Wagner Santos’s research while affiliated with Oswaldo Cruz Foundation and other places

Simple Summary This study aimed to compare the true diagnostic potential of the recombinant chimeric protein Q5 in an ELISA assay using a large number of sera from CVL-suspected dogs. Sera from dogs with a CVL positive diagnosis based on the rapid DPP test (n = 406) and negative samples from healthy dogs (n = 46) were used for ELISA tests using the recombinant Q5. Overall, similar levels of lower sensitivity (67–68%) were seen for both the commercial EIE-LVC test and the Q5 ELISA when all assessed sera were considered, but a much greater sensitivity (92%) was seen for those samples from symptomatic dogs only. In contrast, many negative results were observed for the DPP-positive sera from asymptomatic dogs or from those with no clinical information available. The results reveal a higher-than-expected incidence of likely false-positive results for DPP, reinforcing the need for other recombinant proteins, such as the chimeric Q5, to be investigated as possible alternatives to the currently used CVL diagnostic methods. Abstract Dogs are considered the major domestic reservoir for human visceral leishmaniasis, a serious disease caused by the Leishmania infantum parasite. Diagnosis of canine visceral leishmaniasis (CVL) is critical for disease control, with several methods currently available. Among the serological tests, the DPP rapid test and the EIE-LVC, more commonly used in Brazil, are associated with variable sensitivity and specificity. Research with novel recombinant proteins such as the ELISA with the recombinant chimeric protein Q5 may therefore improve the CVL diagnosis. This study aimed to evaluate the true diagnostic potential of Q5 in an ELISA assay using a large number of CVL-suspected sera (406) with a previous positive diagnosis based on the rapid DPP test. Sera from the DPP-positive dogs, also assessed with the EIE-LVC test, were compared with sera from healthy dogs (n = 46) and used for ELISA tests using the recombinant Q5. The resulting data as well as the correlation with the clinical signs and the environmental characteristics of the animals were analyzed using Medal and GraphPad Prism 8.0. Overall, similar levels of lower sensitivity (67–68%) were seen for both the commercial EIE-LVC test and the Q5 ELISA when all assessed sera were considered, but a much greater sensitivity (92%) was seen for those samples from symptomatic dogs only. In contrast, many negative results were observed for the DPP-positive sera from asymptomatic dogs or those with no clinical information available. A selection of those sera were tested yet again in new ELISA assays using a second batch of the recombinant Q5, purified under milder denaturing conditions, as well as using another recombinant protein (Lci13). The results reveal a higher-than-expected incidence of likely false-positive results for DPP, reinforcing the need for other recombinant proteins, such as the chimeric Q5, to be investigated as possible alternatives to the currently used CVL diagnostic methods.

Background Dogs are considered the major domestic reservoir for the human visceral leishmaniasis, a serious disease caused by the Leishmania infantum parasite. Diagnosis of the canine visceral leishmaniasis (CVL) is critical for disease control, with several methods currently available. Among the serological tests, the DPP rapid test and the EIE-LVC, more commonly used in Brazil, are associated with variable sensitivity and specificity. Research with novel recombinant proteins may therefore improve on the CVL diagnosis, such as the ELISA with the recombinant chimeric protein Q5. This study aimed to compare the Q5 in ELISA with the EIE-LVC (Leishmania major) using a large number ofCVL suspected sera (406) with a previous diagnosis based on the rapid DPP test. Methods Serum samples from dogs CVL positive in the rapid DPP test (n=406) and negative samples from healthy dogs (n=46) were used for ELISA tests using recombinant proteins Q5 and Lci13. The data obtained in the ELISA as well as the correlation with the clinical signs and the Socio-environmental characteristics of the animals were calculated using MedCalc and GraphPad Prism 8.0. Results Overall, similar levels of a lower sensitivity (67-68%) were seen for both the commercial EIE-LVC test and the Q5 ELISA when all assessed sera were considered, but a much greater sensitivity (92%) was seen for those from symptomatic dogs only. In contrast, a large number of negative results were observed for the DPP-positive sera from asymptomatic dogs or those with no clinical information available. A selection of those were tested yet again in new ELISA assays using a second batch of the Q5, purified under milder denaturing conditions, as well as another recombinant protein (Lci13). Conclusions The results reveal a higher-than-expected incidence of false-positive results for DPP, reinforcing the need for other recombinant proteins, such as the chimeric Q5, to be investigated as possible alternatives to the currently used CVL diagnostic methods.