['Previously, we demonstrated that unlike subcutaneous or intramuscular vaccination, intranasal vaccination of BALB/c mice with whole Leishmania amazonensis antigens leads to protection against cutaneous leishmaniasis. Here, the role of parasite serine proteases in the protective immunity was investigated.', 'Serine Proteases were partially purified from both soluble (LaSP-Sol) and extracellular (LaSP-Ex) Leishmania amazonensis promastigote extracts by aprotinin-agarose chromatography. BALB/c mice were intranasally immunized with LaSP-Sol and LaSP-Ex prior to infection with L. amazonensis. LaSP-Ex but not LaSP-Sol vaccination led to significantly smaller lesions and parasite burdens as compared with non-vaccinated controls. Protection was accompanied by systemic Th1 polarization with increased IFN-γ and decreased IL-4 and IL-10 splenic production. Likewise, increased production of IFN-γ, IL-12 and IL-4 concomitant with decreased TGF-β and TNF-α was locally observed in the infected footpad.'] Does intranasal vaccination with extracellular serine proteases of Leishmania amazonensis confer protective immunity to BALB/c mice against infection?