Mixed Adjuvant Formulations Reveal a New Combination That Elicit Antibody Response Comparable to Freund's Adjuvants

Abstract

Adjuvant formulations capable of inducing high titer and high affinity antibody responses would provide a major advance in the development of vaccines to viral infections such as HIV-1. Although oil-in-water emulsions, such as Freund's adjuvant (FCA/FIA), are known to be potent, their toxicity and reactogenicity make them unacceptable for human use. Here, we explored different adjuvants and compared their ability to elicit antibody responses to FCA/FIA. Recombinant soluble trimeric HIV-1 gp140 antigen was formulated in different adjuvants, including FCA/FIA, Carbopol-971P, Carbopol-974P and the licensed adjuvant MF59, or combinations of MF59 and Carbopol. The antigen-adjuvant formulation was administered in a prime-boost regimen into rabbits, and elicitation of antigen binding and neutralizing antibodies (nAbs) was evaluated. When used individually, only FCA/FIA elicited significantly higher titer of nAbs than the control group (gp140 in PBS (p<0.05)). Sequential prime-boost immunizations with different adjuvants did not offer improvements over the use of FCA/FIA or MF59. Remarkably however, the concurrent use of the combination of Carbopol-971P and MF59 induced potent adjuvant activity with significantly higher titer nAbs than FCA/FIA (p<0.05). This combination was not associated with any obvious local or systemic adverse effects. Antibody competition indicated that the majority of the neutralizing activities were directed to the CD4 binding site (CD4bs). Increased antibody titers to the gp41 membrane proximal external region (MPER) and gp120 V3 were detected when the more potent adjuvants were used. These data reveal that the combination of Carbopol-971P and MF59 is unusually potent for eliciting nAbs to a variety of HIV-1 nAb epitopes.

A Fusion Intermediate gp41 Immunogen Elicits Neutralizing Antibodies to HIV-1

“…Carbopol-971P is commonly used for oral or topical application, and MF59 is a licensed adjuvant for influenza vaccine; both can be produced with the good manufacturing practice standard for potential clinical use. This combination has been demonstrated previously to significantly increase binding IgG and neutralization titers in immunization studies with recombinant gp140 as an immunogen (98,112). Formulation of gp41 int -Cys proteoliposomes in this adjuvant combination slightly enlarged the liposome diameter but left them intact, and bnAb 10E8 stayed bound to the gp41 proteoliposomes in the adjuvant mixture.…”

“…The adjuvant used was a combination of Carbopol-971P (Lubrizol) and MF59 (Novartis Vaccines and Diagnostics), formulated according to previous protocols (98). Carbopol-971P was first prepared as a 2% (w/v) suspension in PBS before mixing 1:1 (v/v) with gp140 CA018 or gp41 intCys.…”

“…Serum samples were collected 2 weeks before and 2 weeks after each immunization at weeks Ϫ2, 2, 8, 14, and 20, and a terminal sample was collected at week 22. All antigens were formulated in Carbopol-971P and MF59 as described previously (98).…”

“…Real Time Neutralizing Epitope Competition Assay-The real time neutralizing epitope competition assay was performed as described previously (98). Briefly, gp41 int -fd protein was coated at 100 ng/well onto microwell plates and then blocked with 2% BSA.…”

Alga-Produced Malaria Transmission-Blocking Vaccine Candidate Pfs25 Formulated with a Human Use-Compatible Potent Adjuvant Induces High-Affinity Antibodies That Block Plasmodium falciparum Infection of Mosquitoes

“…The avidity indices of anti-Pfs25 IgG from the four different antigen-adjuvant groups were measured by inhibition of antibody binding to alga-produced rPfs25 antigen in the presence of 8 M urea, and these assays were carried out as previously published (30). Briefly, the ELISA steps were carried out as described in the previous section with protocol changes described as follows.…”