Neutralizing antibodies against conserved domains of p15E of porcine endogenous retroviruses: basis for a vaccine for xenotransplantation?

Abstract

Porcine xenotransplants may offer a potential solution to the problem posed by the limited supply of allotransplants. However, xenotransplantation may be associated with the risk of transmission of microorganisms, in particular of porcine endogenous retroviruses (PERVs) that are an integral part of the porcine genome and able to infect human cells in vitro. Possible strategies to prevent virus transmission include the development of PERV knockout animals or of effective vaccines. When antisera prepared against the main structural proteins of PERV were screened, a goat antiserum against the recombinant ectodomain of the transmembrane envelope protein p15E was found to neutralize PERV infectivity. Epitope mapping using overlapping peptides revealed two epitopes, E1 (GPQQLEK) and E2 (FEGWFN). These sequences are identical for all PERVs and are highly conserved among all gammaretroviruses. Interestingly, antibodies isolated from AIDS patients and specific for sequences of HIV-1 partially homologous with E2 (Mab4E10, LWNWFN) or located in close proximity to E2 (Mab2F5, ELDKWA) are known to neutralize several strains of HIV-1. It is the first report showing epitope mapping of gammaretrovirus-specific neutralizing antibodies and demonstrating similarity to corresponding epitopes in HIV. These domains of the transmembrane proteins of different retroviruses are an effective target for neutralizing antibodies and may be a useful antigen to create an antiretroviral vaccine.

Induction of Antibodies Specific for Gp41 of HIV-1 by Gene Gun DNA Vaccination

“…In all sera from rats immunised with DNA hybrid constructs antibodies against the p15E backbone were detected. This was rather astonishing, because after immunisation with p15E of different gammaretroviruses including KoRV, mainly antibodies against the FPPR and the MPER, but not against other parts of p15E were detected [6][7][8][9][10]. Surprisingly, sera from untreated control rats and from rats immunised with gp41 or gp41-CHR DNA constructs also contained antibodies against p15E of KoRV (Figure 4).…”

“…In contrast to the situation with HIV-1, neutralising antibodies against different gammaretroviruses such as porcine endogenous retrovirus [6,7], feline leukaemia virus [8][9][10] and Koala retrovirus [11] have been easily induced by immunisation with the recombinant ectodomains of their TM proteins. The epitopes recognised by the immune sera were located in the N-terminal fusion peptide proximal region (FPPR) and in the C-terminal MPER of p15E.…”

“…The epitopes recognised by the immune sera were located in the N-terminal fusion peptide proximal region (FPPR) and in the C-terminal MPER of p15E. The MPER of PERV, FeLV and KoRV is homologous to that of gp41 of HIV-1 and despite the evolutionary distance between gammaretroviruses and HIV-1 a limited sequence homology of the epitopes was identified [6][7][8][9][10][11] (Figure 1a). …”

Optimisation of expression and purification of the feline and primate foamy virus transmembrane envelope proteins using a 96 deep well screen

“…However, the extreme insolubility of the TM proteins of the FV is in contrast to solubility of the TM proteins of different gammaretroviruses also expressed in E.coli. As was shown for the porcine endogenous retrovirus (PERV) [41], the feline leukaemia virus (FeLV) [42] and the Koala virus (KoRV) [43] these proteins were partly soluble and were successfully used for induction of neutralising antibodies and serological testing. p15E of PERV is now part of a newly developed assay to screen animals and human recipients for transmission of PERV during experimental and clinical xenotransplantation [44,45].…”

Methods and Tools for Detection and Evaluation of the Risks of Porcine Endogenous Retrovirus in Porcine to Human Xenotransplantation

“…The transmembrane (TM) domain of the PERV envelope was used to derive a goat antiserum that is both neutralizing and can be used for immunoassays such as Western blot and ELISA assays (Fiebig, Stephan et al 2003). Additional studies have reported development of rabbit-based PERV nucleocapsid anti-serum that can be used for Western blot and immunohistochemistry analysis (Krach, Fischer et al 2000) .…”