title: High prevalence of both humoral and cellular immunity to Zaire ebolavirus among rural populations in Gabon.
abstract: To better understand Zaire ebolavirus (ZEBOV) circulation and transmission to humans, we conducted a large serological survey of rural populations in Gabon, a country characterized by both epidemic and non epidemic regions. The survey lasted three years and covered 4,349 individuals from 220 randomly selected villages, representing 10.7% of all villages in Gabon. Using a sensitive and specific ELISA method, we found a ZEBOV-specific IgG seroprevalence of 15.3% overall, the highest ever reported. The seroprevalence rate was significantly higher in forested areas (19.4%) than in other ecosystems, namely grassland (12.4%), savannah (10.5%), and lakeland (2.7%). No other risk factors for seropositivity were found. The specificity of anti-ZEBOV IgG was confirmed by Western blot in 138 individuals, and CD8 T cells from seven IgG+ individuals were shown to produce IFN-gamma after ZEBOV stimulation. Together, these findings show that a large fraction of the human population living in forested areas of Gabon has both humoral and cellular immunity to ZEBOV. In the absence of identified risk factors, the high prevalence of "immune" persons suggests a common source of human exposure such as fruits contaminated by bat saliva. These findings provide significant new insights into ZEBOV circulation and human exposure, and raise important questions as to the human pathogenicity of ZEBOV and the existence of natural protective immunization.
authors.affiliation: Unité des Maladies Virales Emergentes, Centre International de Recherches Médicales de Franceville, Franceville, Gabon.
authors.forename: Pierre
authors.initials: P
authors.lastname: Becquart
authors.forename: Nadia
authors.initials: N
authors.lastname: Wauquier
authors.forename: Tanel
authors.initials: T
authors.lastname: Mahlakõiv
authors.forename: Dieudonné
authors.initials: D
authors.lastname: Nkoghe
authors.forename: Cindy
authors.initials: C
authors.lastname: Padilla
authors.forename: Marc
authors.initials: M
authors.lastname: Souris
authors.forename: Benjamin
authors.initials: B
authors.lastname: Ollomo
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Gonzalez
authors.forename: Xavier
authors.initials: X
authors.lastname: De Lamballerie
authors.forename: Mirdad
authors.initials: M
authors.lastname: Kazanji
authors.forename: Eric M
authors.initials: EM
authors.lastname: Leroy
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000914:Antibodies, Viral / Q000097:blood; D002648:Child; D002675:Child, Preschool; D029043:Ebolavirus / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005681:Gabon / Q000453:epidemiology; D005843:Geography; D019142:Hemorrhagic Fever, Ebola / Q000453:epidemiology / Q000276:immunology* / Q000821:virology; D006801:Humans; D007111:Immunity, Cellular / Q000276:immunology*; D056724:Immunity, Humoral / Q000276:immunology*; D007074:Immunoglobulin G / Q000097:blood; D007223:Infant; D007371:Interferon-gamma / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012424:Rural Population / Q000706:statistics & numerical data; D016036:Seroepidemiologic Studies; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral; D007074:Immunoglobulin G; D007371:Interferon-gamma