Soluble CD40 Ligand in Sera of Subjects Exposed to Leishmania infantum Infection Reduces the Parasite Load in Macrophages.
BACKGROUND
While CD40L is typically a membrane glycoprotein expressed on activated T cells and platelets that binds and activates CD40 on the surface on antigen presenting cells, a soluble derivative (sCD40L) that appears to retain its biological activity after cleavage from cell membrane also exists. We recently reported that sCD40L is associated with clinical resolution of visceral leishmaniasis and protection against the disease. In the present study we investigated if this sCD40L is functional and exerts anti-parasitic effect in L. infantum-infected macrophages.


RESULTS
Macrophages from normal human donors were infected with L. infantum promastigotes and incubated with either sera from subjects exposed to L. infantum infection, monoclonal antibodies against human CD40L, or an isotype control antibody. We then evaluated infection by counting the number of infected cells and the number of parasites in each cell. We also measured a variety of immune modulatory cytokines in these macrophage culture supernatants by Luminex assay. The addition of sCD40L, either recombinant or from infected individuals' serum, decreased both the number of infected macrophages and number of intracellular parasites. Moreover, this treatment increased the production of IL-12, IL-23, IL-27, IL-15, and IL1β such that negative correlations between the levels of these cytokines with both the infection ratio and number of intracellular parasites were observed.


CONCLUSIONS
sCD40L from sera of subjects exposed to L. infantum is functional and improves both the control of parasite and production of inflamatory cytokines of infected macrophages. Although the mechanisms involved in parasite killing are still unclear and require further exploration, these findings indicate a protective role of sCD40L in visceral leishmaniasis.
Laboratório de Biologia Molecular, Hospital Universitário, Universidade Federal de Sergipe, Aracaju, Brazil.
Fabrícia Alvisi
FA
de Oliveira
Laboratório de Biologia Molecular, Hospital Universitário, Universidade Federal de Sergipe, Aracaju, Brazil.
Aline Silva
AS
Barreto
Laboratório de Biologia Molecular, Hospital Universitário, Universidade Federal de Sergipe, Aracaju, Brazil.
Lays G S
LG
Bomfim
Laboratório de Biologia Molecular, Hospital Universitário, Universidade Federal de Sergipe, Aracaju, Brazil.
Talita Rebeca S
TR
Leite
Laboratório de Biologia Molecular, Hospital Universitário, Universidade Federal de Sergipe, Aracaju, Brazil.
Priscila Lima
PL
Dos Santos
Laboratório de Biologia Molecular, Hospital Universitário, Universidade Federal de Sergipe, Aracaju, Brazil; Instituto de Investigação em Imunologia, São Paulo, Brazil.
Roque Pacheco
RP
de Almeida
Laboratório de Biologia Molecular, Hospital Universitário, Universidade Federal de Sergipe, Aracaju, Brazil.
Ângela Maria
ÂM
da Silva
Infectious Disease Research Institute (IDRI), Seattle, Washington, United States of America.
Malcolm S
MS
Duthie
Infectious Disease Research Institute (IDRI), Seattle, Washington, United States of America.
Steven G
SG
Reed
Laboratório de Biologia Molecular, Hospital Universitário, Universidade Federal de Sergipe, Aracaju, Brazil.
Tatiana Rodrigues
TR
de Moura
Laboratório de Biologia Molecular, Hospital Universitário, Universidade Federal de Sergipe, Aracaju, Brazil; Instituto de Investigação em Imunologia, São Paulo, Brazil.
Amélia
A
Ribeiro de Jesus
D000911:Antibodies, Monoclonal / Q000276:immunology; D000953:Antigens, Protozoan / Q000276:immunology; D023201:CD40 Ligand / Q000097:blood* / Q000276:immunology*; D006801:Humans; D007378:Interleukins / Q000276:immunology; D018314:Leishmania infantum / Q000276:immunology*; D007898:Leishmaniasis, Visceral / Q000097:blood* / Q000276:immunology* / Q000469:parasitology; D008213:Lymphocyte Activation / Q000276:immunology; D008264:Macrophages / Q000276:immunology* / Q000469:parasitology*; D059208:Parasite Load / Q000379:methods
D000911:Antibodies, Monoclonal; D000953:Antigens, Protozoan; D007378:Interleukins; D023201:CD40 Ligand