An unexpected IgE anti-receptor binding domain response following natural infection and different types of SARS-CoV-2 vaccines.

Humoral response to SARS-CoV-2 has been studied, predominantly the classical IgG and its subclasses. Although IgE antibodies are typically specific to allergens or parasites, a few reports describe their production in response to SARS-CoV-2 and other viruses. Here, we investigated IgE specific to receptor binding domain (RBD) of SARS-CoV-2 in a Brazilian cohort following natural infection and vaccination.

Assessment of an in-house IgG ELISA targeting SARS-CoV-2 RBD: Applications in infected and vaccinated individuals.

The study evoluated an in-house Spike Receptor Binding Domain Enzyme-Linked Immunosorbent Assay (RBD-IgG-ELISA) for detecting SARS-CoV-2 IgG antibodies in infected and vaccinated individuals. The assay demonstrated a sensitivity of 91%, specificity of 99.25%, and accuracy of 95.

SARS-CoV-2 testing among patients and healthcare professionals in an HIV outpatient clinic in Brazil.

The COVID-19 pandemic in Brazil has been marked by high infection and death rates. The immune response generated by current vaccination might be influenced by previous natural infection, and baseline estimates may help in the evaluation of vaccine-induced serological response. We evaluated previous SARS-CoV-2 testing (RT-PCR), and performed rapid diagnostic tests (RDT) and high throughput electrochemiluminescence immunoassay (ECLIA) before vaccination among people living with HIV (PLWH), users of antiretroviral prophylaxis (PrEP/PEP), and healthcare professionals in an HIV outpatient clinic (HCP-HC).

Safety and immunogenicity of an inactivated SARS-CoV-2 vaccine (CoronaVac) in inadvertently vaccinated healthy children.

Twenty-seven children aged seven months to 5 years were inadvertently vaccinated with a COVID-19 vaccine, the CoronaVac (Sinovac, China), an inactivated SARS-CoV-2 vaccine, in two different cities of Sao Paulo State, Brazil. After the event, these children were monitored by local pediatricians and serum samples were collected at the first visit and 30 days after vaccination and tested for SARS-CoV-2 S1 serology with Ortho total IgG anti-S1 protein and Cpass, an ACE2 receptor binding domain inhibition assay. Only one child had a mild symptom after vaccination, with no other adverse events documented up to the 30 days follow-up.

A simple algorithm for selecting cases to investigate acute and early HIV infections in low- and middle-income countries.

We documented the outcome of an over 10-year (2011-2021) effort to diagnose acute and early HIV infections (AEHI) in an Infectious Diseases Outpatient Clinic with limited resources. Of a total of 132, 119 HIV-RNA tests were performed from 2017 to 2020, 12 cases were identified, using a simple algorithm: risk exposure of 6 weeks or less before the visit and/or symptoms compatible with acute retroviral syndrome 7-30 days after exposure and/or undetermined 3rd generation rapid diagnostic test or serology. AEHI diagnoses varied from 2.

Inhibition of receptor-binding domain-ACE2 interaction after two doses of Sinovac's CoronaVac or AstraZeneca/Oxford's AZD1222 SARS-CoV-2 vaccines.

Practical laboratory proxies that correlate to vaccine efficacy may facilitate trials, identify nonresponders, and inform about boosting strategies. Among clinical and laboratory markers, assays that evaluate antibodies that inhibit receptor-binding domain (RBD) ligation to angiotensin-converting enzyme-2 receptor (receptor-binding inhibition [RBI]) may provide a surrogate for viral neutralization assays. We evaluated RBI before and after a median of 34 days (interquartile range [IQR]: 33-40) of the second dose of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Sinovac's CoronaVac (CN) or AstraZeneca/Oxford's AZD1222 (AZ) vaccines in 166 individuals.

Humoral response to spike S1 and S2 and nucleocapsid proteins on microarray after SARS-CoV-2 infection.

Many aspects of the humoral immune response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), such as its role in protection after natural infection, are still unclear. We evaluated IgA and IgG response to spike subunits 1 and 2 (S1 and S2) and Nucleocapsid proteins of SARS-COV-2 in serum samples of 109 volunteers with viral RNA detected or seroconversion with different clinical evolution (asymptomatic, mild, moderate, and severe coronavirus disease 2019), using the ViraChip® Test Kit. We observed that the quantification of antibodies to all antigens had a positive correlation to disease severity, which was strongly associated with the presence of comorbidities.

Extracellular vesicles isolated from Toxoplasma gondii induce host immune response.

This study established a protocol to purify Toxoplasma gondii tachyzoite microvesicles and exosomes, called as extracellular vesicles (EVs). In addition, the investigations were conducted to determine the kinetic of EV release by tachyzoites and whether EV proteins are able to modulate the host immune response. The particle size and concentration released by tachyzoites in culture medium at different incubation-period were characterized by nanoparticle tracking analysis.