Visceral leishmaniasis (VL) is a neglected tropical disease of global importance caused by parasites of the genus
Leishmania
, and coinfection with human immunodeficiency virus (HIV) is common in countries where both diseases are endemic. In particular, widely used immunological tests for VL diagnosis have impaired sensitivity (Se) and specificity (Sp) in VL/HIV coinfected patients and there is also cross-reactivity with other endemic diseases, e.g., Chagas disease, malaria, and tuberculosis. To develop new antigens to improve the diagnosis of VL and VL/HIV coinfection, we predicted eight specific B-cell epitopes of four
Leishmania infantum
antigens and constructed a recombinant polypeptide chimera antigen called ChimLeish. A serological panel of 195 serum samples was used to compare the diagnostic capabilities of ChimLeish alongside the individual synthetic peptides. ChimLeish reacted with sera from all VL and VL/HIV coinfected patients [Se = 100%; Sp = 100%; area under the curve (AUC) = 1.0]. Peptides showed lower reactivities (Se = 76.8 to 99.2%; Sp = 67.1 to 95.7%; AUC between 0.87 and 0.98) as did a
L. infantum
antigenic preparation used as an antigen control (Se = 56.8%; Sp = 69.5%: AUC = 0.45). Notably, ChimLeish demonstrated a significant reduction (
p
< 0.05) of anti-ChimLeish antibodies after treatment and cure of a small number of patients. Although only a limited serological panel was tested, preliminary data suggest that ChimLeish should be evaluated in larger sample studies for the diagnosis of VL and VL/HIV coinfection.
The COVID-19 pandemic, caused by
the fast transmission and spread
of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is
currently considered a serious health problem, requiring an effective
strategy to contain SARS-CoV-2 dissemination. For this purpose, epitopes
of the SARS-CoV-2 spike (S) and sucleocapsid (N) proteins were identified
by bioinformatics tools, and peptides that mimic these epitopes were
chemically synthesized and then conjugated to superparamagnetic nanoparticles
(SPMNPs). Three peptides from S protein and three from N protein were
used as antigens in a conventional enzyme-linked immunosorbent assay
(ELISA) against serum samples from COVID-19-positive patients, or
from healthy donors, collected before the pandemic. Three peptides
were effective as antigens in conventional peptide-based ELISA, achieving
100% sensitivity and specificity, with high accuracy. The best-performing
peptides, p2pS, p1pN, and p3pN, were associated with superparamagnetic
nanoparticles (SPMNPs) and were used to perform nanomagnetic peptide-based
ELISA. The p2pS–SPMNP conjugate presented 100% sensitivity
and specificity and excellent accuracy (area under the curve (AUC)
= 1.0). However, p1pN and p3pN peptides, when conjugated to SPMNPs,
did not preserve the capacity to differentiate positive sera from
negative sera in all tested samples, yet both presented sensitivity
and specificity above 80% and high accuracy, AUC > 0.9. We obtained
three peptides as advantageous antigens for serodiagnosis. These peptides,
especially p2pS, showed promising results in a nanomagnetic peptide-based
ELISA and may be suitable as a precoated antigen for commercial purposes,
which would accelerate the diagnosis process.
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