We found that gp41Fc not only bound to our recently identified monoclonal antibodies (mAbs) recognizing conformational epitopes, m44 [6], m46 [7] and m48 [8], but also to known broadly neutralizing human mAbs that include 2F5, 4E10, Z13 that recognize linear epitopes in the membrane proximal region (MPER), suggesting that gp41Fc retains critical conformation required for presenting neutralization epitopes and may induce neutralizing antibodies against HIV-1 in vivo. and extend these results which may have implications for the development of vaccine immunogens with enhanced capability to elicit cross-reactive HIV-1-neutralizing antibodies. Keywords:HIV/AIDS, Vaccines, Gp41 == 1. Introduction == Human immunodeficiency computer virus type 1 (HIV-1) has become a growing pandemic since its discovery in the early 1980s. After more than two decades of an intensive search for a viable AIDS vaccine, the goal remains elusive. The elicitation of broadly cross-reactive HIV-1 neutralizing antibodies in humans remains a major challenge in this effort largely due to HIV-1 genetic diversity. The HIV-1 envelope glycoprotein (Env) is known to exist as trimers of heterodimer on native virions that is composed of a non-covalently associated extracellular subunit gp120 and a transmembrane subunit gp41. In natural infections, Env AGN 192836 induces a strong antibody response, but these antibodies usually have a narrow spectrum of neutralization activity. Occasionally some HIV-1-positive individuals induce broadly cross-reactive neutralizing antibodies that are believed to account for the containment of the computer virus [1,2]. Env-based vaccines have been extensively studied. Monomeric gp120 s can AGN 192836 elicit neutralizing antibodies in vivo, but the neutralization activity is restricted to autologous viruses or the spectrum of neutralization activity is usually narrow [3]. Oligomeric forms of Env ectodomain from HIV-1, strain R2 (gp140R2), which contain both gp120 and AGN 192836 a truncated gp41 that lacks both transmembrane domains and cytoplasmic tails, induced better antibody response than gp120R2alone. Rabbit sera immunized with gp140R2neutralized not only the autologous computer virus, but also heterologous viruses from diverse HIV-1 subtypes, suggesting that induction of broad spectrum neutralizing antibodies is an achievable goal in HIV-1 vaccine development [4]. This study utilizes gp41 derived from a dual tropic HIV-1 primary isolate of 89.6. Gp41 is usually relatively conserved compared to gp120, but unstable in the absence of gp120. To stabilize gp41 in the absence of gp120, we constructed a fusion protein, designated as gp41Fc, in which a truncated gp4189.6that lacked a fusion peptide, transmembrane AGN 192836 domain and cytoplasmic tail was fused to human Fc by a long flexible linker. The goal of this fusion protein was to increase its half-life in vivo and enhance its binding to immune cells like macrophages, dendritic cells, and B cells that express receptors specific for Fc [5]. We hypothesize that prolonged exposure to candidate vaccine immunogens could enhance the elicitation of broadly cross-reactive antibodies based on the observation that broadly cross-reactive HIV-1 neutralizing antibodies are typically elicited later than isolate-specific antibodies after contamination. Initially gp41Fc was used to localize the epitopes of a panel of gp41-specific neutralizing antibodies by alanine scanning mutagenesis. We found that gp41Fc not only bound to our recently identified monoclonal antibodies (mAbs) recognizing conformational epitopes, m44 [6], AGN 192836 m46 [7] and m48 [8], but also to known broadly neutralizing human mAbs that include 2F5, 4E10, Z13 that recognize linear epitopes in the membrane proximal region (MPER), suggesting that gp41Fc retains Rabbit polyclonal to SIRT6.NAD-dependent protein deacetylase. Has deacetylase activity towards ‘Lys-9’ and ‘Lys-56’ ofhistone H3. Modulates acetylation of histone H3 in telomeric chromatin during the S-phase of thecell cycle. Deacetylates ‘Lys-9’ of histone H3 at NF-kappa-B target promoters and maydown-regulate the expression of a subset of NF-kappa-B target genes. Deacetylation ofnucleosomes interferes with RELA binding to target DNA. May be required for the association ofWRN with telomeres during S-phase and for normal telomere maintenance. Required for genomicstability. Required for normal IGF1 serum levels and normal glucose homeostasis. Modulatescellular senescence and apoptosis. Regulates the production of TNF protein crucial conformation required for presenting neutralization epitopes and may induce neutralizing antibodies against HIV-1 in vivo. This prompted us to test the possibility of developing this fusion protein as HIV-1 vaccine immunogen by immunizing rabbits with purified recombinant gp41Fc. Here we report the results from the characterization of immune rabbit sera and purified IgGs from two rabbits that had different immune response to gp41Fc. == 2. Materials and methods == == 2.1. Cells, viruses, plasmids, gp120, gp140 and antibodies == 293T cells were purchased from ATCC. Other cell lines and HIV-1 isolates were obtained from the NIH AIDS Research and Reference Reagent Program (ARRRP). Recombinant gp120 and gp140 Envs from primary isolates were produced as described previously [9]. Human mAbs 2F5 and 4E10 were obtained from the ARRRP. Mouse mAbs NC-1 was generously provided by Dr. Shibo Jiang (New York Blood Center). Mouse mAbs T3 and D61 were obtained from Dr. Christopher Broder (Uniformed Services University of the Health Sciences). Fab Z13 and other gp41-specific mAbs m44, m46, m48 were produced in our laboratory. Peripheral blood mononuclear cells (PBMCs) were isolated from the blood of healthy donors. HRP-conjugated streptavidin was purchased from Zymed Laboratories Inc., San Francisco, CA. HIV-1 MN Env (15-mer) peptides (complete set, cat# 6451, Lot# 12).