3.2 Humoral immune responses induced by VSV/RABV-GP vaccination
Next, we evaluated the immunogenicity of VSV/RABV-GP in mice. Eight-week-old BALB/C mice were intraperitoneally immunized either with VSV/RABV-GP or inactivated RABV (Figure 2A). None of the inoculated mice demonstrated any clinical signs or weight loss (data not shown), suggesting that VSV/RABA-GP immunization was safe as an inactivated control. On day 28 of post-immunization, IgM and IgG titers were examined. The IgM titers in mice immunized with VSV/RABV-GP were significantly three times higher than those in mice immunized with inactivated RABV (OD value 1.2 and 3.8, respectively), as shown in Figure 2B. Even in the variation of IgM titer in each mouse, a higher variation was found in the RABV vaccine group, but very low variation was found in the VSV/RABV-GP group (Figure 2B). Comparing IgG titers, both groups showed a strong IgG titer (OD value of 2.9); however, there were no statistical differences between the two groups (Figure 2C). We confirmed that VSV/RABV-GP vaccination induced the same level of IgG with inactivated RABV. Based on these humoral response results, we confirmed that VSV/RABV-GP induced strong antibodies of both IgG and IgM. Moreover, it induced at least the same or a higher antibody titer than inactivated RABV.