Neutrophil extracellular traps and parasite load are associated with dermal matrix remodeling in Leishmania braziliensis infection.

BACKGROUND

Cutaneous leishmaniasis is a chronic parasitic condition. The association of neutrophil extracellular traps with dermal extracellular matrix degradation, parasite load, and leukocyte profiles in cutaneous leishmaniasis lesions remains underexplored. This study aimed to investigate these associations in patients with cutaneous leishmaniasis.

METHODS

Patients (n=78) from Cuiabá, Mato Grosso, Brazil, diagnosed with cutaneous leishmaniasis were included. Biopsy samples were collected.. Species were identified by polymerase chain reaction. Leukocytes, amastigotes, and neutrophil extracellular traps were identified and quantified, and extracellular matrix degradation was assessed using immunohistochemistry, Masson's trichrome, Sirius Red, and reticulin stains. Statistical associations were determined using Pearson's correlation coefficient.

RESULTS

All patients exhibited L. braziliensis infection. Most patients (76.9%) had cellular and exudative reaction lesions, while 23.1% exhibited granulomatous and exudative reaction lesions. A significant correlation was observed between extracellular matrix degradation and amastigote load in cellular and exudative reaction lesions (r=0.599; p=0.0001) but not in granulomatous and exudative reaction lesions (r=0.068; p=0.263). Similarly, in cellular and exudative reaction lesions, neutrophil extracellular trap formation showed a strong positive correlation with amastigote numbers (r=0.423; p=0.0001), a relationship absent in granulomatous and exudative reaction lesions (r=0.0009; p=0.9036).

CONCLUSION

In L. braziliensis infection with cellular and exudative reaction lesions, neutrophil extracellular traps function as an active, proportional defense mechanism against parasite load. However, in granulomatous and exudative reaction lesions, they contribute to a more structured containment but lack a direct proportional relationship to parasite numbers. This distinction provides critical insights into cutaneous leishmaniasis pathogenesis.