Rational design and characterization of the novel, broad and potent bispecific HIV-1 neutralizing antibody iMabm36.
BACKGROUND
Although broadly neutralizing monoclonal antibodies (bNAbs) have always been considered to be a potential therapeutic option for the prophylaxis and treatment of HIV infection, their lack of breadth against all HIV variants has been one of the limiting factors. To provide sufficient neutralization breadth and potency against diverse viruses, including neutralization escape mutants, strategies to combine different bNAbs have been explored recently.


METHODS
We rationally designed and engineered a novel bispecific HIV-1-neutralizing antibody (bibNAb), iMabm36. The potency and breadth of iMabm36 against HIV were extensively characterized in vitro.


RESULTS
iMabm36 comprises the anti-CD4 Ab ibalizumab (iMab) linked to 2 copies of the single-domain Ab m36, which targets a highly conserved CD4-induced epitope. iMabm36 neutralizes a majority of a large, multiclade panel of pseudoviruses (96%, n = 118) at an IC50 concentration of less than 10 µg/mL, with 83% neutralized at an IC50 concentration of less than 0.1 µg/mL. In addition, iMabm36 neutralizes a small panel of replication-competent transmitted-founder viruses to 100% inhibition at a concentration of less than 0.1 µg/mL in a peripheral blood mononuclear cell-based neutralizing assay. Mechanistically, the improved antiviral activity of iMabm36 is dependent on both the CD4-binding activity of the iMab component and the CD4i-binding activity of the m36 component. After characterizing that viral resistance to iMabm36 neutralization was due to mutations residing in the bridging sheet of gp120, an optimized m36 variant was engineered that, when fused to iMab, improved antiviral activity significantly.


CONCLUSIONS
The interdependency of this dual mechanism of action enables iMabm36 to potently inhibit HIV-1 entry. These results demonstrate that mechanistic-based design of bibNAbs can generate potential preventive and therapeutic candidates for HIV/AIDS.
*Aaron Diamond AIDS Research Center, The Rockefeller University, New York, NY; †Institute of Medical Biology, Chinese Academy of Medical Science and Peking Union Medical College, Kunming, China; and ‡Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA.
Ming
M
Sun
Craig S
CS
Pace
Xin
X
Yao
Faye
F
Yu
Neal N
NN
Padte
Yaoxing
Y
Huang
Michael S
MS
Seaman
Qihan
Q
Li
David D
DD
Ho
D000818:Animals; D018033:Antibodies, Bispecific / Q000276:immunology* / Q000494:pharmacology; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000276:immunology*; D057134:Antibodies, Neutralizing / Q000276:immunology*; D000914:Antibodies, Viral / Q000276:immunology*; D015704:CD4 Antigens / Q000276:immunology; D017124:Conserved Sequence; D000939:Epitopes; D015483:HIV Antibodies / Q000276:immunology; D023581:HIV Fusion Inhibitors / Q000737:chemistry / Q000494:pharmacology; D015497:HIV-1 / Q000276:immunology*; D009500:Neutralization Tests; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000276:immunology
D018033:Antibodies, Bispecific; D000911:Antibodies, Monoclonal; D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D015704:CD4 Antigens; D000939:Epitopes; D015483:HIV Antibodies; D023581:HIV Fusion Inhibitors; D011993:Recombinant Fusion Proteins; C481504:ibalizumab