Kristen Branum

Heterologous Prime-Boost HIV-1 Vaccination Regimens in Pre-Clinical and Clinical Trials

Currently, there are more than 30 million people infected with HIV-1 and thousands more are infected each day. Vaccination is the single most effective mechanism for prevention of viral disease, and after more than 25 years of research, one vaccine has shown somewhat encouraging results in an advanced clinical efficacy trial. A modified intent-to-treat analysis of trial results showed that infection was approximately 30% lower in the vaccine group compared to the placebo group. The vaccine was administered using a heterologous prime-boost regimen in which both target antigens and delivery vehicles were changed during the course of inoculations. Here we examine the complexity of heterologous prime-boost immunizations. We show that the use of different delivery vehicles in prime and boost inoculations can help to avert the inhibitory effects caused by vector-specific immune responses. We also show that the introduction of new antigens into boost inoculations can be advantageous, demonstrating that the effect of ‘original antigenic sin’ is not absolute. Pre-clinical and clinical studies are reviewed, including our own work with a three-vector vaccination regimen using recombinant DNA, virus (Sendai virus or vaccinia virus) and protein. Promising preliminary results suggest that the heterologous prime-boost strategy may possibly provide a foundation for the future prevention of HIV-1 infections in humans.

Prevention of experimental autoimmune encephalomyelitis in lewis rats by treatment with an anti-rat CD5 antibody (OX19)☆

Treatment of Lewis rats with a single dose of OX19 antibody, specific for rat CD5, uniformly prevented the development of experimental autoimmune encephalomyelitis (EAE). This protective effect had several notable characteristics: (1) it persisted for at least 10 days; (2) it could be achieved with either high doses of the antibody (> 200 micrograms) or lower doses (100-200 micrograms), which did not deplete T cell populations; and (3) the treated animals were able to mount comparable T cell responses to both myelin basic protein and myelin-unrelated antigens. In addition, antibody treatment consistently prevented the development of adoptively transferred EAE, suggesting that enhanced suppressor cell activity may have contributed to the protection. Antibodies such as OX19 appear capable of blocking the development of EAE, and perhaps other autoimmune diseases as well.

Safety and Immunogenicity of an Intranasal Sendai Virus-Based Human Parainfluenza Virus Type 1 Vaccine in 3- to 6-Year-Old Children

ABSTRACT Human parainfluenza virus type 1 (hPIV-1) is the most common cause of laryngotracheobronchitis (croup), resulting in tens of thousands of hospitalizations each year in the United States alone. No licensed vaccine is yet available. We have developed murine PIV-1 (Sendai virus [SeV]) as a live Jennerian vaccine for hPIV-1. Here, we describe vaccine testing in healthy 3- to 6-year-old hPIV-1-seropositive children in a dose escalation study. One dose of the vaccine (5 × 105, 5 × 106, or 5 × 107 50% egg infectious doses) was delivered by the intranasal route to each study participant. The vaccine was well tolerated by all the study participants. There was no sign of vaccine virus replication in the airway in any participant. Most children exhibited an increase in antibody binding and neutralizing responses toward hPIV-1 within 4 weeks from the time of vaccination. In several children, antibody responses remained above incoming levels for at least 6 months after vaccination. Data suggest that SeV may provide a benefit to 3- to 6-year-old children, even when vaccine recipients have preexisting cross-reactive antibodies due to previous exposures to hPIV-1. Results encourage the testing of SeV administration in young seronegative children to protect against the serious respiratory tract diseases caused by hPIV-1 infections.

Preclinical and Clinical Development of a Multi-Envelope, DNA-Virus-Protein (D-V-P) HIV-1 Vaccine

The human immune system has evolved to recognize antigenic diversity, a strength that has been harnessed by vaccine developers to combat numerous pathogens (e.g., pneumococcus, influenza virus, rotavirus). In each case, vaccine cocktails were formulated to include antigenic variants of the target. To combat HIV-1 diversity, we assembled a cocktail vaccine comprising dozens of envelopes, delivered as recombinant DNA, vaccinia virus, and protein for testing in a clinical trial. One vaccinee has now completed vaccinations with no serious adverse events. Preliminary analyses demonstrate early proof-of-principle that a multi-envelope vaccine can elicit neutralizing antibody responses toward heterologous HIV-1 in humans.

Viridans streptococcal isolates from patients with septic shock induce tumor necrosis factor-α production by murine macrophages

Viridans streptococci are an important cause of bacteremia and septic shock in neutropenic patients, especially patients receiving chemotherapeutic agents that induce severe mucositis. The mechanisms by which viridans streptococci cause septic shock are unclear. We hypothesized that septic shock due to viridans streptococci is attributable to host cytokine production. Three clinical isolates of viridans streptococci were evaluated for their ability to induce production of tumor necrosis factor-alpha (TNF-alpha) by RAW 264.7 murine macrophages. These three strains of viridans streptococci induced TNF-alpha in a dose-dependent fashion, and the kinetics of TNF-alpha induction were similar to those observed with a clinical isolate of Escherichia coli.

Treatment and secondary prophylaxis with ethanol lock therapy for central line-associated bloodstream infection in paediatric cancer: a randomised, double-blind, controlled trial

BACKGROUND Central line-associated bloodstream infections (CLABSIs) affect about 25% of children with cancer, and treatment failure is common. Adjunctive ethanol lock therapy might prevent treatment failure but high-quality evidence is scarce. We evaluated ethanol lock therapy as treatment and secondary prophylaxis for CLABSI in children with cancer or haematological disorders. METHODS This randomised, double-blind, placebo-controlled superiority trial, with two interim futility and efficacy analyses (done when the first 46 and 92 evaluable participants completed study requirements), was done at two paediatric hospitals in the USA and Australia. Patients aged 6 months to 24 years, inclusive, with cancer or a haematological disorder and new CLABSI were eligible. Participants were randomly assigned (1:1) to receive either ethanol lock therapy (70% ethanol) or placebo (heparinised saline) for 2-4 h per lumen daily for 5 days (treatment phase), then for up to 3 non-consecutive days per week for 24 weeks (prophylaxis phase). The primary composite outcome was treatment failure, consisting of attributable catheter removal or death, new or persistent (>72 h) infection, or additional lock therapy during the treatment phase, and recurrent CLABSI during the prophylaxis phase. This trial is registered with ClinicalTrials.gov, number NCT01472965. FINDINGS 94 evaluable participants were enrolled between Dec 14, 2011, and Sept 12, 2016, of whom 48 received ethanol lock therapy and 46 received placebo. The study met futility criteria at the second interim analysis. Treatment failure was similar with ethanol lock therapy (21 [44%] of 48) and placebo (20 [43%] of 46; relative risk [RR] 1·0, 95% CI 0·6-1·6; p=0·98). Some adverse events, including infusion reactions and catheter occlusion, were more frequent in the ethanol lock therapy group than in the placebo group. Catheter occlusion requiring thrombolytic therapy was more common with ethanol lock therapy (28 [58%] of 48) than with placebo (15 [33%] of 46; RR 1·8, 95% CI 1·1-2·9; p=0·012). Discontinuation of lock therapy because of adverse effects or patient request occurred in a similar proportion of participants in the ethanol lock therapy (nine [19%] of 48) and placebo groups (ten [22%] of 46; p=0·72). INTERPRETATION Ethanol lock therapy did not prevent CLABSI treatment failure and it increased catheter occlusion. Routine ethanol lock therapy for treatment or secondary prophylaxis is not recommended in this population. FUNDING American Lebanese Syrian Associated Charities to St Jude Childrens Research Hospital and an Australian Government Research Training Scholarship.

A Multi-Vector, Multi-Envelope HIV-1 Vaccine.

The St. Jude Childrens Research Hospital (St. Jude) HIV-1 vaccine program is based on the observation that multiple antigenically distinct HIV-1 envelope protein structures are capable of mediating HIV-1 infection. A cocktail vaccine comprising representatives of these diverse structures (immunotypes) is therefore considered necessary to elicit lymphocyte populations that prevent HIV-1 infection. This strategy is reminiscent of that used to design a currently licensed and successful 23-valent pneumococcus vaccine. Three recombinant vector systems are used for the delivery of envelope cocktails (DNA, vaccinia virus, and purified protein), and each of these has been tested individually in phase I safety trials. A fourth FDA-approved clinical trial, in which diverse envelopes and vectors are combined in a prime-boost vaccination regimen, has recently begun. This trial will continue to test the hypothesis that a multi-vector, multi-envelope vaccine can elicit diverse B- and T-cell populations that can prevent HIV-1 infections in humans.

Murine Monoclonal Antibodies for Antigenic Discrimination of HIV-1 Envelope Proteins

In the influenza virus field, antibody reagents from research animals have been instrumental in the characterization of antigenically distinct hemagglutinin and neuraminidase membrane molecules. These small animal reagents continue to support the selection of components for inclusion in human influenza virus vaccines. Other cocktail vaccines against variant pathogens (e.g., polio virus, pneumococcus) are similarly designed to represent variant antigens, as defined by antibody reactivity patterns. However, a vaccine cocktail comprising diverse viral membrane antigens defined in this way has not yet been advanced to a clinical efficacy study in the HIV-1 field. In this study, we describe the preparation of mouse antibodies specific for HIV-1 gp140 or gp120 envelope molecules. Our experiments generated renewable reagents able to discriminate HIV-1 envelopes from one another. Monoclonals yielded more precise discriminatory capacity against their respective immunogens than did a small panel of polyclonal human sera derived from recently HIV-1-infected patients. Perhaps these and other antibody reagents will ultimately support high-throughput cartography studies with which antigenically-distinct envelope immunogens may be formulated into a successful HIV-1 envelope cocktail vaccine.

Ethanol Lock Treatment and Secondary Prophylaxis for Central Line-Associated Bloodstream Infection in Pediatric Hematology and Oncology: A Randomized, Double-Blind, Placebo-Controlled, Intervention Trial

Abstract Background Central line-associated bloodstream infection (CLABSI) commonly affects children with cancer and hematological disorders, with significant attributable costs and morbidity. Treatment failure, comprising persistent infection, infection relapse or new infection, occurs in ~50% of cases. Adjunctive ethanol lock therapy (ELT) has been proposed to prevent failure, but has never been tested in a prospective controlled study. Methods A prospective, dual-center, double-blind, block-randomized, placebo-controlled trial of ELT (70% ethanol in water) for CLABSI, given as treatment (2 hours per lumen per day) for 5 days, followed by secondary prophylaxis (2 hours per lumen up to 3 days per week) for 24 weeks, in children with oncologic or hematologic disorders (NCT01472965). Risk of treatment failure was compared between intervention and control groups according to proportional and cumulative incidence models, using intention-to-treat and per-protocol analyses. The study was discontinued at a pre-specified futility analysis. Results Of 94 evaluable participants, 48 were randomized to ELT and 46 to placebo; groups were similar at baseline for all measured variables. Forty-one (43.6%) participants had treatment failure (11 early failure, 9 relapse, and 21 reinfection). There was no difference between patients receiving ELT or placebo for risk of treatment failure (43.8% vs. 43.5%; P = 0.9) or for cumulative incidence of treatment failure in intention to treat (Figure 1) and per-protocol analyses (Figure 2). Catheter occlusion was significantly more common in participants receiving ethanol (58.3% vs. 32.6%, P = 0.01) but other adverse events, including LFT elevations (14.6% vs. 26.1%) and infusion reactions (18.8% vs. 8.7%), were not significantly different between groups. Conclusion Although observational studies suggested ELT might be effective for treatment of CLABSI in pediatric oncology, we found no benefit in treatment outcome and an increase in adverse effects. These results may not apply to patients receiving dialysis or with fungal CLABSI as these were not well-represented. Routine use of ELT for CLABSI in children with oncologic or hematologic disorders is not recommended. Disclosures All authors: No reported disclosures.