Human immune response to cationized proteins. II. Characterization of interaction of cationized diphtheria toxoid...

Area of Science:

• Immunology
• Vaccinology

Background:

• Cationized diphtheria toxoid (cDT) demonstrates superior efficacy over native diphtheria toxoid in stimulating human antigen-specific T cell responses.
• The enhanced immunogenicity of cDT suggests potential mechanisms involving improved interaction with antigen-presenting cells (APCs).

Purpose of the Study:

• To investigate whether the enhanced immunogenicity of cDT is due to its preferential binding to APCs.
• To characterize the binding of cDT to different APC subsets and their subsequent T cell activation potential.

Main Methods:

• Utilized biotin-labeled antigen and flow cytometric analysis to quantify antigen binding to APCs.
• Assessed T cell proliferation in response to antigen-pulsed APCs.

Main Results:

• Demonstrated strong binding of cDT to both monocytes and B cells, surpassing that of native antigen.
• Binding characteristics were consistent across cell types, showing rapid saturation, temperature independence, and inhibition by unlabeled cationized proteins.
• While both cell types bound cDT, only monocytes effectively induced T cell proliferation, potentially due to differences in antigen internalization rates.

Conclusions:

• cDT exhibits preferential binding to monocytes and B cells, contributing to its enhanced immunogenicity.
• Monocytes are more effective than B cells in initiating T cell responses via cDT, possibly due to internalization kinetics.
• Identifying target structures for cationized proteins could enable the development of vaccines with targeted delivery to APCs in vivo.