Formaldehyde treatment of proteins can constrain presentation to T cells by limiting antigen processing

Abstract

Proteins to be used as vaccines are frequently treated with formaldehyde, although little is known about the effects of this treatment on protein antigenicity. To investigate the effect of formaldehyde treatment on antigen recognition by T cells, we compared the in vitro T-cell response to proteins that have been formaldehyde treated with the response to untreated proteins. We found that peripheral blood mononuclear cells from individuals vaccinated with three formaldehyde-treated proteins (pertussis toxin, filamentous hemagglutinin, pertactin) of Bordetella pertussis showed little or no response to the formaldehyde-treated proteins but proliferated very well in response to the corresponding untreated protein. These findings were further confirmed with CD4+ T-cell clones specific for defined epitopes of the bacterial proteins. We found that some epitopes are presented poorly or not at all when formaldehyde-treated proteins are used, whereas other epitopes are equally presented to T-cell clones when either formaldehyde-treated or untreated antigens are used. However, T-cell recognition could be restored by either antigen degradation before formaldehyde treatment or heat denaturation after such treatment. Parallel digestion with trypsin of both formaldehyde-treated and untreated proteins showed that fragments generated from the two forms of the same antigen were different in size. These results demonstrate that formaldehyde treatment can constrain antigen presentation to T cells and that this may be due to an altered proteolytic processing of formaldehyde-treated proteins.

Development and Evaluation of an Immuno-Capture Enzyme-Linked Immunosorbent Assay to Quantify the Mycoplasma capricolum subsp. capripneumoniae (Mccp) Protein in Contagious Caprine Pleuropneumonia (CCPP) Vaccine

“…It was also found that the ICE test was not able to detect and quantify proteins from inactivated Mccp with formaldehyde. This indicates that the target protein may have been degraded or that a change in conformation that could impact the epitope bound by the mAb may have occurred [35,36].…”

Alteration of a model antigen by Au(III) leads to T cell sensitization to cryptic peptides

“…For instance, the modification may induce constraints in the presentation of certain peptides. Examples here are the formaldehyde treatment of Bordetella pertussis proteins, which led to inhibition of the presentation of certain epitopes without affecting others [29], and the naturally occurring N-glycosylation of HIV-pgl20, which inhibited the stimulation of a considerable fraction of patient-derived CD4 ' T cell clones that responded to the nonglycosylated recombinant protein [27]. On the other hand, after immunization of mice with phosphorylcholine-conjugated hen egg lysozyme, T cell hybridomas were obtained that recognized the modified Ag much better than the untreated Ag [39].…”

Pertussis: a matter of immune modulation

“…Higher initial titers of Ptx antibodies may increase the period in which protective antibody levels are maintained. Additional reasons to replace chemically detoxified Ptx are that formaldehyde treatment of Ptx has been shown to constrain antigen presentation to T cells, and that chemical detoxification has a significant effect on protein structure and may destroy protective epitopes (Di Tommaso et al, 1994). Both may affect immunological memory.…”