Simian immunodeficiency viruses containing mutations in the long terminal repeat NF-kappa B or Sp1 binding sites replicate efficiently in T cells and PHA-stimulated PBMCs

Potent and stable attenuation of live-HIV-1 by gain of a proteolysis-resistant inhibitor of NF-kappaB (IkappaB-alphaS32/36A) and the implications for vaccine development

Live-attenuated human immunodeficiency viruses (HIVs) are candidates for Acquired Immunodeficiency Syndrome (AIDS) vaccine. Based on the simian immunodeficiency virus (SIV) model for AIDS, loss-of-function (e.g. deletion of accessory genes such as nef) has been forwarded as a primary approach for creating enfeebled, but replication-competent, HIV-1/SIV. Regrettably, recent evidence suggests that loss-of-function alone is not always sufficient to prevent the emergence of virulent mutants. New strategies that attenuate via mechanisms distinct from loss-of-function are needed for enhancing the safety phenotype of viral genome. Here, we propose gain-of-function to be used simultaneously with loss-of-function as a novel approach for attenuating HIV-1. We have constructed an HIV-1 genome carrying the cDNA of a proteolysis-resistant nuclear factor-kappaB inhibitor (IkappaB-alphaS32/36A) in the nef region. HIV-1 expressing IkappaB-alphaS32/36A down-regulates viral expression and is highly attenuated in both Jurkat and peripheral blood mononuclear cells. We provide formal proof that the phenotypic and attenuating characteristics of IkappaB-alphaS32/36A permit its stable maintenance in a live, replicating HIV-1 despite 180 days of forced ex vivo passaging in tissue culture. As compared with other open-reading frames embedded into HIV/SIV genome, this degree of stability is unprecedented. Thus, IkappaB-alphaS32/36A offers proof-of-principle that artifactually gained functions, when used to attenuate the replication of live HIV-1, can be stable. These findings illustrate gain-of-function as a feasible strategy for developing safer live-attenuated HIVs to be tested as candidates for AIDS vaccine.

Molecular cloning and characterization of viruses isolated from chimpanzees with pathogenic human immunodeficiency virus type 1 infections

We have previously described the development of AIDS in a chimpanzee (C499) infected with human immunodeficiency virus type 1 (HIV-1) and the subsequent pathogenic HIV-1 infection in another chimpanzee (C455) transfused with blood from C499 (F. J. Novembre et al., J. Virol. 71:4086-4091, 1997). In the present study, two virus isolates were derived from these animals: HIV-1JC from peripheral blood mononuclear cells (PBMC) of C499, and HIV-1NC from plasma of C455. These virus isolates were used to generate two infectious molecular clones, termed HIV-1JC16 and HIV-1NC7 (JC16 and NC7, respectively). Comparative analyses of the sequences of the two clones showed that they were highly interrelated but distinct. Based on heteroduplex mobility assays, JC16 and NC7 appear to represent dominant viruses in the uncloned stock population. Compared with amino acid sequences of the parental viruses HIV-1SF2, HIV-1LAV-1b, and HIV-1NDK, JC16 and NC7 showed a number of differences, including insertions, deletions, and point mutations spread throughout the genome. However, insertion/deletion footprints in several genes of both JC16 and NC7 suggested that recombination between SF2 and LAV-1b could have occurred, possibly contributing to the generation of a pathogenic virus. Comparative in vitro analyses of the molecular clones and the uncloned stocks of HIV-1JC and HIV-1NC revealed that these viruses had strikingly similar replicative abilities in mitogen-stimulated PBMC and in macrophages. Compared to the SF2 and LAV-1b isolates of HIV-1, HIV-1JC and HIV-1NC isolates were more similar to LAV-1b with respect to the ability to replicate in mitogen-stimulated PBMC and macrophages. These viruses should prove to be useful in mapping determinants of pathogenesis.