Immune Response with Long-term Memory Triggered by Amorphous Aggregates of Misfolded Anti-EGFR V-7D12 is Directed Against the Native V-7D12 As Well As the Framework of the Analogous V-9G8

We previously demonstrated that amorphous aggregates of misfolded V-7D12 antibodies (V-Mis), a potential anti-EGFR drug, can generate a robust serum IgG response. Here we investigate the immunogenic nature, especially the specificity of the immune response induced by V-Mis. To this end, we used two natively folded and 77% identical anti-EGFR Vs (V-7D12 and V-9G8) that possess a common framework but distinct complementarity determining regions (CDRs). In 60% of mice immunized with V-Mis, the anti-V-7D12 IgG titer was stronger than the anti-V-9G8 titer (Group-1). In the remaining mice (40%; Group-2), the anti-V-7D12 and anti-V-9G8 titer were almost identical. We rationalized these results by hypothesizing that mice in Group-1 produced IgG mostly against the V-7D12's CDRs, whereas in Group-2 mice, they targeted the V's framework. The IgG specificity against V-7D12 and V-9G8 was essentially unchanged over 17 weeks in both groups. Further, in all mice (Group-1&2) re-immunized with native V-7D12, the IgG titer against V-7D12 increased sharply but not against V-9G8. On the other hand, none of the three Group-1 mice re-immunized with native V-9G8 showed immunogenicity against V-7D12 nor V-9G8. Whereas, in Group-2 mice (three/three) re-immunized with V-9G8, the IgG titers against both Vs increased but slowly. Flow-cytometric studies showed that V-Mis immunized mice generated a higher number of effector and central memory T-cells. Overall, these observations indicate that amorphous aggregates made of a misfolded V can induce serum IgG against its natively folded self and analogous Vs having a similar framework but distinct CDRs. Furthermore, a robust long-term immune response with memory was established against its natively folded self but with a nil-to-moderate immune response against natively folded V analogs.