Genome evolution and early introductions of the SARS-CoV-2 Omicron Variant in Mexico (preprint)

A new variant of SARS-CoV-2 Omicron (Pango lineage designation B.1.1.529), was first reported to the World Health Organization (WHO) by South African health authorities on November 24, 2021. The Omicron variant possesses numerous mutations associated with increased transmissibility and immune escape properties. In November 2021, Mexican authorities reported Omicrons presence in the country. In this study, we infer the first introductory events of Omicron and the impact that human mobility can have on the spread of the virus. We also evaluated the adaptive evolutionary processes in Mexican SARS-CoV-2 genomes during the first month of circulation of Omicron. We infer 173 introduction events of Omicron in Mexico in the first two months of detection; subsequently, of the introductions, there was an increase in the prevalence for January. This higher prevalence of the novel variant results in a peak of cases reported, on average, six weeks after a higher mobility trend was reported. The peak of cases reported is due to the BA.1.1 Omicron sub-lineage dominated, followed by BA.1 and BA.15 sub-lineages in the country from January to February 2022. Additionally, we identified the presence of diversifying natural selection in the genomes of Omicron and found mainly five non-synonymous mutations in the RDB domain of the Spike protein, all of them related to evasion of the immune response. In contrast, the other proteins in the genome are highly conserved--however, there are homoplasies mutations in non-structural proteins, indicating a parallel evolution.

Safety and immunogenicity of a live recombinant Newcastle disease virus-based COVID-19 vaccine (Patria) administered via the intramuscular or intranasal route: Interim results of a non-randomized open label phase I trial in Mexico (preprint)

There is still a need for safe, efficient and low-cost coronavirus disease 2019 (COVID-19) vaccines that can stop transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Here we evaluated a vaccine candidate based on a live recombinant Newcastle disease virus (NDV) that expresses a stable version of the spike protein in infected cells as well as on the surface of the viral particle (AVX/COVID-12-HEXAPRO, also known as NDV-HXP-S). This vaccine candidate can be grown in embryonated eggs at low cost similar to influenza virus vaccines and it can also be administered intranasally, potentially to induce mucosal immunity. We evaluated this vaccine candidate in prime-boost regimens via intramuscular, intranasal, or intranasal followed by intramuscular routes in an open label non-randomized non-placebo-controlled phase I clinical trial in Mexico in 91 volunteers. The primary objective of the trial was to assess vaccine safety and the secondary objective was to determine the immunogenicity of the different vaccine regimens. In the interim analysis reported here, the vaccine was found to be safe and the higher doses tested were found to be immunogenic when given intramuscularly or intranasally followed by intramuscular administration, providing the basis for further clinical development of the vaccine candidate. The study is registered under ClinicalTrials.gov identifier NCT04871737. Funding was provided by Avimex and CONACYT.

Isolation and characterization of high affinity and highly stable anti-Chikungunya virus antibodies using ALTHEA Gold Libraries™ (preprint)

Background: More than three million infections were attributed to Chikungunya virus (CHIKV) in the 2014-2016 outbreak in Mexico, Central and South America, with over 500 deaths directly or indirectly related to this viral disease. CHIKV outbreaks are recurrent and no vaccine nor approved therapeutics exist to prevent or treat CHIKV infection. Reliable and robust diagnostic methods are thus critical to control future CHIKV outbreaks. Direct CHIKV detection in serum samples via highly specific and high affinity anti-CHIKV antibodies has shown to be an early and effective clinical diagnosis. Methods:  To isolate highly specific and high affinity anti-CHIKV, Chikungunya virions were isolated from serum of a patient in Veracruz, México. After purification and characterization via electron microscopy, SDS-PAGE and binding to well-characterized anti-CHIKV antibodies, UV-inactivated particles were utilized as selector in a solid-phase panning in combination with ALTHEA Gold Libraries™, as source of antibodies. The screening was based on ELISA and Next-Generation Sequencing. Results: The CHIKV isolate showed the typical morphology of the virus. Protein bands in the SDS-PAGE were consistent with the size of CHIKV capsid proteins. UV-inactivated CHIKV particles bound tightly the control antibodies. The lead antibodies here obtained, on the other hand, showed high expression yield, > 95% monomeric content after a single-step Protein A purification, and importantly, had a thermal stability above 75oC. Most of the antibodies recognized linear epitopes on E2, including the highest affinity antibody called C7. A sandwich ELISA implemented with C7 and a potent neutralizing antibody isolated elsewhere, also specific for E2 but recognizing a discontinuous epitope, showed a dynamic range of 0.2 – 40.0 mg/mL of UV-inactivated CHIKV purified preparation. The number of CHIKV particles estimated based on the concentration of E2 in the extract suggested that the assay could detect clinically meaningful amounts of CHIKV in serum.Conclusions: The newly discovered antibodies offer valuable tools for characterization of CHIKV isolates and development of robust diagnostic tools for CHIKV infection surveillance. Therefore, the strategy here followed using whole viral particles and ALTHEA Gold Libraries™ as universal source of antibodies could expedite the discovery and development of antibodies for detection and control of emergent and quickly spreading viral outbreaks.