Sandhya Vasan

In Vivo Electroporation Enhances the Immunogenicity of an HIV-1 DNA Vaccine Candidate in Healthy Volunteers

Background DNA-based vaccines have been safe but weakly immunogenic in humans to date. Methods and Findings We sought to determine the safety, tolerability, and immunogenicity of ADVAX, a multigenic HIV-1 DNA vaccine candidate, injected intramuscularly by in vivo electroporation (EP) in a Phase-1, double-blind, randomized placebo-controlled trial in healthy volunteers. Eight volunteers each received 0.2 mg, 1 mg, or 4 mg ADVAX or saline placebo via EP, or 4 mg ADVAX via standard intramuscular injection at weeks 0 and 8. A third vaccination was administered to eleven volunteers at week 36. EP was safe, well-tolerated and considered acceptable for a prophylactic vaccine. EP delivery of ADVAX increased the magnitude of HIV-1-specific cell mediated immunity by up to 70-fold over IM injection, as measured by gamma interferon ELISpot. The number of antigens to which the response was detected improved with EP and increasing dosage. Intracellular cytokine staining analysis of ELISpot responders revealed both CD4+ and CD8+ T cell responses, with co-secretion of multiple cytokines. Conclusions This is the first demonstration in healthy volunteers that EP is safe, tolerable, and effective in improving the magnitude, breadth and durability of cellular immune responses to a DNA vaccine candidate. Trial Registration ClinicalTrials.gov NCT00545987

Design of a potent CD1d-binding NKT cell ligand as a vaccine adjuvant

The glycolipid α-galactosylceramide (α-GalCer) has been shown to bind CD1d molecules to activate invariant natural killer T (iNKT) cells, and subsequently induce activation of various immune-competent cells, including dendritic cells, thereby providing a significant adjuvant effect for various vaccines. However, in phase I clinical trials, α-GalCer was shown to display only marginal biological activity. In our search for a glycolipid that can exert more potent stimulatory activity against iNKT cells and dendritic cells and produce an adjuvant effect superior to α-GalCer, we performed step-wise screening assays on a focused library of 25 α-GalCer analogues. Assays included quantification of the magnitude of stimulatory activity against human iNKT cells in vitro, binding affinity to human and murine CD1d molecules, and binding affinity to the invariant t cell receptor of human iNKT cells. Through this rigorous and iterative screening process, we have identified a lead candidate glycolipid, 7DW8-5, that exhibits a superior adjuvant effect than α-GalCer on HIV and malaria vaccines in mice.

Neutralization Profiles of Newly Transmitted Human Immunodeficiency Virus Type 1 by Monoclonal Antibodies 2G12, 2F5, and 4E10

ABSTRACT As the AIDS epidemic continues unabated, the development of a human immunodeficiency virus (HIV) vaccine is critical. Ideally, an effective vaccine should elicit cell-mediated and neutralizing humoral immune responses. We have determined the in vitro susceptibility profile of sexually transmitted viruses from 91 patients with acute and early HIV-1 infection to three monoclonal antibodies, 2G12, 2F5, and 4E10. Using a recombinant virus assay to measure neutralization, we found all transmitted viruses were neutralized by 4E10, 80% were neutralized by 2F5, and only 37% were neutralized by 2G12. We propose that the induction of 4E10-like antibodies should be a priority in designing immunogens to prevent HIV-1 infection.

Clinical development of a novel CD1d-binding NKT cell ligand as a vaccine adjuvant

Natural killer T (NKT) cells are known to play a role against certain microbial infections, including malaria and HIV, two major global infectious diseases. Strategies that can harness and amplify the immunotherapeutic potential of NKT cells can serve as powerful tools in the fight against such diseases. 7DW8-5, a novel glycolipid, may be one such tool. The interaction of 7DW8-5 with CD1d molecules induces activation of NKT cells, thereby activating various immune-competent cells including dendritic cells (DCs) to provide a significant adjuvant effect for several vaccines. This review discusses the discovery and characterization of 7DW8-5 and the practical considerations of its preclinical and clinical development as a potential glycolipid adjuvant for candidate malaria and HIV vaccines.

Immunogenicity, safety, biodistribution and persistence of ADVAX, a prophylactic DNA vaccine for HIV-1, delivered by in vivo electroporation

ADVAX is a DNA-based candidate HIV vaccine that was safe but weakly immunogenic when delivered intramuscularly (IM) in humans. Studies were performed in animal models to determine whether an alternative delivery method, in vivo electroporation (EP), could improve the immunogenicity of ADVAX while maintaining an acceptable safety profile. Immunization of mice with ADVAX with or without EP at weeks 0, 3, and 6, revealed significantly higher gamma interferon ELISpot responses to all antigens in the EP groups. Antigen-specific CD4+ and CD8+ T cell responses, as quantified by intracellular cytokine staining, both improved significantly with EP. Evaluation of repeat-dose toxicity of ADVAX-EP in rabbits did not reveal any safety concerns. Biodistribution studies of ADVAX delivered IM and with EP in rats indicated that the vaccine was localized predominantly to the administration site in both groups. PCR-based quantitation of residual plasmid at Day 60 indicated that the potential for integration events into the host genome was low for both IM and EP delivery. Taken together, these data supported the clinical development of ADVAX delivered with EP in human volunteers.

Prospective Surveillance for Cardiac Adverse Events in Healthy Adults Receiving Modified Vaccinia Ankara Vaccines: A Systematic Review

Background Vaccinia-associated myo/pericarditis was observed during the US smallpox vaccination (DryVax) campaign initiated in 2002. A highly-attenuated vaccinia strain, modified vaccinia Ankara (MVA) has been evaluated in clinical trials as a safer alternative to DryVax and as a vector for recombinant vaccines. Due to the lack of prospectively collected cardiac safety data, the US Food and Drug Administration required cardiac screening and surveillance in all clinical trials of MVA since 2004. Here, we report cardiac safety surveillance from 6 phase I trials of MVA vaccines. Methods Four clinical research organizations contributed cardiac safety data using common surveillance methods in trials administering MVA or recombinant MVA vaccines to healthy participants. ‘Routine cardiac investigations’ (ECGs and cardiac enzymes obtained 2 weeks after injections of MVA or MVA-HIV recombinants, or placebo-controls), and ‘Symptom-driven cardiac investigations’ are reported. The outcome measure is the number of participants who met the CDC-case definition for vaccinia-related myo/pericarditis or who experienced cardiac adverse events from an MVA vaccine. Results Four hundred twenty-five study participants had post-vaccination safety data analyzed, 382 received at least one MVA-containing vaccine and 43 received placebo; 717 routine ECGs and 930 cardiac troponin assays were performed. Forty-five MVA recipients (12%) had additional cardiac testing performed; 22 for cardiac symptoms, 19 for ECG/laboratory changes, and 4 for cardiac symptoms with an ECG/laboratory change. No participant had evidence of symptomatic or asymptomatic myo/pericarditis meeting the CDC-case definition and judged to be related to an MVA vaccine. Conclusions Prospective surveillance of MVA recipients for myo/pericarditis did not detect cardiac adverse reactions in 382 study participants. Trial Registration ClinicalTrials.gov NCT00082446  NCT003766090  NCT00252148  NCT00083603  NCT00301184  NCT00428337

A DNA-Based Candidate HIV Vaccine Delivered via In Vivo Electroporation Induces CD4 Responses toward the α4β7-Binding V2 Loop of HIV gp120 in Healthy Volunteers

ABSTRACT Administration of a clade C/B′ candidate HIV-1 DNA vaccine, ADVAX, by in vivo electroporation (EP) was safe and more immunogenic than intramuscular administration without EP. The breadth and specificity of T-cell responses to full-length Env were mapped. Responses to multiple Env regions were induced, with most focusing on V3/C4 and V2 regions, including the α4β7 integrin-binding domain. The breadth of responses induced by this DNA vaccine regimen was comparable to that of viral-vectored vaccine regimens.

A double-edged sword: the role of NKT cells in malaria and HIV infection and immunity.

NKT cells are known to play a role against certain microbial infections, including malaria and HIV, two major global infectious diseases. NKT cells exhibit either protective or pathogenic role against malaria. They are depleted by HIV infection and have a direct pathogenic role against many opportunistic infections common in end-stage AIDS. This review discusses the various features of the interaction between NKT cells and malaria parasites and HIV, and the potential to harness this interaction for therapeutic and vaccine strategies.

A Glycolipid Adjuvant, 7DW8-5, Enhances CD8+ T Cell Responses Induced by an Adenovirus-Vectored Malaria Vaccine in Non-Human Primates

A key strategy to a successful vaccine against malaria is to identify and develop new adjuvants that can enhance T-cell responses and improve protective immunity. Upon co-administration with a rodent malaria vaccine in mice, 7DW8-5, a recently identified novel analog of α-galactosylceramide (α-GalCer), enhances the level of malaria-specific protective immune responses more strongly than the parent compound. In this study, we sought to determine whether 7DW8-5 could provide a similar potent adjuvant effect on a candidate human malaria vaccine in the more relevant non-human primate (NHP) model, prior to committing to clinical development. The candidate human malaria vaccine, AdPfCA (NMRC-M3V-Ad-PfCA), consists of two non-replicating recombinant adenoviral (Ad) vectors, one expressing the circumsporozoite protein (CSP) and another expressing the apical membrane antigen-1 (AMA1) of Plasmodium falciparum. In several phase 1 clinical trials, AdPfCA was well tolerated and demonstrated immunogenicity for both humoral and cell-mediated responses. In the study described herein, 25 rhesus macaques received prime and boost intramuscular (IM) immunizations of AdPfCA alone or with an ascending dose of 7DW8-5. Our results indicate that 7DW8-5 is safe and well-tolerated and provides a significant enhancement (up to 9-fold) in malaria-specific CD8+ T-cell responses after both priming and boosting phases, supporting further clinical development.

Prevalence of specific neutralizing antibodies against Sendai virus in populations from different geographic areas: implications for AIDS vaccine development using Sendai virus vectors.

A Sendai virus (SeV) vector is being developed for delivery of an HIV immunogen. SeV is not known to cause disease in humans. Because it is genetically and antigenically related to human parainfluenza virus type 1 (hPIV-1), it is important to determine whether pre-existing hPIV-1 antibodies will affect immune responses elicited by a SeV vector-based vaccine. To quantify SeV neutralizing antibodies (NAb) in human serum, a sensitive virus neutralization assay was developed using a SeV vector encoding green fluorescent protein. Samples from 255 HIV-uninfected subjects from Africa, Europe, United States, and Japan, as well as from 12 confirmed hPIV-1-infected patients, were analyzed. SeV NAb titers did not vary significantly after serum was treated with receptor-destroying enzyme, indicating that non-specific hemagglutination inhibitors did not affect the assay sensitivity. A significant correlation was observed between hPIV-1 ELISA and SeV NAb titers. SeV NAb were detected in 92.5% subjects with a median titer of 60.6 and values ranging from 5.9- 11,324. The majority had titers