X4 human immunodeficiency virus type 1 gp120 down-modulates expression and immunogenicity of codelivered antigens

Expansion of myeloid-derived suppressor cells promotes differentiation of regulatory T cells in HIV-1+ individuals

OBJECTIVE

Regulatory T cells (Tregs) contribute to HIV-1 disease progression by impairing antiviral immunity; however, the precise mechanisms responsible for the development of Tregs in the setting of HIV-1 infection are incompletely understood.

DESIGN

In this study, we provide evidence that HIV-induced expansion of monocytic myeloid-derived suppressor cells (M-MDSCs) promote the differentiation of Foxp3 Tregs.

METHODS

We measured MDSC induction and cytokine expression by flow cytometry and analyzed their functions by coculturing experiments.

RESULTS

We observed a dramatic increase in M-MDSC frequencies in the peripheral blood of HIV-1 seropositive (HIV-1) individuals, even in those on antiretroviral therapy with undetectable viremia, when compared with healthy participants. We also observed increases in M-MDSCs after incubating healthy peripheral mononuclear cells (PBMCs) with HIV-1 proteins (gp120 or Tat) or Toll-like receptor 4 ligand lipopolysaccharides in vitro, an effect that could be abrogated in the presence of the phosphorylated signal transducer and activator of transcription 3 inhibitor, STA-21. Functional analyses indicated that M-MDSCs from HIV-1 individuals express higher levels of IL-10, tumor growth factor-β, IL-4 receptor α, p47, programmed death-ligand 1, and phosphorylated signal transducer and activator of transcription 3 - all of which are known mediators of myelopoiesis and immunosuppression. Importantly, incubation of healthy CD4 T cells with MDSCs derived from HIV-1 individuals significantly increased differentiation of Foxp3 Tregs. In addition, depletion of MDSCs from PBMCs of HIV-1 individuals led to a significant reduction of Foxp3 Tregs and increase of IFNγ production by CD4 T effector cells.

CONCLUSIONS

These results suggest that HIV-induced MDSCs promote Treg cell development and inhibit T cell function - a hallmark of many chronic infectious diseases.

Evaluation of humoral, mucosal, and cellular immune responses following co-immunization of HIV-1 Gag and Env proteins expressed by Newcastle disease virus

The combination of multiple HIV antigens in a vaccine can broaden antiviral immune responses. In this study, we used NDV vaccine strain LaSota to generate rNDV (rLaSota/optGag) expressing human codon optimized p55 Gag protein of HIV-1. We examined the effect of co-immunization of rLaSota/optGag with rNDVs expressing different forms of Env protein gp160, gp120, gp140L [a version of gp140 that lacked cytoplasmic tail and contained complete membrane-proximal external region (MPER)] and gp140S (a version of gp140 that lacked cytoplasmic tail and distal half of MPER) on magnitude and breadth of humoral, mucosal and cellular immune responses in guinea pigs and mice. Our results showed that inclusion of rLaSota/optGag with rNDVs expressing different forms of Env HIV Gag did not affect the Env-specific humoral and mucosal immune responses in guinea pigs and that the potent immune responses generated against Env persisted for at least 13 weeks post immunization. The highest Env-specific humoral and mucosal immune responses were observed with gp140S+optGag group. The neutralizing antibody responses against HIV strains BaL.26 and MN.3 induced by gp140S+optGag and gp160+optGag were higher than those elicited by other groups. Inclusion of Gag with gp160, gp140S and gp140L enhanced the level of Env-specific IFN-γ-producing CD8(+) T cells in mice. Inclusion of Gag with gp160 and gp140L also resulted in increased Env-specific CD4(+) T cells. The level of Gag-specific CD8(+) and CD4(+) T cells was also enhanced in mice immunized with Gag along with gp140S and gp120. These results indicate lack of antigen interference in a vaccine containing rNDVs expressing Env and Gag proteins.

Modulation of HIVGP120 Antigen-Specific Immune Responses In Vivo by Δ9-Tetrahydrocannabinol

Approximately 25 % of HIV patients use marijuana for its putative therapeutic benefit; however, it is unknown how cannabinoids affect the immune status of HIV patients. Previously, a surrogate in vitro mouse model was established, which induced CD8(+) T cell proliferation and gp120-specific IFNγ production. ∆(9)-Tetrahydrocannabinol (THC), the predominant psychoactive compound in marijuana, suppressed or enhanced the responses depending on the magnitude of cellular activation. The purpose of the current study was to investigate whether THC produced similar effects in vivo and therefore a mouse model to induce HIVgp120-specific immune responses was established. A gp120-expressing plasmid, pVRCgp120, or a vector plasmid, pVRC2000, was injected intramuscularly into mice, which were also dosed with THC orally. The gp120-specific IFNγ and IL-2 responses were detected when splenocytes were restimulated with gp120-derived peptide 81 (IIGDIRQAHCNISRA), which was identified as being immunodominant. Various cellular populations were activated in response to pVRCgp120 stimulation followed by peptide restimulation, as evidenced by increased expression levels of activation markers (e.g., CD69, CD80, and major histocompatibility complex II [MHC II]). The IFNγ response and cellular activation were enhanced by THC in C57Bl/6 wild type (WT) mice but suppressed or not affected by THC in cannabinoid receptor 1 (CB1) and 2 (CB2) knockout (CB1 (-/-)CB2 (-/-)) mice. Furthermore, CB1 (-/-)CB2 (-/-) mice exhibited augmented IFNγ production when compared to WT mice in the absence of THC. Collectively, our findings demonstrate that under certain conditions, THC enhances HIV antigen-specific immune responses, which occurs through CB1/CB2-dependent and -independent mechanisms.

Altered response hierarchy and increased T-cell breadth upon HIV-1 conserved element DNA vaccination in macaques

HIV sequence diversity and potential decoy epitopes are hurdles in the development of an effective AIDS vaccine. A DNA vaccine candidate comprising of highly conserved p24^gag elements (CE) induced robust immunity in all 10 vaccinated macaques, whereas full-length gag DNA vaccination elicited responses to these conserved elements in only 5 of 11 animals, targeting fewer CE per animal. Importantly, boosting CE-primed macaques with DNA expressing full-length p55^gag increased both magnitude of CE responses and breadth of Gag immunity, demonstrating alteration of the hierarchy of epitope recognition in the presence of pre-existing CE-specific responses. Inclusion of a conserved element immunogen provides a novel and effective strategy to broaden responses against highly diverse pathogens by avoiding decoy epitopes, while focusing responses to critical viral elements for which few escape pathways exist.

Clinical adjuvant combinations stimulate potent B-cell responses in vitro by activating dermal dendritic cells

CD14⁺ dermal DCs (CD14⁺ DDCs) have a natural capacity to activate naïve B-cells. Targeting CD14⁺ DDCs is therefore a rational approach for vaccination strategies aimed at improving humoral responses towards poorly immunogenic antigens, for example, HIV-1 envelope glycoproteins (Env). Here, we show that two clinically relevant TLR ligand combinations, Hiltonol plus Resiquimod and Glucopyranosyl lipid A plus Resiquimod, potently activate CD14⁺ DDCs, as shown by enhanced expression of multiple cytokines (IL-6, IL-10, IL-12p40 and TNF-α). Furthermore, the responses of CD14⁺ DDCs to these TLR ligands were not compromised by the presence of HIV-1 gp120, which can drive immunosuppressive effects in vitro and in vivo. The above TLR ligand pairs were better than the individual agents at boosting the inherent capacity of CD14⁺ DDCs to induce naïve B-cells to proliferate and differentiate into CD27⁺ CD38⁺ B-cells that secrete high levels of immunoglobulins. CD14⁺ DDCs stimulated by these TLR ligand combinations also promoted the differentiation of Th1 (IFN-γ-secreting), but not Th17, CD4⁺ T-cells. These observations may help to identify adjuvant strategies aimed at inducing better antibody responses to vaccine antigens, including, but not limited to HIV-1 Env.

Optimizing cellular immunity against HIV-1 Gag and preventing suppression by HIV-1 gp120

Evaluation of: Böckl K, Wild J, Bredl S et al. Altering an artificial Gagpolnef polyprotein and mode of Env co-administration affects the immunogenicity of a clade C HIV-1 DNA vaccine. PLoS ONE 7(4), e34723 (2012). SIV vaccination studies in monkeys have revealed that Env-directed antibodies are critical for protection against virus acquisition, whereas CD8(+) T-cell responses against the Gag and Pol proteins contribute to control of viremia postinfection. However, designing a vaccine that strongly activates both arms of the immune system, is challenging for a variety of reasons, one being interference of Gag and Env responses. Böckl et al. have studied how to optimize CD8 T-cell responses against Gag, Pol and Nef in the presence of Env co-vaccination. Although Env coadministration suppressed anti-Gag CD8(+) responses, this effect could be counteracted by adjusting the molar ratio of the vaccines and by spatial or temporal separation of the Gag and Env antigens. These results demonstrate that optimal induction of antiviral CD8(+) responses requires careful optimization of vaccine design, composition and administration.

E. coli Heat-labile Enterotoxin B Subunit as a Platform for the Delivery of HIV Gag p24 Antigen

Multiple vaccination strategies have been devised against HIV-1 including delivery of HIV moieties in attenuated or replication defective recombinant microbial agents alone or in combination with priming agents in form of soluble proteins or naked DNA. For the priming agents to be effective, adjuvants might be essential in directing the immune response to a desired outcome. E. coli enterotoxin B subunit (LTB) is an effective adjuvant and carrier for other proteins and epitopes. Here we show that conjugation of HIV gag p24 to LTB enhances the T cell response to gag p24 by increasing rate of T cell division compared to other treatments. Because HIV vaccines are likely to be multivalent, we further investigated whether gag p24 inhibits antigen presentation of an unrelated antigen, OVA. Addition of gag p24 to OVA-responsive DO.11.10 cell culture did not have adverse effects on antigen presentation. Interestingly, the presence of LTB in these cultures significantly increased proliferation of DO.11.10 cells. In all, the results suggest the use of LTB to boost immune responses against HIV gag p24 in systemic priming regimens with oral recombinant HIV vaccines.

Altering an artificial Gagpolnef polyprotein and mode of ENV co-administration affects the immunogenicity of a clade C HIV DNA vaccine

HIV-1 candidate vaccines expressing an artificial polyprotein comprising Gag, Pol and Nef (GPN) and a secreted envelope protein (Env) were shown in recent Phase I/II clinical trials to induce high levels of polyfunctional T cell responses; however, Env-specific responses clearly exceeded those against Gag. Here, we assess the impact of the GPN immunogen design and variations in the formulation and vaccination regimen of a combined GPN/Env DNA vaccine on the T cell responses against the various HIV proteins. Subtle modifications were introduced into the GPN gene to increase Gag expression, modify the expression ratio of Gag to PolNef and support budding of virus-like particles. I.m. administration of the various DNA constructs into BALB/c mice resulted in an up to 10-fold increase in Gag- and Pol-specific IFNγ(+) CD8(+) T cells compared to GPN. Co-administering Env with Gag or GPN derivatives largely abrogated Gag-specific responses. Alterations in the molar ratio of the DNA vaccines and spatially or temporally separated administration induced more balanced T cell responses. Whereas forced co-expression of Gag and Env from one plasmid induced predominantly Env-specific T cells responses, deletion of the only H-2(d) T cell epitope in Env allowed increased levels of Gag-specific T cells, suggesting competition at an epitope level. Our data demonstrate that the biochemical properties of an artificial polyprotein clearly influence the levels of antigen-specific T cells, and variations in formulation and schedule can overcome competition for the induction of these responses. These results are guiding the design of ongoing pre-clinical and clinical trials.

A shift from cell cultures to creatures: in vivo imaging of small animals in experimental regenerative medicine

Although the use of small animals for in vivo experimentation has been widespread, only recently has there been easy availability of techniques that allow noninvasive in vivo imaging of small animals. Because these techniques allow the same individual subject to be followed longitudinally throughout the duration of an experiment, their use is rapidly changing the way small animals are employed in the laboratory. In this review, we focus on six imaging modalities that are increasingly employed for small animal in vivo imaging: optical imaging (OI), magnetic resonance imaging (MRI), computed tomography (CT), single-photon emission tomography (SPECT), ultrasound (US), and positron-emission tomography (PET). Each modality allows for the noninvasive tracking of cells and cell products in vivo. In addition, multimodality imaging, combining two or more of these techniques, has also been increasingly employed to overcome the limitations of each independent technique. After reviewing these available imaging modalities, we detail their experimental application, exemplified by the emerging field of regenerative medicine, referring to publications whose conclusions would otherwise be difficult to support without the availability of in vivo imaging.

R5-SHIV induces multiple defects in T cell function during early infection of rhesus macaques including accumulation of T reg cells in lymph nodes

Background

HIV-1 is a pathogen that T cell responses fail to control. HIV-1gp120 is the surface viral envelope glycoprotein that interacts with CD4 T cells and mediates entry. HIV-1gp120 has been implicated in immune dysregulatory functions that may limit anti-HIV antigen-specific T cell responses. We hypothesized that in the context of early SHIV infection, immune dysregulation of antigen-specific T-effector cell and regulatory functions would be detectable and that these would be associated or correlated with measurable concentrations of HIV-1gp120 in lymphoid tissues.

Methods

Rhesus macaques were intravaginally inoculated with a Clade C CCR5-tropic simian-human immunodeficiency virus, SHIV-1157ipd3N4. HIV-1gp120 levels, antigen-specificity, levels of apoptosis/anergy and frequency and function of Tregs were examined in lymph node and blood derived T cells at 5 and 12 weeks post inoculation.

Results/Conclusions

We observed reduced responses to Gag in CD4 and gp120 in CD8 lymph node-derived T cells compared to the peripheral blood at 5 weeks post-inoculation. Reduced antigen-specific responses were associated with higher levels of PD-1 on lymph node-derived CD4 T cells as compared to peripheral blood and uninfected lymph node-derived CD4 T cells. Lymph nodes contained increased numbers of Tregs as compared to peripheral blood, which positively correlated with gp120 levels; T regulatory cell depletion restored CD8 T cell responses to Gag but not to gp120. HIV gp120 was also able to induce T regulatory cell chemotaxis in a dose-dependent, CCR5-mediated manner. These studies contribute to our broader understanding of the ways in which HIV-1 dysregulates T cell function and localization during early infection.