Disease spectrum of pulmonary tuberculosis. Pulmonary tuberculosis is the most common clinical manifestation of a M. tuberculosis (Mtb) infection. After primary infection, the disease can be spontaneously cleared by the immune system, remain latent, or progress into either subclinical or active infection. In latent, subclinical or active infection, Mtb (green) persist in the lung tissues in granulomas (red). In subclinical and active infection, free Mtb also reside in the lungs. In active disease, free Mtb are also secreted into the airways, which makes active disease contagious. Latent infection can progress into subclinical or active disease, and subclinical disease can progress into active disease, meaning that carriers of latent TB represent a significant disease reservoir.

Vaccination routes and methods in zebrafish. Zebrafish are usually infected by M. marinum via intraperitoneal injection or immersion. Three immunization routes (intramuscular, intraperitoneal and mucosal) are used in zebrafish to evaluate a vaccine's effect on the primary infection (upper panel). With DNA vaccines, the intramuscular injection of the expression construct is followed by electroporation of the target tissue. To assess a vaccine's effect on the reactivation of a latent M. marinum infection, zebrafish with a latent infection are vaccinated (using an intramuscular injection of a DNA vaccine followed by electroporation), after which the latent infection is activated by treatment with the immunosuppressant dexamethasone (lower panel). The figure also depicts the methods commonly used to evaluate the protective effect and the immunogenicity of the candidate vaccines in zebrafish.