Dipartimento di Scienze Veterinarie, Università di Messina, Messina, Italy.
Departament de Medicina i Cirurgia Animals, Facultat de Veterinària, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain.
Parasit Vectors. 2019 Mar 26;12(1):133. doi: 10.1186/s13071-019-3386-y.
Feline leishmaniosis caused by Leishmania infantum is considered a rare disease in endemic areas, whereas subclinical infections are common. Immune response plays a key role in driving the course of L. infantum infection in other host species; however, the feline cell-mediated immune response to L. infantum infection has not yet been investigated. The aim of this study was to determine the cell-mediated immune response specific to L. infantum by means of interferon (IFN)-γ release in whole blood assay from cats living in endemic areas (66 in Sicily and 113 in Catalonia) and to compare with antibody levels to L. infantum [enzyme-linked immunosorbent assay (ELISA) and immunofluorescence antibody test (IFAT)], blood parasite load and retroviral infections.
Most cats (n = 140) were L. infantum antibody negative and only 22% (n = 39) were positive. Only 9 and 2% of tested cats had a feline immunodeficency virus (FIV) infection or a feline leukemia virus (FeLV) infection, respectively. Thirty-two cats out of 179 (18%) produced IFN-γ after stimulation with L. infantum soluble antigen (LSA) while the majority of cats (93%) produced IFN-γ after stimulation with concanavalin A (ConA). Six LSA-IFN-γ-producer cats were seropositive (three to ELISA and five to IFAT) but they were polymerase chain reaction (PCR) negative, while only one cat was antibody- and PCR-positive. Significant positive correlations were found between IFN-γ concentrations after stimulation with LSA and ConA, and between serology and PCR testing. No association was found between FIV status and LSA or ConA-IFN-γ production. Combining PCR, serology and specific IFN-γ concentration results, we found that 36% of cats studied were exposed to L. infantum.
As expected, cats from endemic areas produce IFN-γ after ex vivo blood stimulation with LSA and therefore are able to activate a cell-mediated adaptive immune response against the parasite that is variably associated with antibody or blood PCR positivity. The association of this assay to serological and molecular tests provides a better estimate of cat exposure to L. infantum.
由利什曼原虫引起的猫利什曼病在流行地区被认为是一种罕见疾病，而亚临床感染较为常见。免疫反应在驱动其他宿主物种中利什曼原虫感染的过程中起着关键作用；然而，猫对利什曼原虫感染的细胞介导免疫反应尚未得到研究。本研究的目的是通过在来自流行地区（西西里岛 66 只，加泰罗尼亚 113 只）的猫的全血检测中检测针对利什曼原虫的干扰素（IFN）-γ释放来确定针对利什曼原虫的细胞介导免疫反应，并与针对利什曼原虫的抗体水平（酶联免疫吸附试验（ELISA）和免疫荧光抗体试验（IFAT））、血液寄生虫载量和逆转录病毒感染进行比较。
大多数猫（n=140）对利什曼原虫抗体呈阴性，只有 22%（n=39）呈阳性。接受检测的猫中只有 9%和 2%分别感染了猫免疫缺陷病毒（FIV）或猫白血病病毒（FeLV）。179 只猫中有 32 只（18%）在受到利什曼原虫可溶性抗原（LSA）刺激后产生 IFN-γ，而大多数猫（93%）在受到刀豆蛋白 A（ConA）刺激后产生 IFN-γ。6 只 LSA-IFN-γ产生猫呈血清阳性（3 只 ELISA 阳性，5 只 IFAT 阳性），但 PCR 检测均为阴性，只有 1 只猫抗体和 PCR 均为阳性。在 LSA 和 ConA 刺激后 IFN-γ浓度之间、血清学和 PCR 检测之间均发现显著的正相关关系。未发现 FIV 状态与 LSA 或 ConA-IFN-γ产生之间存在关联。结合 PCR、血清学和特异性 IFN-γ浓度结果，我们发现研究的 36%的猫接触过利什曼原虫。
正如预期的那样，来自流行地区的猫在用 LSA 进行体外血液刺激后产生 IFN-γ，因此能够激活针对寄生虫的细胞介导适应性免疫反应，该反应与抗体或血液 PCR 阳性程度不同相关。该检测方法与血清学和分子检测相结合，可以更好地估计猫接触利什曼原虫的情况。
