Proteins Mimicking Epitope of HIV-1 Virus Neutralizing Antibody Induce Virus-Neutralizing Sera in Mice

Abstract

Background: The development of effective vaccine preventing HIV-1 infection is hindered by enormous antigenic variability and unique biochemical and immunological properties of HIV-1 Env glycoprotein, the most promising target for HIV-1 neutralizing antibody. Functional studies of rare elite neutralizers led to the discovery of broadly neutralizing antibodies. Methods: We employed a highly complex combinatorial protein library derived from a 5 kDa albumin-binding domain scaffold, fused with protein backbone of total 38 kDa, to screen for binders of broadly neutralizing antibody VRC01 paratope. The most specific binders were used for immunization of experimental mice to elicit Env-specific antibodies and to test their neutralization activity using a panel of HIV-1 clade C and B pseudoviruses. Findings: Three most specific binders designated as VRA017, VRA019, and VRA177 exhibited high specificity to VRC01 antibody. Immunized mice produced Env-binding antibodies which neutralize five of eight HIV-1 pseudoviruses. Molecular modelling revealed a high structural similarity of the VRA proteins to VRC01-interacting Env surface. Interpretation: This strategy based on identification of protein replicas of broadly neutralizing antibody paratope as a reverse vaccinology variety represents a novel approach in HIV-1 vaccine development. This approach is not affected by inherited low immungenicity, variability, and unique biochemical properties of HIV-1 Env used as a crucial antigen in majority of contemporary tested vaccines. Funding: Czech Health Research Council 15-32198A, European Regional Development Fund CZ.1.05/1.1.00/02.0109, European Structural Funds, Operational Programme Research, Development and Education of the Ministry of Education, Youth and Sports CZ.02.1.01/0.0/0.0/16_025/0007397 and CZ.02.1.01/0.0/0.0/15_003/, Institutional Research Concepts RVO:86652036 and RO0519. Declaration of Interest: Nothing to declare. Ethical Approval: The vaccination experiments were approved by the Ethics Committee of the Faculty of Medicine and Dentistry (Palacky University in Olomouc), and the Ministry of Education, Youth and Sports, Czech Republic (MSMT-15434/2015-7).