Millions of people in tropical countries are at risk for contracting tuberculosis (TB) each year, with the existing Bacille Calmette-Guerin (BCG) vaccine protecting only against the most severe childhood form. However, many of these people have pre-existing parasitic infections, which are known to reduce the effectiveness of certain vaccines. Thus, it is important to assess the impact of parasitic infections on potential new TB vaccines during testing.
Anne Wajja of the MRC/UVRI Uganda Research Unit and colleagues conducted a clinical trial to test the candidate TB vaccine MVA85A on 36 healthy Ugandan teenagers, half of whom were known to be infected with the flatworm Schistosoma mansoni, the rest having no worm infections. The researchers measured the immune system’s response to the candidate vaccine in each patient and recorded any adverse medical events, hoping to discover if having an S. mansoni infection altered the vaccine’s effectiveness.
They found that all the adolescents showed a positive immune response to the vaccine, with the those infected with S. mansoni responding just as well as uninfected teens. No patients experienced any adverse medical events. Since teenagers in tropical countries are both vulnerable to TB and frequently infected with worms, this is a promising result for the development of TB vaccines for this population.
Research Article: Wajja A, Kizito D, Nassanga B, Nalwoga A, Kabagenyi J, Kimuda S, et al. (2017) The effect of current Schistosoma mansoni infection on the immunogenicity of a candidate TB vaccine, MVA85A, in BCG-vaccinated adolescents: An open-label trial. PLoS Negl Trop Dis 11(5): e0005440. doi:10.1371/journal.pntd.0005440
Image Credit: Julien Harneis, Flickr