Expressão gênica intestinal de uma vacina de DNA via oral utilizando dois métodos de proteção em Tilápia-do-Nilo

Abstract

The control and management of diseases that affect global pisciculture, such as those caused by protozoa, parasites, worms, opportunistic bacteria and fungi, is a prerequisite for the sustainability of this productive sector and a constant challenge, very complex and currently, limited of effective treatment products. In addition, fingerling and juvenile are even more susceptible, in general, to outbreaks of these diseases, as their immune systems are still in formation, so their survival relies on multidisciplinary strategies for the proper management of their health, nutrition, water quality and biosafety measures. Therefore, emphasis on prevention and not only just treatment is necessary. For these reasons, DNA vaccines are gaining increasing attention, due to overcoming disadvantages of other preventive treatments, generally more efficiently. They work by expressing different pathogen proteins in the host, encoded in plasmid vectors. Licensed commercial vaccines today are relatively expensive, which does not generate extensive vaccination strategies. It was evaluated the functionality of the plasmid pExu vector transformed in Lactococcus lactis MG 1363 strains, for fish. This genic L. lactis MG1363 (pExu:mCherry) vaccine was offered orally by either microencapsulation or lyophilization, for the Nile tilapia (Oreochromis niloticus), of elevated commercial interest. 108 Nile tilapia male juveniles, weighing 250 ± 20 g were utilized. 1 dose (equivalent of 1x109 CFU) were administrated orally [microencapsulated (direct administration) and lyophilized (incorporated into fish feed)] to the animals, and the area that presents fluorescence were compared in three intestinal sections (Anterior, Medium, Posterior) at 6, 18, 24, 48, 72, 96, 120, 144, e 168 hours after administration. Both methods allowed the expression of the reporter gene in all regions of interest. Statistical difference was observed (p < 0.001) in mean área of expression from different sections, so that the Posterior section presented inferior expression in relation to others, either by microencapsulation or lyophilization (40% and 87% reduction, respectively). mCherry protein expression was more efficient with lyophilization than microencapsulation (p < 0.001), by express, in average, fluorescence areas 25 thousand, 13 thousand and 4 thousand percent higher, on Anterior, Medium and Posterior sections, respectively. Microencapsulation and lyophilization presented maximum amplitude of expression in the 24 hours and 96 hours intervals, respectively. Such findings are important because they will guide research on new strategies with DNA vaccines, especially those given orally.