Further characterization of Ebola glycoprotein-specific immunoglobulin isotypes obtained from bronchioalveolar lavage fluid revealed that pre-existing immunity correlated with a marked decrease in the production of both IgG and IgA antibodies in mice immunized by intramuscular injection (Figure 4A and 4B ). IgG and IgA levels were the lowest in that were vaccinated orally regardless of whether they had pre-existing immunity ( Figure 4A and 4B). Immunization by the nasal route induced a strong IgG response that was reduced by an average of 25% in the presence of pre-existing immunity. The strongest IgA response was detected in samples obtained from animals given the vaccine by the nasal route. IgA levels, however, were also reduced by 25% in mice with pre-existing immunity to Ad5.