Clonality testing in the lymph nodes from dogs with lymphadenomegaly due to Leishmania infantum infection

PLoS One. 2019 Dec 16;14(12):e0226336. doi: 10.1371/journal.pone.0226336. eCollection 2019.

Abstract

Introduction: In southern European countries, multicentric lymphoma and leishmaniosis are the main differential diagnoses in dogs presented with generalized lymphadenomegaly. The cytological examination is in some cases inconclusive and polymerase chain reaction (PCR) for antigen receptor rearrangement (PARR) has become a common method to confirm or rule out a lymphoproliferative neoplasia. According to the literature, leishmaniosis may lead to clonal arrangements and therefore to a false diagnosis of lymphoma, but this assumption is made from a single leishmania infected dog. Therefore, the objective of this study was to prospectively evaluate results from PARR in dogs with lymphadenomegaly due to clinical leishmaniosis at the moment of diagnosis.

Materials and methods: 31 dogs with a diagnosis of leishmaniosis based on the LeishVet guidelines were included in the study. Samples from enlarged lymph nodes were taken for cytological examination, clonality testing and Leishmania infantum PCR.

Results: All 31 dogs had medium to high positive antibody titers against Leishmania spp. and 30/31 had a positive Leishmania PCR from the lymph node. A polyclonal arrangement for B cells (immunoglobulin heavy chain gene) and T cells (T-cell receptor gamma chain gene) antigen receptors was found in 28/31 dogs. Two out of 31 dogs showed a monoclonal arrangement for Ig with high (1:2) and low (1:7) polyclonal background respectively; and one of the 31 dogs showed a monoclonal arrangement for T cell receptor with low (1:3) polyclonal background.

Conclusion: Infections with Leishmania infantum resulted in clonal rearrangement, and therefore in a possible false diagnosis of lymphoma, in 3 out of 31 dogs (9.7%). Although, PARR is a useful method to differentiate lymphoma from reactive lymphoid hyperplasia in dogs with leishmaniosis, mono-/biclonal results should be interpreted carefully, especially in the presence of any degree of polyclonal background, and together with other clinicopathological findings.

MeSH terms

  • Animals
  • Clonal Evolution* / genetics
  • Clonal Evolution* / immunology
  • Diagnosis, Differential
  • Dog Diseases / diagnosis
  • Dog Diseases / genetics
  • Dog Diseases / immunology*
  • Dog Diseases / pathology
  • Dogs
  • Female
  • Gene Rearrangement, B-Lymphocyte
  • Gene Rearrangement, T-Lymphocyte
  • Genetic Testing / methods
  • Genetic Testing / veterinary
  • Leishmania infantum / genetics
  • Leishmania infantum / immunology*
  • Leishmaniasis, Visceral / diagnosis*
  • Leishmaniasis, Visceral / genetics
  • Leishmaniasis, Visceral / immunology
  • Leishmaniasis, Visceral / pathology
  • Lymph Nodes / immunology
  • Lymph Nodes / metabolism*
  • Lymphadenopathy / diagnosis*
  • Lymphadenopathy / genetics
  • Lymphadenopathy / immunology
  • Lymphadenopathy / parasitology
  • Lymphoma / diagnosis
  • Lymphoma / genetics
  • Lymphoma / veterinary
  • Male
  • Polymerase Chain Reaction / methods
  • Polymerase Chain Reaction / veterinary
  • Prospective Studies
  • Splenomegaly / diagnosis
  • Splenomegaly / veterinary

Grants and funding

The commercial company LABOKLIN GmbH & Co. KG provided funding in the form of salaries to authors AML, AKJ, EM and AK and performed clonality testing and Leishmania PCR, but did not have any additional role in the study design, data collection, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.