Assessment of interferon-γ levels and leishmanin skin test results in persons recovered for leishmaniasis

Abstract

Patients who recover from leishmaniasis usually show development of strong immunity and induction of interferon-γ (IFN-γ) and delayed type hypersensitivity. In a randomized trial, we analyzed the IFN-γ response by using a Quantiferon-Leishmania assay against three Leishmania peptide antigens and compared it with results of the leishmanin skin test (LST) in persons residing in areas in Iran to which zoonotic cutaneous leishmaniasis (ZCL, 181 persons), anthroponotic cutaneous leishmaniasis (ACL, 104 persons), and zoonotic visceral leishmaniasis (ZVL, 67 persons) are endemic. The percentage of persons with an IFN-γ-positive response (> 0.2 IU/mL) to three antigens and the mean concentration of IFN-γ induced by the antigens were higher for persons from areas endemic for ZVL than for persons from areas endemic for ZCL and ACL. The percentage of persons with LST-positive results (≥ 5 mm indurations) was 99%, 94%, and 70% for areas with ZCL, ACL, and ZVL, respectively. Our data indicate that the LST is significantly more sensitive than IFN-γ levels in persons who have been cured of cutaneous leishmaniasis than in persons who have been cured of ZVL.

Figure 1.

Mean concentration of interferon-γ (IFN-γ against Leishmania antigen A (Leish) A and Leish C antigens in persons cured of zoonotic cutaneous leishmaniasis (ZCL), anthroponotic cutaneous leishmaniasis (ACL), and zoonotic visceral leishmaniasis (ZVL) in leishmaniasis-endemic areas in Iran, according to the time of assay in relation to recovery from the disease. The IFN-γ response to either Leish A or Leish C did not vary in persons from the ZCL area throughout the study. The magnitude of the IFN-γ response in persons from the ZVL area was significantly higher than that of persons from the ACL area against Leish A (P = 0.003, by t-test) and Leish C (P = 0.030, by t-test) during the early period (1–12 months post-recovery). However for ZCL, the difference was only significant for Leish A (P = 0.017) during the same period. No significant difference was seen in other periods between persons from different regions. *P = 0.017 and 0.030; **P = 0.003.

Figure 2.

Linear regression of log 2 values of the interferon-γ (IFN-γ response compared with leishmanin skin test indurations for Leishmania antigen A (Leish) A and Leish B in area of Iran endemic for zoonotic cutaneous leishmaniasis (ZCL-1) (panels 1 and 2), for Leish A and Leish C in areas endemic for ZCL-2 (panel 3 and 4), in areas endemic for anthroponotic cutaneous leishmaniasis (ACL) (panels 5 and 6), and in areas endemic for zoonotic visceral leishmaniasis (ZVL) (panel 7 and 8). No statistically significant correlation was found between leishmanin skin test indurations and IFN-γ responses of persons from different areas.