Leishmania infantum-specific IFN-? production in stimulated blood from cats living in areas where canine leishmaniosis is endemic

Priolo, Vito; Martínez-Orellana, Pamela; Pennisi, Maria Grazia; Masucci, Marisa; Prandi, David; Ippolito, Dorotea; Bruno, Federica; Castelli, Germano; Solano-Gallego, Laia

The frequency of cats producing IFN-γ after stimulation with LSA or ConA is summarized in Table 2 according to their provenience and clinical status. A higher number of cats produced IFN-γ after stimulation with ConA (166/179, 93%) than with LSA (32/179, 18%) (Fisher's exact test, P < 0.0001) ( Table 2 ). Levels of IFN-γ according to serological and PCR results, and clinical status are summarized in Table 3 . The median of the IFN-γ concentration of LSA-IFN-γ producer cats (IFNγ-p) was significantly lower than concentration obtained with ConA stimulation [1115 pg/ml (25-75) = 199.9-2931 pg/ ml] (Wilcoxon signed-rank test, Z = -11.108, P < 0.0001). The unique IFNγ-p cat positive to Leishmania-PCR (125 L. infantum amastigotes/ml) tested high positive by both IFAT (titer 40960) and ELISA (> 346.3 EU). This cat was adult, FeLV-positive, suffered from squamous cell carcinoma and Leishmania amastigotes were detected at cytological evaluation of the neoplastic cutaneous lesion. Sick and apparently healthy cats had the same prevalences of IFNγ-p individuals (Table 2) ; however, sick IFNγ-p cats had a significantly higher level of LSA IFN-γ (Mann-Whitney U-test, Z = 47, P = 0.0056) ( Table 3) . The prevalence of cats producing IFN-γ after stimulation with ConA was above 90% in both groups (Table 2) ; however, among 64 cats exposed to L. infantum (i.e. positive to at least one specific test), sick individuals (n = 25) had a significantly higher median concentration [2159 pg/ml; (25-75) = 965.3-4508 pg/ml] than apparently healthy cats (n = 39) [1712.5 pg/ml; (25-75) = 87.1-2946 pg/ml] (Mann-Whitney U-test, Z = 339, P = 0.0117). The concentration of IFN-γ produced after stimulation with ConA was significantly higher in the IFNγ-p group (Mann-Whitney U-test, Z = 1473, P = 0.0008) ( Table 3) and IFN-γ concentrations after ConA or LSA stimulations were positively correlated (Spearman's correlation coefficient, r s = 0.264, P = 0.0001). Additionally, ELISA antibody levels were positively correlated with IFN-γ