Heterologous Flavivirus Infection-Enhancing Antibodies in Sera of Nigerians

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  • * Department of Virology, College of Medicine, University of Ibadan, Ibadan, Nigeria
  • | Rockefeller Foundation, 1133 Avenue of the Americas, New York, 10036
  • | Department of Tropical and Medical Microbiology, University of Hawaii, Honolulu, Hawaii 96816
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Human sera collected from Nigerians were examined for plaque reduction neutralizing and infection-enhancing antibodies against dengue 2, yellow fever, and West Nile viruses. Neutralization tests showed that 17 of 19 sera contained flavivirus neutralizing antibody; 11 were positive to all 3 viruses, 5 to dengue and yellow fever, and 1 to dengue virus only. Two sera had no detectable neutralizing antibody to any of the flaviviruses. Enhancement assays showed that 17 flavivirus neutralizing antibody-positive sera contained infection-enhancing antibodies to dengue 2, and 16 had antibody to yellow fever. Although 11 sera were positive for West Nile neutralizing antibody, 17 enhanced this virus. Heterologous infection-enhancing antibody titers were lower than the homologous ones. Broadly reacting sera and those with high neutralizing antibody titers produced the highest infection-enhancing antibody titers.