A multicentric evaluation of the recombinant Leishmania infantum antigen-based immunochromatographic assay for the serodiagnosis of canine visceral leishmaniasis

Abstract

Background: Visceral leishmaniasis (VL) is a serious public health challenge in Brazil and dogs are considered to be the main urban reservoir of the causative agent. The culling of animals to control VL in some countries makes the accurate diagnosis of canine VL (CVL) essential. Recombinant antigens rLci1A and rLci2B were selected from a cDNA library of Leishmania infantum amastigotes due to their strong potential as candidates in diagnostic testing for CVL. The present multicentric study aimed to evaluate the sensitivity of a prototype test using these antigens (DPP rLci1A/rLci2B) against 154 sera obtained from symptomatic dogs within three endemic areas of VL in Brazil. The specificity was evaluated using 40 serum samples from negative dogs and dogs infected with other pathogens. Sensitivity and specificity rates of DPP rLci1A/rLci2B prototype were compared to rates from other diagnostic tests currently in use by the Brazilian Ministry of Health, including DPPLVC, EIELVC.

Findings: DPP rLci1A/rLci2B prototype offered similar performance to that offered by DPPLVC rapid test, as follows: sensitivity of 87% (CI 81-91) and 88% (CI 82-93) and specificity of 100% (CI 91-100) and 97% (CI 87-100), respectively for DPP rLci1A/rLci2B and DPPLVC. When results of these two tests were considered concomitantly, sensitivity increased to 93.5% (CI 89-96).

Conclusions: The recombinant antigens rLci1A and rLci2B represent promising candidates for use in a multi-antigen rapid test for CVL. The inclusion of novel antigens to the DPP rLci1A/rLci2B prototype model could offer additionally enhanced sensitivity to detect animals infected by L. infantum.

Figure 1

Positivity rates of DPP rLci1A / rLci2B regarding detection of serum samples from L. infantum-infected dogs. The antigens rLci1A / rLci2B were individually impregnated at concentrations of 0.35/0.20 mg/mL and 0.70/0.70 mg/mL, respectively. Positivity rates for either proteins were analyzed both individually and collectively. A total of 154 canine serum samples were obtained from the three INCT-DT laboratories included in this study.