Two Doses of Candidate TB Vaccine MVA85A in Antiretroviral Therapy (ART) Naive Subjects Gives Comparable Immunogenicity to One Dose in ART plus Subjects

Tuberculosis (TB) is a global public health problem exacerbated by the HIV epidemic. Here we evaluate a candidate TB vaccine, MVA85A, in a Phase I study in HIV-infected adults in Senegal. 24 patients were enrolled: Group 1:12, antiretroviral therapy (ART) naive, adults, with CD4 counts > 300 and HIV RNA load,100 000 copies/ml. Group 2: 12 adults, stable on ART, with CD4 counts > 300, and an undetectable HIV RNA load. Safety was evaluated by occurrence of local and systemic adverse events (AEs) and by monitoring of CD4 count, HIV RNA load, haematology and biochemistry. Immunogenicity was evaluated by ex-vivo interferon-gamma ELISpot assay. 87.7% of AEs were mild; 11.6% were moderate; and 0.7% were severe. 29.2% of AEs were systemic; 70.8% were expected local AEs. There were no vaccine-related Serious Adverse Events (SAEs) or clinically significant effects on HIV RNA load or CD4 count. In ART naive subjects, the first MVA85A immunisation induced a significant immune response at 1 and 4 weeks post-immunisation, which contracted to baseline by 12 weeks. Durability of immunogenicity in subjects on ART persisted out to 24 weeks post-vaccination. A second dose of MVA85A at 12 months enhanced immunogenicity in ART naive subjects. Subjects on ART had higher responses after the first vaccination compared with ART naive subjects; responses were comparable after 2 immunisations. In conclusion, MVA85A is well-tolerated and immunogenic in HIV-infected subjects in Senegal. A two dose regimen in ART naive subjects is comparable in immunogenicity to a single dose in subjects on ART.