Neutralizing antibodies plays a primary role in protective immunity by preventing severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) from entering the cells. Therefore, characterization of antiviral immunity is important for protection against SARS-CoV-2. In this study, the neutralizing effect of the anti-SARS-CoV-2 S1 protein IgG, which was detected using the chemiluminescence microparticle immunoassay (CMIA)-based SARS-CoV-2 IgG II Quant (Abbott, Waukegan, IL, USA) test in SARS-CoV-2 infected and/or vaccinated individuals, was investigated with a surrogate virus neutralization test (sVNT). In total, 120 Seropositive individuals were included in this study. They were divided into two groups: Vaccinated (n = 60) and Vaccinated + Previously Infected (n = 60). A commercial sVNT, the ACE2–RBD Neutralization Test (Dia.Pro, Milan, Italy), was used to assess the neutralizing effect. The assay is performed in two steps: screening and titration. The screening showed positive results in all seropositive samples. Low titration in 1.7%, medium titration in 5%, and high titration in 93.3% of the Vaccinated group, and medium titration in 1.7% and high titration in 98.3% of the other group, as obtained from the ACE2-RBD titration test. A strong positive and significant correlation was found between the SARS-CoV-2 IgG II Quant test and the ACE2-RBD titration test at the 1/32 titration level for both groups (p < 0.001 for both). This study shows that the SARS-CoV-2 IgG detected using the CMIA method after SARS-CoV-2 infection and/or vaccination has a high neutralizing titration by using the sVNT. In line with these data, knowledge that seropositivity determined by CMIA also indicates a strong neutralizing effect contributes to countrywide planning for protecting the population.

Background/Objectives: T. pallidum subsp. pallidum is a spirochete that only causes disease in humans as the causative agent of syphilis. HIV and syphilis have common transmission routes. In the present study, our aim was to evaluate the presence of syphilis coinfection in people living with HIV using conventional and reverse algorithms and to investigate its effects on laboratory parameters. Methods: The traditional algorithm for syphilis begins testing with the non-treponemal test. If the non-treponemal test is reactive, a treponemal test is then used to confirm syphilis infection. The reverse algorithm for syphilis begins testing with the treponemal test. If this test is reactive, then a non-treponemal test is performed. When the non-treponemal test is non-reactive, a second treponemal test is performed. Results: A total of 200 patients were included in the study. While 22 patients were determined to be syphilis-positive using the traditional algorithm, 37 patients were determined to be syphilis-positive using the reverse algorithm. Most of the patients who had syphilis coinfection were homosexual. Conclusions: It was found that syphilis coinfection had no effects on CD4+ T-lymphocyte and CD8+ T-lymphocyte values, CD4/CD8 rates, and HIV RNA amounts. People living with HIV must be screened and followed up for syphilis and other sexually transmitted diseases at certain intervals.