[Show abstract][Hide abstract] ABSTRACT: A guiding principle for HIV vaccine design has been that cellular and humoral immunity work together to provide the strongest degree of efficacy. However, three efficacy trials of Ad5-vectored HIV vaccines showed no protection. Transmission was increased in two of the trials, suggesting that this vaccine strategy elicited CD4+ T-cell responses that provide more targets for infection, attenuating protection or increasing transmission. The degree to which this problem extends to other HIV vaccine candidates is not known. Here, we show that a gp120-CD4 chimeric subunit protein vaccine (full-length single chain) elicits heterologous protection against simian-human immunodeficiency virus (SHIV) or simian immunodeficiency virus (SIV) acquisition in three independent rhesus macaque repeated low-dose rectal challenge studies with SHIV162P3 or SIVmac251. Protection against acquisition was observed with multiple formulations and challenges. In each study, protection correlated with antibody-dependent cellular cytotoxicity specific for CD4-induced epitopes, provided that the concurrent antivaccine T-cell responses were minimal. Protection was lost in instances when T-cell responses were high or when the requisite antibody titers had declined. Our studies suggest that balance between a protective antibody response and antigen-specific T-cell activation is the critical element to vaccine-mediated protection against HIV. Achieving and sustaining such a balance, while enhancing antibody durability, is the major challenge for HIV vaccine development, regardless of the immunogen or vaccine formulation.
Proceedings of the National Academy of Sciences 03/2015; 112(9):E992-E999. DOI:10.1073/pnas.1423669112 · 9.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To target the HIV CD4i envelope epitope, we primed rhesus macaques with replicating Ad-rhFLSC (HIV-1BaLgp120 linked to macaque CD4 D1 and D2), with or without Ad-SIVgag and Ad-SIVnef. Macaques were boosted with rhFLSC protein. Memory T-cells in PBMC, bronchoalveolar lavage and rectal tissue, antibodies with neutralizing and ADCC activity, and Env-specific secretory IgA in rectal secretions were elicited. Although protective neutralizing antibody levels were induced, SHIVSF162P4 acquisition following rectal challenge was not prevented. Rapid declines in serum ADCC activity, Env-specific memory B cells in PBMC and bone marrow, and systemic and mucosal memory T cells were observed immediately post-challenge together with delayed anamnestic responses. Innate immune signaling resulting from persisting Ad replication and the TLR-4 booster adjuvant may have been in conflict and reoriented adaptive immunity. A different adjuvant paired with replicating Ad, or a longer post-prime interval allowing vector clearance before boosting might foster persistent T- and B-cell memory.
[Show abstract][Hide abstract] ABSTRACT: The quest for a prophylactic AIDS vaccine is ongoing, but it is now clear that the successful vaccine must elicit protective antibody responses. Accordingly, intense efforts are underway to identify immunogens that elicit these responses. Regardless of the mechanism of antibody-mediated protection, be it neutralization, Fc-mediated effector function, or both, antibody persistence and appropriate T-cell help are significant problems confronting the development of a successful AIDS vaccine. Here, we discuss the evidence illustrating the poor persistence of antibody responses to Env, the envelope glycoprotein of HIV-1, and the related problem of CD4(+) T-cell responses that compromise vaccine efficacy by creating excess cellular targets of HIV-1 infection. Finally, we propose solutions to both problems that are applicable to all Env-based AIDS vaccines regardless of the mechanism of antibody-mediated protection.
Proceedings of the National Academy of Sciences 10/2014; 111(44). DOI:10.1073/pnas.1413550111 · 9.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background and aims
Hydrogen sulfide (H2S), together with nitric oxide (NO) and carbon monoxide (CO), belongs to a family of endogenous signaling mediators termed “gasotransmitters”. Recent studies suggest that H2S modulates many cellular processes and it has been recognized to play a central role in inflammation, in the cardiovascular and nervous systems. By infecting monocytes/macrophages with Mycoplasma fermentans (M.F.), a well-known pro-inflammatory agent, we evaluated the effects of H2S.
M.F.-infected cells were analyzed by ELISA and real time RT-PCR to detect the M.F. effects on MCP-1 and on MMP-12 expression. The role of two different H2S donors (NaHS and GYY4137) on MF-infected cells was determined by treating infected cells with H2S and then testing the culture supernatants for MCP-1 and on MMP-12 production by ELISA assay. In order to identify the pathway/s mediating H2S- anti-inflammatory activity, cells were also treated with specific pharmaceutical inhibitors. Cytoplasmic and nuclear accumulation of NF-κB heterodimers was analyzed.
We show that H2S was able to reduce the production of pro-inflammatory cytokine MCP-1, that was induced in monocytes/macrophages during M.F. infection. Moreover, MCP-1 was induced by M.F. through Toll-like receptor (TLR)-mediated nuclear factor-κB (NF-κB) activation, as demonstrated by the fact that TLR inhibitors TIRAP and MyD88 and NF-κB inhibitor IKK were able to block the cytokine production. In contrast H2S treatment of M.F. infected macrophages reduced nuclear accumulation of NF-κB heterodimer p65/p52.
Our data demonstrate that under the present conditions H2S is effective in reducing Mycoplasma-induced inflammation by targeting the NF-κB pathway. This supports further studies for possible clinical applications.
Journal of Translational Medicine 05/2014; 12(1):145. DOI:10.1186/1479-5876-12-145 · 3.99 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Shortly after the discovery of human herpesvirus 6 (HHV-6), two distinct variants, HHV-6A and HHV-6B, were identified. In 2012, the International Committee on Taxonomy of Viruses (ICTV) classified HHV-6A and HHV-6B as separate viruses. This review outlines several of the documented epidemiological, biological, and immunological distinctions between HHV-6A and HHV-6B, which support the ICTV classification. The utilization of virus-specific clinical and laboratory assays for distinguishing HHV-6A and HHV-6B is now required for further classification. For clarity in biological and clinical distinctions between HHV-6A and HHV-6B, scientists and physicians are herein urged, where possible, to differentiate carefully between HHV-6A and HHV-6B in all future publications.
Archives of Virology 11/2013; 159(5). DOI:10.1007/s00705-013-1902-5 · 2.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Human Immunodeficiency Virus Type I (HIV-1) infection is associated with a high incidence of B-cell lymphomas. The role of HIV in these lymphomas is unclear and currently there are no valid in vivo models for better understanding HIV-related lymphomagenesis. Transgenic (Tg) 26 mice have a 7.4-kb pNL4-3 HIV-1 provirus lacking a 3.1-kb sequence encompassing parts of the gag-pol region. Approximately 15% of these HIV Tg mice spontaneously develop lymphoma with hallmark pre-diagnostic markers including skin lesions, diffuse lymphadenopathy and an increase in pro-inflammatory serum cytokines. Here we describe the phenotypic and molecular characteristics of the B cell leukemia/lymphoma in the Tg mice.
The transformed B cell population consists of CD19+pre-BCR+CD127+CD43+CD93+ precursor B cells. The tumor cells are clonal and characterized by an increased expression of several cellular oncogenes. Expression of B cell-stimulatory cytokines IL-1beta, IL-6, IL-10, IL-12p40, IL-13 and TNFalpha and HIV proteins p17, gp120 and nef were elevated in the Tg mice with lymphoma.
Increased expression of HIV proteins and the B-cell stimulatory factors is consistent with the interpretation that one or more of these factors play a role in lymphoma development. The lymphomas share many similarities with those occurring in HIV/AIDS+ patients and may provide a valuable model for understanding AIDS-related lymphomagenesis and elucidating the role played by HIV-1.
[Show abstract][Hide abstract] ABSTRACT: Recent identification of large numbers of new broadly neutralizing antibodies (bnAbs) against HIV-1 is leading a vaccine path based on their epitopes. However, majority of the newly identified bnAbs have apparent unusually high levels of mutation, which raises a high bar for a vaccine to generate this type of Ab response. Here we show by phylogenetic analysis that these highly mutated bnAbs cluster into two families of VH genes that are distant from known VH germline genes. It is recognized that the number of human Ab germline genes is not always the same due to genetic polymorphism. Our studies on diversity of VH germline genes also find that diversity of VH germline genes is common. These observations indicate that the diversity of Ab germline genes may limit the induction of these bnAbs at the population level. Here we describe a new potent bnAb, N60-B1.1 that neutralizes 40% of a panel of 118 tier 2,3 viruses with an average IC50 of 0.44 ug/ml. The neutralization pattern of N60-B1.1 is complementary to other bnAbs in that it potently neutralizes viruses that are more resistant to these other antibodies. This bnAb is encoded by VH4-39*07 that is somatically mutated 13.3% at the nucleotide level, which is within the normal somatic mutation rate for vaccine induced antibodies. It uses a single point mutated light chain of germline (CDRL3) VK3-15*01. Theoretically, the induction of "N60-B1.1-like" bnAb will not be limited by the somatic mutation bottleneck that is required for other bnAbs against HIV-1. Therefore, rational design of Env immunogens that preferentially expose "N60-B1.1-like" epitopes to elicit bnAb responses is a promising direction for the development of a protective HIV-1 vaccine.
[Show abstract][Hide abstract] ABSTRACT: The HIV-1 envelope glycoprotein (Env) undergoes conformational transitions consequent to CD4 binding and coreceptor engagement during viral entry. The physical steps in this process are becoming defined, but less is known about their significance as targets of antibodies potentially protective against HIV-1 infection. Here we probe the functional significance of transitional epitope exposure by characterizing 41 human mAbs specific for epitopes exposed on trimeric Env after CD4 engagement. These mAbs recognize three epitope clusters: cluster A, the gp120 face occluded by gp41 in trimeric Env; cluster B, a region proximal to the coreceptor-binding site (CoRBS) and involving the V1/V2 domain; and cluster C, the coreceptor-binding site. The mAbs were evaluated functionally by antibody-dependent, cell-mediated cytotoxicity (ADCC) and for neutralization of Tiers 1 and 2 pseudoviruses. All three clusters included mAbs mediating ADCC. However, there was a strong potency bias for cluster A, which harbors at least three potent ADCC epitopes whose cognate mAbs have electropositive paratopes. Cluster A epitopes are functional ADCC targets during viral entry in an assay format using virion-sensitized target cells. In contrast, only cluster C contained epitopes that were recognized by neutralizing mAbs. There was significant diversity in breadth and potency that correlated with epitope fine specificity. In contrast, ADCC potency had no relationship with neutralization potency or breadth for any epitope cluster. Thus, Fc-mediated effector function and neutralization coselect with specificity in anti-Env antibody responses, but the nature of selection is distinct for these two antiviral activities.
Proceedings of the National Academy of Sciences 12/2012; 110(1). DOI:10.1073/pnas.1217609110 · 9.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The HIV-1 envelope glycoprotein (Env) undergoes ordered conformational transitions after CD4 binding and co-receptor engagement during viral entry. While the physicochemical steps of viral entry are becoming defined, less is known about their immunochemical correlates and their roles as targets of protective antibodies. We describe studies that define the functional significance of epitope exposure during the first step of viral entry, the binding of gp120 to CD4. A panel of 41 human monoclonal antibodies (mAbs) were isolated that recognize epitopes which become exposed on trimeric Env only after CD4 engagement. These mAbs recognize clusters of epitopes mapping to three regions of gp120: a. Cluster A, the domain of gp120 occluded by interaction with gp41; b. Cluster B, a region proximal to the classical co-receptor binding site (CoRBS) involving the V1/V2 region; and Cluster C, the CoRBS. The mAbs were characterized for neutralization of Tier 1 and Tier 2 pseudoviruses and by antibody dependent cell mediated cytotoxicity (ADCC). mAbs recognizing all three clusters mediated ADCC but there was a strong bias in potency for mAbs that recognize Clusters A and B. Surprisingly, ADCC potency correlated inversely with CDR-H3 length but not with somatic hypermutation. By contrast, mAbs binding Cluster C epitopes were neutralizing but there was significant diversity in breadth and potency that correlated with epitope fine specificity and somatic hypermutation. ADCC potency did not correlate with neutralization breadth or potency. Thus, both neutralization and Fc-mediated effector function are co-selected with specificity but the nature of selection is distinct for these two anti-viral activities.
[Show abstract][Hide abstract] ABSTRACT: T-cell-derived soluble factors that inhibit both X4 and R5 HIV are recognized as important in controlling HIV. Whereas three β chemokines, regulated-on-activation normal T-cell expressed and secreted (RANTES), macrophage inflammatory protein (MIP)-1α, and MIP-1β, account for the suppression of R5 HIV by blockade of HIV entry, the major components responsible for the inhibition of X4 HIV strains have not been identified previously. We identify these factors primarily as a mixture of three β chemokines [macrophage-derived chemokine (MDC), thymus and activation-regulated chemokine (TARC), and I-309] and two RNases (angiogenin and RNase 4) of lesser potency and show that in a clade B population, some correlate with clinical status and are produced by both CD4(+) and CD8(+) T cells (chemokines, angiogenin) or only by CD8(+) T cells (RNase 4). The antiviral mechanisms of these HIV X4-suppressive factors differ from those of the previously described HIV R5-suppressive β chemokines.
Proceedings of the National Academy of Sciences 03/2012; 109(14):5411-6. DOI:10.1073/pnas.1202240109 · 9.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Anticytokine (AC) immune therapies derived from vaccine procedures aim at enhancing natural immune defense mechanisms ineffective to contain abnormally produced cytokines and counteract their pathogenic effects. Given their short half-life, cytokines, the production of which by effector immune cells (T and B lymphocytes, antigen-presenting cells (APCs), natural killer (NK) and endothelial cells) is inducible and controlled by negative feedback regulation, (1) exert locally their signaling to paracrine/autocrine target responder cells carrying high-affinity membrane receptors and (2) are commonly present at minimal concentration in the body fluid (lymph, serum). Aberrant signaling triggered by cytokines, uncontrolly released by effector immune cells or produced by cancer and other pathologic cells, contribute to the pathogenesis of chronic diseases including cancer, viral infections, allergy, and autoimmunity. To block these ectopic cytokine signaling and prevent their pathogenic effects, AC Abs supplied either by injections (passive AC immune therapy) or elicited by immunization with cytokine-derived immunogenes called Kinoids (active AC immune therapy) proved to be experimentally effective and safe. In this review, we detailed the rationale and the requirements for the use of AC immunotherapies in humans, the proof of efficacy of these medications in animal disease models, and their current clinical development and outcome, including adverse side effects they may generate. We particularly show that, to date, the benefit:risk ratio of AC immune therapies is highly positive.
Advances in Immunology 01/2012; 115:187-227. DOI:10.1016/B978-0-12-394299-9.00007-2 · 5.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Human T-cell lymphoma virus (HTLV)-1 was the first human retrovirus to be discovered. It has been recognized as the cause of adult T-cell leukemia (ATL). In addition to giving a historical perspective on HTLV-1 and other retrovirus research, this paper discusses the origin of HTLV-1; the modes of transmission and global epidemiology of HTLV-1 infection; the genome of HTLV-1 and the mechanism of HTLV-1-induced leukemogenesis; the role of HTLV-1 in other diseases, and recent breakthroughs in ATL therapy.
Best practice & research. Clinical haematology 12/2011; 24(4):559-65. DOI:10.1016/j.beha.2011.09.012 · 2.55 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Immune suppressive activities exerted by regulatory T-cell subsets have several specific functions, including self-tolerance and regulation of adaptive immune reactions, and their dysfunction can lead to autoimmune diseases and contribute to AIDS and cancer. Two functionally distinct regulatory T-cell subsets are currently identified in peripheral tissues: thymus-developed natural T regulatory cells (nTregs) controlling self-tolerance and antiinflammatory IL-10-secreting type 1 regulatory T cells (Tr1) derived from Ag-stimulated T cells, which regulate inflammation-dependent adaptive immunity and minimize immunopathology. We establish herein that cell contact-mediated nTreg regulatory function is inhibited by inflammation, especially in the presence of the complement C3b receptor (CD46). Instead, as with other T-cell subsets, the latter inflammatory conditions of stimulation skew nTreg differentiation to Tr1 cells secreting IL-10, an effect potentiated by IFN-α. The clinical relevance of these findings was verified in a study of 152 lupus patients, in which we showed that lupus nTreg dysfunction is not due to intrinsic defects but is rather induced by C3b stimulation of CD46 and IFN-α and that these immune components of inflammation are directly associated with active lupus. These results provide a rationale for using anti-IFN-α Ab immunotherapy in lupus patients.
Proceedings of the National Academy of Sciences 11/2011; 108(47):18995-9000. DOI:10.1073/pnas.1113301108 · 9.81 Impact Factor