Haematophagous organisms represent one of the largest vectors of human diseases of the animal kingdom. Their saliva contains a cocktail of proteins and peptides to suppress the human immune system to prolong their feeding time and harvest more blood.1 Compromising the immune system at the site of the bite provides the optimal conditions for establishing an infection of an opportunistic blood-borne pathogen. Tyrosine sulfation has been demonstrated to be a vital PTM on many anti-coagulant salivary proteins of haematophagous organisms.2-5 However, there has been limited exploration on the prevalence and effect of tyrosine sulfation on immunomodulatory peptides. This work has focused on the synthesis of a library of immunomodulatory peptides from blood-feeding organisms to explore the effect of tyrosine sulfation on their activity.