Development of an Antigen Detection ELISA for Bancroftian Filariasis Using Bm SXP-Specific Recombinant Monoclonal Antibody

Abstract

Lymphatic filariasis is a mosquito-borne parasitic disease responsible for morbidity and disability that affects 1.2 billion people worldwide, mainly the poor communities. Currently, filarial antigen testing is the method of choice for the detection of bancroftian filariasis, and to date, there are two commonly used tests. In the present study, a recently reported recombinant monoclonal antibody (5B) specific to BmSXP filarial antigen was used in developing an ELISA for the detection of circulating filarial antigen in sera of patients with bancroftian filariasis. The performance of the ELISA was evaluated using 124 serum samples. The ELISA was positive with all sera from microfilaremic bancroftian filariasis patients (n = 34). It also showed 100% diagnostic specificity when tested with sera from 50 healthy individuals and 40 patients with other parasitic diseases. The developed assay using the novel 5B recombinant monoclonal antibody could potentially be a promising alternative antigen detection test for bancroftian filariasis.

Figure 1.

Western blot of the BmSXP recombinant antigen probed with the anti-BmSXP IgG polyclonal antibody. Arrow indicates the size of the BmSXP recombinant antigen at ∼22 kDa. This figure appears in color at www.ajtmh.org.

Figure 2.

Verification of the 5B monoclonal antibody conjugated with horseradish peroxidase (HRP). (A) SDS PAGE profile of the 5B monoclonal antibody protein and BmSXP antigen. (B) Western blot analysis of the BmSXP antigen probed with 5B-HRP. Arrow indicates the size of BmSXP recombinant antigen at ∼22 kDa. This figure appears in color at www.ajtmh.org.

Figure 3.

Receiver operating characteristic curve from analysis of results from 75 serum samples tested with the newly developed antigen detection 5B-ELISA. This figure appears in color at www.ajtmh.org.

Figure 4.

Distribution of the optical density readings of human serum samples tested using the antigen detection 5B-ELISA. The cutoff value of 0.309 is indicated as a line on the graph. This figure appears in color at www.ajtmh.org.

Figure 5.

ELISA results using spiked dried blood samples. The cutoff optical density (OD) value of 0.309 is indicated as a line on the graph. For each sample, the percentage reductions in OD values of serum compared with eluted blood spots were TP3 (49%), W170 (24%), W10 (44%), 15 (29%), and W61 (20%).