Humoral immunoresponse elicited against an adenoviral-based SARS-CoV-2 coronavirus vaccine in elderly patients.

The early sequencing of the SARS-CoV-2 viral genome allowed for a speedy development of effective vaccines against the virus. Nevertheless, age-related immunosenescence, the inability to mount strong immune responses, still represents a major obstacle. Here, in a group of 149 elderly volunteers (70-96 years old), evolution of the humoral immune response over time to Gam-COVID-Vac (Sputnik V), a vaccine based on heterologous recombinant adenovirus-26 (Ad26) and adenovirus-5 (Ad5) carrying the Spike genome, was analyzed by an anti-RBD ELISA. At 28 days post vaccination (dpv), a seroconversion rate of 91% was achieved, showing the importance of administering at least two doses of Gam-COVID-Vac to elicit a robust immune response, especially in elderly individuals without previous SARS-CoV-2 infection. Interestingly, IgG specific antibodies that reached their highest titers around 28 dpv (median = 740), persisted without significant decrease after 60 dpv (median = 650). After 90 dpv, IgG titers began to drop, and at 180 dpv only 44.7% of the elderly individuals remained with detectable anti-RBD IgG antibodies. No significant differences were observed in specific humoral immune responses between genders at early times point. However, at 60 dpv anti-RBD titers were more persistent in elderly females, and only dropped at 90 dpv (p < 0.0001). As expected, the highest antibodies titers were elicited in the youngest subgroup (70-74 years). Our results show that Gam-COVID-Vac was able to deal with the ageing of the immune system, eliciting a robust immune response in an elderly cohort, which lasted approximately 90 dpv at high levels, and protected against COVID-19.

Long-term analysis of antibodies elicited by SPUTNIK V: A prospective cohort study in Tucumán, Argentina.

BACKGROUND: Gam-COVID-Vac (SPUTNIK V) has been granted emergency use authorization in 70 nations and has been administered to millions worldwide. However, there are very few peer-reviewed studies describing its effects. Independent reports regarding safety and effectiveness could accelerate the final approval by the WHO. We aimed to study the long-term humoral immune response in naïve and previously infected volunteers who received SPUTNIK V. METHODS: Humoral immune responses, assayed by anti-SARS-CoV-2-spike-RBD IgG ELISA and neutralization assays, were measured in 602 healthcare workers at 0, 14, 28, 60 and 180 days after receiving SPUTNIK V between December 2020 and July 2021 in Tucumán, Argentina. FINDINGS: Seroconversion was detected in 97% of individuals after 28 days post-vaccination (dpv) (N = 405). Anti-RBD titers began to decrease after 60 dpv (N = 328), but remained detectable in 94% at 90 dpv (N = 224). At 180 dpv, anti-RDB titers persisted in 31% (N = 146). Previous infection triggered an increased immune response to the first dose and increased neutralization activity against variants of concern (VOC). Second doses in previously infected individuals further increased titers, even 90 dpv (N = 75). Basal antibody titers had more influence on post-vaccination anti-RBD responses than the time elapsed between diagnosis and vaccination (N = 274). INTERPRETATION: Data presented herein provides essential knowledge regarding the kinetics of antibodies induced by SPUTNIK V up to six months after immunization, and suggests that when considering one-dose vaccination policies for individuals with previous SARS-CoV-2 infection, serological studies to determine basal titers may be important, independent of when diagnosis occurred. FUNDING: Tucumán Public Health System (SIPROSA), Argentinean National Research Council (CONICET), National University of Tucumán (UNT).

Elevated Humoral Immune Response to SARS-CoV-2 at High Altitudes Revealed by an Anti-RBD "In-House" ELISA.

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has caused a global pandemic with dramatic health and socioeconomic consequences. The Coronavirus Disease 2019 (COVID-19) challenges health systems to quickly respond by developing new diagnostic strategies that contribute to identify infected individuals, monitor infections, perform contact-tracing, and limit the spread of the virus. In this brief report, we developed a highly sensitive, specific, and precise "In-House" ELISA to correctly discriminate previously SARS-CoV-2-infected and non-infected individuals and study population seroprevalence. Among 758 individuals evaluated for anti-SARS-CoV-2 serology in the province of Tucumán, Argentina, we found a weak correlation between antibodies elicited against the RBD, the receptor-binding domain of the Spike protein, and the nucleocapsid (N) antigens of this virus. Additionally, we detected mild levels of anti-RBD IgG antibodies in 33.6% of individuals diagnosed with COVID-19, while only 19% showed sufficient antibody titers to be considered as plasma donors. No differences in IgG anti-RBD titers were found between women and men, neither in between different age groups ranging from 18 to 60. Surprisingly, individuals from a high altitude village displayed elevated and longer lasting anti-RBD titers compared to those from a lower altitude city. To our knowledge, this is the first report correlating altitude with increased humoral immune response against SARS-CoV-2 infection.