Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is characterized by high contagiousness, as well as variable clinical manifestations and immune responses. The antibody response to SARS-CoV-2 is directly related to viral clearance and the antibodies' ability to neutralize the virus and confer long-term immunity. Nevertheless, the response can also be associated with disease severity and evolution. This study correlated the clinical characteristics of convalescent COVID-19 patients with immunoglobulin A (IgA) and IgG anti-SARS-CoV-2 antibodies. This study included 51 COVID-19 health care professionals who were candidates for convalescent plasma donation from April to June 2020. The subjects had symptomatic COVID-19 with a polymerase chain reaction-confirmed diagnosis. We measured anti-SARS-CoV-2 IgA and IgG antibodies after symptom recovery, and the subjects were classified as having mild, moderate, or severe symptoms. Anti-SARS-CoV-2 antibodies were positive in most patients (90.2%). The antibody indexes for IgA and IgG did not differ significantly between patients presenting with mild or moderate symptoms. However, they were significantly higher in patients with severe symptoms. Our study showed an association between higher antibody indexes and severe COVID-19 cases, and several hypotheses regarding the association of the antibody dynamics and severity of the disease in SARS-CoV-2 infection have been raised, although many questions remain unanswered.

Introduction: Previous retrospective studies have demonstrated that the concentration of chemokine ligand CXCL13 in cerebrospinal fluid (CSF-CXCL13) is a promising biomarker in the diagnosis of neurosyphilis and, additionally, in the monitoring of therapeutic efficacy. Objective: To describe three cases of patients with neurosyphilis (NS) treated at Hospital Universitário Gaffrée e Guinle, in Rio de Janeiro, Brazil, with suspected active syphilis with neurological symptoms. Case report: Three patients from Rio de Janeiro, Brazil, were investigated for symptomatic NS. The concentration of CSF-CXCL13 was prospectively performed by enzyme-linked immunosorbent assay (ELISA) in all participants at baseline and in follow-up visits at 3 months after therapy. CSF-CXCL13 concentrations were significantly higher in all three patients with established NS. The CSF-CXCL13 concentrations decreased after 3 months of therapy compared to baseline in all cases reported. The added high concentration of CSF-CXCL13 plus CSF-TPHA reactivity above 1:40 titer agreed with the diagnosis of NS in 100% of the cases. Conclusion: In this case series, we present three cases of NS diagnosed using CXCL13 in CSF as a complementary test. These case series suggest that the clinical use of CSF-CXCL13 is useful as a supplementary biomarker for NS and for monitoring the effectiveness of NS therapy, especially in patients with nonreactive CSF-VDRL, excluding other neurologic diseases.

The considerable HIV-1 genetic diversity has several implications for viral adaptive and evolutionary capabilities. Its genetic diversity is due to its high mutational rates derived from the error-prone viral reverse transcriptase activity, which generates highly heterogeneous viral populations. Moreover, genetic diversity can also increase due to intra- or intersubtype viral genomic recombination following multiple infections. This study examines HIV-1 intersubtype recombinant viruses and their increased genomic diversity over a 12-month period in five individuals from São Paulo state, Brazil. We collected peripheral blood mononuclear cells once every three months from selected participants at five distinct visits. Molecular clones of 1.15 Kbp fragments of the Pol polyprotein, spanning the protease and a portion of the reverse transcriptase (RT) genes, were generated by bulk PCR. Pol sequences were used for evolutionary analysis, including phylogenetics (using TnT), genetic diversity (using Highlighter), and hypermutation frequency (using Hypermut). Recombination detection experiments were conducted with a jumping profile-hidden Markov model (jpHMM), SimPlot++, and RDP5. We observed great genetic diversity and frequent recombination events in all patients. Furthermore, most of the patients presented hypermutations. These findings highlight the dynamic nature of HIV-1 genetic diversity, driven by frequent recombination and hypermutation, which can accelerate viral adaptation and diversification, underscoring the challenges for treatment, prevention, and disease control.