Antibody affinity versus dengue morphology influences neutralization

Abstract

Different strains within a dengue serotype (DENV1-4) can have smooth, or “bumpy” surface morphologies with different antigenic characteristics at average body temperature (37°C). We determined the neutralizing properties of a serotype cross-reactive human monoclonal antibody (HMAb) 1C19 for strains with differing morphologies within the DENV1 and DENV2 serotypes. We mapped the 1C19 epitope to E protein domain II by hydrogen deuterium exchange mass spectrometry, cryoEM and molecular dynamics simulations, revealing that this epitope is likely partially hidden on the virus surface. We showed the antibody has high affinity for binding to recombinant DENV1 E proteins compared to those of DENV2, consistent with its strong neutralizing activities for all DENV1 strains tested regardless of their morphologies. This finding suggests that the antibody could out-compete E-to-E interaction for binding to its epitope. In contrast, for DENV2, HMAb 1C19 can only neutralize when the epitope becomes exposed on the bumpy-surfaced particle. Although HMAb 1C19 is not a suitable therapeutic candidate, this study with HMAb 1C19 shows the importance of choosing a high-affinity antibody that could neutralize diverse dengue virus morphologies for therapeutic purposes.

Morphological Diversity and Dynamics of Dengue Virus Affecting Antigenicity

“…In contrast with the DENV2 strain NGC, there was no differences observed in the deuterium exchange across peptides of E and M proteins in DENV1 strain PVP159 at 37 °C compared to 28 °C [ 60 ]. This supports the previous observation regarding the cryoEM images of DENV1 strain PVP159 that showed that the virus did not undergo expansion and remained smooth-surfaced at 37 °C [ 14 , 50 ]. The DENV1 strain PVP159 structural proteins (E, M and C) showed motions only at 40 °C [ 60 ].…”

“…On the other hand, for DENV1 strain PVP159, there is no detected movement of the E protein shell. Only when incubation temperature is increased from 37 to 40 • C, then E protein shell movement is detected, consistent with the HDXMS experiments [60] and the previous cryoEM studies [50].…”

“…Some DENV serotypes and strains generate high percentage of mature compact DENV particles, e.g., DENV2 strain PVP94/07 [ 50 ] and DENV4 strain 06K2270DK1 [ 51 ]. Other strains produce mature virus with the compact smooth surface DENV at mosquito physiological temperature (28 °C), but this changes to a bumpy surface structure when incubated at a higher temperature (37 or 40 °C) [ 46 , 50 ]. One example is DENV2 strain NGC, that has been passaged in C6/36 mosquito cell line extensively.…”

“…Another study also found that in addition to increased dynamics of E proteins on virus surface, high affinity of antibodies could help them to bind to cryptic epitopes. HMAb 1C19 binds to a partially hidden epitope (hi- and ij-loops) on DII [ 50 ]. HMAb 1C19 has been shown to have high affinity to DENV1 recombinant E protein and a much lower affinity to that of DENV2, as determined by biolayer interferometry (BLI).…”

Improved epitope resolution of the prefusion trimer-specific antibody AM14 bound to the RSV F glycoprotein

“…Stabilization of the PreF form of the RSV F protein (DS-Cav1) has enabled 3D structure determination and the elucidation of epitopes for antibodies targeting a plethora of antigenic sites. 17,28 The recent emergence of single-particle cryo-EM has allowed the solution of medium-to-high-resolution structures of antibodyantigen complexes for viruses such as HIV, [32][33][34][35][36] influenza, [37][38][39][40] and Dengue, [41][42][43] as well as for an RSV PostF-FabR4.C6 complex, 44 and most recently vaccine-elicited antibodies bound to DS-Cav1. 45 Using single particle cryo-EM, we were able to achieve an overall resolution of 3.4 Å, which produced a 3D reconstruction of comparable quality to a 3.6 Å DS-Cav1-AM14 X-ray structure also reported here.…”