Long-term Sudan Virus Ebola Survivors Maintain Multiple Antiviral Defense Mechanisms

Background The critical issues of sustained memory immunity following ebolavirus disease among long-term survivors are still unclear.Methods Here, we examine virus-specific immune and inflammatory responses following in vitro challengd in 12 Sudan virus (SUDV) long-term survivors from Uganda's 2000-2001 Gulu outbreak, 15 years after recovery. Total RNA from isolated SUDV-stimulated and unstimulated peripheral blood mononuclear cells was extracted and analyzed. Matched serum samples were also collected to determine SUDV IgG levels and functionality.Results We detected persistent humoral (58%, 7 of 12) and cellular (33%, 4 of 12) immune responses in SUDV long-term survivors and identified critical molecular mechanisms of innate and adaptive immunity. Gene expression in immune pathways, the interferon signaling system, antiviral defense response, and activation and regulation of T- and B-cell responses were observed. SUDV long-term survivors also maintained robust virus-specific IgG antibodies capable of polyfunctional responses, including neutralizing and innate Fc effector functions.Conclusions Data integration identified significant correlations among humoral and cellular immune responses and pinpointed a specific innate and adaptive gene expression signature associated with long-lasting immunity. This could help identify natural and vaccine correlates of protection against ebolavirus disease. Our study in naturally recovered long-term Sudan virus survivors revealed durable polyfunctional humoral and cellular memory immune responses with distinctive gene expression signatures, which may provide long-lasting protective immunity and help to define the ebolavirus correlate of protection.