Certain treatments to combat the Ebola virus, notably those based on monoclonal antibodies 1, have increased the survival rate of patients suffering from the disease and are now recommended. Researchers from IRD, Inserm, ANRS Emerging Infectious Diseases and INRB have assessed, for the first time, the antibody response of survivors of the tenth Ebola epidemic in the Democratic Republic of Congo (DRC) who received specific anti-viral drugs. This study of the "Ebola Victors" cohort was initiated as part of the French response to the Ebola epidemic, and was part of the Franco-Congolese roadmap signed by the Congolese and French presidents. Its results, published on November 30 in The Lancet infectious Diseases, show that monoclonal antibodies could have a negative impact on the production of anti-Ebola antibodies over time, potentially increasing the risk of reinfection or reactivation.
Ebola virus disease is a serious infection with a case-fatality rate ranging from 30% to 90% in the absence of treatment. Between 2018 and 2020, in the provinces of North Kivu, South Kivu and Ituri (DRC), the tenth Ebola epidemic was the longest and deadliest ever recorded to date in the country, and the second largest in the world, after the 2013-2016 epidemic in West Africa.
Experience gained from previous epidemics has led to the adoption of preventive measures and the implementation of new strategies to combat the virus. Specific anti-Ebola drugs, in particular monoclonal antibodies, have improved patient care and survival. In this study, to better understand the long-term effects of these treatments, researchers assessed the humoral immune response 2 in survivors treated with anti-Ebola drugs during the tenth Ebola epidemic in the DRC.
Participants in the observational study, "Ebola Victors", were recruited on the day of discharge from the Ebola Treatment Center (ETC) and followed for up to 12 months. Of the 787 survivors included in the study, the researchers studied the antibody response of 358 of them: on discharge, almost a quarter were seronegative for at least two antigens of the virus. Those who had received specific treatments against Ebola, in particular monoclonal antibodies (Ansuvimab), experienced a rapid decline in their antibody levels to the virus over time. These results raise a number of questions, notably concerning the impact of these antibodies on viral persistence in immune-privileged sites, with a risk of relapse or persistent clinical manifestations (sequelae), and also on the risk of reinfection in these patients.
This study underlines the need for further research into the human reservoir of the Ebola virus, in order to better understand the factors involved in the persistence and resurgence of the virus, and thus develop drugs capable of eradicating it. From a public health point of view, it is important to continue monitoring people declared cured of Ebola virus infection, and to discuss the advisability of vaccinating them to help prevent any resurgence or reinfection. Finally, this study illustrates the importance of interventions during epidemics, combining three essential actions: care, research and the ability of teams to mobilize.
1 antibodies manufactured specifically to treat a disease
˛ characterized by the excretion in serum of antibodies specific to a given antigen