SARS-CoV-2 is a novel β-coronavirus that caused the COVID-19 pandemic disease, which spread rapidly, infecting more than 134 million people, and killing almost 2.9 million thus far. Based on the urgent need for therapeutic and prophylactic strategies, the identification and characterization of antibodies has been accelerated, since they have been fundamental in treating other viral diseases. Here, we summarized in an integrative manner the present understanding of the immune response and physiopathology caused by SARS-CoV-2, including the activation of the humoral immune response in SARS-CoV-2 infection and therefore, the synthesis of antibodies. Furthermore, we also discussed about the antibodies that can be generated in COVID-19 convalescent sera and their associated clinical studies, including a detailed characterization of a variety of human antibodies and identification of antibodies from other sources, which have powerful neutralizing capacities. Accordingly, the development of effective treatments to mitigate COVID-19 is expected. Finally, we reviewed the challenges faced in producing potential therapeutic antibodies and nanobodies by cell factories at an industrial level while ensuring their quality, efficacy, and safety.

Recent studies have demonstrated that immune-related recombinant proteins can enhance immune function, increasing host survival against infectious diseases in salmonids. This research evaluated inclusion bodies (IBs) of antimicrobial peptides (CAMP^IB and HAMP^IB) and a cytokine (IL1β^IB and TNFα^IB) as potential immunostimulants in farmed salmonids. For this purpose, we produced five IBs (including iRFP^IB as a control), and we evaluated their ability to modulate immune marker gene expression of three IBs in the RTS11 cell line by RT–qPCR. Additionally, we characterized the scale-up of IBs production by comparing two different scale systems. The results showed that CAMP^IB can increase the upregulation of tnfα, il1β, il8, and il10, HAMP^IB significantly increases the upregulation of tnfα, inos, and il10, and IL1β^IB significantly upregulated the expression of tnfα, il1β, and cox2. A comparison of IL1β^IB production showed that the yield was greater in shake flasks than in bioreactors (39 ± 1.15 mg/L and 14.5 ± 4.08 mg/L), and larger nanoparticles were produced in shake flasks (540 ± 129 nm and 427 ± 134 nm, p < 0.0001, respectively). However, compared with its shake flask counterpart, the IL1β^IB produced in a bioreactor has an increased immunomodulatory ability. Further studies are needed to understand the immune response pathways activated by IBs and the optimal production conditions in bioreactors, such as a defined medium, fed-batch production, and mechanical bacterial lysis, to increase yield.

Piscirickettsia salmonis is the primary bacterial pathogen affecting Chilean salmon farming, resulting in annual economic losses of approximately US$700 million. The limited effectiveness of antibiotics and current vaccines underscores the need to enhance upstream cultivation strategies for producing biomass suitable for vaccine production. In this study, two shake flask designs—baffled (BF) and standard non-baffled (NF)—were compared to evaluate how differences in mass and momentum transfer impact the metabolic activity and physiological behavior of P. salmonis under axenic, submerged batch conditions. Despite a 2.5-fold increase in oxygen transfer in BF flasks, the results indicated that this configuration had a negative impact on bacterial performance. Specific growth rates were reduced by 22–39%, and volumetric productivity decreased by 23% compared to NF. Glutamate was fully consumed in NF but remained partially unused in BF, indicating a reduced uptake under shear or oxidative stress. Respiratory activity also differed: NF cultures exhibited distinct peaks in oxygen transfer rate during growth, while BF cultures showed flatter, more constant profiles. Importantly, exopolysaccharide (EPS) production, a trait associated with virulence and immunogenicity, was over fivefold higher in NF (1.48 g/L) than in BF (0.27 g/L). These findings demonstrate that the physical conditions imposed by flask design have a significant influence on P. salmonis growth, respiration, and EPS output. Adjusting cultivation conditions at this early stage can enhance the consistency and quality of biomass used in bacterin-based vaccines. This approach provides a practical tool to improve upstream standardization and supports the development of more effective control strategies for piscirickettsiosis in the aquaculture industry.