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Enhanced antibody-mediated neutralization of HIV-1 variants that are resistant to fusion inhibitors

View Article: PubMed Central - PubMed

ABSTRACT

Background: HIV-1 typically develops resistance to any single antiretroviral agent. Combined anti-retroviral therapy to reduce drug-resistance development is necessary to control HIV-1 infection. Here, to assess the utility of a combination of antibody and fusion inhibitor treatments, we investigated the potency of monoclonal antibodies at neutralizing HIV-1 variants that are resistant to fusion inhibitors.

Results: Mutations that confer resistance to four fusion inhibitors, enfuvirtide, C34, SC34, and SC34EK, were introduced into the envelope of HIV-1JR-FL, a CCR5-tropic tier 2 strain. Pseudoviruses with these mutations were prepared and used for the assessment of neutralization sensitivity to an array of antibodies. The resulting neutralization data indicate that the potencies of some antibodies, especially of those against the CD4 binding site, V3 loop, and membrane-proximal external region epitopes, were increased by the mutations in gp41 that conferred resistance to the fusion inhibitors. C34-, SC34-, and SC34EK-resistant mutants showed more sensitivity to monoclonal antibodies than enfuvirtide-resistant mutants. An analysis of C34-resistant mutations revealed that the I37K mutation in gp41 HR1 is a key mutation for C34 resistance, low infectivity, neutralization sensitivity, epitope exposure, and slow fusion kinetics. The N126K mutation in the gp41 HR2 domain contributed to C34 resistance and neutralization sensitivity to anti-CD4 binding site antibodies. In the absence of L204I, the effect of N126K was antagonistic to that of I37K. The results of a molecular dynamic simulation of the envelope trimer confirmation suggest that an I37K mutation induces the augmentation of structural fluctuations prominently in the interface between gp41 and gp120. Our observations indicate that the “conformational unmasking” of envelope glycoprotein by an I37K mutation is one of the mechanisms of neutralization sensitivity enhancement. Furthermore, the enhanced neutralization of C34-resistant mutants in vivo was shown by its high rate of neutralization by IgG from HIV patient samples.

Conclusions: Mutations in gp41 that confer fusion inhibitor resistance exert enhanced sensitivity to broad neutralizing antibodies (e.g., VRC01 and 10E8) and other conventional antibodies developed in HIV-1 infected patients. Therefore, next-generation fusion inhibitors and monoclonal antibodies could be a potential combination for future regimens of combined antiretroviral therapy.

Electronic supplementary material: The online version of this article (doi:10.1186/s12977-016-0304-7) contains supplementary material, which is available to authorized users.

No MeSH data available.


MD simulation of the HIV-1 gp41 trimer. Molecular modeling and MD simulation of the extracellular portion of the HIV-1 JR-FL gp41 trimer with and without a I37K mutation were performed using modules in the Molecular Operating Environment and the AMBER 11 program package [46]. a The distribution of the RMSFs of three protomers consisting of the gp41 trimer. Double-arrow heads indicate regions between positions 20 and 65 in protomers 1, 2, and 3. b Structures of the extracellular portion of the HIV-1 JR-FL gp41 trimer with and without a I37K mutation. The structures at 100 ns of MD simulations are shown. The amino acid residues between positions 20 and 65 in protomers 1 (red), 2 (blue), and 3 (green) are highlighted
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Fig7: MD simulation of the HIV-1 gp41 trimer. Molecular modeling and MD simulation of the extracellular portion of the HIV-1 JR-FL gp41 trimer with and without a I37K mutation were performed using modules in the Molecular Operating Environment and the AMBER 11 program package [46]. a The distribution of the RMSFs of three protomers consisting of the gp41 trimer. Double-arrow heads indicate regions between positions 20 and 65 in protomers 1, 2, and 3. b Structures of the extracellular portion of the HIV-1 JR-FL gp41 trimer with and without a I37K mutation. The structures at 100 ns of MD simulations are shown. The amino acid residues between positions 20 and 65 in protomers 1 (red), 2 (blue), and 3 (green) are highlighted

Mentions: Our data suggest that the I37K mutation in gp41 has global effects on the physical properties of the gp120/gp41 trimer. The amino acid residue at position 37 of gp41 is located at the interface between gp41 and gp120 in the Env trimer [66]. To gain structural insights into the biological effects of the I37K mutation, we conducted structural modeling and MD simulations of the extracellular portion of HIV-1JR-FL gp41 trimer with and without an I37K substitution. Using 2000 snapshots of the structures from the last 20 ns of each MD simulation, we examined the atomic fluctuations of individual amino acid residues by calculating the RMSF of the Cα atoms [46]. The results revealed a marked increase in the RMSFs of the gp41 with I37K mutations (Fig. 7a). Notably, RMSFs at positions 20–65 in the N-terminal portions of the gp41 extensively increased in all three protomers consisting of the gp41 trimer with the I37K mutation (Fig. 7a, double-headed arrows). Notably, this region is located in the protein–protein interface between gp41 and gp120 in the Env trimer (Fig. 7b) [40]. The results suggest that the I37K mutation induces augmentation of structural fluctuations prominently in the interfaces between gp41 and gp120 in the Env trimer.Fig. 7


Enhanced antibody-mediated neutralization of HIV-1 variants that are resistant to fusion inhibitors
MD simulation of the HIV-1 gp41 trimer. Molecular modeling and MD simulation of the extracellular portion of the HIV-1 JR-FL gp41 trimer with and without a I37K mutation were performed using modules in the Molecular Operating Environment and the AMBER 11 program package [46]. a The distribution of the RMSFs of three protomers consisting of the gp41 trimer. Double-arrow heads indicate regions between positions 20 and 65 in protomers 1, 2, and 3. b Structures of the extracellular portion of the HIV-1 JR-FL gp41 trimer with and without a I37K mutation. The structures at 100 ns of MD simulations are shown. The amino acid residues between positions 20 and 65 in protomers 1 (red), 2 (blue), and 3 (green) are highlighted
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5037607&req=5

Fig7: MD simulation of the HIV-1 gp41 trimer. Molecular modeling and MD simulation of the extracellular portion of the HIV-1 JR-FL gp41 trimer with and without a I37K mutation were performed using modules in the Molecular Operating Environment and the AMBER 11 program package [46]. a The distribution of the RMSFs of three protomers consisting of the gp41 trimer. Double-arrow heads indicate regions between positions 20 and 65 in protomers 1, 2, and 3. b Structures of the extracellular portion of the HIV-1 JR-FL gp41 trimer with and without a I37K mutation. The structures at 100 ns of MD simulations are shown. The amino acid residues between positions 20 and 65 in protomers 1 (red), 2 (blue), and 3 (green) are highlighted
Mentions: Our data suggest that the I37K mutation in gp41 has global effects on the physical properties of the gp120/gp41 trimer. The amino acid residue at position 37 of gp41 is located at the interface between gp41 and gp120 in the Env trimer [66]. To gain structural insights into the biological effects of the I37K mutation, we conducted structural modeling and MD simulations of the extracellular portion of HIV-1JR-FL gp41 trimer with and without an I37K substitution. Using 2000 snapshots of the structures from the last 20 ns of each MD simulation, we examined the atomic fluctuations of individual amino acid residues by calculating the RMSF of the Cα atoms [46]. The results revealed a marked increase in the RMSFs of the gp41 with I37K mutations (Fig. 7a). Notably, RMSFs at positions 20–65 in the N-terminal portions of the gp41 extensively increased in all three protomers consisting of the gp41 trimer with the I37K mutation (Fig. 7a, double-headed arrows). Notably, this region is located in the protein–protein interface between gp41 and gp120 in the Env trimer (Fig. 7b) [40]. The results suggest that the I37K mutation induces augmentation of structural fluctuations prominently in the interfaces between gp41 and gp120 in the Env trimer.Fig. 7

View Article: PubMed Central - PubMed

ABSTRACT

Background: HIV-1 typically develops resistance to any single antiretroviral agent. Combined anti-retroviral therapy to reduce drug-resistance development is necessary to control HIV-1 infection. Here, to assess the utility of a combination of antibody and fusion inhibitor treatments, we investigated the potency of monoclonal antibodies at neutralizing HIV-1 variants that are resistant to fusion inhibitors.

Results: Mutations that confer resistance to four fusion inhibitors, enfuvirtide, C34, SC34, and SC34EK, were introduced into the envelope of HIV-1JR-FL, a CCR5-tropic tier 2 strain. Pseudoviruses with these mutations were prepared and used for the assessment of neutralization sensitivity to an array of antibodies. The resulting neutralization data indicate that the potencies of some antibodies, especially of those against the CD4 binding site, V3 loop, and membrane-proximal external region epitopes, were increased by the mutations in gp41 that conferred resistance to the fusion inhibitors. C34-, SC34-, and SC34EK-resistant mutants showed more sensitivity to monoclonal antibodies than enfuvirtide-resistant mutants. An analysis of C34-resistant mutations revealed that the I37K mutation in gp41 HR1 is a key mutation for C34 resistance, low infectivity, neutralization sensitivity, epitope exposure, and slow fusion kinetics. The N126K mutation in the gp41 HR2 domain contributed to C34 resistance and neutralization sensitivity to anti-CD4 binding site antibodies. In the absence of L204I, the effect of N126K was antagonistic to that of I37K. The results of a molecular dynamic simulation of the envelope trimer confirmation suggest that an I37K mutation induces the augmentation of structural fluctuations prominently in the interface between gp41 and gp120. Our observations indicate that the “conformational unmasking” of envelope glycoprotein by an I37K mutation is one of the mechanisms of neutralization sensitivity enhancement. Furthermore, the enhanced neutralization of C34-resistant mutants in vivo was shown by its high rate of neutralization by IgG from HIV patient samples.

Conclusions: Mutations in gp41 that confer fusion inhibitor resistance exert enhanced sensitivity to broad neutralizing antibodies (e.g., VRC01 and 10E8) and other conventional antibodies developed in HIV-1 infected patients. Therefore, next-generation fusion inhibitors and monoclonal antibodies could be a potential combination for future regimens of combined antiretroviral therapy.

Electronic supplementary material: The online version of this article (doi:10.1186/s12977-016-0304-7) contains supplementary material, which is available to authorized users.

No MeSH data available.