A Nanobody/Monoclonal Antibody "hybrid" sandwich technology offers an improved immunoassay strategy for detection of African trypanosome infections

PLoS Negl Trop Dis. 2024 Jul 1;18(7):e0012294. doi: 10.1371/journal.pntd.0012294. eCollection 2024 Jul.

Abstract

The scarcity of reliable devices for diagnosis of Animal African trypanosomiasis (AAT) presents a limitation to control of the disease. Existing high-sensitivity technologies such as PCR are costly, laborious, time-consuming, complex, and require skilled personnel. Hence, utilisation of most diagnostics for AAT is impracticable in rural areas, where the disease occurs. A more accessible point-of-care test (POCT) capable of detecting cryptic active infection, without relying on expensive equipment, would facilitate AAT detection. In turn, early management, would reduce disease incidence and severity. Today, several ongoing research projects aim at modifying complex immunoassays into POCTs. In this context, we report the development of an antigen (Ag) detection sandwich ELISA prototype for diagnosis of T. congolense infections, which is comprised of nanobody (Nb) and monoclonal antibody (mAb) reagents. The Nb474H used here, originated from a past study. Briefly, the Nb was engineered starting from mRNA of peripheral blood lymphocytes of an alpaca immunized with soluble lysate of Trypanosoma congolense (TC13). T. congolense glycosomal fructose-1,6-bisphosphate aldolase (TcoALD) was discovered as the cognate Ag of Nb474H. In this study, splenocytes were harvested from a mouse immunized with recombinant TcoALD and fused with NS01 cells to generate a hybridoma library. Random screening of the library on TcoALD retrieved a lone binder, designated IgM8A2. Using Nb474H as Ag-capture reagent in combination with the IgM8A2 monoclonal antibody Ag-detection reagent resulted in a tool that effectively detects native TcoALD released during infection by T. congolense parasites. Hitherto, development of POCT for detection of active trypanosome infection is elusive. The Nanobody/Monoclonal Antibody (Nb/mAb) "hybrid" sandwich technology offers prospects for exploration, using the unique specificity of Nb as a key determinant in Ag capturing, while using the versatility of monoclonal Ab to adapt to various detection conditions.

MeSH terms

  • Animals
  • Antibodies, Monoclonal* / immunology
  • Antibodies, Protozoan* / blood
  • Antibodies, Protozoan* / immunology
  • Antigens, Protozoan / immunology
  • Enzyme-Linked Immunosorbent Assay* / methods
  • Mice
  • Sensitivity and Specificity
  • Single-Domain Antibodies / immunology
  • Trypanosoma congolense* / immunology
  • Trypanosomiasis, African* / diagnosis
  • Trypanosomiasis, African* / immunology

Substances

  • Antibodies, Monoclonal
  • Antibodies, Protozoan
  • Single-Domain Antibodies
  • Antigens, Protozoan

Grants and funding

This work was funded by the H2020-EU.3.2.1.1 Program for Controlling and progressively minimizing the burden of animal trypanosomosis, a Horizon 2020 project (COMBAT). SM received the grant. COMBAT is a European Union grant and its URL is https://www.combat-project.eu/. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.