Identification of a novel tetrapeptide structure of the Mycobacterium avium glycopeptidolipid that functions as a specific target for the host antibody response

► We perform mass spectrometric analysis of glycopeptidolipids produced by Mycobacterium avium. ► We find a new glycopeptidolipid species in which phenylalanine is replaced by valine. ► We detect specific antibody responses to the new glycopeptidolipid species.