodium falciparum parasite populations, acquired immunity, and burden of the disease, is needed to guide malaria elimination strategies. Therefore the impacts of implemented strategies need to be monitored overtime to anticipate the consequences of changing malaria epidemiology. To gain insights on the impact of malaria control interventions on anti-malarial antibodies responses, we closely investigated the dynamics of IgG antibodies responses to P. falciparum antigens in relation to decrease malaria transmission resulting from successful control interventions in a West African setting. Methods: A total of 1235 sera obtained in 2000 (n=218), 2002 (n=186), 2008 (n=269), 2010 (n=288) and 2012 (n=274) from inhabitants of Dielmo (Senegal) aged 3.4 to 90.9 years old were tested by ELISA to investigate the prevalence and magnitude of antibody responses to crude schizont extracts obtained from a locally adapted P. falciparum strain (Pf0703). The threshold for positivity was defined as an OD ratio >2. Statistical analyses were performed using R software and threshold of significance was set at 0.05 Results: The prevalence of anti-sch0703 antibodies progressively decreased from 97.25% in 2000 to 57.3% in 2012. When categorized between various age groups, the seroprevalence increased significantly (P<0.5) with age from 47.19% in children <7 years old to 89.45% in >=15 years old. The seroprevalence within age groups through the different periods significantly dropped after the implementation of insecticides nets in 2008. Similarly, the magnitude of IgG antibody responses in positive responders decreased progressively from 2000 to 2012 despite limited variation in the different age groups. Mean levels of IgG antibodies fluctuated from 2002 to 2012 indicating a moderate to no relationship between the magnitude of IgG antibodies responses and malaria interventions. Discussion and conclusion: While the data suggest that all implemented control strategies (rapid diagnostic test, ACT treatment and LLINs use) contributed to the decrease of immune responses to P. falciparum antigens, the role of LLINS was the most pronounced as revealed by the significant decline in seroprevalence and magnitude of antibodies responses observed after 2008. Implementation of LLINS was reported associated with a substantial reduction of Anopheles mosquitos and a decreased of the entomological inoculation rates to its lowest value in 2012 when parasite carriage almost disappeared in Dielmo villagers. The rapid decrease of protective immunity allows new infections to be rapidly detected and treated, but also favors the re-establishment of human-vector contacts contributed in boosting immune responses to P. falciparum malaria antigens.