In vivo and ex vivo studies support the immunostimulant and immunoprotective effect of Damiana (Turnera diffusa Willd) in Almaco Jack (Seriola rivoliana).

Damiana (Turnera diffusa Willd) was evaluated in vitro for antioxidant and antibacterial activities against Staphylococcus aureus and Streptococcus pyogenes (as a preliminary screening assessment) by high-performance thin-layer chromatography (HPTLC)-Direct bioautography. A study was performed in vivo to evaluate the effects of Damiana enriched diets at 0.5 % on immune parameters in mucus and serum and gene expression in Almaco Jack (Seriola rivoliana) intestine after two and four weeks; an infection with Aeromonas hydrophila at 1x107 colony forming units (CFU) followed and an ex vivo study was carried out using head-kidney leukocytes. Ferric reducing ability of plasma (FRAP) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assays showed high antioxidant activities in Damiana leaves; even in the ABTS assay, Damiana at 300 µg/mL showed similar activity to ascorbic acid - the standard control. Damiana exhibited strong in vitro antimicrobial activity against S. aureus and S. pyogenes. In vivo studies showed a strong enhancement of myeloperoxidase, nitric oxide, superoxide dismutase, and catalase activities in mucus and serum of S. rivoliana supplemented with Damiana; their immunological response enhanced after infection with A. hydrophila. IL-1ß, TNF-α, and IL-10 gene expressions upregulated in the fish intestine challenged with the bacterium. Piscidin and macrophage (MARCO) receptor gene expression up-regulated at week 4 and down-regulated after infection. Intestinal histology results confirm that Damiana not cause inflammation or damage. Finally, the ex vivo study confirmed the immunostimulant and protective effects of Damiana through increased phagocytic, respiratory burst, myeloperoxidase activities and nitric oxide generation before and upon the bacterial encounter. These results support the idea that Damiana has the potential as an immunostimulant additive for diets in aquaculture by enhancing immune parameters and protecting Almaco Jack against A. hydrophila infections upon four weeks of supplementation.

An Algae-Made RBD from SARS-CoV-2 Is Immunogenic in Mice.

Despite the current advances in global vaccination against SARS-CoV-2, boosting is still required to sustain immunity in the population, and the induction of sterilizing immunity remains as a pending goal. Low-cost oral immunogens could be used as the basis for the design of affordable and easy-to-administer booster vaccines. Algae stand as promising platforms to produce immunogens at low cost, and it is possible to use them as oral delivery carriers since they are edible (not requiring complex purification and formulation processes). Herein, a Chlamydomonas-made SARS-CoV-2 RBD was evaluated as an oral immunogen in mice to explore the feasibility of developing an oral algae-based vaccine. The test immunogen was stable in freeze-dried algae biomass and able to induce, by the oral route, systemic and mucosal humoral responses against the spike protein at a similar magnitude to those induced by injected antigen plus alum adjuvant. IgG subclass analysis revealed a Th2-bias response which lasted over 4 months after the last immunization. The induced antibodies showed a similar reactivity against either Delta or Omicron variants. This study represents a step forward in the development of oral vaccines that could accelerate massive immunization.

The Potential of Algal Biotechnology to Produce Antiviral Compounds and Biopharmaceuticals.

The emergence of the Coronavirus Disease 2019 (COVID-19) caused by the SARS-CoV-2 virus has led to an unprecedented pandemic, which demands urgent development of antiviral drugs and antibodies; as well as prophylactic approaches, namely vaccines. Algae biotechnology has much to offer in this scenario given the diversity of such organisms, which are a valuable source of antiviral and anti-inflammatory compounds that can also be used to produce vaccines and antibodies. Antivirals with possible activity against SARS-CoV-2 are summarized, based on previously reported activity against Coronaviruses or other enveloped or respiratory viruses. Moreover, the potential of algae-derived anti-inflammatory compounds to treat severe cases of COVID-19 is contemplated. The scenario of producing biopharmaceuticals in recombinant algae is presented and the cases of algae-made vaccines targeting viral diseases is highlighted as valuable references for the development of anti-SARS-CoV-2 vaccines. Successful cases in the production of functional antibodies are described. Perspectives on how specific algae species and genetic engineering techniques can be applied for the production of anti-viral compounds antibodies and vaccines against SARS-CoV-2 are provided.