Ann M. Ginsberg

The current state of tuberculosis vaccines

Tuberculosis continues to persist despite widespread use of BCG, the only licensed vaccine to prevent TB. BCGs limited efficacy coupled with the emergence of drug-resistant strains of Mycobacterium tuberculosis emphasizes the need for a more effective vaccine for combatting this disease. However, the development of a TB vaccine is hindered by the lack of immune correlates, suboptimal animal models, and limited funding. An adolescent/adult vaccine would have the greatest public health impact, but effective delivery of such a vaccine will require a better understanding of global TB epidemiology, improved infrastructure, and engagement of public health leaders and global manufacturers. Here we discuss the current state of tuberculosis vaccine research and development, including our understanding of the underlying immunology as well as the challenges and opportunities that may hinder or facilitate the development of a new and efficacious vaccine.

Optimization and Interpretation of Serial QuantiFERON Testing to Measure Acquisition of Mycobacterium tuberculosis Infection

Rationale: Conversion from a negative to positive QuantiFERON‐TB test is indicative of Mycobacterium tuberculosis (Mtb) infection, which predisposes individuals to tuberculosis disease. Interpretation of serial tests is confounded by immunological and technical variability. Objectives: To improve the consistency of serial QuantiFERON‐TB testing algorithms and provide a data‐driven definition of conversion. Methods: Sources of QuantiFERON‐TB variability were assessed, and optimal procedures were identified. Distributions of IFN‐&ggr; response levels were analyzed in healthy adolescents, Mtb‐unexposed control subjects, and patients with pulmonary tuberculosis. Measurements and Main Results: Individuals with no known Mtb exposure had IFN‐&ggr; values less than 0.2 IU/ml. Among individuals with IFN‐&ggr; values less than 0.2 IU/ml, 0.2‐0.34 IU/ml, 0.35‐0.7 IU/ml, and greater than 0.7 IU/ml, tuberculin skin test positivity results were 15%, 53%, 66%, and 91% (P < 0.005), respectively. Together, these findings suggest that values less than 0.2 IU/ml were true negatives. In short‐term serial testing, “uncertain” conversions, with at least one value within the uncertainty zone (0.2‐0.7 IU/ml), were partly explained by technical assay variability. Individuals who had a change in QuantiFERON‐TB IFN‐&ggr; values from less than 0.2 to greater than 0.7 IU/ml had 10‐fold higher tuberculosis incidence rates than those who maintained values less than 0.2 IU/ml over 2 years (P = 0.0003). By contrast, “uncertain” converters were not at higher risk than nonconverters (P = 0.229). Eighty‐seven percent of patients with active tuberculosis had IFN‐&ggr; values greater than 0.7 IU/ml, suggesting that these values are consistent with established Mtb infection. Conclusions: Implementation of optimized procedures and a more rigorous QuantiFERON‐TB conversion definition (an increase from IFN‐&ggr; <0.2 to >0.7 IU/ml) would allow more definitive detection of recent Mtb infection and potentially improve identification of those more likely to develop disease.

Innovative clinical trial designs to rationalize TB vaccine development

A recent trial of a leading tuberculosis (TB) vaccine candidate in 3000 South African infants failed to show protection over that from BCG alone, and highlights the difficulties in clinical development of TB vaccines. Progression of vaccine candidates to efficacy trials against TB disease rests on demonstration of safety and immunogenicity in target populations and protection against challenge in preclinical models, but immunologic correlates of protection are unknown, and animal models may not be predictive of results in humans. Even in populations most heavily affected by TB the sample sizes required for Phase 2b efficacy trials using TB disease as an endpoint are in the thousands. Novel clinical trial models have been developed to evaluate candidate TB vaccines in selected populations using biologically relevant outcomes and innovative statistical approaches. Such proof of concept studies can be used to more rationally select vaccine candidates for advancement to large scale trials against TB disease.

Designing an adaptive phase II/III trial to evaluate efficacy, safety and immune correlates of new TB vaccines in young adults and adolescents.

This article summarises the consensus arrived at a meeting of South African and international stakeholders on specific late phase clinical trial design issues integrating the investigation of immune correlates as an integral part of a phase III protocol for a preventative TB vaccine in an adolescent/adult population. The challenge ahead is to optimize the planning for phase 3 TB vaccine preventative trials, under resource constraints, given that there are no known correlates of protection to shorten and increase the efficiencies of efficacy trials. An adaptive, multi-arm, group sequentially designed trial protocol is proposed incorporating design features that address uncertainties arising from both advances in the field and dynamic study populations and disease states. Such a design allows modifications that protect research subjects, save time, and maximize the impact of scarce financial resources. Further, the protocol underwent joint review by regulators from several African nations at a meeting of the African Vaccine Regulatory Forum (AVAREF), a regional regulatory harmonization initiative, and recommendations are included.

TB vaccines in clinical development

The 4th Global Forum on TB Vaccines, convened in Shanghai, China, from 21 - 24 April 2015, brought together a wide and diverse community involved in tuberculosis vaccine research and development to discuss the current status of, and future directions for this critical effort. This paper summarizes the sessions on TB Vaccines in Clinical Development, and Clinical Research: Data and Findings. Summaries of all sessions from the 4th Global Forum are compiled in a special supplement of Tuberculosis. [August 2016, Vol 99, Supp S1, S1-S30].

Prevention of M. tuberculosis Infection with H4:IC31 Vaccine or BCG Revaccination

Background Recent Mycobacterium tuberculosis (M.tb) infection predisposes to tuberculosis disease, the leading global infectious disease killer. We tested safety andefficacy of H4:IC31® vaccination or Bacille Calmette-Guerin (BCG) revaccination for prevention of M.tb infection. Methods QuantiFERON-TB Gold In-tube (QFT) negative, HIV-uninfected, remotely BCG-vaccinated adolescents were randomized 1:1:1 to placebo, H4:IC31® or BCG revaccination (NCT02075203). Primary outcomes were safety and acquisition of M.tb infection, defined by initial QFT conversion tested 6-monthly over two years. Secondary outcomes were immunogenicity and sustained M.tb infection, defined by sustained QFT conversion without reversion three and six months post-conversion. Statistical significance for efficacy proof-of-concept was set at 1-sided p<0.10. Results 990 participants were enrolled. Both vaccines had acceptable safety profiles and were immunogenic. QFT conversion occurred in 134 and sustained conversion in 82 participants. Neither H4:IC31® nor BCG prevented initial QFT conversion, with efficacy point estimates of 9.4% (95% confidence interval: -36.2, 39.7; one-sided p=0.32) and 20.1% (-21.0, 47.2; one-sided p=0.14), respectively. However, BCG did prevent sustained QFT conversion with an efficacy of 45.4% (6.4, 68.1; one-sided p=0.013); H4:IC31® efficacy was 30.5% (-15.8, 58.3; one-sided p=0.08). QFT reversion rate from positive to negative was 46% in BCG, 40% in H4:IC31 and 25% in placebo recipients. Conclusions This first proof-of-concept, prevention of M.tb infection trial showed that sustained infection can be prevented by vaccination in a high-transmission setting and confirmed feasibility of this strategy to inform clinical development of new vaccine candidates. Evaluation of BCG revaccination to prevent tuberculosis disease in M.tb- uninfected populations is warranted.BACKGROUND Recent Mycobacterium tuberculosis infection confers a predisposition to the development of tuberculosis disease, the leading killer among global infectious diseases. H4:IC31, a candidate subunit vaccine, has shown protection against tuberculosis disease in preclinical models, and observational studies have indicated that primary bacille Calmette–Guérin (BCG) vaccination may offer partial protection against infection. METHODS In this phase 2 trial, we randomly assigned 990 adolescents in a high‐risk setting who had undergone neonatal BCG vaccination to receive the H4:IC31 vaccine, BCG revaccination, or placebo. All the participants had negative results on testing for M. tuberculosis infection on the QuantiFERON‐TB Gold In‐tube assay (QFT) and for the human immunodeficiency virus. The primary outcomes were safety and acquisition of M. tuberculosis infection, as defined by initial conversion on QFT that was performed every 6 months during a 2‐year period. Secondary outcomes were immunogenicity and sustained QFT conversion to a positive test without reversion to negative status at 3 months and 6 months after conversion. Estimates of vaccine efficacy are based on hazard ratios from Cox regression models and compare each vaccine with placebo. RESULTS Both the BCG and H4:IC31 vaccines were immunogenic. QFT conversion occurred in 44 of 308 participants (14.3%) in the H4:IC31 group and in 41 of 312 participants (13.1%) in the BCG group, as compared with 49 of 310 participants (15.8%) in the placebo group; the rate of sustained conversion was 8.1% in the H4:IC31 group and 6.7% in the BCG group, as compared with 11.6% in the placebo group. Neither the H4:IC31 vaccine nor the BCG vaccine prevented initial QFT conversion, with efficacy point estimates of 9.4% (P=0.63) and 20.1% (P=0.29), respectively. However, the BCG vaccine reduced the rate of sustained QFT conversion, with an efficacy of 45.4% (P=0.03); the efficacy of the H4:IC31 vaccine was 30.5% (P=0.16). There were no clinically significant between‐group differences in the rates of serious adverse events, although mild‐to‐moderate injection‐site reactions were more common with BCG revaccination. CONCLUSIONS In this trial, the rate of sustained QFT conversion, which may reflect sustained M. tuberculosis infection, was reduced by vaccination in a high‐transmission setting. This finding may inform clinical development of new vaccine candidates. (Funded by Aeras and others; C‐040‐404 ClinicalTrials.gov number, NCT02075203.)

Safety and immunogenicity of the novel tuberculosis vaccine ID93 + GLA-SE in BCG-vaccinated healthy adults in South Africa: a randomised, double-blind, placebo-controlled phase 1 trial

BACKGROUND A vaccine that prevents pulmonary tuberculosis in adults is needed to halt transmission in endemic regions. This trial aimed to assess the safety and immunogenicity of three administrations at varying doses of antigen and adjuvant of an investigational vaccine (ID93 + GLA-SE) compared with placebo in previously BCG-vaccinated healthy adults in a tuberculosis endemic country. METHODS In this randomised, double-blind, placebo-controlled phase 1 trial, we enrolled HIV-negative, previously BCG-vaccinated adults (aged 18-50 years), with no evidence of previous or current tuberculosis disease, from among community volunteers in the Worcester region of Western Cape, South Africa. Participants were randomly assigned to receive varying doses of ID93 + GLA-SE or saline placebo at day 0, day 28, and day 112. Enrolment into each cohort was sequential. Cohort 1 participants were Mycobacterium tuberculosis uninfected (as defined by negative QuantiFERON [QFT] status), and received 10 μg ID93 plus 2 μg GLA-SE, or placebo; in cohorts 2-4, QFT-negative or positive participants received escalating doses of vaccine or placebo. Cohort 2 received 2 μg ID93 plus 2 μg GLA-SE; cohort 3 received 10 μg ID93 plus 2 μg GLA-SE; and cohort 4 received 10 μg ID93 plus 5 μg GLA-SE. Dose cohort allocation was sequential; randomisation within a cohort was according to a randomly-generated sequence (3 to 1 in cohort 1, 5 to 1 in cohorts 2-4). The primary endpoint was safety of ID93 + GLA-SE as defined by solicited and unsolicited adverse events up to 28 days after each study injection and serious adverse events for the duration of the study. Specific immune responses were measured by intracellular cytokine staining, flow cytometry, and ELISA. All analyses were done according to intention to treat, with additional per-protocol analyses for immunogenicity outcomes. This trial is registered with ClinicalTrials.gov, number NCT01927159. FINDINGS Between Aug 30, 2013, and Sept 4, 2014, 227 individuals consented to participate; 213 were screened (three participants were not included as study number was already met and 11 withdrew consent before screening occurred, mostly due to relocation or demands of employment). 66 healthy, HIV-negative adults were randomly allocated to receive the vaccine (n=54) or placebo (n=12). All study participants received day 0 and day 28 study injections; five participants did not receive an injection on day 112. ID93 + GLA-SE was well tolerated; no severe or serious vaccine-related adverse events were recorded. Vaccine dose did not affect frequency or severity of adverse events, but mild injection site adverse events and flu-like symptoms were common in M tuberculosis-infected participants compared with uninfected participants. Vaccination induced durable antigen-specific IgG and Th1 cellular responses, which peaked after two administrations. Vaccine dose did not affect magnitude, kinetics, or profile of antibody and cellular responses. Earlier boosting and greater T-cell differentiation and effector-like profiles were seen in M tuberculosis-infected than in uninfected vaccinees. INTERPRETATION Escalating doses of ID93 + GLA-SE induced similar antigen-specific CD4-positive T cell and humoral responses, with an acceptable safety profile in BCG-immunised, M tuberculosis-infected individuals. The T-cell differentiation profiles in M tuberculosis-infected vaccinees suggest priming through natural infection. While cohort sample sizes in this phase 1 trial were small and results should be interpreted in context, these data support efficacy testing of two administrations of the lowest (2 μg) ID93 vaccine dose in tuberculosis endemic populations. FUNDING Aeras and the Paul G Allen Family Foundation.

Safety and immunogenicity of an inactivated whole cell tuberculosis vaccine booster in adults primed with BCG: A randomized, controlled trial of DAR-901.

Background Development of a tuberculosis vaccine to boost BCG is a major international health priority. SRL172, an inactivated whole cell booster derived from a non-tuberculous mycobacterium, is the only new vaccine against tuberculosis to have demonstrated efficacy in a Phase 3 trial. In the present study we sought to determine if a three-dose series of DAR-901 manufactured from the SRL172 master cell bank by a new, scalable method was safe and immunogenic. Methods We performed a single site, randomized, double-blind, controlled, Phase 1 dose escalation trial of DAR-901 at Dartmouth-Hitchcock Medical Center in the United States. Healthy adult subjects age 18–65 with prior BCG immunization and a negative interferon-gamma release assay (IGRA) were enrolled in cohorts of 16 subjects and randomized to three injections of DAR-901 (n = 10 per cohort), or saline placebo (n = 3 per cohort), or two injections of saline followed by an injection of BCG (n = 3 per cohort; 1–8 x 106 CFU). Three successive cohorts were enrolled representing DAR-901 at 0.1, 0.3, and 1 mg per dose. Randomization was performed centrally and treatments were masked from staff and volunteers. Subsequent open label cohorts of HIV-negative/IGRA-positive subjects (n = 5) and HIV-positive subjects (n = 6) received three doses of 1 mg DAR-901. All subjects received three immunizations at 0, 2 and 4 months administered as 0.1 mL injections over the deltoid muscle alternating between right and left arms. The primary outcomes were safety and immunogenicity. Subjects were followed for 6 months after dose 3 for safety and had phlebotomy performed for safety studies and immune assays before and after each injection. Immune assays using peripheral blood mononuclear cells included cell-mediated IFN-γ responses to DAR-901 lysate and to Mycobacterium tuberculosis (MTB) lysate; serum antibody to M. tuberculosis lipoarabinomannan was assayed by ELISA. Results DAR-901 had an acceptable safety profile and was well-tolerated at all dose levels in all treated subjects. No serious adverse events were reported. Median (range) 7-day erythema and induration at the injection site for 1 mg DAR-901 were 10 (4–20) mm and 10 (4–16) mm, respectively, and for BCG, 30 (10–107) mm and 38 (15–55) mm, respectively. Three mild AEs, all headaches, were considered possibly related to DAR-901. No laboratory or vital signs abnormalities were related to immunization. Compared to pre-vaccination responses, three 1 mg doses of DAR-901 induced statistically significant increases in IFN-γ response to DAR-901 lysate and MTB lysate, and in antibody responses to M. tuberculosis lipoarabinomannan. Ten subjects who received 1 mg DAR-901 remained IFN-γ release assay (IGRA) negative after three doses of vaccine. Conclusions A three-injection series of DAR-901 was well-tolerated, had an acceptable safety profile, and induced cellular and humoral immune responses to mycobacterial antigens. DAR-901 is advancing to efficacy trials. Trial registration ClinicalTrials.gov NCT02063555

Phase 2b Controlled Trial of M72/AS01E Vaccine to Prevent Tuberculosis

Background: A tuberculosis vaccine to interrupt transmission is urgently needed. We assessed the safety and efficacy of the candidate tuberculosis vaccine, M72/AS01E, against progression to bacteriologically-confirmed active pulmonary tuberculosis disease in adults with latent Mycobacterium tuberculosis (Mtb) infection. Methods: In a randomized, double-blind, placebo-controlled, phase 2b trial conducted in Kenya, South Africa and Zambia, human immunodeficiency virus (HIV)-negative adults aged 18-50 years with latent Mtb infection (positive by interferon-gamma release assay) were randomized (1:1) to receive two doses of either M72/AS01E or placebo intramuscularly on days 0 and 30. Clinical suspicion of tuberculosis was confirmed from sputum using a polymerase chain reaction test and/or mycobacterial culture. Results: This paper reports the primary analysis, conducted after a mean follow-up of 2.3 years. 1786 participants received M72/AS01E and 1787 received placebo. In the vaccine group, 10 cases met the primary case definition (bacteriologically-confirmed active pulmonary tuberculosis confirmed prior to treatment, not associated with HIV infection) versus 22 cases in the placebo group (0.3 vs. 0.6 cases per 100 person-years, respectively): vaccine efficacy 54.0% (90% confidence interval 13.9-75.4; 95%CI 2.9-78.2; p=0.04). Solicited and unsolicited adverse events within 7 days post-injection were more frequent among M72/AS01E recipients (91.2%) than placebo recipients (68.9%), the difference attributed mainly to injection site reactions and flu-like symptoms. Serious adverse events, potential immune-mediated diseases and deaths occurred with similar low frequencies between groups. Conclusions: M72/AS01E was associated with a clinically acceptable safety profile and provided 54.0% protection for Mtb-infected adults against active pulmonary tuberculosis disease.BACKGROUND A vaccine to interrupt the transmission of tuberculosis is needed. METHODS We conducted a randomized, double‐blind, placebo‐controlled, phase 2b trial of the M72/AS01E tuberculosis vaccine in Kenya, South Africa, and Zambia. Human immunodeficiency virus (HIV)–negative adults 18 to 50 years of age with latent M. tuberculosis infection (by interferon‐γ release assay) were randomly assigned (in a 1:1 ratio) to receive two doses of either M72/AS01E or placebo intramuscularly 1 month apart. Most participants had previously received the bacille Calmette–Guérin vaccine. We assessed the safety of M72/AS01E and its efficacy against progression to bacteriologically confirmed active pulmonary tuberculosis disease. Clinical suspicion of tuberculosis was confirmed with sputum by means of a polymerase‐chain‐reaction test, mycobacterial culture, or both. RESULTS We report the primary analysis (conducted after a mean of 2.3 years of follow‐up) of the ongoing trial. A total of 1786 participants received M72/AS01E and 1787 received placebo, and 1623 and 1660 participants in the respective groups were included in the according‐to‐protocol efficacy cohort. A total of 10 participants in the M72/AS01E group met the primary case definition (bacteriologically confirmed active pulmonary tuberculosis, with confirmation before treatment), as compared with 22 participants in the placebo group (incidence, 0.3 cases vs. 0.6 cases per 100 person‐years). The vaccine efficacy was 54.0% (90% confidence interval [CI], 13.9 to 75.4; 95% CI, 2.9 to 78.2; P=0.04). Results for the total vaccinated efficacy cohort were similar (vaccine efficacy, 57.0%; 90% CI, 19.9 to 76.9; 95% CI, 9.7 to 79.5; P=0.03). There were more unsolicited reports of adverse events in the M72/AS01E group (67.4%) than in the placebo group (45.4%) within 30 days after injection, with the difference attributed mainly to injection‐site reactions and influenza‐like symptoms. Serious adverse events, potential immune‐mediated diseases, and deaths occurred with similar frequencies in the two groups. CONCLUSIONS M72/AS01E provided 54.0% protection for M. tuberculosis–infected adults against active pulmonary tuberculosis disease, without evident safety concerns. (Funded by GlaxoSmithKline Biologicals and Aeras; ClinicalTrials.gov number, NCT01755598.)

The TLR-4 agonist adjuvant, GLA-SE, improves magnitude and quality of immune responses elicited by the ID93 tuberculosis vaccine: first-in-human trial

Tuberculosis (TB) is the leading cause of infectious death worldwide. Development of improved TB vaccines that boost or replace BCG is a major global health goal. ID93 + GLA-SE is a fusion protein TB vaccine candidate combined with the Toll-like Receptor 4 agonist adjuvant, GLA-SE. We conducted a phase 1, randomized, double-blind, dose-escalation clinical trial to evaluate two dose levels of the ID93 antigen, administered intramuscularly alone or in combination with two dose levels of the GLA-SE adjuvant, in 60 BCG-naive, QuantiFERON-negative, healthy adults in the US (ClinicalTrials.gov identifier: NCT01599897). When administered as 3 injections, 28 days apart, all dose levels of ID93 alone and ID93 + GLA-SE demonstrated an acceptable safety profile. All regimens elicited vaccine-specific humoral and cellular responses. Compared with ID93 alone, vaccination with ID93 + GLA-SE elicited higher titers of ID93-specific antibodies, a preferential increase in IgG1 and IgG3 subclasses, and a multifaceted Fc-mediated effector function response. The addition of GLA-SE also enhanced the magnitude and polyfunctional cytokine profile of CD4+ T cells. The data demonstrate an acceptable safety profile and indicate that the GLA-SE adjuvant drives a functional humoral and T-helper 1 type cellular response.Tuberculosis: novel vaccine formulation elicits strong immune responsesA tuberculosis vaccine containing an immunity-potentiating agent stimulated strong immune responses in a first-in-human trial. Tuberculosis (TB) is the world’s foremost cause of infectious disease deaths, yet lacks an effective vaccine for adult humans. Rhea Coler, of the Infectious Disease Research Institute, Seattle, and a team from the United States and South Africa, tested their prophylactic on 60 healthy US adults. The vaccine consisted of ID93, a fusion of TB therapeutic target proteins, and GLA-SE—a supplement to boost immune responses. The candidate proved safe in all participants, with mild-to-moderate adverse effects, and provoked promising immune responses. The formulation was significantly more effective with GLA-SE than without. Further studies will elucidate the therapeutic benefit of this formulation and its ability to combat the pathogenicity of TB.