Disease Model Module
The third module of the MIMIC™ platform is the Disease Model module. This module measures the effect of a vaccine on the immune response to an infection or an infectious disease. Thus, one could measure the effectiveness of a vaccine candidate to neutralize or clear a pathogen. This module enables the “Clinical Trial in a Test Tube”™ application of the MIMIC™ technology.
To date, this module has been used for influenza and latent tuberculosis (Mtb) as model diseases. In the case of influenza, we generated influenza-specific IgG antibody secreting cells via the MIMIC™ system. MIMIC™-generated Abs involved the collection of LTE module supernatants from 12 donors stimulated with influenza antigen (Fluzone®). Supernatants were then assayed by hemagglutinin inhibition (HAI) for neutralizing activity. Controls included ‘hyperimmune’ serum, virus controls and serum controls. Responses against titrated virus stocks of H1N1 (New Caledonia) indicated that all donors yielded detectable levels of HAI antibodies with titers that ranged from 1:16 to > 1:32 (our highest dilution in this initial study). This result suggests that the MIMIC™-generated antibodies are functional and that the model accurately predicts the human response to an influenza virus after vaccination.
MIMIC™ analysis of influenza via HAI
Disease Model Development
One successful intracellular pathogen disease model has been M. tuberculosis, which infects alveolar macrophages and causes tuberculosis (TB) in humans. The Mtb model is a close analog to many biodefense infectious diseases such as Burkholderia, Junin, Tularemia, Yersinia pestis, etc. As for Mtb, it infects macrophages in the lung to form granulomatous structures. Granulomas are hallmark of tuberculosis infection and are considered an equilibrium condition between host and pathogen. Formation of granulomas is a protective response by the host to prevent spread of infection to healthy tissue. Mtb is said to go into a dormant state in granulomas until resuscitated by a suppressed immune system as in AIDS patients and elderly subjects.
To achieve the goal of testing Mtb as an intracellular pathogen model using the Disease Model module of the MIMIC™ system, Mtb-induced in vitro granuloma formation was successfully recapitulated by adding PBMC cells from healthy human donors with different ratios of Mtb in an extracellular matrix. Uninfected macrophages do not show granuloma formation (right micrograph).
Mtb-induced granuloma formation in three dimensional extracellular matrix. Left (200× magnification): 5×105 PBMC were added with 2.5×103 Mtb at 1:1 ratio (one Mtb per macrophage). Right (100× magnification): Uninfected PBMCs under same experimental conditions do not show granuloma formation (right micrograph).
Development of dormancy is an important phenomenon associated with TB infection. Mtb undergo latency in granulomas and characteristically show resistance to antibiotic Rifampicin (Rif). Rifampicin kills actively growing and/or metabolically active Mtb whereas truly dormant Mtb, which are metabolically inactive yet alive, are resistant to its action. Performing this assay, VaxDesign investigators along with the University of Central Florida have been able to demonstrate that the in vitro granuloma formation is truly dormant.
Other Models
VaxDesign can create other disease modules for the MIMIC™ platform, as new commercial applications are developed for other diseases. We plan to develop disease models for Yersinia pestis, HIV, and VEEV, among others.