Abstract
The membrane-proximal external region (MPER) of the HIV-1 gp41 consists of epitopes for the broadly cross-neutralizing monoclonal antibodies 2F5 and 4E10. However, antigens containing the linear sequence of these epitopes are unable to elicit potent and broad neutralizing antibody responses in vaccinated hosts, possibly because of inappropriate conformation of these epitopes. Here we designed a recombinant antigen, designated NCM, which comprises the N- and C-terminal heptad repeats that can form a six-helix bundle (6HB) core and the MPER domain of gp41. Two mutations (T569A and I675V) previously reported to expose the neutralization epitopes were introduced into NCM to generate mutants named NCM(TA), NCM(IV), and NCM(TAIV). Our results showed that NCM and its mutants could react with antibodies specific for 6HB and MPER of gp41, suggesting that these antigens are in the form of a trimer of heterodimer (i.e., 6HB) with three exposed MPER tails. Antigen with double mutations, NCM(TAIV), elicited much stronger antibody response in rabbits than immunogens with single mutation, NCM(TA) and NCM(IV), or no mutation, NCM. The purified MPER-specific antibodies induced by NCM(TAIV) exhibited broad neutralizing activity, while the purified 6HB-specific antibodies showed no detectable neutralizing activity. Our recombinant antigen design supported by an investigation of its underlying molecular mechanisms provides a strong scientific platform for the discovery of a gp41 MPER-based AIDS vaccine.
Highlights
As the acquired immunodeficiency syndrome (AIDS) pandemic continues to expand globally, the search for a preventive vaccine is an absolute priority in combating its causative agent, human immunodeficiency virus type 1 (HIV-1)
Monoclonal antibodies 2F5, 4E10 and Z13, target the adjacent linear epitopes located in the membrane-proximal external region (MPER) of gp41 [5,6], which plays a crucial role in membrane fusion and viral entry
NCMs, including non-mutated NCM and three mutants, NCM(TA), NCM(IV) and NCM(TAIV) (Fig. 1A), were composed of NHR, CHR and MPER region derived from gp41 of a clade B strain HXB2
Summary
As the acquired immunodeficiency syndrome (AIDS) pandemic continues to expand globally, the search for a preventive vaccine is an absolute priority in combating its causative agent, human immunodeficiency virus type 1 (HIV-1). We hypothesized that introducing these two mutations into an MPER-based HIV-1 vaccine candidate might increase its immunogenicity to elicit stronger MPER-specific antibodies with broad neutralizing activity. The neutralizing activity of antibodies on infection by HIV-1 R5 strain Bal and primary isolates was performed as described before [28].
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