Single-component multilayered self-assembling protein nanoparticles presenting glycan-trimmed uncleaved prefusion optimized envelope trimmers as HIV-1 vaccine candidates

Uncleaved prefusion-optimized (UFO) design can stabilize diverse HIV-1 envelope glycoproteins (Envs). Single-component, self-assembling protein nanoparticles (1c-SApNP) can display 8 or 20 native-like Env trimers as vaccine candidates. We characterize the biophysical, structural, and antigenic properties of 1c-SApNPs that present the BG505 UFO trimer with wildtype and modified glycans. For 1c-SApNPs, glycan trimming improves recognition of the CD4 binding site without affecting broadly neutralizing antibodies (bNAbs) to major glycan epitopes. In mice, rabbits, and nonhuman primates, glycan trimming increases the frequency of vaccine responders (FVR) and steers antibody responses away from immunodominant glycan holes and glycan patches. The mechanism of vaccine-induced immunity is examined in mice. Compared with the UFO trimer, the multilayered E2p and I3-01v9 1c-SApNPs show 420 times longer retention in lymph node follicles, 20-32 times greater presentation on follicular dendritic cell dendrites, and up-to-4 times stronger germinal center reactions. These findings can inform future HIV-1 vaccine development.

Comparison of oral, nebulized and combination antibiotic treatment of Bordetella bronchiseptica in baboons (Papio spp.)

Incidence of Bordetella pertussis, the causative agent of whooping cough, is rising in some global human populations despite high vaccination rates, and significant research is underway to address the issue. Baboons are an established model for pertussis research, but like many mammals, they can be naturally infected with Bordetella bronchiseptica. Because B. bronchiseptica interferes with B. pertussis research, it must be excluded from baboons under consideration for enrollment in pertussis studies. In addition to research-related concerns, B. bronchiseptica can sometimes cause clinical disease in baboons and other nonhuman primates. This study examined the use of antibiotics to clear B. bronchiseptica in naturally infected baboons. Thirty-five juvenile baboons were divided into five treatment groups: oral sulfamethoxazole/trimethoprim (TMS), nebulized gentamicin (gentamicin), combination (TMS + gentamicin) in positive animals, combination (TMS + gentamicin) as a prophylactic in exposed animals and no treatment (control). Combination of oral TMS and nebulized gentamicin given to positive animals was most effective, producing long-term clearance in 11 out of 12 treated animals. To avoid unnecessary use of antibiotics, our primary management strategy is screening and separating to allow natural clearance and limiting exposure to non-infected animals, but this study investigates an antibiotic regimen that could be used in special circumstances.

Functional convergence of a germline-encoded neutralizing antibody response in rhesus macaques immunized with HCV envelope glycoproteins

Human IGHV1-69-encoded broadly neutralizing antibodies (bnAbs) that target the hepatitis C virus (HCV) envelope glycoprotein (Env) E2 are important for protection against HCV infection. An IGHV1-69 ortholog gene, VH1.36, is preferentially used for bnAbs isolated from HCV Env-immunized rhesus macaques (RMs). Here, we studied the genetic, structural, and functional properties of VH1.36-encoded bnAbs generated by vaccination, in comparison to IGHV1-69-encoded bnAbs from HCV patients. Global B cell repertoire analysis confirmed the expansion of VH1.36-derived B cells in immunized animals. Most E2-specific, VH1.36-encoded antibodies cross-neutralized HCV. Crystal structures of two RM bnAbs with E2 revealed that the RM bnAbs engaged conserved E2 epitopes using similar molecular features as human bnAbs but with a different binding mode. Longitudinal analyses of the RM antibody repertoire responses during immunization indicated rapid lineage development of VH1.36-encoded bnAbs with limited somatic hypermutation. Our findings suggest functional convergence of a germline-encoded bnAb response to HCV Env with implications for vaccination in humans.

Antibody Responses to Immunization With HCV Envelope Glycoproteins as a Baseline for B-Cell-Based Vaccine Development

BACKGROUND & AIMS

We investigated antibody responses to hepatitis C virus (HCV) antigens E1 and E2 and the relevance of animal models for vaccine development. We compared antibody responses to vaccination with recombinant E1E2 complex in healthy volunteers, non-human primates (NHPs), and mice.

METHODS

We analyzed 519 serum samples from participants in a phase 1 vaccine trial (ClinicalTrials.gov identifier NCT00500747) and compared them with serum or plasma samples from C57BL/6J mice (n = 28) and rhesus macaques (n = 4) immunized with the same HCV E1E2 antigen. Blood samples were collected at different time points and analyzed for antibody binding, neutralizing activity, and epitope specificity. Monoclonal antibodies from the immunized NHPs were isolated from single plasmablasts and memory B cells, and their immunogenetic properties were characterized.

RESULTS

Antibody responses of the volunteers, NHPs, and mice to the non-neutralizing epitopes on the E1 N-terminus and E2 hypervariable region 1 did not differ significantly. Antibodies from volunteers and NHPs that neutralized heterologous strains of HCV primarily interacted with epitopes in the antigen region 3. However, the neutralizing antibodies were not produced in sufficient levels for broad neutralization of diverse HCV isolates. Broadly neutralizing antibodies similar to the human V_H1-69 class antibody specific for antigen region 3 were produced in the immunized NHPs.

CONCLUSIONS

In an analysis of vaccinated volunteers, NHPs, and mice, we found that recombinant E1E2 vaccine antigen induces high-antibody titers that are insufficient to neutralize diverse HCV isolates. Antibodies from volunteers and NHPs bind to the same neutralizing epitopes for virus neutralization. NHPs can therefore be used as a preclinical model to develop HCV vaccines. These findings also provide useful baseline values for development of vaccines designed to induce production of neutralizing antibodies.

Subclinical Infection of Macaques and Baboons with A Baboon Simarterivirus

Simarteriviruses (Arteriviridae: Simarterivirinae) are commonly found at high titers in the blood of African monkeys but do not cause overt disease in these hosts. In contrast, simarteriviruses cause severe disease in Asian macaques upon accidental or experimental transmission. Here, we sought to better understand the host-dependent drivers of simarterivirus pathogenesis by infecting olive baboons (n = 4) and rhesus monkeys (n = 4) with the simarterivirus Southwest baboon virus 1 (SWBV-1). Surprisingly, none of the animals in our study showed signs of disease following SWBV-1 inoculation. Three animals (two rhesus monkeys and one olive baboon) became infected and sustained high levels of SWBV-1 viremia for the duration of the study. The course of SWBV-1 infection was highly predictable: plasma viremia peaked between 1 × 10⁷ and 1 × 10⁸ vRNA copies/mL at 3–10 days post-inoculation, which was followed by a relative nadir and then establishment of a stable set-point between 1 × 10⁶ and 1 × 10⁷ vRNA copies/mL for the remainder of the study (56 days). We characterized cellular and antibody responses to SWBV-1 infection in these animals, demonstrating that macaques and baboons mount similar responses to SWBV-1 infection, yet these responses are ineffective at clearing SWBV-1 infection. SWBV-1 sequencing revealed the accumulation of non-synonymous mutations in a region of the genome that corresponds to an immunodominant epitope in the simarterivirus major envelope glycoprotein GP5, which likely contribute to viral persistence by enabling escape from host antibodies.

Characterization of γδT cells in naïve and HIV-infected chimpanzees and their responses to T-cell activators in vitro

BACKGROUND

γδT cells are effector cells that eliminate cancer and virus-infected cells. Chimpanzees are an endangered species that can naturally and experimentally be infected with SIV and HIV, respectively, but no information about the functionality of γδT cells during chronic lentiviral infection is currently available.

METHODS

Healthy and HIV-infected chimpanzee γδT cells were characterized by flow cytometry. γδT subsets were studied after stimulation with T-cell activators, and the release of cytokines was analyzed by Luminex assay.

RESULTS

γδT-cell subsets, Vδ1 and Vδ2Vγ9, showed different patterns in the expression of CD4, CD195, CD159a, and CD159c. Stimulation of γδT cells resulted in increased levels of CD4 and HLA-DR, which is more pronounced in Vδ1 T cells. Distinct cytokine patterns were found between healthy and HIV-infected chimpanzees.

CONCLUSIONS

Analyses of major chimpanzee γδT subsets show similarities to human γδT cells and suggest different functionality and roles in their immune response against HIV infection.

Hepatitis C virus clearance correlates with HLA-DR expression on proliferating CD8+ T cells in immune-primed chimpanzees

Vaccination of chimpanzees against hepatitis C virus (HCV) using T-cell-based vaccines targeting nonstructural proteins has not resulted in the same levels of control and clearance as those seen in animals reexposed after HCV clearance. We hypothesized that the outcome of infection depends on the different subtypes of activated T cells. We used multicolor flow cytometry to evaluate activation (CD38+/HLA-DR+) and proliferation (Ki67+/Bcl-2-low) profiles of CD4+ and CD8+ T cells in peripheral blood before and after challenge in chimpanzees vaccinated using DNA/adenovirus, mock-vaccinated, and chimpanzees that had spontaneously cleared infection (rechallenged). The frequencies of activated or proliferating CD8+ T cells peaked at 2 weeks postchallenge in the vaccinated and rechallenged animals, coinciding with reductions in viral titers. However, the magnitude of the responses did not correlate with outcome or sustained control of viral replication. In contrast, proliferation of the CD8+ T cells coexpressing HLA-DR either with or without CD38 expression was significantly higher at challenge in animals that rapidly cleared HCV and remained so throughout the follow-up period.

CONCLUSION

Our data suggest that the appearance of proliferating HLA-DR+/CD8+ T cells can be used as a predictor of a successfully primed memory immune response against HCV and as a marker of effective vaccination in clinical trials.

Siderophore-mediated iron trafficking in humans is regulated by iron

Siderophores are best known as small iron binding molecules that facilitate microbial iron transport. In our previous study we identified a siderophore-like molecule in mammalian cells and found that its biogenesis is evolutionarily conserved. A member of the short chain dehydrogenase family of reductases, 3-hydroxy butyrate dehydrogenase (BDH2) catalyzes a rate-limiting step in the biogenesis of the mammalian siderophore. We have shown that depletion of the mammalian siderophore by inhibiting expression of bdh2 results in abnormal accumulation of cellular iron and mitochondrial iron deficiency. These observations suggest that the mammalian siderophore is a critical regulator of cellular iron homeostasis and facilitates mitochondrial iron import. By utilizing bioinformatics, we identified an iron-responsive element (IRE; a stem-loop structure that regulates genes expression post-transcriptionally upon binding to iron regulatory proteins or IRPs) in the 3'-untranslated region of the human BDH2 (hBDH2) gene. In cultured cells as well as in patient samples we now demonstrate that the IRE confers iron-dependent regulation on hBDH2 and binds IRPs in RNA electrophoretic mobility shift assays. In addition, we show that the hBDH2 IRE associates with IRPs in cells and that abrogation of IRPs by RNAi eliminates the iron-dependent regulation of hBDH2 mRNA. The key physiologic implication is that iron-mediated post-transcriptional regulation of hBDH2 controls mitochondrial iron homeostasis in human cells. These observations provide a new and an unanticipated mechanism by which iron regulates its intracellular trafficking.

A novel, highly selective inhibitor of pestivirus replication that targets the viral RNA-dependent RNA polymerase

We report on the highly potent and selective antipestivirus activity of 5-[(4-bromophenyl)methyl]-2-phenyl-5H-imidazo[4,5-c]pyridine (BPIP). The 50% effective concentration (EC50) for inhibition of bovine viral diarrhea virus (BVDV)-induced cytopathic effect formation was 0.04 +/- 0.01 microM. Comparable reduction of viral RNA synthesis (EC50 = 0.12 +/- 0.02 microM) and production of infectious virus (EC50= 0.074 +/- 0.003 microM) were observed. The selectivity index (ratio of 50% cytostatic concentration/EC50) of BPIP was approximately 2,000. BPIP was inactive against the hepatitis C virus subgenomic replicon and yellow fever virus but demonstrated weak activity against GB virus. Drug-resistant mutants were at least 300-fold less susceptible to BPIP than wild-type virus; showed cross-resistance to N-propyl-N-[2-(2H-1,2,4-triazino[5,6-b]indol-3-ylthio)ethyl]-1-propanamine (VP32947), and carried the F224S mutation in the viral RNA-dependent RNA polymerase (RdRp). When the F224S mutation was introduced into an infectious clone, the drug-resistant phenotype was obtained. BPIP did not inhibit the in vitro activity of recombinant BVDV RdRp, but did inhibit the activity of replication complexes (RCs). Computational docking revealed that F224 is located at the top of the finger domain of the polymerase. Docking of BPIP in the crystal structure of the BVDV RdRp revealed aromatic ring stacking, some hydrophobic contacts, and a hydrogen bond. Since two structurally unrelated compounds, i.e., BPIP and VP32947, target the same region of the BVDV RdRp, this position may be expected to be critical in the functioning of the polymerase or assembly of the RC. The potential of BPIP for the treatment of pestivirus and hepacivirus infections is discussed.

Conserved transactivating and pro-apoptotic functions of hepadnaviral X protein in ortho- and avihepadnaviruses

Two established activities of the multifunctional human hepatitis B virus X-protein are its transactivating and pro-apoptotic potential. We analysed whether X-proteins from other orthohepadnaviruses and the newly discovered avihepadnaviral X-proteins have similar functions as HBx. Previously, we have shown that HBx suppresses oncogenic transformation of primary rat embryo fibroblasts (REF) by induction of apoptosis. Using this system, we found that the wildtype X-proteins of woodchuck, ground squirrel, arctic squirrel and woolly monkey hepatitis B virus exhibit similar levels of pro-apoptotic activity as HBx, whereas mutants with carboxyterminal deletions were severely impaired in this activity. A strong correlation between the pro-apoptotic and transactivating abilities of the mammalian X-proteins was found. The newly discovered avihepadnaviral X-like proteins showed similar and Raf-MAPK pathway-dependent transactivating abilities and induced apoptosis in the REF-assay. Our data indicate that the transactivating and pro-apoptotic activities reside in the carboxyterminal half of orthohepadnaviral X and are conserved in avihepadnaviral X-proteins.

An infectious molecular clone of a Japanese genotype 1b hepatitis C virus

We describe an infectious molecular clone of a Japanese genotype 1b strain of hepatitis C virus (HCV-N). The molecularly cloned sequence of HCV-N was compared with alignments of other HCV sequences, leading to the identification of 15 unique, nonconservative amino acid substitutions within the HCV-N open reading frame (ORF). These were repaired to the consensus genotype 1b residue, and the infectivity of RNA transcribed from the repaired clone was assessed by intrahepatic inoculation of a chimpanzee. Viral RNA was first detected in the serum of this chimpanzee 3 weeks following inoculation, and was intermittently present over the next 14 weeks. A strong and persistent anti-HCV serological response developed 13 weeks following inoculation, with seroconversion in the recombinant immunoblot assay (RIBA). A weaker, transient serological response, characterized by seroconversion in a third-generation enzyme-linked immunosorbent assay (ELISA) but not RIBA, occurred between weeks 1 and 5. This may have represented an anamnestic response to HCV antigens translated directly from the intrahepatically inoculated RNA, because the animal previously had undergone 2 unsuccessful attempts at rescue of HCV by intrahepatic RNA inoculation. There was neither biochemical nor histological evidence of liver disease. Although this is within the range of expected outcomes in an HCV-naive chimpanzee, prior immunologic priming may have modified the infection in this animal. The HCV-N clone is the first infectious molecular clone of HCV that is comprised entirely of genotype 1b sequence, and it contains an ORF sequence that is significantly divergent from that of a previously described genotype 1a/1b chimera.

Lack of susceptibility of baboons to infection with hepatitis B virus

Historically, hepatitis B virus (HBV) has been considered species specific and unable to infect baboons. Based on this premise, two patients with HBV endstage liver disease underwent baboon liver xenotransplantation. To study whether baboons are susceptible to HBV infection, four baboons (two receiving immunosuppressive therapy) were inoculated with HBV. Animals were followed for 6 months: clinical examinations and biochemical studies were normal, hepatitis B surface antigen and hepatitis B core antigen staining of biopsies was negative, and HBV serology remained negative. HBV polymerase chain reaction was transiently positive in one animal, which most likely reflects the initial inoculation. This pilot study corroborates historical evidence and beliefs that baboons are resistant to HBV.

Development of a clinical protocol for hepatic gene transfer: lessons learned in preclinical studies

Strategies for hepatic gene therapy have been proposed that involve isolation of primary hepatocytes and introduction of recombinant genes into these cells in culture, followed by autologous hepatocellular transplantation (HCT). Consideration of clinical applications requires data suggesting that HCT can be performed safely in human subjects in addition to data indicating that recombinant gene expression can reverse a disease process. This report describes preclinical studies that underlie a clinical trial of HCT in which hepatocytes would be labeled with a marker gene to facilitate assessment of engraftment in the recipient. Human hepatocytes were harvested from liver segments preserved in Belzar's solution and transduced with an amphotropic retroviral vector carrying a recombinant marker gene (neomycin phosphotransferase II). Human hepatocytes were recovered from monolayer culture, stained with the fluorescent dye 1,1'-dioctadecyl-3,3,3,3'-tetra-methylindo-carbocyanine perchlorate (DiI) and transplanted into severe combined immunodeficient mice by splenic injection. Engrafted hepatocytes were identified in the liver and spleen of severe combined immunodeficient mice but not immunocompetent controls. Two large animal models of HCT are described. In a dog model, neomycin phosphotransferase II-containing hepatocytes were identified in the liver 7 wk after transplantation. In a baboon model, autologous HCT with DiI-stained cells demonstrated that transplanted cells assume a normal morphology and constitute up to 5% of hepatocytes. These data demonstrate transduction and transplantation of human hepatocytes and the feasibility of HCT in large animals. On the basis of these studies, the proposed clinical trial for gene transfer and transplantation in human subjects has been approved by the National Institutes of Health and the Food and Drug Administration.(ABSTRACT TRUNCATED AT 250 WORDS)