Abstract
Lymphatic filariasis is a complex parasitic disease having a spectrum of clinical parameters which are critical in deciding the severity of the pathogenesis. Individuals residing in the endemic areas are categorized into different clinical groups such as: EC (endemic controls-free of disease and infection), AS (asymptomatic carriers- free of disease but carries both antigens and microfilaria (Mf) in circulation), CR (cryptic-free of disease and Mf but having circulatory antigen) and CH (chronic-having manifestations of elephantiasis and hydrocele). The immune response to the parasitic infection is well studied, whereas the protective mechanism explaining the fate of antigenemia and filaremia between AS and CR group remains unexplained. Increased anti-Mf antibodies have been implicated for Mf clearance in experimental infection models whereas its role in clinical filariasis is not known. Here, we followed up two groups of 24 and 33 CR cases for 18 and 36 months respectively and analyzed both the clinical parameters and the anti-filarial antibody response. The humoral response to both whole filarial antigen and Mf antigens as well as recombinant active parasitic antigens was significantly higher in CR cases than AS individuals, whereas the clinical parameters remain unchanged. This study made insights into the protective immune mechanism responsible for the clearance of Mf from circulation in CR individuals.
Highlights
Lymphatic filariasis (LF) caused by Wuchereria bancrofti is a major public health problem contributing to about 90% of the 120 million people affected across the globe [1,2,3]
There was no significant change in clinical manifestations, Mf status (Table 1) and Circulating filarial antigen (CFA) density (Fig 1) after the time period
Release of the bacterial endosymbiont Wolbachia and intensity of the host response have been implicated for the degree of filarial infection whereas precise mechanism responsible for parasite clearance and clinical manifestations between CR and AS group remains a matter of intense debate [18,19,20,21,22]
Summary
Lymphatic filariasis (LF) caused by Wuchereria bancrofti is a major public health problem contributing to about 90% of the 120 million people affected across the globe [1,2,3]. In India, 23 states /UTs are known to be endemic to LF and 553 million people are at risk of infection with 31 million parasite carriers and 23 million with symptomatic filariasis [4]. Clinical manifestations such as lymphedema, elephantiasis and/or hydrocele are associated with this disease. Presence of Mf and filarial antigen in circulation, people residing in endemic areas have been classified into different clinical categories, such as: EC (endemic control -free of disease and infection), AS (asymptomatic carriers- free of disease but having antigens and microfilaremia in circulation) and CR (free of disease, free of Mf but having circulatory filarial antigen, CFA) and CH (disease with CFA) [5].
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