AI Article Synopsis
- The study investigates the binding motifs of CTLA-4 in humans (MYPPPY) and pigs (LYPPPY), focusing on the critical role of the methionine (M) vs. leucine (L) amino acids in binding to CD80.
- Mutations in both porcine and human CTLA-4 were made to analyze their binding affinity to CD80+ cells, revealing that the porcine L is essential for interacting with porcine CD80, while the human M is crucial for binding to human CD80.
- Results suggest that human CTLA-4-based drugs can be tested in porcine models, while porcine CTLA-4 drugs are limited to swine applications, which may provide insights for xeno
Article Abstract
The binding motif of human CTLA-4 is well known to be MYPPPY and for porcine CTLA-4 the binding motif is LYPPPY. Is this single amino acid difference of methionine (M) versus leucine (L) critical for the CTLA-4 binding? Recently, we have reported that the recombinant soluble porcine CTLA-4 was incapable of binding to human CD80. In this study we mutated L to M in the binding motif of the soluble porcine CTLA-4 and mutated M to L in the binding motif of the soluble human CTLA-4. We then analyzed how these mutations affected the binding affinity of the mutants to both porcine and human CD80(+) cells. The soluble porcine CTLA-4-L97M mutant partially lost its binding affinity to porcine CD80 compared to the wild-type and conferred very weak binding ability to human CD80. These results indicate that the L in the binding motif of porcine CTLA-4 is important for determining its binding ability to porcine CD80. Wild-type soluble human CTLA-4 binds to both human and porcine CD80 with comparable affinity, however, the soluble human CTLA-4-M97L mutant almost lost its binding ability to human CD80 and increased its binding ability to porcine CD80. These results indicate that M in the human CTLA-4 binding motif is extremely critical for its binding to human CD80. Those data suggest that the human CTLA-4 based recombinant protein drugs such as human CTLA-4-Ig can be used and/or tested in a porcine model. Conversely, the use of porcine CTLA-4 based recombinant protein drugs such as porcine CTLA-4-Ig is restricted to swine models. The difference in binding specificity of CTLA-4 observed in this study may be useful for studies such as pig to nonhuman primate xeno-transplantation. Porcine CTLA-4- and human CTLA-4-M97L mutant-based recombinant protein drugs can be used to specifically block the direct presentation by donor antigen presenting cells in pig to nonhuman primate xeno-transplantation. Human CTLA-4-M97L mutant-based recombinant protein drugs will be more ideal as it is without immunogenicity to human being.
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| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3721328 | PMC |
| http://dx.doi.org/10.1016/j.humimm.2013.04.002 | DOI Listing |
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