Ammonium tetrathiomolybdate (TTM) and disulfiram (DSF) are copper (Cu) chelators in cancer clinical trials partly because Cu chelation: a) restricts the activity of Cu-binding MEK1/2 enzymes which drive tumourigenesis by KRAS or BRAF oncogenic mutations and b) enhances uptake of oxaliplatin (OxPt), clinically used in advanced KRAS-mutant colorectal carcinomas (CRC). Whereas TTM decreases intracellular Cu trafficking, DSF can reach other Cu-dependent intracellular proteins. Since the use of individual or combined Cu chelation may help or interfere with anti-cancer therapy, this study investigated whether TTM modifies the response to DSF supplemented with: 1) UO126, a known MEK1/2 inhibitor; 2) other Cu chelators like neocuproine (NC) or 1, 10-o-phenanthroline (OPT) in wt p53 melanoma cells differing in BRAF or KRAS mutations; 3) OxPt in mutant p53 CRC cells devoid of KRAS and BRAF mutations or harbouring either KRAS or BRAF mutations. TTM was not toxic against (V600E-mut-BRAF) A375 and (G12D-mut-KRAS/hig)(h) (c-myc) C8161 melanoma cells. Moreover, TTM protected both melanoma types from toxicity induced by DSF, NC and co-treatment with sub-lethal levels of DSF and the MEK inhibitor, UO126. Toxicity by co-treatment with DSF OPT was poorly reversed by TTM in C8161 melanoma cells. In contrast to the greater toxicity of 0.1 mu M DSF against mutant p53 CRC cells irrespective of their KRAS mutation, TTM did not protect (G12V-mut-KRAS/high c-myc) SW620 CRC from DSF OxPt compared to (KRAS-WT/BRAF-WT) Caco-2 CRC. Our results show that DSF co-treatment with: a) MEK inhibitors may enhance tumour suppression; b) OxPt in CRC may counteract impaired response to cetuximab by KRAS/BRAF mutations and c) as a single treatment, TTM may be less effective than DSF and decreases the efficacy of the latter.

SARS-CoV-2 vaccines have contributed to attenuating the burden of the COVID-19 pandemic by promoting the development of effective immune responses, thus reducing the spread and severity of the pandemic. A clinical trial with the Sputnik-V vaccine was conducted in Venezuela from December 2020 to July 2021. The aim of this study was to explore the antibody reactivity of vaccinated individuals towards different regions of the spike protein (S). Neutralizing antibody (NAb) activity was assessed using a commercial surrogate assay, detecting NAbs against the receptor-binding domain (RBD), and a plaque reduction neutralization test. NAb levels were correlated with the reactivity of the antibodies to the spike regions over time. The presence of Abs against nucleoprotein was also determined to rule out the effect of exposure to the virus during the clinical trial in the serological response. A high serological reactivity was observed to S and specifically to S1 and the RBD. S2, although recognized with lower intensity by vaccinated individuals, was the subunit exhibiting the highest cross-reactivity in prepandemic sera. This study is in agreement with the high efficacy reported for the Sputnik V vaccine and shows that this vaccine is able to induce an immunity lasting for at least 180 days. The dissection of the Ab reactivity to different regions of S allowed us to identify the relevance of epitopes outside the RBD that are able to induce NAbs. This research may contribute to the understanding of vaccine immunity against SARS-CoV-2, which could contribute to the design of future vaccine strategies.

The COVID-19 pandemic was characterized by the emergence and succession of SARS-CoV-2 variants able to evade the antibody response induced by natural infection and vaccination. To evaluate the IgG reactivity and neutralizing capacity of the serum of individuals vaccinated with Sputnik V (105 volunteers vaccinated) against different viral variants. IgG reactivity to the Spike protein (S) was evaluated by ELISA. A plaque reduction neutralization test was performed using different viral variant isolates. At 42 days post-vaccination, the frequency of recognition and reactivity to the S protein of the Omicron variant was lower compared to that of the other variants. In general, a higher average neutralization titer was seen against the ancestral variant compared to the variants, especially Omicron. However, some sera exhibited a higher neutralization titer to the Gamma variant compared to the ancestral variant, suggesting unapparent exposure during the clinical trial. Antibodies induced by Sputnik V can recognize, persist, and neutralize SARS-CoV-2 variants, with Omicron being the one that best evades this response. These results represent a unique report on the humoral response induced by a globally lesser-studied vaccine in terms of efficacy and immune escape, offering insights into developing vaccines targeting unknown coronaviruses.

The COVID-19 pandemic was characterized by the emergence and succession of SARS-CoV-2 variants able to evade the antibody response induced by natural infection and vaccination. In this study, IgG reactivity and neutralizing capacity of the serum of individuals vaccinated with Sputnik V was determined against the spike glycoprotein (S) of the ancestral and different viral variants. At 42 days’ post vaccination, the frequency of recognition and reactivity to S protein of the omicron variant was lower compared to the other variants. There was higher reactivity to Alpha and Delta S protein compared to ancestral S protein. A higher neutralization titer was seen against the ancestral variant compared to the variants, especially Omicron. Some sera exhibited a higher neutralization titer to the Gamma variant, compared to the ancestral variant. This may be due to exposure to this variant during the period of its spread in the country, which coincided with the period of the clinical trial. A correlation was found between reactivity to S and neutralization titer to each variant. These results suggest that antibodies induced by Sputnik-V can recognize, persist and neutralize the SARS-CoV-2 variants circulating in Venezuela, with Omicron being the one that best evades this response.

Keywords: COVID-19, SARS-CoV-2, Antibody, ELISA, Spike, S1, S2, RBD, epitopes, Neutralization