Dissection of human immunodeficiency virus type 1 entry with neutralizing antibodies to gp41 fusion intermediates.
Human immunodeficiency virus type 1 (HIV-1) entry requires conformational changes in the transmembrane subunit (gp41) of the envelope glycoprotein (Env) involving transient fusion intermediates that contain exposed coiled-coil (prehairpin) and six-helix bundle structures. We investigated the HIV-1 entry mechanism and the potential of antibodies targeting fusion intermediates to block Env-mediated membrane fusion. Suboptimal temperature (31.5 degrees C) was used to prolong fusion intermediates as monitored by confocal microscopy. After transfer to 37 degrees C, these fusion intermediates progressed to syncytium formation with enhanced kinetics compared with effector-target (E/T) cell mixtures that were incubated only at 37 degrees C. gp41 peptides DP-178, DP-107, and IQN17 blocked fusion more efficiently (5- to 10-fold-lower 50% inhibitory dose values) when added to E/T cells at the suboptimal temperature prior to transfer to 37 degrees C. Rabbit antibodies against peptides modeling the N-heptad repeat or the six-helix bundle of gp41 blocked fusion and viral infection at 37 degrees C only if preincubated with E/T cells at the suboptimal temperature. Similar fusion inhibition was observed with human six-helix bundle-specific monoclonal antibodies. Our data demonstrate that antibodies targeting gp41 fusion intermediates are able to bind to gp41 and arrest fusion. They also indicate that six-helix bundles can form prior to fusion and that the lag time before fusion occurs may include the time needed to accumulate preformed six-helix bundles at the fusion site.
Golding
Hana
H
Division of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Bldg. 29A Room 1A21, 8800 Rockville Pike, Bethesda, MD 20892, USA. goldingh@cber.fda.gov
Zaitseva
Marina
M
de Rosny
Eve
E
King
Lisa R
LR
Manischewitz
Jody
J
Sidorov
Igor
I
Gorny
Miroslaw K
MK
Zolla-Pazner
Susan
S
Dimitrov
Dimiter S
DS
Weiss
Carol D
CD
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D015726:Giant Cells; D015483:HIV Antibodies / Q000276:immunology*; D015700:HIV Envelope Protein gp41 / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D023581:HIV Fusion Inhibitors / Q000494:pharmacology*; D015497:HIV-1 / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D006801:Humans; D008561:Membrane Fusion / Q000187:drug effects*; D018613:Microscopy, Confocal; D009500:Neutralization Tests; D010455:Peptides / Q000494:pharmacology; D011487:Protein Conformation; D011817:Rabbits; D013696:Temperature
D000911:Antibodies, Monoclonal; D015483:HIV Antibodies; D015700:HIV Envelope Protein gp41; D023581:HIV Fusion Inhibitors; D010455:Peptides