New Study Reports Improved Efficacy of Tuberculosis Vaccine by Changing Vaccination Method
Global Impact of Tuberculosis
The World Health Organization (WHO) reported that in 2018, tuberculosis (TB) resulted in 1.5 million deaths worldwide, making it the leading cause of death from a single infectious agent. The WHO has identified multidrug-resistant TB as a significant health security threat. Despite these troubling statistics, TB remains preventable and treatable, with incidence rates decreasing by approximately two percent annually. The United Nations has set a goal to end the TB epidemic by 2030 as part of its Sustainable Development Goals.
Understanding Tuberculosis
Tuberculosis is caused by the bacterium Mycobacterium tuberculosis and is transmitted through the air when an infected person coughs, sneezes, or talks. Individuals living with HIV/AIDS are 19 times more susceptible to developing active TB infections. Additionally, undernourished individuals and smokers also face a higher risk.
Vaccinating against TB in early childhood is crucial for controlling the infection. Currently, the only approved vaccine is the Bacillus Calmette-Guérin (BCG) vaccine, which is typically administered at birth via an intradermal injection. However, some evidence suggests that the vaccine may be less effective in adolescents and adults.
Recent Study on Vaccination Method
A new study has revealed that altering the administration route of the tuberculosis vaccine from an intradermal injection to an intravenous approach significantly enhances its effectiveness in preventing infection. Conducted by researchers from the National Institutes of Health’s National Institute of Allergy and Infectious Diseases, in collaboration with the University of Pittsburgh School of Medicine, the findings were published in the January 2020 issue of Nature.
The researchers investigated how the BCG vaccine’s dosage and administration route impacted the immune response and protection after exposure to Mtb in rhesus macaques. The monkeys received the BCG vaccine through intradermal, aerosol, or intravenous methods. Six months post-vaccination, the monkeys were exposed to a low dose of a highly pathogenic strain of Mtb, and their immune responses were analyzed at various biological levels.
Findings on Intravenous BCG Vaccination
Analysis of the immune response showed that only the intravenous BCG vaccination led to a significant increase in T cells specifically responsive to the mycobacterial antigens, with a tenfold increase in overall T cells compared to other vaccination methods. In vitro experiments indicated higher expression of genes associated with TB protection in the intravenous group.
Following the challenge with Mtb bacteria, the infection and disease progression were monitored through CT scans of the lungs. Monkeys vaccinated intravenously exhibited no signs of increased cellular activity indicative of active infection, and fewer granulomas were observed in their lungs. Remarkably, six out of ten monkeys in the intravenous group showed no granulomas at all. The Mtb bacteria were rapidly eliminated in this group, with only three monkeys displaying minimal levels of the bacteria in lung tissue. In contrast, those vaccinated via intradermal or aerosol routes, as well as unvaccinated monkeys, exhibited more severe infections.
Overall, the intravenous administration of the tuberculosis vaccine demonstrated superior protection through a more robust and sustained immune response, particularly within the lungs. The researchers noted that this study “represents a major step forward in the field of TB vaccine research.”
References
Darrah, P.A., Zeppa, J.J., Maiello, P. et al. Prevention of tuberculosis in macaques after intravenous BCG immunization. Nature 577, 95–102 (2020) doi:10.1038/s41586-019-1817-8
Press release retrieved from – https://www.eurekalert.org/pub_releases/2020-01/nioa-cro123019.php
WHO statistics on TB prevalence obtained from – https://www.who.int/news-room/fact-sheets/detail/tuberculosis
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