DNA-Encoding Enzymatically Active HIV-1 Reverse Transcriptase, but Not the Inactive Mutant, Confers Resistance to Experimental HIV-1 Challenge

Abstract

The present study was undertaken to examine the immunogenicity of a single plasmid DNA representing the reverse transcriptase (RT) of HIV-1. Plasmids containing the enzymatically active RT as well as a mutated nonenzymatically active RT with nucleotide (nt)-binding motifs of YMDD and YMLL, respectively, were used to immunize mice. Both constructs induced similar good antibody and T cell responses, with a tendency towards antibody directed to peptides representing the active and mutated sites. Immunized mice were challenged with a murine pseudotype HIV-1/MuLV infected spleen cells. Seven out of 10 mice immunized with RT had no recoverable HIV-1, while 10 individuals immunized with the RT mutant and all the 18 controls had high levels of recoverable HIV-1. This indicates that mutation of RT reduces the desired immunogenicity.

Genetic Immunization with Multiple HIV-1 Genes Provides Protection against HIV-1/MuLV Pseudovirus Challenge in vivo

“…In contrast to other small animal models for HIV, we have a non-pathogenic in vivo model [Andäng et al, 1999;Isaguliants et al, 2000;Spetz et al, 2002]. Even though the analysis of protective immunity or the capacity to measure clearance of HIV-infected cells in vivo is restricted to a 2-week period after the challenge, we believe that this model could function as an inexpensive small animal model to test experimental HIV vaccines.…”

“…Using such pseudotyped virus, HIV-1 genes could be delivered to murine spleen cells, as we have shown in vitro [Andäng et al, 1999]. It proved possible to infect both murine macrophage cell lines and T-cell lines with HIV-1 even though the virus replication is considerably lower than in human T cells [Dickie et al, 1996;Andäng et al, 1999;Isaguliants et al, 2000]. The aim of the present study was to transfer infected cells to establish an in vivo model and to define the HIV-1-specific immune responses elicited by the infection.…”

Induction of HIV-1-Specific Immunity After Vaccination with Apoptotic HIV-1/Murine Leukemia Virus-Infected Cells

“…Using such a pseudovirus, we have previously shown that it is possible to deliver HIV-1 genes into murine splenocytes (26). We have also demonstrated that HIV-1/MuLV-infected splenocytes can provide a continuous release of infectious HIV-1 in vivo and in vitro 4 (27). HIV-1 RNA and isolation of infectious HIV-1 could be demonstrated up to 14 days after inoculation with live HIV-1/MuLV-infected cells.…”

The rationale behind a vaccine based on multiple HIV antigens

“…The wildtype RT DNA induces anti-RT specific IgG titers [32]. The wild-type RT plasmid (pRTwt) and the YMDD mutated RT plasmid (pRTmut) were compared head-to-head as immunogens, and induction of similar antibody titers was seen [10] (Fig. 2C).…”

“…One of the most potent of all HIV-1 antigens in eliciting CTL reactivity is the Gag (p24) antigen, and ongoing trials with the Gag antigen show promising induction of cellular immunity in primates and humans (reviewed in [9]). The HIV-1 reverse transcriptase (RT) has also been evaluated and experimental challenge experiments suggesting that it is a potent vaccine target [10]. The generation of CTL against epitopes that are conserved among different strains of HIV is the rationale for focusing upon CTL and these antigens.…”