CpG oligodeoxynucleotide augments the antileishmanial activity of miltefosine against experimental visceral leishmaniasis

Objectives: To evaluate the combination of CpG oligodeoxynucleotide (CpG ODN) and miltefosine for the treatment of experimental visceral leishmaniasis (VL). Methods: The experiments were carried out using BALB/c mice and hamsters, infected with Leishmania donovani. CpG ODN was administered at various doses by the intraperitoneal (ip) route. The dose of CpG ODN (1 nM/single dose) showing best antileishmanial activity was given as free and liposomal forms with a subcurative dose of miltefosine, namely 2.5 and 5 mg/kg x 5 days in mice and hamsters, respectively. Results: Among the various groups of mice, co-administered liposomal CpG ODN and miltefosine showed the best inhibitory effect (85% inhibition) compared with free CpG ODN and miltefosine, and miltefosine, free CpG ODN and liposomal CpG ODN separately. Production of Th1 cytokines, nitric oxide (NO), reactive oxygen species (ROS) and H2O2 was enhanced. A remarkable increase in the phagocytosis index was also observed, indicating overall immunological support to antileishmanial activity of miltefosine by CpG ODN. Similar responses were observed in hamsters. Conclusions: Promising antileishmanial efficacy was observed in animals treated with liposomal CpG ODN and miltefosine, strongly supported by enhancement of Th1 cytokines as well as NO, ROS and H2O2 levels. The correlation of experimental findings in both the models (mouse and hamster) strengthens the potential of CpG ODN as an immunomodulator in combination with miltefosine against VL.