Total serum IgD from healthy and sick dogs with leishmaniosis

Abstract

Background: Canine leishmaniosis (CanL) due to Leishmania infantum is characterized by the development of both cellular and humoral immune responses. The dysfunction of T cell-mediated immunity leads to a lack of proliferation of T cells in response to Leishmania antigens with the consequence of parasite dissemination that seems to be related to a T cell exhaustion mediated by regulatory B cells expressing immunoglobulin D (IgD). The aim of this study was to determine and compare the total serum IgD in dogs with clinical leishmaniosis and in clinically healthy dogs.

Results: A total of 147 dog sera were studied. All dogs were tested for L. infantum-specific antibodies by quantitative ELISA. Interferon-gamma (IFN-γ) production was also determined by sandwich ELISA after blood stimulation with L. infantum soluble antigen (LSA) or concanavalin A (ConA). The quantification of total IgD was performed using a human IgD sandwich ELISA quantification set. Dogs were classified in three different groups. Group 1 included 40 clinically healthy non-infected dogs, all serologically negative to L. infantum-specific antibodies and non-producers of IFN-γ upon LSA stimulation. Group 2 included 63 clinically healthy infected dogs that were LSA IFN-γ producers (n = 61) and/or IFN-γ non-producers (n = 2) as well as negative to medium seropositive to L. infantum antigen. Finally, Group 3 included 44 dogs with clinical leishmaniosis (IFN-γ producers, n = 23; and IFN-γ non-producers, n = 21) that were negative to highly positive to L. infantum-specific antibodies. No significant differences were observed when the total IgD concentration was compared within groups. Additionally, total IgD of sick IFN-γ producers and IFN-γ non-producers was not significantly different. Finally, total IgD concentration was not statistically related to demographic parameters such as age, sex and breed.

Conclusions: The results of this study demonstrated that there were no differences between groups in total serum IgD. Total serum IgD does not appear to be a marker of disease in CanL.

Keywords: Canine leishmaniosis; IFN-γ; IL-10; IgD; Leishmania infantum; PD-1.

Fig. 1

a Specific L. infantum IFN-γ concentration based on IFN-γ producers and IFN-γ non-producers in healthy non-infected, healthy infected and sick dogs. b IFN-γ concentration after ConA stimulation based on IFN-γ producers and IFN-γ non-producers in healthy non-infected, healthy infected and sick dogs. White circles represent individual data of each dog, boxes represent minimum and maximum values of quartiles, the bands inside represent the second quartile (median). Statistical results of LSA IFN-γ: Group 1 (healthy non-infected) < Group 2 (healthy infected) (Mann-Whitney U-test: Z = -8.31, P < 0.0001), Group 1 (healthy non-infected) < Group 3 (sick) (Mann-Whitney U-test: Z = -3.81, P = 0.0001), Group 2 (healthy infected) < Group 3 (sick) (Mann-Whitney U-test: Z = -3.28, P = 0.001). ConA IFN-γ: Group 1(healthy non-infected) < Group 2 (healthy infected) (Mann-Whitney U-test: Z = -2.67, P = 0.008). Abbreviations: LSA, Leishmania soluble antigen; ConA, concanavalin A; IFN-γ, interferon gamma

Fig. 2

a Specific L. infantum antibodies levels in healthy non-infected, healthy infected and sick dogs classified based on LeishVet clinical staging. b Total serum IgD concentrations in healthy non-infected, healthy infected and sick dogs classified based on LeishVet clinical staging. White circles represent individual data of each animal, boxes represent minimum and maximum values of quartiles, the bands inside represent the second quartile (median). Statistical results of L. infantum specific antibodies by ELISA: Group 1 (healthy non-infected) < Group 2 (healthy infected) (Mann-Whitney U-test: Z = -4.46, P < 0.0001), Group 1 (healthy non-infected) < Group 3 (sick) (Mann-Whitney U-test: Z = −9.59, P < 0.0001), Group 2 (healthy infected) < Group 3 (sick) (Mann-Whitney U-test: Z = -7.84, P < 0.0001), mild stages (I and IIa) < severe stages (IIb, III and IV) (Mann-Whitney U-test: Z = -3.07, P = 0.002), stage I < stage IIa (Mann-Whitney U-test: Z = -4.45, P < 0.0001), stage I < stage IIb (Mann-Whitney U-test: Z = -3.07, P = 0.002), stage I < Stage III (Mann-Whitney U-test: Z = -3.25, P = 0.001), stage I < stage IV (Mann-Whitney U-test: Z = -2.85, P = 0.004), stage IIa < stage IV (Mann-Whitney U-test: Z = -2.59, P = 0.01)

Fig. 3

Total serum IgD concentrations in IFN-γ producers and IFN-γ non-producers sick dogs classified based on LeishVet clinical staging. Circles represent individual data of each dog, the horizontal line represents the mean and the vertical lines represent the standard deviation. No statistical differences were observed within LeishVet clinical stages. Abbreviations: LSA, Leishmania soluble antigen; ConA, concanavalin A; IFN-γ, interferon gamma