A killed Leishmania vaccine with sand fly saliva extract and saponin adjuvant displays immunogenicity in dogs.

Abstract

A vaccine against canine visceral leishmaniasis (CVL), comprising Leishmania braziliensispromastigote protein, sand fly gland extract (SGE) and saponin adjuvant, was eval-uated in dog model, in order to analyse the immunogenicity of the candidate vaccine. The vaccine candidate elicited strong antigenicity in dogs in respect of specific SGE andLeishmania humoral immune response. The major saliva proteins recognized by serum from immunized dogs exhibited molecular weights of 35 and 45 kDa, and were related to the resistance pattern against Leishmaniainfection. Immunophenotypic analysis revealed increased circulating CD21 + B-cells and CD5 + T-cells, reflected by higher counts of CD4 + and CD8 + T-cells. The observed interac-tion between potential antigen-presenting cells (evaluated as CD14 + monocytes) and lymphocyte activation status indicated a relationship between innate and adaptive immune responses. The higher frequency in L. chagasi antigen-specific CD8 + T-lymphocytes, and their positive association with intense cell proliferation, in addition to the progressively higher production of serum nitric oxide levels, showed a profile compatible with anti-CVL vaccine potential. Further studies on immunological response after challenge with L. chagasi may provide important information that will lead to a better understanding on vaccine trial and efficacy.