Figure 4.

Immunogenicity of GPC-I53-50A and GPC-I53-50NP in rabbits and protective efficacy of GPC-I53-50NP in guinea pigs

(A) Schematic representation of the rabbit immunization schedule with color coding for each immunogen.

(B) Midpoint binding titers against GPC-I53-dn5B at weeks 0, 4, 6, 18, and 30.

(C) Midpoint NAb titers against autologous pseudovirus (lineage IV) at weeks 6, 18, and 30 (left panel). Endpoint NAb titers against authentic LASV (lineage IV) at week 30 (right panel). The dotted line indicates the lower limit of detection.

(D) Midpoint NAb titers against heterologous pseudoviruses (lineages II, III, and V) at week 30.

(E) Correlation plot of autologous NAb titers versus heterologous NAb titers (lineages II or III). The r and p values are shown for two-tailed Spearman correlations (n = 7 rabbits; all rabbits with an autologous neutralization ID₅₀ > 20).

(F) Schematic representation of the guinea pig challenge study schedule.

(G) Midpoint binding titers against GPC-I53-dn5B at weeks 0, 4, 6, 16, and 18. The dark gray line represents the median.

(H) CD16 expression on NK cells after incubation with GPC-specific serum antibodies from vaccinated and control guinea pigs. The lower dotted line represents median CD16 levels after incubation with a combination of phorbol myristate acetate (PMA) and ionomycin (positive control) whereas the upper dotted line represents median CD16 levels in the absence of serum antibodies (negative control).

(I) Binding to monocytes (THP-1 cells) by GPC-specific serum antibodies from vaccinated and control guinea pigs. The lower dotted line represents median monocytes binding in the absence of serum antibodies (negative control).

(J) Median RNA viral loads in vaccinated and control guinea pigs after challenge. The shaded area indicates the range. Statistical differences between two groups (days 6 and 9: n = 4 for vaccinated, n = 5 for controls; day 12: n = 4 for vaccinated and controls) were determined using two-tailed Mann-Whitney U-tests (^∗p < 0.05).

(K) Kaplan-Meier curve showing survival over time for vaccinated and control guinea pigs (n = 4 for vaccinated, n = 5 for controls at day 0) following a LASV challenge. Statistical difference between the two groups was determined using log-rank tests (^∗∗p < 0.01). The same color coding was used as in (H). In (B)–(D), (H), and (I), the median titers are indicated by a bar. Statistical differences between groups were analyzed using the two-tailed Mann-Whitney U-test (^∗p < 0.05; ^∗∗p < 0.01; n = 6 rabbits for both groups in B–D; n = 5 guinea pigs for both groups in H and I).