Limits...
Antibody-antigen kinetics constrain intracellular humoral immunity

View Article: PubMed Central - PubMed

ABSTRACT

During infection with non-enveloped viruses, antibodies stimulate immunity from inside cells by activating the cytosolic Fc receptor TRIM21. This intracellular humoral response relies on opsonized viral particles reaching the cytosol intact but the antigenic and kinetic constraints involved are unknown. We have solved the structure of a potent TRIM21-dependent neutralizing antibody in complex with human adenovirus 5 hexon and show how these properties influence immune activity. Structure-guided mutagenesis was used to generate antibodies with 20,000-fold variation in affinity, on-rates that differ by ~50-fold and off-rates by >175-fold. Characterization of these variants during infection revealed that TRIM21-dependent neutralization and NFκB activation was largely unaffected by on-rate kinetics. In contrast, TRIM21 antiviral activity was exquisitely dependent upon off-rate, with sub-μM affinity antibodies nevertheless unable to stimulate signaling because of fast dissociation kinetics. These results define the antibody properties required to elicit an efficient intracellular immune response during viral infection.

No MeSH data available.


9C12 CDR interactions with hexon.(a) Surface representation of hexon (monomers in shades of green). Secondary structure of VL (blue) and VH (gray) with CDR loops marked in yellow. The 9C12 CDRs interact with HVRs from two hexon monomers. (b,c) Interacting residues from hexon (top, cyan & green) with residues from 9C12 (bottom, VH in yellow, VL in blue/gray). Dashed lines indicate putative hydrogen bonds. Two different views are shown corresponding to residues mutated in Figs 3(b) and 4(c).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5121590&req=5

f2: 9C12 CDR interactions with hexon.(a) Surface representation of hexon (monomers in shades of green). Secondary structure of VL (blue) and VH (gray) with CDR loops marked in yellow. The 9C12 CDRs interact with HVRs from two hexon monomers. (b,c) Interacting residues from hexon (top, cyan & green) with residues from 9C12 (bottom, VH in yellow, VL in blue/gray). Dashed lines indicate putative hydrogen bonds. Two different views are shown corresponding to residues mutated in Figs 3(b) and 4(c).

Mentions: The principal hexon epitopes bound by 9C12 are contained within HVRs 2 and 8 (Fig. 1d). Of these, HVR8 forms a finger-like projection into the center of the VH-VL binding site, whilst HVR2 contacts VH exclusively (Fig. 1c and d). With the exception of L2, all antibody CDR loops contribute to the interface (Fig. 2a). At one side of the interface, D52 from L2 makes a bifurcated hydrogen bond with residues K431 and Q434 from HVR8 (Fig. 2b). On the other side, E181 from HVR2 makes a bifurcated hydrogen bond with the peptidyl nitrogens of G53 and T55 from H2 (Fig. 2c). At the center of the interface, E435 of HVR8 hydrogen bonds with the main-chain of H1 residue G32 (Fig. 2b). A number of contacts are also made between HVR8 and H3, including between the side-chain of Q97 and the main chain of G433 and E435 and between the main-chain atoms of S99 and N436 (Fig. 2b). In addition to these hydrogen-bond interactions, W51 from H2 makes a cation-π interaction with K180 from HVR2 (Fig. 2b). Lysine-tryptophan cation-π interactions are less common than those involving arginine but stronger at 3.3 kcal/mol16.


Antibody-antigen kinetics constrain intracellular humoral immunity
9C12 CDR interactions with hexon.(a) Surface representation of hexon (monomers in shades of green). Secondary structure of VL (blue) and VH (gray) with CDR loops marked in yellow. The 9C12 CDRs interact with HVRs from two hexon monomers. (b,c) Interacting residues from hexon (top, cyan & green) with residues from 9C12 (bottom, VH in yellow, VL in blue/gray). Dashed lines indicate putative hydrogen bonds. Two different views are shown corresponding to residues mutated in Figs 3(b) and 4(c).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5121590&req=5

f2: 9C12 CDR interactions with hexon.(a) Surface representation of hexon (monomers in shades of green). Secondary structure of VL (blue) and VH (gray) with CDR loops marked in yellow. The 9C12 CDRs interact with HVRs from two hexon monomers. (b,c) Interacting residues from hexon (top, cyan & green) with residues from 9C12 (bottom, VH in yellow, VL in blue/gray). Dashed lines indicate putative hydrogen bonds. Two different views are shown corresponding to residues mutated in Figs 3(b) and 4(c).
Mentions: The principal hexon epitopes bound by 9C12 are contained within HVRs 2 and 8 (Fig. 1d). Of these, HVR8 forms a finger-like projection into the center of the VH-VL binding site, whilst HVR2 contacts VH exclusively (Fig. 1c and d). With the exception of L2, all antibody CDR loops contribute to the interface (Fig. 2a). At one side of the interface, D52 from L2 makes a bifurcated hydrogen bond with residues K431 and Q434 from HVR8 (Fig. 2b). On the other side, E181 from HVR2 makes a bifurcated hydrogen bond with the peptidyl nitrogens of G53 and T55 from H2 (Fig. 2c). At the center of the interface, E435 of HVR8 hydrogen bonds with the main-chain of H1 residue G32 (Fig. 2b). A number of contacts are also made between HVR8 and H3, including between the side-chain of Q97 and the main chain of G433 and E435 and between the main-chain atoms of S99 and N436 (Fig. 2b). In addition to these hydrogen-bond interactions, W51 from H2 makes a cation-π interaction with K180 from HVR2 (Fig. 2b). Lysine-tryptophan cation-π interactions are less common than those involving arginine but stronger at 3.3 kcal/mol16.

View Article: PubMed Central - PubMed

ABSTRACT

During infection with non-enveloped viruses, antibodies stimulate immunity from inside cells by activating the cytosolic Fc receptor TRIM21. This intracellular humoral response relies on opsonized viral particles reaching the cytosol intact but the antigenic and kinetic constraints involved are unknown. We have solved the structure of a potent TRIM21-dependent neutralizing antibody in complex with human adenovirus 5 hexon and show how these properties influence immune activity. Structure-guided mutagenesis was used to generate antibodies with 20,000-fold variation in affinity, on-rates that differ by ~50-fold and off-rates by >175-fold. Characterization of these variants during infection revealed that TRIM21-dependent neutralization and NFκB activation was largely unaffected by on-rate kinetics. In contrast, TRIM21 antiviral activity was exquisitely dependent upon off-rate, with sub-μM affinity antibodies nevertheless unable to stimulate signaling because of fast dissociation kinetics. These results define the antibody properties required to elicit an efficient intracellular immune response during viral infection.

No MeSH data available.