Gentamicin-Attenuated Leishmania infantum Vaccine: Protection of Dogs against Canine Visceral Leishmaniosis in Endemic Area of Southeast of Iran

Abstract

An attenuated line of Leishmania infantum (L. infantum H-line) has been established by culturing promastigotes in vitro under gentamicin pressure. A vaccine trial was conducted using 103 naive dogs from a leishmaniosis non-endemic area (55 vaccinated and 48 unvaccinated) brought into an endemic area of southeast Iran. No local and/or general indications of disease were observed in the vaccinated dogs immediately after vaccination. The efficacy of the vaccine was evaluated after 24 months (4 sandfly transmission seasons) by serological, parasitological analyses and clinical examination. In western blot analysis of antibodies to L. infantum antigens, sera from 10 out of 31 (32.2%) unvaccinated dogs, but none of the sera from vaccinated dogs which were seropositive at >100, recognized the 21 kDa antigen of L. infantum wild-type (WT). Nine out of 31 (29%) unvaccinated dogs, but none of vaccinated dogs, were positive for the presence of Leishmania DNA. One out of 46 (2.2%) vaccinated dogs and 9 out of 31 (29%) unvaccinated dogs developed clinical signs of disease. These results suggest that gentamicin-attenuated L. infantum induced a significant and strong protective effect against canine visceral leishmaniosis in the endemic area.

Dogs vaccinated with gentamicin‐attenuated Leishmania infantum or infected with wild‐type parasite can be distinguished by Western blotting

“…We previously reported the generation of L. infantum , attenuated by gentamicin . Leishmania infantum H‐line vaccine induced a significant and strong protective effect against natural CVL in an endemic area of south‐east Iran . We aim to exploit this strain as a vaccine to control CVL in dogs and therefore need to identify a technique, which would allow us to distinguish between vaccinated dogs and dogs infected with L. infantum WT through natural infection in a field trial of vaccine.…”

“…These results also provide a diagnostic technique for distinguishing between dogs vaccinated with L. infantum H‐line and dogs challenged with wild‐type parasite that can be applied for field trial of vaccine against CVL in dogs. Several studies reported the high sensitivity and specificity of Western blotting to demonstrate the presence of specific anti‐ Leishmania antibodies in the sera of dogs . Moreover, it has been reported that the GP36 antigen of fucose mannose ligand (FML) was recognized with sera of kala‐azar patients .…”

“…Recently, we reported that none of dogs vaccinated with L. infantum H‐line, but 9 of 31 (29%) unvaccinated dogs were positive for the presence of Leishmania DNA in a vaccine field trial. In addition, sera from 10 of 31 (32·2%) unvaccinated dogs but none of the sera from vaccinated dogs which were seropositive at >100 recognized the 21 kDa antigen of L. infantum WT . A specific diagnostic test to distinguish between dogs vaccinated with L. infantum H‐line or infected with wild‐type parasites could be a valuable tool in the implementation of canine vaccination in the natural CVL.…”

Assessment of Vaccine-Induced Immunity Against Canine Visceral Leishmaniasis

“…Partial protection against CVL has been reported after immunization with sonicated or autoclaved promastigotes (41, 42), with purified and recombinant Leishmania proteins (43–46), with parasite DNA (47, 48), and with attenuated Leishmania strains (49). A review summarizing the few efficacy studies performed in dogs, involving different types of Leishmania antigen (purified proteins, recombinant proteins or DNA), adjuvants and post-vaccination Leishmania infantum challenge, indicated different levels of protection to be obtained by the different vaccine candidates (50).…”

Leishmania vaccines entered in clinical trials: A review of literature

“…Some research has shown that live attenuated form of Leishmania infantum ( L. infantum ) could be considered as an appropriate tool for the prevention of the canine Leishmaniasis. [27] In this regard, a field study was conducted among 103 dogs, grouped vaccinated ( n = 55) and control ( n = 44) trials. The process of Leishmania culture was done under the pressure of gentamicin (20 μg/ml).…”