No abstract

Piscirickettsia salmonis is an intracellular bacterium that was first isolated and identified in fish cells. Several types of cell lines have been explored for their ability to provide the bacterium with a host cell to replicate in. Tissue culture has been used for growth and cultivation for nearly two decades, until the facultative nature of P. salmonis was confirmed upon the development of blood- and cysteine-based agar. Since then, research has continued to drive the creation of novel agar and broth formulations in order to improve the efficacy of cultivation of P. salmonis. Until now, the techniques and components used for growth have not been thoroughly discussed. In this review, the methods and formulations for growth of P. salmonis in tissue culture and cell-free media will be examined.

Despite the remarkable success of SARS-CoV-2 vaccines, the rise of variants, some of which are more resistant to the effects of vaccination, highlights the potential need for additional COVID-19 vaccines. We used the Multiple Antigen-Presenting System (MAPS) technology, in which proteins are presented on a polysaccharide polymer to induce antibody, Th1, Th17 and CD8+ T cell responses, to engineer a novel vaccine targeting SARS-CoV-2. This vaccine contains a fragment of the spike (S) protein receptor-binding domain (RBD) sequence of the original D614G strain and was used to immunize nonhuman primates (NHP) for assessment of immunological responses and protection against SARS-CoV-2 challenge. The SARS-CoV-2 MAPS vaccine generated robust neutralizing antibodies as well as Th1, Th17 and cytotoxic CD8 T-cell responses in NHPs. Furthermore, MAPS-immunized NHPs had significantly lower viral loads in the nasopharynx and lung compared to control animals. Taken together, these findings support the use of the MAPS platform to make a SARS-CoV-2 vaccine. The nature of the platform also could enable its use for the inclusion of different variants in a single vaccine.

In response to the COVID-19 pandemic, the international scientific and biopharmaceutical community has rallied with unprecedented speed to develop effective vaccines to combat this novel pathogen. Despite this remarkable success, the rise of SARS-CoV-2 variants, some of which appear more resistant to the effects of vaccination, highlights the potential need for additional COVID vaccines. We used the MAPS technology, in which proteins are presented on a polysaccharide polymer to induce antibody, Th1, Th17 and CD8+ T cell responses, to engineer a COVID-19 vaccine. The COVID-19 MAPS vaccine contained a fragment of the S-RBD sequence of the original strain. Nonhuman primates (NHP) were immunized twice with the COVID-19 MAPS for assessment of immunological responses. NHPs were then challenged with SARS-CoV-2 and protection was assessed by measuring the viral load in the lung and in the nasopharynx. The COVID-19 MAPS vaccine generated robust neutralizing antibodies in all three animal species as well as Th1, Th17 and cytotoxic CD8 T-cell responses in NHPs. Following viral challenge, MAPS-immunized NHPs had significantly lower viral load both in the nasopharynx and the lung than control animals. This difference was appreciable in the earliest stages following challenge. A COVID-19 MAPS vaccine containing the RBD of the D614G SARS-CoV-2 strain was very immunogenic in mice, rabbits and NHPs, generated de novo T cell responses and was highly protective against viral challenge in NHPs. These results, as well as the plug-and-play nature of the MAPS technology, in which different RBD variants can be included in a single vaccine preparation, suggest that the MAPS platform could be used to make a vaccine to target multiple variants of SARS-CoV-2.

Piscirickettsia salmonis is a facultative, intracellular pathogen which is the causative agent of piscirickettsiosis in several fresh and saltwater fish species. The disease has caused significant economic losses particularly to Chilean aquaculture. Isolation and growth of the pathogen is generally carried out in cell culture, however alternative media have been published for growth in liquid and agar culture. We investigate the growth of P. salmonis in three defined artificial media through optical density, cell counts, and a P. salmonis-specific TaqMan assay. Despite previous indications that iron was essential for in vitro growth, iron restriction was achieved and induced protein variations between mediums upon 1D and 2D PAGE-gel electrophoresis analysis. Furthermore, we analyze the immune response in Atlantic salmon to P. salmonis using immune serum. These protein differences could indicate how intracellular pathogens grow in different in vitro systems and provide additional insight for future vaccine development.