A Third Generation Leishmania Vaccine Protects Against an Heterospecie Infection

FREZARD, FREDERIC; FERNANDES, ANA PAULA; SOUZA LANZA, JULIANE; CARGNELUTTI DIEGO ESTEBAN; GERMANO MARIA JOSE; MACKERN-OBERTI, JUAN PABLO

Buenos Aires

Simposio; XIX Simposio Internacional sobre Enfermedades Desatendidas; 2019

Fundación Mundo Sano

Background: Increasingly cases of leishmaniasis in different countries have been detected. In Argentina, there are three principal species responsible of american tegumentary leishmaniasis: L. braziliensis, L. amazonensis, L. guyanensis; and only one specie causes visceral leishmaniasis: L. infantum. Therefore, it is very important to develop an effective vaccine against this disease. The objective of the present study was to evaluate the efficacy of a vaccine formulated with recombinant protein LOxy (rLOxy) from L. infantum combinated with oligodeoxynucleotides containing CpG motifs (CpG ODN) and/or poliinosinic-policitidilic acid [Poly (I:C)], using cationic liposome as a delivery system against an heterospecie infection by L. amazonensis.Materials and methods: The protein rLOxy was expressed in bacteria E. coli (C41) containing the plasmid pET21aLOxy, and purified by Histidine tail affinity chromatography of rAg. Cationic liposomes (LC) containing rLOxy were prepared by the DRV (dehydration and rehydration vesicles) method. Anionic immunoadjuvants were used separately or in combination in the formulations. The liposomes were characterized regarding to the size, polydispersity index and zeta potential by Dinamic Light Scattering (DLS) and Nanotracking analysis (NTA). BALB/c female mice were subcutaneously immunized with different formulations in a final rLOxy amount of 10 μg/dose and 18 μg/dose of either Poly (I:C) or CpG or both with or without LC. Blood was collected 20 days after each dose, for analysis of IgG?s levels by ELISA. 20 days after the last immunization animals were infected with 104 L. amazonensis promastigotes by intradermic route in right footpad. Footpad swelling of infected mice was weekly measured. Eleven weeks after challenge, animals were euthanized and the protective effect induced by the vaccination was evaluated. Results: The results showed that addition of immunoadjuvants CpG and Poly (I:C) to the liposomal formulations induces formation of polydisperse solutions, decreases diameter, but Z potential remains positive. In addition, formulations containing CpG had grater seroconversion with high levels of IgG1 and IgG2a antibodies after immunizations. Footpad swelling and parasite load were significantly lower in the groups vaccinated with LC + rLOxy + CpG + Poly (I:C) respect to control group. It could be due to LOxy is a conservative protein between both specie of Leishmania.Conclusions: This work shows the protective efficacy of rLOxy + LC + CpG + Poly (I:C) formulation against L. amazonensis, reaching an heterospecie protection.