IMMUNOMODULATORY PROPERTIES OF MAXADILAN, THE VASODILATOR PEPTIDE FROM SAND FLY SALIVARY-GLAND EXTRACTS

Sand flies are the arthropod vector of leishmaniasis and salivary glan d extracts from these flies exacerbate leishmaniasis in vivo. The mech anism of exacerbation appears to be due to immunomodulatory effects of the saliva on host immune function but the active component is unknow n. The following studies reveal that maxadilan, the vasodilatory pepti de present in sand fly salivary gland extracts, has immunomodulatory p roperties. To examine the effect of maxadilan on T cell proliferation, the peptide was added to murine spleen cells stimulated with either c oncanavalin A or plate-bound anti-T cell receptor antibody. Inhibition of proliferation was noted in a dose-dependent manner for both sets o f experiments (P < 0.05). To examine the effect of maxadilan on alloan tigen presentation, the peptide was added to mixed lymphocyte and mixe d epidermal cell lymphocyte reactions. Inhibition of proliferation was found in these culture systems. Maxadilan also inhibited the delayed- type hypersensitivity reaction in mice (P < 0.05). These observations suggest a role for maxadilan in the pathogenesis of leishmaniasis sinc e the peptide may inhibit the immune response at the site of parasite inoculation, allowing the infection to proceed.