Important B-cell epitopes for neutralization of human immunodeficiency virus type 1 Tat in serum samples of humans and different animal species immunized with Tat protein or peptides

Abstract

The Tat regulatory protein of human immunodeficiency virus type 1 (HIV-1) is secreted by infected cells and plays a key role in viral pathogenesis and replication. Tat protein has been proposed as a target antigen for vaccine design since anti-Tat antibodies may interfere with virus spread and disease progression. The aim of this study was to analyse the serum antibody response of mice, rabbits, macaques and humans immunized with recombinant Tat, synthetic Tat, Tat toxoid or Tat peptides and to examine the biological properties of these antibodies in terms of Tat-induced transactivation and HIV-1 replication. Only sera with antibody specificity to both N-terminal and basic functional domains were able to inhibit extracellular Tat-dependent transactivation significantly in vitro. Antibodies from a human subject immunized with Tat also reduced HIV-1 replication in acutely infected T cells and blocked reactivation of virus replicating low levels in chronically infected cells by exogenous Tat. These results demonstrate that immunization with Tat protein or a combination of synthetic Tat peptides elicits the production of Tat-neutralizing serum antibodies and suggest that Tat vaccination could be used to block in vivo extracellular Tat autocrine/paracrine transactivation of HIV-1 replication.

The binding affinity of double‐stranded RNA motifs to HIV‐1 Tat protein affects transactivation and the neutralizing capacity of anti‐Tat antibodies elicited after intranasal immunization

“…Both dsRNA motifs potentiated the anti-Tat antibody responses, which were comparable to those elicited in the presence of CT. Analysis of the fine-specificity of anti-Tat IgG antibodies using synthetic peptides revealed strong reactivity with peptides 1-20 and 44-61, which represent important epitopes [10,[19][20][21][22][31][32][33][34][35]. However, only sera of mice immunized with sTat and pI:pC motif inhibited Tat-driven transactivation.…”

“…The specificity of serum antibodies was determined using ELISA plates coated with peptides 1-20 and 44-61, which have been reported to represent critical neutralizing B cell epitopes of Tat protein [19][20][21][22] and have limited antigenic polymorphism among HIV-1 strains [23]. Although all tested sera reacted with both peptides (Fig.…”

HIV-1 Tat-Based Vaccines: An Overview and Perspectives in the Field of HIV/AIDS Vaccine Development

“…In addition, evidence exists that natural IgM antibodies reacting with Tat may provide an early initial defense against the pathological effects of Tat after HIV infection and influence the course of AIDS progression [131,132]. Similarly, immunization with Tat elicits antibody responses in rodents, monkeys, and humans able to block the activity of extracellular Tat on cellular entry, gene expression, and replication [4,84,[133][134][135][136][137][138][139][140][141][142]. Moreover, strong anti-Tat antibody responses correlated with an efficient reduction in plasma viremia and long-term protection in Tat protein-vaccinated monkeys challenged intrarectally with an heterologous SHIV virus [143].…”

Effects of different routes of administration on the immunogenicity of the Tat protein and a Tat-derived peptide

“…It has been recently shown that antibodies directed against the N-terminus region of Tat, which is the most immunogenic in terms of humoral responses, 32,33 protect monkeys from infection acquisition, 15 suggesting that the Tat 1-20 peptide constitutes an interesting candidate for a preventive vaccine. To assess how different routes of administration may affect humoral immunogenicity of peptide vaccines, mice were vaccinated 3 times (at days 1, 14 and 28), by ID or OM route, with Tat 1-20 peptide (EPVDPRLEPWKHPGSQPKT, synthesized by solid phase method and purified by HPLC to >98% purity by UF Peptides, University of Ferrara, Italy), encompassing an immunodominant Tat epitope, 32,33 at the dose of 7mg.…”

“…To assess how different routes of administration may affect humoral immunogenicity of peptide vaccines, mice were vaccinated 3 times (at days 1, 14 and 28), by ID or OM route, with Tat 1-20 peptide (EPVDPRLEPWKHPGSQPKT, synthesized by solid phase method and purified by HPLC to >98% purity by UF Peptides, University of Ferrara, Italy), encompassing an immunodominant Tat epitope, 32,33 at the dose of 7mg. This dose contains the same number of molecules of 30mg of Tat protein.…”