A Nonneutralizing Anti-HIV-1 Antibody Turns into a Neutralizing Antibody When Expressed on the Surface of HIV-1-Susceptible Cells: A New Way to Fight HIV

Abstract

During HIV-1 infection or vaccination, HIV-1 envelope spikes elicit Ab responses. Neutralizing Abs block viral entry by recognizing epitopes on spikes critical for their interaction with receptor, coreceptors or fusion. In contrast, nonneutralizing Abs fail to do so because they recognize epitopes either buried or exposed but not critical for viral entry. Previously, we produced a high-affinity human mAb against the cluster II determinant of gp41. This Ab or its recombinant Fab and single-chain Fv have been repeatedly shown to bind to HIV-1 gp160 or gp41, but fail to block viral entry. We report that, surprisingly, expression of this nonneutralizing anti-HIV-1 gp41 single-chain Fv on the surface of human CD4 T cells markedly inhibits HIV-1 replication and cell-cell fusion. The inhibition targets the HIV-1 envelope at the level of viral entry, regardless of HIV-1 tropism. Although this bona fide nonneutralizing Ab does not neutralize HIV-1 entry when produced as a soluble protein, it acts as a neutralizing Ab when expressed on the cell surface. Expressing Abs on the surface of HIV-1-susceptible cells can be a new way to fight HIV-1.

A Nonneutralizing Anti-HIV Type 1 Antibody Turns into a Broad Neutralizing Antibody When Expressed on the Surface of HIV Type 1-Susceptible Cells. II. Inhibition of HIV Type 1 Captured and Transferred by DC-SIGN

“…The experiment has been repeated three more times with similar results. Therefore, similar to what was found previously, 17 these results indicated that the m-scFv specifically targets the HIV-1 envelope.…”

“…2D). These results indicated that the m-scFv not only can inhibit laboratory-adapted HIV-1 strains as shown in a previous report, 17 but it also can effectively inhibit primary isolates. Moreover, although the monoclonal antibody (TG15) (from which the m-scFv was derived) was originally derived from a human B cell hybridoma generated from a subtype B HIV-1-infected individual, it not only neutralizes HIV-1 from B subtypes (shown in the previous studies 17 as well as studies with LEE ET AL.…”

“…Cell line THP-1, that is Raji B cells according to the report by Wu et al, 24 was maintained in complete RPMI 1640 medium [RPMI 1640 supplemented with 10% FBS, 2 mM L-glutamine, 1 mM sodium pyruvate, penicillin (100 U/ml), streptomycin (100 g/ml), and 2-mercaptoethanol (2-ME)]. Stable transduced CEMss cell lines, CEMss-eGFP and CEMssm-scFv, were generated before 17 and maintained in complete DMEM supplemented with 1.5 mg/ml G418.…”

“…The inhibition is at the level of viral entry, HIV-1 envelope specific, and was not affected by virus tropism. 17 Therefore, this nonneutralizing antibody can be turned into a neutralizing antibody by expressing it on the surface of HIV-1-susceptible cells. In this recently published study, cellfree viruses of laboratory-adapted HIV-1 strains from subtype B were used to infect human CD4 T cell lines.…”

Vif Substitution Enables Persistent Infection of Pig-Tailed Macaques by Human Immunodeficiency Virus Type 1

“…Antibody directed against ␤-actin served as a protein loading control. Initially, infections of the TRIM5 expressing and control cells were performed with increasing amounts (2 to 100 ng) of HIV-GFP/VSV pseudotyped virus (51). Two days after infection, the cells were analyzed by flow cytometry for green fluorescent protein (GFP) expression.…”