Abstract
Despite enormous difficulties to induce antibodies neutralizing HIV-1, especially broadly neutralizing antibodies directed against the conserved membrane proximal external region (MPER) of the transmembrane envelope protein, such antibodies can be easily induced in the case of gammaretroviruses, among them the porcine endogenous retroviruses (PERVs). In addition to neutralizing antibodies directed against the transmembrane envelope protein p15E, neutralizing antibodies were also induced by immunization with the surface envelope protein gp70. PERVs represent a special risk for xenotransplantation using pig tissues or organs since they are integrated in the genome of all pigs and infect human cells and a vaccine may protect from transmission to the recipient. To investigate the effect of simultaneous immunization with both proteins in detail, a study was performed in hamsters. Gp70 and p15E of PERV were produced in E. coli, purified and used for immunization. All animals developed binding antibodies against the antigens used for immunization. Sera from animals immunized with p15E recognized epitopes in the MPER and the fusion peptide proximal region (FPPR) of p15E. One MPER epitope showed a sequence homology to an epitope in the MPER of gp41 of HIV-1 recognized by broadly neutralizing antibodies found in HIV infected individuals. Neutralizing antibodies were detected in all sera. Most importantly, sera from animals immunized with gp70 had a higher neutralizing activity when compared with the sera from animals immunized with p15E and sera from animals immunized with gp70 together with p15E had a higher neutralizing activity compared with sera from animals immunized with each antigen alone. These immunization studies are important for the development of vaccines against other retroviruses including the human immunodeficiency virus HIV-1.
Highlights
A vaccine is the best protection from an infection with retroviruses including the human immunodeficiency virus HIV-1
We recently reported neutralizing antibodies after immunization with the transmembrane envelope protein p15E of porcine endogenous retroviruses (PERVs) in goats [4] and rats [12]
Analyzes of the epitopes recognized by antibodies specific for p15E of PERV In order to map the epitopes in p15E recognized by the immune sera, two different methods were performed
Summary
A vaccine is the best protection from an infection with retroviruses including the human immunodeficiency virus HIV-1. Since retroviruses integrate a DNA copy of their genome into the genome of the target cell, were they may persist undetected from the immune system if not expressed, only vaccines based on neutralizing antibodies can prevent virus infection and integration. Neutralizing antibodies have been found in HIV-1 infected individuals, most of them are directed against the surface envelope protein gp120, and only some against the transmembrane envelope protein [1,2]. We recently reported neutralizing antibodies after immunization with the transmembrane envelope protein p15E of PERV in goats [4] and rats [12]. When immunizing with the surface envelope protein gp much higher titers of neutralizing antibodies were induced compared with p15E [12]. Since studies in rats were hampered by the high prevalence of preexisting antibodies against p15E, A
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