[1] Univ Pittsburgh, Ctr Vaccine Res, Pittsburgh, PA 15260 USA
[2] Univ Pittsburgh, Sch Med, Dept Microbiol & Mol Genet, Pittsburgh, PA 15260 USA
[3] Univ Pittsburgh, Sch Med, Dept Pathol, Pittsburgh, PA 15260 USA
[4] Univ Pittsburgh, Grad Sch Publ Hlth, Dept Infect Dis & Microbiol, Pittsburgh, PA 15261 USA
[5] Univ Cincinnati, Dept Pediat, Cincinnati Childrens Hosp, Div Immunobiol, Cincinnati, OH USA