Newcastle disease virus vector-based SARS-CoV-2 vaccine candidate AVX/COVID-12 activates T cells and is recognized by antibodies from COVID-19 patients and vaccinated individuals.

Introduction: Several effective vaccines for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been developed and implemented in the population. However, the current production capacity falls short of meeting global demand. Therefore, it is crucial to further develop novel vaccine platforms that can bridge the distribution gap. AVX/COVID-12 is a vector-based vaccine that utilizes the Newcastle Disease virus (NDV) to present the SARS-CoV-2 spike protein to the immune system. Methods: This study aims to analyze the antigenicity of the vaccine candidate by examining antibody binding and T-cell activation in individuals infected with SARS-CoV-2 or variants of concern (VOCs), as well as in healthy volunteers who received coronavirus disease 2019 (COVID-19) vaccinations. Results: Our findings indicate that the vaccine effectively binds antibodies and activates T-cells in individuals who received 2 or 3 doses of BNT162b2 or AZ/ChAdOx-1-S vaccines. Furthermore, the stimulation of T-cells from patients and vaccine recipients with AVX/COVID-12 resulted in their proliferation and secretion of interferon-gamma (IFN-γ) in both CD4+ and CD8+ T-cells. Discussion: The AVX/COVID-12 vectored vaccine candidate demonstrates the ability to stimulate robust cellular responses and is recognized by antibodies primed by the spike protein present in SARS-CoV-2 viruses that infected patients, as well as in the mRNA BNT162b2 and AZ/ChAdOx-1-S vaccines. These results support the inclusion of the AVX/COVID-12 vaccine as a booster in vaccination programs aimed at addressing COVID-19 caused by SARS-CoV-2 and its VOCs.

Challenges in the development of vaccines against COVID-19. / Retos en el desarrollo de vacunas contra COVID-19.

In the face of the urgent need for a COVID-19 vaccine, currently more than 90 vaccine candidates are being developed using different strategies, such as inactivated or attenuated SARS-CoV-2 virus, viral vectors expressing antigens of this virus, nucleic acids or purified viral proteins. These vaccines are in preclinical development and at least six of them have already been injected into volunteers in safety clinical trials. However, the characteristics of the protective immune responses are still unknown; therefore, there is not evidence to indicate that these vaccines will induce protection and if this will be long-lasting. The development of SARS-CoV-2 vaccines is vital; nevertheless, it is also important to unveil the characteristics of the protective immune responses to guide the design of a vaccine that generates a long-lasting protection against COVID-19.

Ante la urgente necesidad de una vacuna contra el virus causante de COVID-19, actualmente se han desarrollado más de 90 vacunas candidatas a partir de diferentes estrategias, como el uso del virus SARS-CoV-2 inactivado o atenuado, vectores virales que expresan antígenos de este virus, ácidos nucleicos o proteínas virales purificadas. Estas vacunas se encuentran en estudios preclínicos y al menos seis de ellas ya han sido inyectadas en voluntarios de ensayos clínicos de seguridad. Sin embargo, aún se desconocen las características de la respuesta inmune protectora y, por lo tanto, no hay evidencia que indique si estas vacunas lograrán inducir inmunidad y si esta será de larga duración. El desarrollo de vacunas contra el SARS-CoV-2 es imperante; no obstante, lo es también determinar las características de la respuesta inmune protectora para que guíe el diseño de una vacuna que genere protección de larga duración contra el COVID-19.

The role of T Cells in SARS-CoV-2 Infection. / El papel de los linfocitos T en la infección por SARS-CoV-2.

T lymphocytes (or T cells) are characterized by having an essential role in the control of acute viral infections. SARS-CoV-2 infection is an acute viral infection that mainly affects the respiratory tract causing COVID-19 disease, which presents with mild, moderate and critical symptoms that can lead to the death of the patient. The induction of populations of CD4+ and CD8+ T cell with a functional memory phenotype could be decisive in the control of viral replication and therefore be determinants in the course of the disease. In this opinion article, we will review the reported evidence regarding the presence, phenotype, and function of circulating T cell populations and the site of infection to understand their possible role in controlling viral replication, in the severity of the disease, and the importance of T-cell-mediated protection in the development of vaccines against SARS-CoV-2 infection.

Los linfocitos T se caracterizan por tener un papel esencial en el control de infecciones virales agudas. La infección por SARS-CoV-2 es una infección viral aguda que afecta principalmente el tracto respiratorio y causa la enfermedad COVID-19, la cual cursa con síntomas leves, moderados y críticos que pueden llevar a la muerte del paciente. La inducción de poblaciones de linfocitos T CD4+ y CD8+ con fenotipos de memoria funcionales podrían ser esenciales en el control de la replicación viral y, por lo tanto, determinantes en el curso de la enfermedad. En este artículo de opinión revisaremos las evidencias reportadas en cuanto a la presencia, fenotipo y función de las poblaciones de linfocitos T en circulación y en el sitio de infección para entender su posible papel en el control de la replicación viral, en la severidad de la enfermedad y la importancia de la protección mediada por linfocitos T en el desarrollo de vacunas contra la infección por SARS-CoV-2.