Development and validity assessment of ELISA test with recombinant chimeric protein of SARS-CoV-2.

Serological tests developed for COVID-19 diagnostic are based on antibodies specific for SARS-CoV-2 antigens. Most of the antigens consist of a fragment or a whole amino acid sequence of the nucleocapsid or spike proteins. We evaluated a chimeric recombinant protein as an antigen in an ELISA test, using the most conserved and hydrophilic portions of the S1-subunit of the S and Nucleocapsid (N) proteins. These proteins, individually, indicated a suitable sensitivity of 93.6 and 100% and a specificity of 94.5 and 91.3%, respectively. However, our study with the chimera containing S1 and N proteins of SARS-CoV-2 suggested that the recombinant protein could better balance both the sensitivity (95.7%) and the specificity (95.5%) of the serological assay when comparing with the ELISA test using the antigens N and S1, individually. Accordingly, the chimera showed a high area under the ROC curve of 0.98 (CI 95% 0.958-1). Thus, our chimeric approach could be used to assess the natural exposure against SARS-CoV-2 virus over time, however, other tests will be necessary to better understand the behaviour of the chimera in samples from people with different vaccination doses and/or infected with different variants of the virus.

Characterization of Leishmania species from Central-West Region of Brazil.

Leishmaniasis represents a complex of diseases with a broad clinical spectrum and epidemiological diversity. Involving a variety of agents, reservoirs, and vectors, cutaneous leishmaniasis (CL) presents different transmission patterns, which makes its control especially difficult. Epidemiological characterization with identification of existing Leishmania species in a particular region is essential for understanding this parasitosis epidemiology. Because similar results may be observed in places with overlapping transmission of visceral and cutaneous leishmaniasis, contributing to knowledge about the epidemiological cycle of cutaneous leishmaniasis is of global interest. This study proposes to identify the different species of Leishmania present in human CL cases in the state of Mato Grosso do Sul, Brazil. Slides of imprint tissue were selected from patients diagnosed with CL from 2009 to 2013 at the Laboratório de Parasitologia Clínica, Universidade Federal de Mato Grosso do Sul. The slides were scraped and extracted genetic material was amplified with PCR addressing the Leishmania spp. kDNA region. The reaction product was subjected to RFLP for the specific identification of Leishmania. Forty-three samples (82.7%) amplified with PCR were considered positive. Of these, it was possible to determine the species in 40 samples (76.9%) through analysis of electrophoresis profiles. Leishmania (Viannia) braziliensis, Leishmania (Leishmania) amazonensis, and Leishmania (Leishmania) infantum were identified as the etiologic agents of CL in Mato Grosso do Sul. The results of this study permit a more detailed understanding of CL epidemiology and the geographical distribution of its agents.

Leishmania (V.) braziliensis infecting bats from Pantanal wetland, Brazil: First records for Platyrrhinus lineatus and Artibeus planirostris.

In the New World genus Leishmania parasites are etiological agents of neglected zoonoses known as leishmaniasis. Its epidemiology is very complex due to the participation of several species of sand fly vectors and mammalian hosts, and man is an accidental host. Control is very difficult because of the different epidemiological patterns of transmission observed. Studies about Leishmania spp. infection in bats are so scarce, which represents a large gap in knowledge about the role of these animals in the transmission cycle of these pathogens, especially when considering that Chiroptera is one of the most abundant and diverse orders among mammals. Leishmaniasis in Mato Grosso do Sul, Brazil are remarkably frequent, probably due to the abundance of its regional mastofauna. The recent record of L. braziliensis in bats from this state indicates the need to clarify the role of these mammals in the transmission cycle. In this study we evaluated the presence of Leishmania parasites in the skin of different species of bats, using PCR directed to Leishmania spp. kDNA for screening followed by PCR/RFLP analysis of the hsp70 gene for the identification of parasite species. Leishmania species identification was confirmed by PCR directed to the G6PD gene of L. braziliensis, followed by sequencing of the PCR product. Samples from 47 bats were processed, of which in three specimens (6.38%) was detected the presence of Leishmania sp. kDNA. PCR/RFLP and sequencing identified the species involved in the infection as L. braziliensis in all of them. This is the first report of Leishmania braziliensis in bats from Pantanal ecosystem and the first record of this species in Platyrrhinus lineatus and Artibeus planirostris, bats with a wide distribution in South America. These results reinforce the need to deepen the knowledge about the possibility of bats act as reservoirs of Leishmania spp. especially considering their ability of dispersion and occupation of anthropic environments.