Enzymatic removal of mannose moieties can increase the immune response to HIV-1 gp120 in vivo

Abstract

The Env glycoproteins gp120 and gp41 are used in humoral immunity-based vaccines against human immunodeficiency virus (HIV-1) infection. One among many obstacles to such a vaccine is the structural defenses of Env glycoproteins that limit their immunogenicity. For example, gp120 mannose residues can induce immunosuppressive responses in vitro, including IL-10 expression, via mannose C-type lectin receptors on antigen-presenting cells. Here, we have investigated whether mannose removal alters gp120 immunogenicity in mice. Administering demannosylated gp120 (D-gp120) in the TH2-skewing adjuvant Alum induced ~50-fold higher titers of anti-gp120 IgG, compared to unmodified gp120. While the IgG subclass profile was predominantly TH2-associated IgG1, Abs of the TH1-associated IgG2a and IgG3 subclasses were also detectable in D-gp120 recipients. Immunizing with D-gp120 also improved T-cell responses. Giving an IL-10 receptor blocking MAb together with unmodified gp120 in Alum increased the anti-gp120 IgG titer, implicating IL-10 as a possible mediator of auto-suppressive responses to gp120.

Partial Enzymatic Deglycosylation Preserves the Structure of Cleaved Recombinant HIV-1 Envelope Glycoprotein Trimers

“…There was no detectable size reduction when gp120 WT was treated with ␣1-2-, ␣1-6-, or ␣1-2,3-mannosidase, implying either that the enzymes were inactive or that they removed too little carbohydrate for any size reduction to be visible using SDS-PAGE. In contrast, a small, but clear size reduction (ϳ5 kDa) was observed when gp120 WT was exposed to ␣1-2,3,6-mannosidase, which is consistent with our earlier findings (21,22) (Fig. 2A).…”

Enhancing the Quality of Antibodies to HIV-1 Envelope by GagPol-Specific Th Cells

“…This approach has been pursued for HIV-1 Env-based Ags before (16,17,20). Although Env-specific immune responses could be enhanced, only minor alterations of the quality of immune responses were observed.…”

“…However, even in the presence of Th1-promoting adjuvants, the IgG1 predominance in the Env-specific humoral immune response persisted (17,20). Furthermore, coapplication of Th1-associated cytokines or the removal of mannose residues to alter the C-type lectin receptor engagement similarly failed to overcome the bias (15)(16)(17). These results demonstrate the need for novel means to modify the subclass distribution of Ab responses against viral surface proteins that do not per se induce protective immunity.…”

“…However, the Ab response to HIV-1 envelope (Env)-based immunogens was heavily biased toward the Th2-associated IgG1 subclass (15)(16)(17). A common approach to modify the Th cell profile and the Ig subclass distribution is the incorporation of appropriate adjuvants within the vaccine regimen (18,19).…”

“…A common approach to modify the Th cell profile and the Ig subclass distribution is the incorporation of appropriate adjuvants within the vaccine regimen (18,19). However, even in the presence of Th1-promoting adjuvants, the IgG1 predominance in the Env-specific humoral immune response persisted (17,20). Furthermore, coapplication of Th1-associated cytokines or the removal of mannose residues to alter the C-type lectin receptor engagement similarly failed to overcome the bias (15)(16)(17).…”