Medical Doctor, Infectious Disease Specialist, PhD in Human Pathology
RESEARCH, TEACHING, or OTHER INTERESTS
Infectious Diseases
35
Scopus Publications
Scopus Publications
Prevalence of anti-Trypanosoma cruzi and anti-Leishmania infantum antibodies in domestic dogs from Tremedal, Bahia: insights from the Oxente Chagas Bahia Project Tycha Bianca Sabaini Pavan, Larissa Carvalho Medrado Vasconcelos, Isabela Machado Serrano, Denis Augusto Argolo Campos, Ângelo Antônio Oliveira Silva, et al. Parasites and Vectors, 2025 Background Chagas disease (CD) and visceral leishmaniasis (VL) are two important zoonotic diseases that present significant public health challenges in Latin America. Domestic dogs, due to their close contact with humans, serve as key reservoirs for both Trypanosoma cruzi (the causative agent of CD) and Leishmania infantum (the causative agent of VL), making them important sentinels in disease surveillance. This study, conducted as part of the Oxente Chagas Bahia Project, aimed to assess the seroprevalence of anti-T. cruzi and anti-L. infantum antibodies in domestic dogs from Tremedal, Bahia, Brazil. Methods Serum samples from 17 dogs were analyzed using indirect enzyme-linked immunosorbent assay (ELISA) (using recombinant antigens (IBMP-8.1, IBMP-8.2, IBMP-8.3, IBMP-8.4) for T. cruzi and the TR DPP® rapid test and ELISA for L. infantum. Results The results showed that 5.9% (1/17) of the dogs tested were seropositive for T. cruzi, indicating the presence of the parasite in the region. Similarly, 5.9% (1/17) of the dogs were confirmed to be positive for L. infantum by ELISA, although the results of the TR DPP® test initially suggested a higher prevalence (41.2%), highlighting the risk of false-positive results. Conclusions These findings underscore the critical role of dogs in CD and VL surveillance, given their involvement in both domestic and peridomestic transmission cycles. The study also emphasizes the need for confirmatory testing to ensure diagnostic accuracy, which will contribute to more effective disease control strategies in endemic areas. This work highlights the importance of a One Health approach in which human and animal health are closely monitored to mitigate the transmission of zoonotic diseases. Graphical Abstract
Development and Validation of ELISA for In Vitro Diagnosis of SARS-CoV-2 Infection Larissa de Carvalho Medrado Vasconcelos, Leonardo Maia Leony, Ângelo Antônio Oliveira Silva, Aquiles Assunção Camelier, Antônio Carlos Bandeira, et al. Covid, 2025 (1) Background: The ongoing global health threat posed by SARS-CoV-2 requires reliable and accessible diagnostic tools, especially in resource-limited settings where RT-qPCR may be impractical. This study describes the development and validation of two enzyme-linked immunosorbent assays (ELISA) designed to detect anti-SARS-CoV-2 IgG antibodies employing recombinant S1 and S2 spike protein subunits. (2) Methods: The assays were optimized and validated using serum samples from 354 RT-qPCR-confirmed hospitalized patients and 337 pre-pandemic blood donors. (3) Results: The S1-based ELISA achieved a 52.8% sensitivity and a specificity of 93.5%, with an area under the ROC curve (AUC) of 71.6%. In contrast, the S2-based ELISA demonstrated superior diagnostic performance, with a sensitivity of 63.7%, a specificity of 99.7%, and an AUC of 83.1%. Cross-reactivity analysis using sera from individuals with unrelated infectious diseases confirmed the high specificity of the S2-ELISA. Time-stratified analysis revealed that sensitivity increased with time, peaking between 15 and 21 days post-symptom onset. Compared to commercial serological assays, the S2-ELISA demonstrated comparable or improved performance, particularly in specificity and diagnostic odds ratio. (4) Conclusions: The S2-ELISA offers a robust, highly specific, and operationally simple tool for serological detection of SARS-CoV-2 infection. Its strong diagnostic performance and accessibility make it well-suited for implementation in diverse epidemiological settings, particularly where molecular testing is limited. The development of affordable, validated serological assays such as this is critical for strengthening surveillance, understanding transmission dynamics, and informing public health responses.
Advancing syphilis diagnosis: multi-phase study evaluation of a TpN17-based double-antigen sandwich ELISA for detecting Treponema pallidum specific antibodies Ângelo Antônio Oliveira Silva, Larissa Carvalho Medrado Vasconcelos, Natália Erdens Maron Freitas, Talita Andrade Oliva, Miralba Freire Carvalho Ribeiro Silva, et al. Frontiers in Microbiology, 2025 Syphilis, a sexually transmitted infection caused by the bacterium Treponema pallidum, has high incidence rates among adults, pregnant women, and newborns. Diagnostic procedures typically involve a treponemal test (such as ELISA, CMIA, and IFI), followed by a non-treponemal test (VDRL and RPR). This study aimed to assess the diagnostic performance of a double antigen sandwich ELISA (DAgS-ELISA) using the recombinant protein TpN17, analyzing serum samples from both infected and not infected with T. pallidum. A total of 712 samples were deemed eligible and recharacterized using VDRL, ELISA, and FTA-ABS, with 613 ultimately included in the evaluation: 180 T. pallidum-positive, 169 T. pallidum-negative, and 264 positive samples for other diseases. The assay was standardized using checkerboard titration and evaluated based on the area under the ROC curve (AUC), sensitivity, specificity, accuracy, likelihood values, diagnostic ratio, and Cohen’s Kappa index (κ). In phase I, positive and negative samples showed statistical differences (p < 0.0001) for the TpN17 protein. The ROC curve (AUC) was 98.7% and Cohen’s Kappa of 0.91, indicating almost perfect agreement with the reference tests. Phase II results demonstrated an AUC of 97.5%, specificity of 100%, sensitivity of 88.9%, accuracy of 94.3%, a positive likelihood ratio of 1.512, a negative likelihood ratio of 0.11, and a diagnostic odds ratio of 13,600, with a Cohen’s Kappa of 0.89. Cross-reactivity was observed in samples positive for Chagas disease (11.5%), HBV (2.6%), HCV (6.4%), and HTLV-1/2 (6.8%). Overall, TpN17 exhibited high diagnostic performance across all clinical stages of syphilis. Future research should expand the sample panel and explore new proteins to enhance DAgS-ELISA’s effectiveness and applicability for syphilis diagnosis across diverse clinical settings.
Performance Assessment of Treponemal and Nontreponemal Tests for the Diagnosis of Acquired Syphilis Ângelo Antônio Oliveira Silva, Ayla Araújo Lima, Larissa de Carvalho Medrado Vasconcelos, Rosângela Andrade de Almeida, Natália Erdens Maron de Freitas, et al. American Journal of Tropical Medicine and Hygiene, 2024 There are a variety of nontreponemal test (NTT) and treponemal test (TT) kits for the serologic diagnosis of syphilis. Because of the complexity of the infection (multiple clinical stages) and the different antigens used in these kits, a systematic evaluation of the accuracy of the currently available commercial tests is warranted. Our objective was to evaluate the performance of commercially available tests for the diagnosis of syphilis infection. In this study, we analyzed one NTT (Venereal Disease Research Laboratory [VDRL] test, Wiener Laboratories, Rosario, Argentina) and two TTs (fluorescent treponemal antibody absorption [FTA-ABS] test, Euroimmun, Lübeck, Germany, and syphilis recombinant ELISA v. 4.0 test [ELISA], Wiener Laboratories, Rosario, Argentina) using a panel of 187 samples, including serum samples from 31 individuals with primary syphilis, 77 with secondary syphilis, and 79 with latent syphilis. An additional 192 samples from uninfected individuals and 323 serum samples from individuals with other diseases were included. The sensitivities of the VDRL, ELISA, and FTA-ABS tests were 97.9%, 100%, and 96.3%, respectively. The VDRL and ELISA tests showed a specificity of 100%, and the FTA-ABS test showed a specificity of 99.5%. Accuracy was 98.9% for the VDRL test, 100% for the ELISA, and 97.9% for the FTA-ABS test. For primary, secondary, and latent syphilis, the ELISA achieved a diagnostic performance of 100%, whereas the sensitivity for the VDRL and FTA-ABS tests ranged from 96.8% to 98.7% and 93.7% to 98.7%, respectively. No difference was observed when the tests were used as traditional or reverse algorithms. In general, all three tests are able to discriminate positive and negative samples for syphilis, regardless of the diagnostic algorithm.
High seroprevalence of Leishmania infantum is linked to immune activation in people with HIV: a two-stage cross-sectional study in Bahia, Brazil Laise de Moraes, Luciane Amorim Santos, Liã Bárbara Arruda, Maria da Purificação Pereira da Silva, Márcio de Oliveira Silva, et al. Frontiers in Microbiology, 2023 Visceral leishmaniasis is an opportunistic disease in HIV-1 infected individuals, unrecognized as a determining factor for AIDS diagnosis. The growing geographical overlap of HIV-1 and Leishmania infections is an emerging challenge worldwide, as co-infection increases morbidity and mortality for both infections. Here, we determined the prevalence of people living with HIV (PWH) with a previous or ongoing infection by Leishmania infantum and investigated the virological and immunological factors associated with co-infection. We adopted a two-stage cross-sectional cohort (CSC) design (CSC-I, n = 5,346 and CSC-II, n = 317) of treatment-naïve HIV-1-infected individuals in Bahia, Brazil. In CSC-I, samples collected between 1998 and 2013 were used for serological screening for leishmaniasis by an in-house Enzyme-Linked Immunosorbent Assay (ELISA) with SLA (Soluble Leishmania infantum Antigen), resulting in a prevalence of previous or ongoing infection of 16.27%. Next, 317 PWH were prospectively recruited from July 2014 to December 2015 with the collection of sociodemographic and clinical data. Serological validation by two different immunoassays confirmed a prevalence of 15.46 and 8.20% by anti-SLA, and anti-HSP70 serology, respectively, whereas 4.73% were double-positive (DP). Stratification of these 317 individuals in DP and double-negative (DN) revealed a significant reduction of CD4+ counts and CD4+/CD8+ ratios and a tendency of increased viral load in the DP group, as compared to DN. No statistical differences in HIV-1 subtype distribution were observed between the two groups. However, we found a significant increase of CXCL10 (p = 0.0076) and a tendency of increased CXCL9 (p = 0.061) in individuals with DP serology, demonstrating intensified immune activation in this group. These findings were corroborated at the transcriptome level in independent Leishmania- and HIV-1-infected cohorts (Swiss HIV Cohort and Piaui Northeast Brazil Cohort), indicating that CXCL10 transcripts are shared by the IFN-dominated immune activation gene signatures of both pathogens and positively correlated to viral load in untreated PWH. This study demonstrated a high prevalence of PWH with L. infantum seropositivity in Bahia, Brazil, linked to IFN-mediated immune activation and a significant decrease in CD4+ levels. Our results highlight the urgent need to increase awareness and define public health strategies for the management and prevention of HIV-1 and L. infantum co-infection.
The emergence of arboviruses changes the profile of viral meningitis in Salvador, Bahia: A case series Tamiris T. Dias, Laura B. Tauro, Lara E. N. Macêdo, Liz O. Brito, Victor H. O. Ribeiro, et al. Frontiers in Tropical Diseases, 2022 BackgroundRecently, different arboviruses became endemic in Brazil mostly causing acute febrile illnesses, however, neurological manifestations have also been reported. This study aimed to investigate which viruses were involved in the meningitis etiology and the contribution of the circulating arboviruses in Salvador, Bahia, Brazil.MethodsFrom June 2014 to February 2016, 170 patients with suspected viral meningitis were identified in Couto Maia Hospital, Salvador-BA, Brazil. Their CSF samples were investigated for possible viral etiology by reverse transcription-PCR (RT-PCR) for different arboviruses: DENV, ZIKV and CHIKV; and for the EV; and by PCR for the HHV1-5 complex (HSV1-2, VZV, EBV and CMV). Also, ELISA was carried out in a subgroup of remaining samples for detection of DENV IgM and NS1 antigen, CHIKV IgM and ZIKV IgM.ResultsThirty-seven patients were PCR or ELISA positive for at least one of the studied viruses (overall positivity 21.8%). EV was the agent most frequently detected (10 cases; 27.0%), along with all four DENV serotypes (10 cases; 27.0%); followed by CHIKV (6 cases; 16.2%), ZIKV (6 cases; 16.2%), and Varicella zoster virus (VZV) (1 case; 2.7%). Four cases (10.8%) presented viral co-infection detected: DENV1 + CHIKV, DENV1 + EV, DENV4 + ZIKV, and CHIKV + ZIKV. Arboviruses (DENV, CHIKV and ZIKV) accounted for the great majority of cases (26 cases; 70.3%) of all single and co-infections: DENV has been the most frequently detected arbovirus (13 cases; 35.1%). Among non-arboviral meningitis, the most common etiology was the EV (11 cases; 29.7%).ConclusionsArboviruses accounted for the majority of identified viruses among patients with suspected viral meningitis. In areas where they are endemic it is crucial to increase viral surveillance and consider them in the differential diagnosis of meningitis.
Chromobacterium violaceum in siblings, Brazil Isadora Cristina de Siqueira, Juarez Dias, Hilda Ruf, Eduardo Antonio G. Ramos, Elves Anderson Pires Maciel, et al. Emerging Infectious Diseases, 2005
