Refined innate plasma signature after rVSVΔG-ZEBOV-GP immunization is shared among adult cohorts in Europe and North America


During the last decade Ebola virus has caused several outbreaks in Africa. The recombinant vesicular stomatitis virus-vectored Zaire Ebola (rVSVΔG-ZEBOV-GP) vaccine has proved safe and immunogenic but is reactogenic. The authors, led by Prof. Claire-Anne Siegrist and GCIR member Prof. Arnaud Didierlaurent, previously identified the first innate plasma signature response after vaccination in Geneva as composed of five monocyte-related biomarkers peaking at day 1 post-immunization that correlates with adverse events, biological outcomes (haematological changes and viremia) and antibody titers. In this follow-up study, they sought to identify additional biomarkers in the same Geneva cohort and validate those identified markers in a US cohort.

Additional biomarkers were identified using multiplexed protein biomarker platform O-link and confirmed by Luminex. Principal component analysis (PCA) evaluated if these markers could explain a higher variability of the vaccine response (and thereby refined the initial signature). Multivariable and linear regression models evaluated the correlations of the main components with adverse events, biological outcomes, and antibody titers. External validation of the refined signature was conducted in a second cohort of US vaccinees (n=142).

Eleven additional biomarkers peaked at day 1 post-immunization: MCP2, MCP3, MCP4, CXCL10, OSM, CX3CL1, MCSF, CXCL11, TRAIL, RANKL and IL15. PCA analysis retained three principal components (PC) that accounted for 79% of the vaccine response variability. PC1 and PC2 were very robust and had different biomarkers that contributed to their variability. PC1 better discriminated different doses, better defined the risk of fever and myalgia, while PC2 better defined the risk of headache. The authors also found new biomarkers that correlated with reactogenicity, including transient arthritis (MCP-2, CXCL10, CXCL11, CX3CL1, MCSF, IL-15, OSM). Several innate biomarkers are associated with antibody levels one and six months after vaccination. Refined PC1 correlated strongly in both data sets (Geneva: r = 0.97, P < 0.001; US: r = 0.99, P< 0.001).

Eleven additional biomarkers refined the previously found 5-biomarker Geneva signature. The refined signature better discriminated between different doses, was strongly associated with the risk of adverse events and with antibody responses and was validated in a separate cohort.

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Why is it important?

Recognizing the essential factors of vaccine-induced immunity is crucial for developing effective vaccines and improving vaccine coverage in populations at risk.

Ebola virus disease (EVD) has a high mortality rate and can lead to uncontrollable epidemics, as seen in the major Ebola outbreak from 2014 to 2016. The rVSVΔG-ZEBOV-GP vaccine (Ervebo®) was found to be safe and effective in clinical trials in the United States, Europe, and Africa, leading to its accelerated approval by WHO for high-risk countries in 2019.

The vaccine is highly effective against EVD, but causes substantial inflammation after immunization, including viral dissemination and arthritis in some individuals. Only a few studies have explored its immunogenicity profile and associations with inflammatory responses. The authors of this article, working with a cohort of patients in Geneva, have identified a total of sixteen biomarkers induced early after vaccination that was strongly associated with the risk of adverse events and with antibody responses. The finding was further validated in an US cohort receiving the same vaccine. Knowledge of these markers is crucial to enable the rational development of new vaccines and to optimize the efficacy and safety of the Ebola vaccine.

1 Feb 2024