Isolation, Characterization, cDNA Cloning, and Antimicrobial Properties of Two Distinct Subfamilies of α-Defensins from Rhesus Macaque Leukocytes

Experiments to isolate and characterize rhesus macaque myeloid α-defensins (RMADs) were conducted. Seven RMAD peptides were isolated and sequenced, and the cDNAs encoding six of these peptides and one other α-defensin from bone marrow were also characterized. Four of the RMADs were found to be highly similar to human neutrophil α-defensins HNP-1 to HNP-3, while the remaining four peptides were much more similar to human enteric α-defensin HD-5. Two α-defensin pairs differed only by the presence or absence of an additional arginine at the amino termini of their mature peptides, indicative of alternate posttranslational processing. The primary translation products of RMAD-1 to -8 are 94- and 96-amino-acid prepropeptides that are highly similar to those of human α-defensins. Immunolocalization experiments revealed a granular cytoplasmic pattern in the cytoplasms of neutrophils, indistinguishable from the pattern observed after immunostaining of human myeloid α-defensins in polymorphonuclear leukocytes. Each of the purified peptides was tested for its in vitro activities against Staphylococcus aureus 502a, Listeria monocytogenes EGD, Escherichia coli ML35, and Cryptococcus neoformans 271A. Several of the peptides were microbicidal for the gram-positive bacteria and C. neoformans at defensin concentrations in the range of 2 to 5 μM. All of the peptides were bacteriostatic against E. coli, but none were bactericidal for this organism. This study is the first to characterize the sequences and activities of α-defensins from nonhuman primates, data that should aid in delineating the role of these peptides in rhesus macaque host defense.