Olumuyiwa Owolabi

Immunogenicity of the Tuberculosis Vaccine MVA85A Is Reduced by Coadministration with EPI Vaccines in a Randomized Controlled Trial in Gambian Infants

Coadministration with standard vaccines may reduce immunogenicity of tuberculosis vaccine. Timing Is Everything Anyone who bought a house right before the housing bubble burst knows that it’s not only what you do but when you do it that matters. Likewise, when introducing a new vaccine, timing is crucial—it may be easier to ensure compliance if the immunization is offered when the patient is already visiting the doctor. However, some vaccines may not be as effective if given at the same time as other shots. Ota et al. explored this phenomenon for a new tuberculosis (TB) vaccine in a clinical trial of Gambian infants. The Expanded Program on Immunization (EPI) provides a country-specific schedule of standard vaccinations to increase vaccine coverage in underserved populations. The current vaccine for TB, Bacille Calmette-Guérin (BCG), is used in the EPI; however, BCG is only partially effective against TB, especially in adults. Ota et al. tested MVA85A, a novel vaccine designed to enhance BCG, in infants in Gambia. They found that MVA85A was safe and well tolerated and successfully induced a cellular immune response in recipients. Coadministration of MVA85A and the EPI vaccines did not affect the antibody responses to the latter but did reduce the immunogenicity of MVA85A. Thus, the EPI schedule may have to be modified for successful vaccination before the introduction of MVA85A and potentially other new T cell–inducing vaccines as well. In vaccination, as in life, timing is everything. New tuberculosis vaccines are urgently needed to curtail the current epidemic. MVA85A is a subunit vaccine that could enhance immunity from BCG vaccination. To determine MVA85A safety and immunogenicity as well as interactions with other routine vaccines administered in infancy, we randomized healthy 4-month-old infants who had received Bacille Calmette-Guérin at birth to receive Expanded Program on Immunization (EPI) vaccines alone, EPI and MVA85A simultaneously, or MVA85A alone. Adverse events were monitored throughout. Blood samples obtained before vaccination and at 1, 4, and 20 weeks after vaccination were used to assess safety and immunogenicity. The safety profile of both low and standard doses was comparable, but the standard dose was more immunogenic and therefore was selected for the second stage of the study. In total, 72 (first stage) and 142 (second stage) infants were enrolled. MVA85A was safe and well tolerated and induced a potent cellular immune response. Coadministration of MVA85A with EPI vaccines was associated with a significant reduction in MVA85A immunogenicity, but did not affect humoral responses to the EPI vaccines. These results provide important information regarding timing of immunizations, which is required for the design of infant efficacy trials with MVA85A, and suggest that modifications to the standard EPI schedule may be required to incorporate a new generation of T cell–inducing vaccines.

Comparison of the Prevalence of Common Bacterial Pathogens in the Oropharynx and Nasopharynx of Gambian Infants

Background CRM- based pneumococcal conjugate vaccines generally have little impact on the overall prevalence of pneumococcal carriage because of serotype replacement. In contrast, protein vaccines could substantially reduce the overall prevalence of pneumococcal carriage with potential microbiological and clinical consequences. Therefore, trials of pneumococcal protein vaccines need to evaluate their impact on carriage of other potentially pathogenic bacteria in addition to the pneumococcus. Methods As a prelude to a trial of an investigational pneumococcal vaccine containing pneumococcal polysaccharide conjugates and pneumococcal proteins, the prevalence of carriage of Streptococcus pneumoniae, Haemophilus influenzae, Moraxella species and Staphylococcus aureus in the nasopharynx of 1030 Gambian infants (median age 35 weeks) was determined. An oropharyngeal swab was obtained at the same time from the first 371 infants enrolled. Standard microbiological techniques were used to evaluate the bacterial flora of the pharynx and to compare that found in the oropharynx and in the nasopharynx. Results The overall pneumococcal carriage rate was high. Isolation rates of S. pneumoniae and Moraxella species were significantly higher using nasopharyngeal rather than oropharyngeal swabs (76.1% [95% CI 73.4%,78.7%] vs. 21.3% [95% CI 17.2%,25.8%] and 48.9% [95% CI 45.8%, 52.0%] vs. 20.5% % [95% CI 16.5%,25.0%] respectively). In contrast, S. aureus and H. influenzae were isolated more frequently from oropharyngeal than from nasopharyngeal swabs (65.0% [95% CI 59.9%, 69.8%] vs. 33.6% [95% CI 30.7%, 36.5%] and 31.8% [95% CI 16.5%, 25.0%] vs. 22.4% [95% CI 19.9%, 25.1%] respectively). No group A β haemolytic streptococci were isolated. Conclusion Collection of an oropharyngeal swab in addition to a nasopharyngeal swab will provide little additional information on the impact of a novel pneumococcal vaccine on pneumococcal carriage but it might provide additional, valuable information on the impact of the vaccine on the overall microbiota of the pharynx.

A new TB vaccine, MVA85A, induces durable antigen-specific responses 14 months after vaccination in African infants.

This study aimed to evaluate the durability of the immunogenicity of MVA85A beyond infancy. Participants in an immunogenicity study of MVA85A administered at age of 4 months had additional evaluation 14 months after initial vaccination for IFN-γ ELISPOT responses to Ag85A peptide and ESAT6/CFP-10 and tuberculin skin test (TST). 112 children participated in this study. The anthropometry, biochemical and haematological safety profile were similar between the MVA85A recipients and controls. MVA85A recipients still had significantly higher immune responses to Ag85A compared to the controls. The majority of these children had negative responses to the TST as well as the ESAT6/CFP-10 antigens. In summary, MVA85A-vaccinated children had a persistently higher Ag85A immune response 14 months following vaccination than controls. All the children had negligible evidence of latent infection with M. tuberculosis (Mtb), suggesting that deploying a prophylactic vaccine against Mtb infection at this age could still be effective in this setting.

Efficacy of a novel, protein-based pneumococcal vaccine against nasopharyngeal carriage of Streptococcus pneumoniae in infants: A phase 2, randomized, controlled, observer-blind study

BACKGROUND Conserved pneumococcal proteins are potential candidates for inclusion in vaccines against pneumococcal diseases. In the first part of a two-part study, an investigational vaccine (PHiD-CV/dPly/PhtD-30) containing 10 pneumococcal serotype-specific polysaccharide conjugates (10VT) combined with pneumolysin toxoid and pneumococcal histidine triad protein D (30μg each) was well tolerated by Gambian children. Part two, presented here, assessed the efficacy of two PHiD-CV/dPly/PhtD formulations against pneumococcal nasopharyngeal carriage (NPC) prevalence in infants. METHODS In this phase 2, randomized, controlled, observer-blind trial, healthy infants aged 8-10weeks, recruited from a peri-urban health center, were randomized (1:1:1:1:1:1) into six groups. Four groups received PHiD-CV/dPly/PhtD (10 or 30μg of each protein), PHiD-CV, or 13-valent pneumococcal conjugate vaccine at ages 2-3-4months (3+0 infant schedule) and two groups PHiD-CV/dPly/PhtD-30 or PHiD-CV at 2-4-9months (2+1 infant schedule). The primary objective was impact on non-10VT NPC at ages 5-9-12months. Secondary objectives included confirmatory analysis of protein dose superiority and safety/reactogenicity. Impact on pneumococcal NPC acquisition, bacterial load, and ply and phtD gene sequencing were explored. RESULTS 1200 infants were enrolled between June 2011 and May 2012. Prevalences of pneumococcal (60-67%) and non-10VT (55-61%) NPC were high at baseline. Across all post-vaccination time points, efficacy of PHiD-CV/dPly/PhtD-10 and PHiD-CV/dPly/PhtD-30 against non-10VT NPC (3+0 schedule) was 1.1% (95% CI -21.5, 19.5) and 2.1% (-20.3, 20.3), respectively; efficacy of PHiD-CV/dPly/PhtD-30 (2+1 schedule) was 0.5% (-22.1, 18.9) versus PHiD-CV. No differences were observed in pneumococcal NPC acquisition, clearance, or bacterial load. Both protein-based vaccines elicited immune responses to pneumococcal proteins. CONCLUSIONS In this high carriage prevalence setting, inclusion of pneumococcal proteins in the PHiD-CV/dPly/PhtD investigational vaccine had no impact on pneumococcal NPC in infants, regardless of protein dose or schedule. Future evaluations will assess its impact against pneumococcal disease endpoints. FUNDING PATH, GlaxoSmithKline Biologicals SA. ClinicalTrials.gov identifier NCT01262872.

Complex Anemia in Tuberculosis: The Need to Consider Causes and Timing When Designing Interventions

BACKGROUND Anemia is common in tuberculosis, and multiple etiologies necessitate targeted interventions. The proportion of iron-responsive anemia due to iron deficiency compared with iron-unresponsive anemia due to impaired iron absorption/redistribution from tuberculosis-associated immune activation or inflammation is unknown. This impedes selection of safe and effective treatment and appropriate intervention timing. METHODS Baseline hemoglobin, ferritin, hepcidin, soluble transferrin receptor (sTfR), and transferrin were measured in 45 patients with confirmed pulmonary tuberculosis (cases), 47 tuberculin skin test (TST)-positive controls, and 39 TST-negative controls in The Gambia. Tuberculosis cases were additionally followed 2 and 6 months after tuberculosis treatment initiation. Mutually exclusive anemia categories based on iron biomarker concentrations were iron deficiency anemia (IDA), anemia of inflammation (AI), and multifactorial anemia (IDA+AI). RESULTS Anemia was more frequent in tuberculosis cases (67%) than in TST-positive (36%) or TST-negative (21%) controls. AI was the predominant anemia at tuberculosis diagnosis, declining from 36% to 8% after 6 months of treatment; however, a corresponding reduction was not evident for anemia with iron-responsive components (IDA, IDA+AI). Iron biomarkers discriminated between active tuberculosis and TST-positive or TST-negative controls, as well as between active untreated and treated tuberculosis. This was most noticeable for hepcidin, which decreased from a median of 84.0 ng/mL at diagnosis to 9.7 ng/mL after 2 months (P < .001). CONCLUSIONS Tuberculosis chemotherapy is associated with significant reductions in AI, but IDA and IDA+AI remain unresolved. Iron-based interventions are needed for IDA and IDA+AI, and monitoring of iron biomarkers reveals a window for intervention opening as early as 2 months into tuberculosis treatment.

Contextualizing the Informed Consent Process in Vaccine Trials in Developing Countries

Introduction: Most sponsors of clinical trials in Africa propose the use of complicated informed consenting procedures as in developed countries, including the translation of informed consent forms into local languages. Although well intentioned, this practice may be irrelevant and of no added value in settings where local languages are only spoken but not written. Recognizing this challenge, the ethics committee in The Gambia recommend a consent procedure that takes into account these local realities. The objective of this paper was to assess the effectiveness of this new procedure in conveying key trial information among participants in a vaccine trial in The Gambia. Methods: Consent was obtained from 1200 parents using the new procedure. Comprehension was then assessed using a tool that contained questions on key aspects of the trial. Results: Although the majority of respondents had no formal education, almost all of them had a sound understanding of the trial. Variables such as age, gender, education, ethnicity and occupation had minimal effect on comprehension. Discussion and Conclusion: Our data suggest that the new consent procedure is effective in conveying key research information to research participants. The procedure is promising in that it has eliminated the need for repeatedly translating and back-translating informed consents. It also guarantees that the study team expresses research concepts in the same way.

Use of lateral flow assays to determine IP-10 and CCL4 levels in pleural effusions and whole blood for TB diagnosis.

One of the key problems in combating TB is the lack of fast and accurate diagnostic tests that are affordable and easy to use in resource-limited settings. We have used a field-friendly up-converting phosphor (UCP) reporter technology in a lateral flow (LF) based test for the diagnosis of respiratory infections. In this study we analysed samples obtained from patients presenting with symptoms suggestive of TB but prior to confirmation by microbiology in The Gambia. Following clinical and microbiological evaluation they were classified as either having TB or other respiratory disorder (ORD). Analysis of blood was performed for those with pulmonary TB and pleural fluid for those with pleural TB. UCP-LF test for detection and quantitation of IP-10 and CCL4 were used being the two chemokine markers that have been shown to increase in active TB disease. UCP-LF test accurately determined concentrations of both markers as compared to ELISA and multiplex cytokine array. However, only IP-10 could discriminate between TB and ORD, and this was significantly enhanced by analysing the site of infection (pleural fluid), which showed 92% correct classification. Future work will assess the use of multiple markers to increase diagnostic accuracy.

Rapid diagnosis of tuberculosis using ex vivo host biomarkers in sputum

To the Editor: Tuberculosis continues to be a major public health problem in developing countries [1]. One of the roadblocks in reducing tuberculosis transmission is the lack of accurate laboratory-free diagnostic tests for use at the point of care. If tuberculosis is to be eliminated, we need a robust, low-cost and safe point-of-care diagnostic test, which in turn requires identification of appropriate biomarkers [2]. Rapid tests based on microfluidics (lateral flow tests) hold great promise for tuberculosis diagnostics. They are easy to use, cheap, provide an answer within minutes, do not require specialised equipment and are stable at room temperature, making them ideal for use in high tuberculosis burden, resource-poor settings. To date, however, no such test has been developed for tuberculosis due to lack of sensitivity related to the markers and/or sample type. Development of tests based on host biomarkers requires evaluation of different sample types [3]–[5] and markers other than interferon (IFN)-γ [5] to provide differential diagnosis of active tuberculosis, latent infection and other respiratory disorders. We have previously shown that a combination of three host factors in pleural fluid resulted in 96% correct classification of tuberculosis among other respiratory diseases (ORD) (including bacterial pneumonia) regardless of HIV status [6]. However, this sample type is not easy to obtain and we therefore wanted to determine if we could use ex vivo sputum, which is noninvasive and easy to obtain in adult pulmonary tuberculosis patients. Subjects were consecutively recruited from the outpatient clinic and ward at the Medical Research Council Unit, Fajara, the Gambia. All subjects were adults (≥18 years of age) with symptoms suggestive of tuberculosis. Subjects were subsequently classified into two groups: those with culture-confirmed tuberculosis and those with ORD. 75% of the tuberculosis and …

Haematological and biochemical reference values of Gambian infants

To establish haematological and biological reference values for Gambian infants.

Elevated serum 25-hydroxy (OH) vitamin D levels are associated with risk of TB progression in Gambian adults

Summary Background Vitamin D is essential in the host defence against tuberculosis (TB) as an immune modulator. The aim of this study was to determine the level of 25-hydroxyvitamin D (25 (OH) D) from adult TB index cases before and after treatment and their exposed household contacts (HHC) in The Gambia. Methods Serum from adult index TB cases and their TB-exposed household contacts (HHC) was analysed for 25(OH) D and Vitamin D binding protein (VDBP) concentrations. Tuberculin skin test (TST) status was used as a measure of Mycobacterium tuberculosis (Mtb) infectivity in the HHC. In addition, HHC who later progressed to active TB (incident cases) were assessed alongside non-progressors to determine the influence of 25 (OH) D levels on TB risk. Results Eighty-three TB cases, 46 TST+ and 52 TST− HHC were analysed. Generally levels of 25(OH) D were considered insufficient in all subjects. However, median levels of 25(OH) D and VDBP were significantly higher in TB cases compared to both TST+ and TST− HHC at recruitment and were significantly reduced after TB therapy (p < 0.0001 for all). In addition, levels of serum 25(OH) D at recruitment were significantly higher in TB progressors compared to non-progressors (median (IQR): 25.0(20.8–29.2) in progressors and 20.3 (16.3–24.6) ng/ml in non-progressors; p = 0.007). Conclusion In The Gambia, an equatorial country, 25(OH) D levels are higher in serum of TB progressors and those with active disease compared to latently infected and uninfected subjects. These results contrast to findings in non-equatorial countries.