Heterologous expression of scFv fragment against Vairimorpha (Nosema) ceranae hexokinase in Sf9 cell culture inhibits microsporidia intracellular growth.

[Display omitted] • scFv library against microsporidia Vairimorpha ceranae hexokinase was constructed. • representativeness of constructed mouse immune library is 5 million transformants. • scFv-antibody inhibiting V. ceranae growth was selected by the library panning. • V. ceranae growth in Sf9 cell culture was confirmed by reverse transcription PCR. Secretion of hexokinase (HK) by microsporidia into infected cells suggests an important role for this enzyme for the intracellular development of parasites. To verify whether the expression of HK-specific antibodies in the host cell cytoplasm can suppress the growth of microsporidia, we constructed an immune library of recombinant scFv fragments against the enzyme of the honey bee pathogen Vairimorpha (Nosema) ceranae (Vc HK) with a representativeness of about 5 million bacterial transformants. Two variants of Vc HK-specific recombinant antibodies were selected by library panning and expressed in lepidopteran Sf9 cell line. Infecting of cells expressing two selected and control scFv fragments with V. ceranae spores was followed by their cultivation for 4 days. Analysis of parasite β-tubulin as well as spore wall protein SWP32 transcripts in infected cultures by reverse transcription PCR and real-time qPCR showed (1) V. ceranae growth in cells heterologous to bee pathogens, (2) its inhibition by one of the selected Vc HK-specific recombinant antibodies. The latter result once again emphasizes an important role of microsporidia hexokinases in their relationships with infected host cells and suggests further focusing on the mechanisms of such suppression, as well as on the search for new V. ceranae - inhibiting scFv fragments. [ABSTRACT FROM AUTHOR]