Figure 8

Immunogenicity of LASV Z+GPC and Z+GPC+NP in a prime + 2 boosts regimen in BALB/c mice. Groups of 10 BALB/c mice were immunized i.p. with either 100 μL of sterile TNE, or 10 μg of LASV VLP formulated in the same buffer using a prime + 2 boosts regimen, 3 weeks apart. Three weeks after the second boost all mice were sacrificed and sera were subjected to murine IgG endpoint titer determinations by ELISA on homologous VLP or recombinant LASV proteins coated on Nunc Maxisorp plates. Endpoint titers were calculated using background subtraction binding values generated with normal mouse sera on recombinant VLP and LASV proteins. LASV Z+GPC immunizations generated significant titers against whole VLP (mean = 12,800), but generally low titers to viral GP1 and GP2, with means of 444 and 700, respectively (8A). A similar immunization schedule with LASV Z+GPC+NP VLP resulted in significantly higher endpoint titers to both glycoproteins, with means of 6,800 and 10,400 for GP1 and GP2, respectively (8B), and to whole VLP (mean = 32,000). Significant IgG titers were also generated to NP (mean = 2,000). Endpoint titers generated by sham immunized murine sera to recombinant LASV proteins were at the lower limit of detection of the assay (mean = 10), with slight increased non-specific titers against Z+GPC VLP (mean = 18) and Z+GPC+NP (mean = 50). The immunization schedule used in these experiments is graphically outlined in 7C.