PpSP32-like protein as a marker of human exposure to Phlebotomus argentipes in Leishmania donovani foci in Bangladesh

Phlebotomus argentipes is a predominant vector of Leishmania donovani, the protozoan parasite causing visceral leishmaniasis in the Indian subcontinent. In hosts bitten by P. argentipes, sand fly saliva elicits the production of specific anti-salivary protein antibodies. Here, we have utilised these antibodies as markers of human exposure to P. argentipes in a visceral leishmaniasis endemic area in Pabna district, Bangladesh. The use of whole salivary gland homogenate as an antigen to detect these antibodies has several limitations, therefore it is being superseded by the use of specific recombinant salivary proteins. We have identified three major P. argentipes salivary antigenic proteins recognised by sera of bitten humans, expressed them in a recombinant form (rPagSP04, rPagSP05 and rPagSP06) and tested their applicability in ELISA and immunoblot. One of them, PpSP32-like protein rPagSP06, was identified as the most promising antigen, showing highest resemblance and correlation with the IgG response to P. argentipes salivary gland homogenate. Furthermore, we have validated the applicability of rPagSP06 in a large cohort of 585 individuals and obtained a high correlation coefficient for anti-rPagSP06 and anti-P. argentipes saliva IgG responses. The anti-rPagSP06 and anti-P. argentipes salivary gland homogenate IgG responses followed a similar right-skewed distribution. This is the first report of screening human sera for anti-P. argentipes saliva antibodies using recombinant salivary protein. The rPagSP06 was proven to be a valid antigen for screening human sera for exposure to P. argentipes bites in a visceral leishmaniasis endemic area. (c) 2021 The Author(s). Published by Elsevier Ltd on behalf of Australian Society for Parasitology. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Centre for Research of Pathogenicity and Virulence of Parasites [CZ.02.1.01/0.0/0.0/16_0 19/0000759]; Charles University Research Centre [UNCE/SCI/012-204072/2018]; European Union's Horizon 2020 research and innovation program [731060]; project entitled Research and Development of Prevention and Diagnosis for Neglected Tropical Diseases - JST/JICA (Japan Science and Technology Agency/Japan International Cooperation Agency); Science and Technology Research Partnership for Sustainable Development, Japan
We gratefully thank Barbora Kalouskova and Ondrej Vanek from the Department of Biochemistry, Charles University, Czech Republic, for expression and purification of the recombinant pro-teins, and Karel Harant and Pavel Talacko from the Laboratory of Mass Spectrometry, Biocev, Charles University, for proteomic and mass spectrometric analyses. We appreciate the assistance of Vit Dvorak for language revision and Helena Kulikova and Lenka Krejcirikova from Charles University for excellent technical and administrative support. We also appreciate the support given by Sarkar Santana Rani and Fashiur Rahman from Mymensingh Med-ical College, and Shahidul Islam from Health Inspector of Chatmo-hor, Bangladesh, Bumpei Tojo, Yasutaka Osada, Sara Kato, Rina Hobo, and Keita Yoshii from The University of Tokyo, Japan, during the blood and sand fly collection period in Pabna, Bangladesh. This work was supported by the projects entitled Centre for Research of Pathogenicity and Virulence of Parasites [CZ.02.1.01/0.0/0.0/16_0 19/0000759] and Charles University Research Centre [UNCE/SCI/012-204072/2018] . The research stay of Chizu Sanjoba at Charles University was funded by the European Union's Horizon 2020 research and innovation program under grant agreement No 731060 (Infravec2) . This study was also supported by a project entitled Research and Development of Prevention and Diagnosis for Neglected Tropical Diseases, supported by JST/JICA (Japan Science and Technology Agency/Japan International Cooperation Agency) and the Science and Technology Research Partnership for Sustainable Development, Japan. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.