Immunodiagnostic Properties of Wucheraria bancrofti SXP-1, a Potential Filarial Diagnostic Candidate Expressed in Tobacco Plant, Nicotiana tabacum

Molecular Farming Strategy for the Rapid Production of Protein-Based Reagents for Use in Infectious Disease Diagnostics

Recombinant proteins are a major breakthrough in biomedical research with a wide range of applications from diagnostics to therapeutics. Strategic construct design, consistent expression platforms, and suitable upstream and downstream techniques are key considerations to produce commercially viable recombinant proteins. The recombinant antigenic protein production for use either as a diagnostic reagent or subunit vaccine formulation is usually carried out in prokaryotic or eukaryotic expression platforms. Microbial and mammalian systems dominate the biopharmaceutical industry for such applications. However, there is no universal expression system that can meet all the requirements for different types of proteins. The adoptability of any expression system is likely based on the quality and quantity of the proteins that can be produced from it. The huge demand of recombinant proteins for different applications requires an inexpensive production platform for rapid development. The molecular farming scientific community has been promoting the plant system for nearly 3 decades as a cost-effective alternative to produce high-quality proteins for research, diagnostic, and therapeutic applications. Here, we discuss how plant biotechnology could offer solutions for the rapid and scalable production of protein antigens as low-cost diagnostic reagents for use in functional assays.

Immunodiagnostic potential of Wuchereria bancrofti L1 antigen-based filarial immunoglobulin G4 detection assay

Background

After mass drug administration to eliminate human lymphatic filariasis, there is a need for surveillance to detect the measurable endpoint of the program.

Methods

An immunodominant seroreactive clone, WbL1, was identified through immunoscreening of a Wuchereria bancrofti L3 complementary DNA expression library. Recombinant WbL1 (rWbL1) was analysed with sera from W. bancrofti patients. Diagnostic evaluation was carried out by developing an enzyme-linked immunosorbent assay (ELISA) to detect the filarial-specific antibodies in various categories of filarial sera samples against recombinant WbL1 (rWbL1) protein.

Results

Performance parameters of the test in terms of immunoglobulin G (IgG) and IgG4 detection displayed significant sensitivity and specificity values up to 77% and 100%, respectively. Our results showed filarial antibodies against rWbL1 to be highly reactive with microfilaremic and clinical filarial sera samples compared with the endemic and non-endemic control sera samples. Reasonably satisfactory performance of the test was also confirmed from the multicentric evaluation of an anti-WbL1 IgG4 detection ELISA. This test was found to be minimally reactive with other nematode parasites and protozoan infections.

Conclusions

The anti-WbL1 IgG4 detection test can be considered as a field test for initial screening and epidemiological monitoring of filarial infections in filariasis-endemic areas.