The Significance of a Common Idiotype (1F7) on Antibodies against Human Immune Deficiency Virus Type 1 and Hepatitis C Virus.

In this review, we trace the concept and potential functional role of regulatory idiotypes in the immune response to human immunodeficiency virus type 1 (HIV-1), simian immunodeficiency virus, and hepatitis C virus (HCV). A major idiotype involved in these viral infections is recognized and defined by a murine monoclonal antibody (1F7). Antibodies expressing the idiotype defined by 1F7 are dominant in HIV-1 infection and are also found on many broadly neutralizing antibodies against HIV-1. This regulatory idiotypic axis offers opportunities for exploitation in vaccine development for HIV-1, HCV, and other chronic viral infections.

Live simian immunodeficiency virus vaccine correlate of protection: local antibody production and concentration on the path of virus entry.

We sought design principles for a vaccine to prevent HIV transmission to women by identifying correlates of protection conferred by a highly effective live attenuated SIV vaccine in the rhesus macaque animal model. We show that SIVmac239Δnef vaccination recruits plasma cells and induces ectopic lymphoid follicle formation beneath the mucosal epithelium in the rhesus macaque female reproductive tract. The plasma cells and ectopic follicles produce IgG Abs reactive with viral envelope glycoprotein gp41 trimers, and these Abs are concentrated on the path of virus entry by the neonatal FcR in cervical reserve epithelium and in vaginal epithelium. This local Ab production and delivery system correlated spatially and temporally with the maturation of local protection against high-dose pathogenic SIV vaginal challenge. Thus, designing vaccines to elicit production and concentration of Abs at mucosal frontlines could aid in the development of an effective vaccine to protect women against HIV-1.

Live simian immunodeficiency virus vaccine correlate of protection: immune complex-inhibitory Fc receptor interactions that reduce target cell availability.

Principles to guide design of an effective vaccine against HIV are greatly needed, particularly to protect women in the pandemic's epicenter in Africa. We have been seeking these principles by identifying correlates of the robust protection associated with SIVmac239Δnef vaccination in the SIV-rhesus macaque animal model of HIV-1 transmission to women. We identified one correlate of SIVmac239Δnef protection against vaginal challenge as a resident mucosal system for SIV-gp41 trimer Ab production and neonatal FcR-mediated concentration of these Abs on the path of virus entry to inhibit establishment of infected founder populations at the portal of entry. In this study, we identify blocking CD4(+) T cell recruitment to thereby inhibit local expansion of infected founder populations as a second correlate of protection. Virus-specific immune complex interactions with the inhibitory FcγRIIb receptor in the epithelium lining the cervix initiate expression of genes that block recruitment of target cells to fuel local expansion. Immune complex-FcγRIIb receptor interactions at mucosal frontlines to dampen the innate immune response to vaginal challenge could be a potentially general mechanism for the mucosal immune system to sense and modulate the response to a previously encountered pathogen. Designing vaccines to provide protection without eliciting these transmission-promoting innate responses could contribute to developing an effective HIV-1 vaccine.

On the benefits of sin: can greater understanding of the 1F7-idiotypic repertoire freeze enhance HIV vaccine development?

Antibodies (Abs) induced during infections with immunodeficiency viruses are subject to a form of original antigenic sin, termed repertoire freeze. This phenomenon encompasses conditions in which antigen (Ag)-specific B-cells and free Ab induced against early viral variants recognize viral escape mutants sufficiently to compete for Ag with naïve B-cells. As previously activated Ag-specific Abs and B-cells are more abundant than their naïve counterparts, they out-compete naïve B-cells and can be selected to undergo repeated rounds of somatic hypermutation and affinity maturation that drive repeated rounds of immune selection and viral escape. This situation prevents or diminishes the ability of B-cells carrying novel Ab-specificities to become activated and produce free Ab, facilitating viral escape. The enactment of repertoire freeze is illustrated in several features of anti-HIV antibodies, including persistently skewed κ/λ light chain ratios, preferential variable region gene usage, and the accumulation of Abs with extensive mutations within their variable regions. Furthermore, several investigators documented the presence of anti-viral Abs carrying a common idiotype, designated 1F7, from early infection onwards. In fact, anti-idiotypic suppression of these Abs in SHIV-infected rhesus macaques allowed the development of Abs that more effectively neutralized autologous contemporaneous viruses. Although most research suggests that repertoire freeze is undesirable for controlling an active infection, recent evidence has demonstrated that potentially protective broadly neutralizing Abs (BnAbs) develop within the freeze susceptible 1F7-idiotypic repertoire. This observation suggests that repeated rounds of selection of 1F7-idiotypic Abs may drive the extensive variable region mutation that characterizes BnAbs. In this review, we address how the demonstrated overlap between 1F7-idiotypic repertoire freeze and potentially protective Ab responses can be unravelled to generate novel vaccine concepts. Furthermore, we address how idiotypic regulation of the humoral immune response could be useful for sustaining protective Ab responses.

Protective effects of anti-ricin A-chain antibodies delivered intracellularly against ricin-induced cytotoxicity.

AIM: To evaluate the ability of anti-ricin A-chain antibodies, delivered intracellularly, to protect against ricin-induced cytotoxicity in RAW264.7 cells. METHODS: Anti-deglycosylated ricin A-chain antibody and RAC18 anti-ricin A-chain monoclonal antibody were delivered intracellularly by encapsulating in liposomes or via conjugation with the cell-penetrating MTS-transport peptide. RAW264.7 cells were incubated with these antibodies either before or after ricin exposure. The changes in cytotoxicity were estimated by MTT assay. Co-localization of internalized antibody and ricin was evaluated by fluorescence microscopy. RESULTS: Internalized antibodies significantly increased cell viability either before or after ricin exposure compared to the unconjugated antibodies. Fluorescence microscopy confirmed the co-localization of internalized antibodies and ricin inside the cells. CONCLUSION: Intracellular delivery of antibodies to neutralize the ricin toxin after cellular uptake supports the potential use of cell-permeable antibodies for post-exposure treatment of ricin intoxication.

Characterization of conserved properties of hemagglutinin of H5N1 and human influenza viruses: possible consequences for therapy and infection control.

BACKGROUND: Epidemics caused by highly pathogenic avian influenza virus (HPAIV) are a continuing threat to human health and to the world's economy. The development of approaches, which help to understand the significance of structural changes resulting from the alarming mutational propensity for human-to-human transmission of HPAIV, is of particularly interest. Here we compare informational and structural properties of the hemagglutinin (HA) of H5N1 virus and human influenza virus subtypes, which are important for the receptor/virus interaction. RESULTS: Presented results revealed that HA proteins encode highly conserved information that differ between influenza virus subtypes H5N1, H1N1, H3N2, H7N7 and defined an HA domain which may modulate interaction with receptor. We also found that about one third of H5N1 viruses which are isolated during the 2006/07 influenza outbreak in Egypt possibly evolve towards receptor usage similar to that of seasonal H1N1. CONCLUSION: The presented results may help to better understand the interaction of influenza virus with its receptor(s) and to identify new therapeutic targets for drug development.

Endowing self-binding feature restores the activities of a loss-of-function chimerized anti-GM2 antibody.

Our previous studies have described a rare type of antibody that spontaneously binds to itself, or homodimerizes. This self-binding, or autophilic antibody provides stronger protection against bacterial infection than a non-self-binding antibody with identical specificity and affinity, due to an increase of polymeric avidity. Furthermore, we have shown that a peptide derived from the self-binding domain of the autophilic T15 antibody can be crosslinked to the Fc carbohydrate of monoclonal antibodies specific for the B-cell receptor of B-cell tumors. These peptide-crosslinked antibodies can exert self-binding properties, leading to an increase in binding efficiency to the target cells as well as an increase in potential to induce apoptosis. Herein, we report a novel finding that crosslinking of the autophilic T15 peptide rescues a loss-of-function chimerized (ch) anti-GM2 antibody. The parental antibody demonstrates in vivo anti-tumor activity against melanoma xenografts. The T15 peptide-conjugated antibody shows the ability to bind to itself, as well as an increased binding to its antigen, ganglioside GM2. Moreover, the peptide-conjugated antibody also demonstrates an increased ability to bind to two GM2-positive tumor cell lines and notably important, restores its ability to induce apoptosis in two types of tumor cells. These results provide strong support for the clinical potential of the autophilic technology.

Therapeutic applications of superantibodies.

Superantibody technology represents a method to enhance the potency and utility of monoclonal antibodies. The blueprint for superantibody technology is taken from rare naturally occurring superantibodies with unique sequence regions, conferring specific biological functions not detected on most antibodies. In superantibody technology, peptides with specific amino acid sequences are crosslinked to antibodies using affinity-site-specific chemistry. Three types of superantibodies have been engineered: dimerizing superantibodies with enhanced effector potency, superantibodies with the ability to penetrate living cells and superantibodies as vaccines with built-in molecular adjuvant. Collectively, superantibody technology generates a new class of antibodies with higher levels of therapeutic potency.

TransMabs: cell-penetrating antibodies, the next generation.

Intracellular proteins are becoming attractive targets in diagnosis and for therapy such as in signal pathways, on enzymes, transcription factors and structural proteins. Antibodies have been used therapeutically for extracellular pathogens and for targeting cell-surface antigens. Antibodies normally do not pass easily through intact cellular or subcellular membranes in living cells. Methods to shuttle antibodies into living cells are either labour-intensive and/or compromise the structural and functional integrity of the cell or require the integration of genes for heavy and light chain production through gene therapy approaches. A new technology platform, 'SuperAntibody Technology', enables antibodies to be shuttled into living cells without harming them. Such cell-penetrating antibodies open new diagnostic and therapeutic windows. The term 'TransMabs' has been coined for these antibodies. Proof of principle has been achieved with a 17-amino acid peptide with membrane translocating properties, conjugated with anti-caspase-3 antibody. Such a TransMab inhibits significantly in vitro apoptosis-related events, such as caspase-3 activity, DNA fragmentation and spectrin cleavage. Anti-caspase-3 TransMab, therefore, could be utilised to inhibit apoptosis in a variety of diseases, such as Alzheimer's, Huntington's and Parkinson's. Unlike peptide inhibitors available at present, this TransMab is not expected to have invivo toxic side effects and can only target activated forms of the enzyme. This paper discusses the advantages and limitations of cell-penetrating antibodies (TransMabs) compared with existing small molecule drug development approaches.

AIDS vaccine: state of the art at the beginning of the third millennium.

This overview briefly summarizes the current status of global AIDS epidemic, especially pointing out how this pandemic looked in the last year of the second millennium. We also give a brief overview of the state of the art in development of AIDS vaccines together with a short summary of the supporting data and obstacles in this development.

Avoiding deceptive imprinting of the immune response to HIV-1 infection in vaccine development.

Lymphocyte clonal restriction is caused by priming the immune system with an antigen and has been referred to infectious disease study as "original antigenic sin" (OAS), described first for influenza by Francis. OAS is a dominant feature of a normal immune response. Benefits of OAS come from the initial contact with the pathogen, which induces immunological memory. Memory is achieved by priming B and T cells of an immunologically naïve host, and confers protection against infection with the antigen-related pathogen. Thus, a restricted antibody response to viral or parasite antigens is not per se pathogenic. However, the interplay between a "locked-in" immune response and the high genetic variation of the pathogenic agent can result in a deception of the immune system. In the following, clonal restriction of the immune response to HIV is described by giving examples of restricted anti-HIV antibody formation in maternally infected children. Clonal restriction results in host resistance of infected individuals to emerging HIV variants and quasispecies. The problems of classical approaches of vaccine design in AIDS and the lack of protection in vaccinated patients is reviewed.

AIDSVAX results: an important open question.

Research and clinical data reported during last 10 years indicate the possibility that AIDS vaccines based on the HIV-1 envelope protein gp120 may be worse then useless. A correct assessment of the safety of these AIDS vaccines can not be possible without data which will allow comparison of the disease status between breakthrough HIV infected vaccinated volunteers and those from the control group. Results of the recently finished clinical trial of AIDSVAX represent a good base for this important analysis.