Leishmania amazonensisis one of the major etiologic agents of a broad spectrum of clinical forms of leishmaniasis and has a wide geographical distribution in the Americas, which overlaps with the areas of transmission of many otherLeishmaniaspecies. The LACK and A2 antigens are shared by variousLeishmaniaspecies. A2 was previously shown to induce a potent Th1 immune response and protection againstL. donovaniinfection in BALB/c mice. LACK is effective againstL. majorinfection, but no significant protection againstL. donovaniinfection was observed, in spite of the induction of a potent Th1 immune response. In an attempt to select candidate antigens for an American leishmaniasis vaccine, we investigated the protective effect of these recombinant antigens (rLACK and rA2) and recombinant interleukin-12 (rIL-12) againstL. amazonensisinfection in BALB/c mice. As expected, immunization with either rA2-rIL-12 or rLACK-rIL-12 induced a robust Th1 response prior to infection. However, only the BALB/c mice immunized with rA2-rIL-12 were protected against infection. Sustained gamma interferon (IFN-γ) production, high levels of anti-A2 antibodies, and low levels of parasite-specific antibodies were detected in these mice after infection. In contrast, mice immunized with rLACK-rIL-12 displayed decreased levels of IFN-γ and high levels of both anti-LACK and parasite-specific antibodies. Curiously, the association between rA2 and rLACK antigens in the same vaccine completely inhibited the rA2-specific IFN-γ and humoral responses and, consequently, the protective effect of the rA2 antigen againstL. amazonensisinfection. We concluded that A2, but not LACK, fits the requirements for a safe vaccine against American leishmaniasis.

Eugenia unifloraL. is a member of the Myrtaceae family and is commonly known as Brazilian cherry tree. In this study, we evaluated the chemical composition ofEugenia unifloraL. essential oil (EuEO) by using gas chromatography-mass spectrometry (GC-MS) and assessed its anti-Leishmaniaactivity. We also explored the potential mechanisms of action and cytotoxicity of EuEO. Thirty-two compounds were identified, which constituted 92.65% of the total oil composition. The most abundant components were sesquiterpenes (91.92%), with curzerene (47.3%),γ-elemene (14.25%), andtrans-β-elemenone (10.4%) being the major constituents. The bioactivity shown by EuEO against promastigotes (IC₅₀, 3.04 μg·mL⁻¹) and amastigotes (IC₅₀, 1.92 μg·mL⁻¹) suggested significant anti-Leishmaniaactivity. In the cytotoxicity determination, EuEO was 20 times more toxic to amastigotes than to macrophages. Hemolytic activity was 63.22% at the highest concentration tested (400 μg·mL⁻¹); however, there appeared to be no toxicity at 50 μg·mL⁻¹. While the data show that EuEO activity is not mediated by nitric oxide production, they do suggest that macrophage activation may be involved in EuEO anti-Leishmaniaactivity, as evidenced by increases in both the phagocytic capacity and the lysosomal activity. More studies are needed to determinein vivoactivity as well as additional mechanisms of the anti-Leishmaniaactivity.