Diagnostic usefulness of immunohistochemical evaluation of CD1a antigen and polyclonal anti-Leishmania antibodies in cutaneous Leishmaniasis

Background. Different immunohistochemical markers to detect amastigotes in cutaneous Leishmaniasis have been proposed with variable diagnostic usefulness. Objectives. To evaluate the diagnostic usefulness of immunohistochemical amastigotes identification by specific polyclonal anti-Leishmania antibodies and CD1a expression (clone EP3622) in a series of PCR confirmed cutaneous Leishmaniasis. Materials and methods. Thirty-three skin samples corresponding to PCR confirmed cutaneous Leishmaniasis were included in the study. All samples were stained with Hematoxylin-eosin and Giemsa. Moreover, immunohistochemical studies with anti-CD1a and anti-Leishmania antibodies were performed. The patients clinical features and the observed histopathological features were also recorded. Results. From the selected 33 biopsies, Leishmania spp. amastigotes were detected in 48.4% of cases with conventional Hematoxylin-eosin stain and in 57.5% of cases by Giemsa staining. In 31/33 cases, anti-CD1a allowed us to identify parasitic structures, and in 33/33 cases amastigotes were detected with anti-Leishmania antibodies. Concordance between both techniques, antiCD1a and anti-Leishmania, was 94% [CI 95%: (79,8%-99,3%)]; p value <0.05. The sensitivity of anti-CD1a in comparison with the PCR was 94%, with a positive predictive value of 100%. Two cases of low parasitic index were negative for CD1a immunostaining. In cases with high parasitic index, anti-CD1a stained amastigotes in superficial and deep dermis. Only a few cases were originally diagnosed with the available histological techniques, needing PCR for Leishinania spp. identification. Conclusions. Anti-CD1a antibody seems to be a useful technique to identify amastigotes when PCR and anti-Leishmania antibodies are not available. The sensitivity to detect amastigotes is increased when the CD1a immunostaining is added to the classical Haematoxylin - eosin and Giemsa staining.

Automated summary

The study demonstrated that the specific polyclonal anti-Leishmania antibodies and CD1a expression are valuable in identifying amastigotes in cutaneous Leishmaniasis, with high sensitivity and positive predictive value. Adding CD1a immunostaining to traditional staining methods can enhance the detection of amastigotes, particularly in cases where PCR confirmation is not available.