Immunization of mice with the nef gene from Human Immunodeficiency Virus type 1: Study of immunological memory and long-term toxicology

Abstract

BackgroundThe human immunodeficiency virus type 1 (HIV-1) regulatory protein, Nef, is an attractive vaccine target because it is involved in viral pathogenesis, is expressed early in the viral life cycle and harbors many T and B cell epitopes. Several clinical trials include gene-based vaccines encoding this protein. However, Nef has been shown to transform certain cell types in vitro. Based on these findings we performed a long-term toxicity and immunogenicity study of Nef, encoded either by Modified Vaccinia virus Ankara or by plasmid DNA. BALB/c mice were primed twice with either DNA or MVA encoding Nef and received a homologous or heterologous boost ten months later. In the meantime, the Nef-specific immune responses were monitored and at the time of sacrifice an extensive toxicological evaluation was performed, where presence of tumors and other pathological changes were assessed.ResultsThe toxicological evaluation showed that immunization with MVAnef is safe and does not cause cellular transformation or other toxicity in somatic organs.Both DNAnef and MVAnef immunized animals developed potent Nef-specific cellular responses that declined to undetectable levels over time, and could readily be boosted after almost one year. This is of particular interest since it shows that plasmid DNA vaccine can also be used as a potent late booster of primed immune responses. We observed qualitative differences between the T cell responses induced by the two different vectors: DNA-encoded nef induced long-lasting CD8+ T cell memory responses, whereas MVA-encoded nef induced CD4+ T cell memory responses. In terms of the humoral immune responses, we show that two injections of MVAnef induce significant anti-Nef titers, while repeated injections of DNAnef do not. A single boost with MVAnef could enhance the antibody response following DNAnef prime to the same level as that observed in animals immunized repeatedly with MVAnef. We also demonstrate the possibility to boost HIV-1 Nef-specific immune responses using the MVAnef construct despite the presence of potent anti-vector immunity.ConclusionThis study shows that the nef gene vectored by MVA does not induce malignancies or other adverse effects in mice. Further, we show that when the nef gene is delivered by plasmid or by a viral vector, it elicits potent and long-lasting immune responses and that these responses can be directed towards a CD4+ or a CD8+ T cell response depending on the choice of vector.

A prime-boost vaccination protocol optimizes immune responses against the nucleocapsid protein of the SARS coronavirus

“…In this work, we performed a sideby-side comparison of different strategies to optimize the immune responses against the NC protein of the SARS-CoV. The live attenuated MVA vector was used for protein delivery to achieve good and long lasting systemic and local T-cell responses [33]. For the induction of humoral immune responses, recombinant NC protein was co-administered with a systemic or a mucosal adjuvant by different routes (intramuscular and intranasal).…”

In vitro Delivery of HIV-1 Nef Antigen by Histidine-rich nona-arginine and Latarcin 1 peptide

“…The results showed that vaccination with MVA-nef was safe and could induce Nef-specific CD4 + T-cell responses [19]. Moreover, vaccination with MVA-nef was associated with recognition of new HIV-1 T-cell epitopes and an increase in CD4 + and CD8 + T cells [5,22].…”

“…The HIV genome consists of two single-stranded RNA molecules enclosed within the core of the virus and includes about nine genes encoding structural, regulatory, and accessory proteins involved in the viral life cycle [2][3][4]. Among the accessory proteins encoded by the HIV genome, Nef protein is an attractive vaccine target; it is involved in viral pathogenesis, is expressed early in the viral life cycle, and harbors several T and B cell epitopes [5]. Nef is a 27-32 kDa protein, which is associated with high viral load and progression to AIDS [6].…”

Improving the potency of DNA vaccine encoding HIV-1 Nef antigen using two endogenous adjuvants in mouse model

“…The results showed that DNA construct expressing Nef elicited long-lasting CD8 + T cell memory responses, while MVA expressing Nef induced CD4 + T cell memory responses. Indeed, the type of the expression vector could direct the responses towards CD4 + or CD8 + T cell responses (42). In this study, we evaluated immune responses induced by various DNA immunizations in BALB/c mice model.…”