Table 1.

Differences in immune responses induced by live parasites vs killed parasite antigens in leishmaniasis

Host species	Leishmania spp.	Experimental design	Major differences found	Reference
Mouse (C57BL/6 or BALB/c)	L. major	Early responses in draining lymph node cells were assessed after inoculation of 5 × 106 live or killed L. major into naive mice	Cells from mice inoculated with killed parasites produced significantly more IL-4 and less IFN-γ than those from mice injected with live parasites	[24]
Mouse (C57BL/6)	L. major	Mice with healed L. major infections were compared to mice vaccinated with autoclaved L. major antigen + CpG ODN using infected sand fly challenge	Mice immunized with autoclaved L. major antigen + CpG ODN were protected against needle injection of parasites but not against infected sand fly challenge. On the other hand, mice that were healed from experimental L. major infections were highly resistant to sand fly transmitted infection	[42]
Human	L. amazonensis; L, mexicana; L. guyanensis; L. major (vaccine); L. braziliensis (infection)	PBMC from subjects immunized with a killed vaccine composed of five Leishmania strains and from ACL patients were stimulated in vitro with L. braziliensis crude antigen extract	The majority of the responding cells of the vaccinated subjects were CD8+ T cells, in contrast to the results of a group of patients, whose Leishmania antigen-reactive cells were mainly CD4+ T cells	[47]
Human	L. amazonensis (vaccine); L. braziliensis (infection)	The expression of Vβ chains of TCR was assessed in cells from ACL patients and healthy volunteers before and after vaccination	Vaccination led to a broad expansion of the TCR Vβ repertoire both in CD4+ and in CD8+ T cells. On the other hand, the patients showed a significant decrease in the expression of certain TCRs both in CD4+ and in CD8+ T cells when compared to healthy controls from the same leishmaniasis endemic area	[48]
Human	L. amazonensis (vaccine); L. braziliensis (infection)	Cytokine responses of PBMC from ACL patients and subjects immunized with a vaccine composed of killed promastigotes to La and to the recombinant protein LACK, both from L. amazonensis, were compared	The IFN-γ levels stimulated by La were significantly higher and the levels of IL-10 significantly lower than those stimulated by LACK in the patient group, whereas LACK induced a significantly higher IFN-γ production and a significantly lower IL-10 production compared with those induced by La in the vaccinated group LACK also induced a significantly higher frequency of IFN-γ-producing cells than did La in the vaccinated group	[49]

Abbreviations: ACL American cutaneous leishmaniasis, CpG ODN CpG oligodeoxynucleotides, IFN-γ Interferon- γ, IL-10 interleukin-10, La whole-cell promastigote antigen extract, LACK Leishmania homologue of receptors for activated C kinase, PBMC peripheral blood mononuclear cells, TCR T-cell receptors