Chiaramonte M G, Zwirner N W, Caropresi S L, Heredia V, Taranto N J, Malchiodi E L
Cátedra de immunología, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Argentina.
Medicina (B Aires). 1996;56(3):259-68.
In many regions of South America there are overlapping endemic areas for American Trypanosomiasis (Chagas' disease) and Leishmaniasis. T. cruzi and Leishmania spp, the causative agents of these parasitoses belong to the Trypanosomatidae family and share various antigens that cause cross-reactivity in serological diagnosis when complex antigenic mixtures are used. We studied patients who sought medical attention because of cutaneous or mucocutaneous lesions typical of leishmaniasis infection. These patients were from the province of Salta where Trypanosomiasis and Leishmaniasis are endemic diseases. Sixty-two patients gave a positive Montenegro skin test and, of these, 53 (85, 48%) showed the presence of amastigotes in Giemsa stained smears of dermal scrapings. Seven patients were not included because they were negative for both assays. We analyzed the leishmaniasic sera against homologous antigens to study the immune response and against complex heterologous antigens from T. cruzi to evaluate cross-reactivity phenomena. We also tested these sera against specific antigens for diagnosis of Chagas' disease in order to search for mixed infections. When complex antigens from leishmania were used, the sera showed an unusually strong antibody response 100% positive by IFA, 88.7% by ELISA and 80.6% by immunoblotting. Furthermore, significant cross-reactivity was found when conventional antigens for the serodiagnosis of Chagas' disease were used: 74.19% by IHA, 91.93% by IFA, and 76.80% by ELISA. We have previously purified by immunoaffinity, using a monoclonal antibody, an antigen termed Ag163B6 which is not present in L. mexicana. This antigen has shown the ability to specifically differentiate sera of chronic chagasic patients from those of leishmaniasic patients in ELISA. Furthermore, recent studies from our laboratory by immunoblotting, have demonstrated that chronic chagasic patients exhibit a specific reactivity pattern against T. cruzi epimastigotes that can be distinguished from those presented by leishmaniasic patients in spite of cross-reactive antigens. According to the results obtained in these assays, we classified the patients in two groups: 1) Patients with evidence of T. cruzi infection, those who tested positive in at least one assay: 2) Patients with no evidence of T. cruzi infection who were negative for both assays. More than 50% (32/62) of the patients showed strong evidence of mixed infection with T. cruzi. On the other hand, high cross-reactivity between these two parasitoses was shown in the second group without any evidence of T. cruzi infection since 18 out of 30 were positive in at least two conventional serological reactions. This implies that they would be misdiagnosed as chagasics if conventional reactions were used. These results emphasize the importance of the use of defined antigens and appropriate techniques for the differential diagnosis of these parasitoses, which is more important in areas endemic for both of them.
在南美洲的许多地区，美洲锥虫病（恰加斯病）和利什曼病的流行区域相互重叠。这些寄生虫病的病原体克氏锥虫和利什曼原虫属属于锥虫科，当使用复杂的抗原混合物时，它们具有多种会导致血清学诊断中出现交叉反应的抗原。我们研究了因利什曼病感染典型的皮肤或黏膜皮肤病变而就医的患者。这些患者来自萨尔塔省，恰加斯病和利什曼病在该省均为地方病。62例患者的蒙氏皮肤试验呈阳性，其中53例（85.48%）在吉姆萨染色的皮肤刮片涂片中显示有前鞭毛体。7例患者因两项检测均为阴性而未被纳入。我们分析了利什曼病血清针对同源抗原以研究免疫反应，并针对来自克氏锥虫的复杂异源抗原以评估交叉反应现象。我们还针对用于恰加斯病诊断的特异性抗原检测了这些血清，以寻找混合感染情况。当使用来自利什曼原虫的复杂抗原时，血清显示出异常强烈的抗体反应，免疫荧光法（IFA）检测100%呈阳性，酶联免疫吸附测定（ELISA）为88.7%，免疫印迹法为80.6%。此外，当使用恰加斯病血清学诊断的传统抗原时，发现了显著的交叉反应：间接血凝试验（IHA）为74.19%，免疫荧光法为91.93%，酶联免疫吸附测定为76.80%。我们之前使用单克隆抗体通过免疫亲和法纯化了一种名为Ag163B6的抗原，该抗原在墨西哥利什曼原虫中不存在。这种抗原已显示出在酶联免疫吸附测定中能够特异性区分慢性恰加斯病患者和利什曼病患者血清的能力。此外，我们实验室最近通过免疫印迹法进行的研究表明，尽管存在交叉反应抗原，但慢性恰加斯病患者对克氏锥虫前鞭毛体表现出一种特定的反应模式，这与利什曼病患者的反应模式不同。根据这些检测结果，我们将患者分为两组：1）有克氏锥虫感染证据的患者，即至少一项检测呈阳性的患者；2）无克氏锥虫感染证据的患者，两项检测均为阴性。超过50%（32/62）的患者显示出克氏锥虫混合感染的有力证据。另一方面，在没有任何克氏锥虫感染证据的第二组患者中，这两种寄生虫病之间也显示出高度交叉反应，因为30例中有18例至少在两项传统血清学反应中呈阳性。这意味着如果使用传统反应，他们会被误诊为恰加斯病患者。这些结果强调了使用特定抗原和适当技术进行这些寄生虫病鉴别诊断的重要性，在两种疾病均为地方病的地区这一点更为重要。
