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TB vaccine candidate seen as safe, effective for teens with schistosomiasis
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MVA85A, a model candidate tuberculosis vaccine, demonstrated similar immunogenicity, safety and cellular responses when administered to adolescents infected with Schistosoma mansoni compared with uninfected adolescents, according to a study published in PLOS Neglected Tropical Diseases.
“Adolescents are an important target population for a TB vaccine because TB presents as the pulmonary — transmissible — form in adolescents and young adults,” Anne Wajja, from the Co-infection Studies Program at MRC/UVRI Uganda Research Unit, Entebbe, and colleagues wrote. “However, adolescents harbor a high prevalence and intensity of helminth infection in countries where helminths are endemic.”
Due to the ability of helminths to affect vaccine efficacy and immunogenicity, the researchers assessed the safety of the vaccine and how S. mansoni interacts with it. This phase 2 open-label trial included 36 adolescents from Uganda; 18 had no detectable helminth infection and 18 only had S. mansoni.
All participants were previously BCG vaccinated and healthy. The researchers measured the immunogenicity of MVA85A through Ag85A–specific interferon gamma ELISpot assay. Additionally, they evaluated TB- and schistosome-specific responses with whole-blood stimulation, multiplex cytokine assay and antibody ELISAs.
For adolescents, vaccination with MVA85A increased Ag85A–specific cellular responses significantly in both groups with no differences established. Those infected with S. mansoni had demonstrated higher Ag85A–specific IgG4; however, no changes were demonstrated regarding antibody levels after vaccination. No serious adverse events were observed, and most reactogenicity events were mild or moderate and were quickly resolved.
“It may not be possible to extrapolate these findings to other vaccines and other species of helminth,” Wajja and colleagues wrote. “There is substantial evidence of variability between populations in vaccine immunogenicity, notably, impaired responses to yellow fever vaccine were observed in Uganda compared to Switzerland in a study that found reduced vaccine virus replication and neutralizing antibody production and persistence in the context of elevated innate and adaptive immune-response activation among Ugandan volunteers.” — by Katherine Bortz
Disclosure: The researchers report no relevant financial disclosures.
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