Seroconversion and Abundance of IgG Antibodies against S1-RBD of SARS-CoV-2 and Neutralizing Activity in the Chilean Population

COVID-19 is a pandemic caused by SARS-CoV-2. In Chile, half a million people have been infected and more than 16,000 have died from COVID-19. As part of the clinical trial NCT04384588, we quantified IgG against S1-RBD of SARS-CoV-2 (anti-RBD) in recovered people in Santiago and evaluated their suitability as COVID-19 convalescent plasma donors. ELISA and a luminescent SARS-CoV-2 pseudotype were used for IgG and neutralizing antibody quantification. 72.9% of the convalescent population (468 of 639) showed seroconversion (5-55 μg/mL anti-RBD IgG) and were suitable candidates for plasma donation. Analysis by gender, age, and days after symptom offset did not show significant differences. Neutralizing activity correlated with an increased concentration of anti-RBD IgG (p<0.0001) and showed a high variability between donors. We confirmed that the majority of the Chilean patients have developed anti-SARS-CoV-2 antibodies. The quantification of anti-RBD IgG in convalescent plasma donors is necessary to increase the detection of neutralizing antibodies

Neoadjuvant nivolumab modifies the tumor immune microenvironment in resectable glioblastoma

Glioblastoma is the most common primary central nervous system malignancy and has a poor prognosis. Standard first-line treatment, which includes surgery followed by adjuvant radio-chemotherapy, produces only modest benefits to survival1,2. Here, to explore the feasibility, safety and immunobiological effects of PD-1 blockade in patients undergoing surgery for glioblastoma, we conducted a single-arm phase II clinical trial (NCT02550249) in which we tested a presurgical dose of nivolumab followed by postsurgical nivolumab until disease progression or unacceptable toxicity in 30 patients (27 salvage surgeries for recurrent cases and 3 cases of primary surgery for newly diagnosed patients). Availability of tumor tissue pre- and post-nivolumab dosing and from additional patients who did not receive nivolumab allowed the evaluation of changes in the tumor immune microenvironment using multiple molecular and cellular analyses. Neoadjuvant nivolumab resulted in enhanced expression of chemokine transcripts, higher immune cell infiltration and augmented TCR clonal diversity among tumor-infiltrating T lymphocytes, supporting a local immunomodulatory effect of treatment. Although no obvious clinical benefit was substantiated following salvage surgery, two of the three patients treated with nivolumab before and after primary surgery remain alive 33 and 28 months later