Immune and pathological parameters in BALB/c mice infected with different doses of Leishmania (Leishmania) amazonensis

MARÍA JOSÉ GERMANÓ; EDUARDO ALBERTO SCODELLER; MARÍA CRISTINA SALOMÓN; DIEGO ESTEBAN CARGNELUTTI; MARÍA BELÉN SÁNCHEZ; JUAN PABLO MACKERN OBERTI

Toledo

Congreso; 6th World Congress on Leishmaniasis; 2017

Background: Currently, several experimental vaccines against leishmaniasis have been developed; these often are ineffective due to the high number of parasites employed in the challenge, resulting in a high susceptibility of the mice. Since the dose can influence the development of the disease, the aim of this study was to investigate the impact of the inoculation of different parasite dose (low, medium and high) on immunopathological response in BALB/c mice after infection with L. (L.) amazonensis (MHOM/VE/84/MEL).Methodology: Five mice BALB/c per group were intradermally injected into the right footpad with different inoculum of L. (L.) amazonensis promastigotes per mouse (0; 102; 104; 106). During 13 weeks their swelling footpad were evaluated. After 13 weeks of infection, levels of anti-Leishmania total IgG, IgG1 and IgG2a antibody were determined in the sera from each animal by enzyme-linked immunosorbent assay. At the end of protocol (week 13) animals were killed, splenic index was evaluated and the percentage of CD11b+ cells at infection site and spleen was detected by flow cytometry.Results: These show that using 104 and 106 parasites per mice, an increase in footpad swelling was observed accompanied by high levels of total IgG. Higher levels of IgG1 than IgG2a isotype with a significant increase of splenic index was shown. Only animals infected with the highest dose of L. (L) amazonensis promastigotes showed a significant increase of percentage of CD11b+ cells at spleen, and animals infected with moderated (104) and high (106) doses showed this effect at infection site. Inoculation of the lowest dose of L. (L.) amazonensis (102) did not lead to the pathology development. These animals showed no footpad swelling and their anti-Leishmania antibodies levels, spleen index and the amount of inflammatory cells at spleen and infection site were similar to uninfected group.Conclusions: According to results, it can be concluded that the infection of susceptible BALB/c mice with a high (106) and medium (104) inoculum results in progressive disease with a predominant Th2-like immune response, being 104 parasites per mice a good choice to be used in our experimental vaccines studies.