Epidemic Preparedness—Leishmania tarentolae as an Easy-to-Handle Tool to Produce Antigens for Viral Diagnosis: Application to COVID-19

Abstract

To detect and prevent emerging epidemics, discovery platforms are urgently needed, for the rapid development of diagnostic assays. Molecular diagnostic tests for COVID-19 were developed shortly after the isolation of SARS-CoV-2. However, serological tests based on antiviral antibody detection, revealing previous exposure to the virus, required longer testing phases, due to the need to obtain correctly folded and glycosylated antigens. The delay between the identification of a new virus and the development of reliable serodiagnostic tools limits our readiness to tackle future epidemics. We suggest that the protozoan Leishmania tarentolae can be used as an easy-to-handle microfactory for the rapid production of viral antigens to face emerging epidemics. We engineered L. tarentolae to express the SARS-CoV-2 receptor-binding domain (RBD) and we recorded the ability of the purified RBD antigen to detect SARS-CoV-2 infection in human sera, with a sensitivity and reproducibility comparable to that of a reference antigen produced in human cells. This is the first application of an antigen produced in L. tarentolae for the serodiagnosis of a Coronaviridae infection. On the basis of our results, we propose L. tarentolae as an effective system for viral antigen production, even in countries that lack high-technology cell factories.

Leishmania tarentolae as an Antigen Delivery Platform: Dendritic Cell Maturation after Infection with a Clone Engineered to Express the SARS-CoV-2 Spike Protein

“…This protozoan has already been assayed in a murine model as a live vaccine against L. donovani , the aetiological agent of visceral leishmaniasis in humans [ 11 ]. In addition, similarly to BCG, L. tarentolae has also been manipulated for the expression of proteins from pathogenic Leishmania species, as well as from viruses, and tested as a living vaccine vehicle in murine models (e.g., [ 12 , 13 , 14 , 15 , 16 , 17 ]). A major feature that makes this microorganism interesting as a potential vaccine vehicle is that, upon its inoculation into mammalian tissues, it is expected to target DCs and other phagocytic cells [ 11 , 18 ].…”

Leishmania tarentolae: a vaccine platform to target dendritic cells and a surrogate pathogen for next generation vaccine research in leishmaniases and viral infections

“…In the first study, an antigen from the hepatitis E virus capsid protein, produced in L. tarentolae, was successfully used in an enzyme-linked immunosorbent assay (ELISA) for the detection of antiviral antibodies in porcine sera [54]. In a more recent study, antigens from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were thoroughly tested on sera from humans affected by coronavirus disease 2019 (COVID-19) and found to display diagnostic performances comparable to those achieved by antigens produced in human cells [55].…”

Regulating the product quality of COVID-19 antigen testing reagents: A tripartite evolutionary game analysis under China's legal framework

“…Williams et al discovered that using plant platforms producing recombinant proteins as COVID-19 diagnostic reagents might reduce the cost of diagnostic kits ( 33 ). According to Varotto-Boccazzi et al, L. tarentolae is an efficient method for viral antigen synthesis in low-tech cell factories, with sensitivity and repeatability equivalent to reference antigens generated in human cells ( 34 ). Kritikos et al suggested that RATs might assist in the reduction of the sporadically observed reagent scarcity in RT-PCR tests ( 35 ).…”