THE ROLE OF SOLUBLE LEISHMANIA PROTEINS AND THE INDUCTION OF INFLAMMATORY RESPONSES IN AMERICAN TEGUMENTARY LEISHMANIASIS

JULIA PIMENTEL, M. FERNANDA GARCÍA BUSTOS, PAULA RAGONE, ANDREA MESÍAS, DIEGO MARCO, PAOLA BARROSO, MANUELA BONO, CRISTINA BONO, CECILIA PÉREZ BRANDÁN, CECILIA PARODI

Congreso; LXXI Reunión Anual de la Sociedad Argentina de Inmunología; 2023

American tegumentary leishmaniasis (ATL) displays two main clinical forms:cutaneous (CL) and mucosal (ML). ML is more resistant to treatment anddisplays a more severe and longer evolution. Since both forms are caused bythe same Leishmania species, the inflammatory response of the host may be animportant factor determining the evolution of the disease.The aims of this work are to assess the specificity of soluble Leishmania proteins(SLP)for CL and ML patients in the in vitro induction of IFNγ. We also pretend toevaluate if cytokine induction varies depending on the Leishmania spp. used,pointed also to the relation of the induction to the clinical form of the disease andanalyzing if ATL patients are capable to maintain longtime specific responses.Methods: We prepared a Leishmania lysate (SLP) from L. (V.) braziliensis(MHOM/BR/75/M2903) and L. (L.) amazonensis (MHOM/VE/84/MEL) massivecultures of promastigotes in the exponential phase of growth. Then we culturedfreshly isolated PBMCs from the studied groups (1x106 cells/ml; 37°C, 5% CO2)in 24 wells plates in presence or absence of SLP mix composed by equalconcentrations (20 μg/ml) of L. (V.) braziliensisand L. (L.) amazonensis.Additionally PBMCs were stimulated with each strain separately. We collectedculture supernatants after 7 days to assess the levels of IFNγ by ELISA. Studiedgroups: CL (n=9), ML (n=11), HS (healthy subjects, n=14) and DD (patients withdifferential diagnosis as vasculitis, psoriasis, n=16).Results: We determined that SLP specifically induced the production of IFNγ ofCL (2360±596) and ML patients (3475±1717), with scarce concentrationsobtained from the control groups (p˂ 0,0001). The addition of both speciesseparately showed that L. (V.) braziliensis (3487±785) was responsible forhigher IFNγ amounts than L. (L.) amazonensis (1344±641) (p=0,0093) analyzingCL cases, but this effect was not observed in ML, with similar concentrations ofthe cytokine recorded for both strains (1867±1258; 1299±1056 respectively).Next, we performed the follow up of 4 CL patients with good response to therapyduring 1, 3 and 6-10 months post-treatment obtaining similar levels of IFNγ ineach studied point.Conclusions: The specific induction of IFNγ produced by SLP in vitro on PBMCsfrom ATLpatients could be a useful tool to accompany classical methods indifficult diagnosis cases. L. (V.) braziliensisis responsible for the majority (>90%)of the infections found in the Northwest of Argentina, but we reported here thanL. (V.) braziliensis proteins only induced increased concentration of IFNγ in CLpatients. Possibly, T cell exhaustion produced in the chronic ML form couldaccount for less capacity to mount stronger responses against the causativeagent. In this regard, the results obtained during CL follow up indicate that atleast 6-10 months after healing of the lesions, strong inflammatory specificresponses are still maintained.*Results expressed as Media±SE(pg/ml)