[Tracheal replacement using the abdominal aorta. Comments on a case report]

Recombinant Invasive Lactococcus lactis Carrying a DNA Vaccine Coding the Ag85A Antigen Increases INF-γ, IL-6, and TNF-α Cytokines after Intranasal Immunization

Tuberculosis (TB) remains a major threat throughout the world and in 2015 it caused the death of 1.4 million people. The Bacillus Calmette-Guérin is the only existing vaccine against this ancient disease; however, it does not provide complete protection in adults. New vaccines against TB are eminently a global priority. The use of bacteria as vehicles for delivery of vaccine plasmids is a promising vaccination strategy. In this study, we evaluated the use of, an engineered invasive Lactococcus lactis (expressing Fibronectin-Binding Protein A from Staphylococcus aureus) for the delivery of DNA plasmid to host cells, especially to the mucosal site as a new DNA vaccine against tuberculosis. One of the major antigens documented that offers protective responses against Mycobacterium tuberculosis is the Ag85A. L. lactis FnBPA⁺ (pValac:Ag85A) which was obtained and used for intranasal immunization of C57BL/6 mice and the immune response profile was evaluated. In this study we observed that this strain was able to produce significant increases in the amount of pro-inflammatory cytokines (IFN-γ, TNF-α, and IL-6) in the stimulated spleen cell supernatants, showing a systemic T helper 1 (Th1) cell response. Antibody production (IgG and sIgA anti-Ag85A) was also significantly increased in bronchoalveolar lavage, as well as in the serum of mice. In summary, these findings open new perspectives in the area of mucosal DNA vaccine, against specific pathogens using a Lactic Acid Bacteria such as L. lactis.

The fate of homograft tracheal transplants in sheep

OBJECTIVE

An established method of tracheal substitution is not yet available, but homograft tracheal transplantation might provide a realistic tracheal replacement. With the objective of sequentially examining the healing of tracheal homografts, we have established a suitable large-animal model.

METHODS

Five sheep received orthotopic tracheal transplantation of a 4-cm cervical tracheal homograft. The trachea was supported for 6 weeks with a self-expanding polyester stent. The plan was to euthanize the animals after 2, 4, 8, 12 and 16 weeks, or whenever complications occurred.

RESULTS

The implantation itself was performed without complications. After 2 weeks the homograft was firmly encapsulated by connective tissue, without signs of necrosis or abscess. The original mucous membrane no longer existed; the cartilage rings were exposed. In all animals that were euthanized at the later dates, the homografts were completely absorbed and replaced by inflammatory scar tissue. This, in turn, was covered with a shiny cellular surface layer.

CONCLUSIONS

The results from this animal experiment reveal-contrary to data published to date-that tracheal homografts are not incorporated but absorbed. They are replaced by scar/granulation tissue that cannot secure the stability of the trachea. Therefore, further experiments with respect to the biocompatability of homografts appear to be necessary.