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[This corrects the article DOI: 10.3389/fimmu.2023.1080238.].

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Advances in antigen targeting in veterinary medicine have gained traction over the years as an alternative approach for diseases that remain a challenge for traditional vaccines. In addition to the nature of the immunogen, antigen-targeting success relies heavily on the chosen receptor for its direct influence on the elicited response that will ensue after antigen uptake. Different approaches using antibodies, natural or synthetic ligands, fused proteins, and DNA vaccines have been explored in various veterinary species, with pigs, cattle, sheep, and poultry as the most frequent models. Antigen-presenting cells can be targeted using a generic approach, such as broadly expressed receptors such as MHC-II, CD80/86, CD40, CD83, etc., or focused on specific cell populations such as dendritic cells or macrophages (Langerin, DC-SIGN, XCR1, DC peptides, sialoadhesin, mannose receptors, etc.) with contrasting results. Interestingly, DC peptides show high specificity to DCs, boosting activation, stimulating cellular and humoral responses, and a higher rate of clinical protection. Likewise, MHC-II targeting shows consistent results in enhancing both immune responses; an example of this strategy of targeting is the approved vaccine against the bovine viral diarrhea virus in South America. This significant milestone opens the door to continuing efforts toward antigen-targeting vaccines to benefit animal health. This review discusses the recent advances in antigen targeting to antigen-presenting cells in veterinary medicine, with a special interest in pigs, sheep, cattle, poultry, and dogs.

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Dendritic cell (DC) targeting by DEC205+ cells effectively promotes the internalization of antigens that may trigger a specific immune response. In this study, we evaluated the ability of a recombinant antibody, anti-DEC205 (rAb ZH9F7), to trigger cellular endocytosis in subpopulations of DCs and targeted cells after intradermal injection and subsequent migration toward lymph nodes. Furthermore, the cellular immune response was evaluated in pigs after intradermal application of the antigenized rAb ZH9F7 combined with porcine circovirus type 2 cap antigen (rAb ZH9F7-Cap). We demonstrated that rAb ZH9F7 recognized conventional type 1 and 2 DCs from the blood and skin and monocytes. It promoted receptor-mediated endocytosis and migration of cDCs and moDCs toward regional lymph nodes. Intradermal application of rAb ZH9F7-Cap induced a higher frequency of IFN-γ-secreting CD4+CD8+ T lymphocytes and antibodies against Cap protein than that in the control group. In conclusion, the rAb ZH9F7-Cap system promoted the target of skin cDC1 and cDC2, provoking migration to the regional lymph nodes and inducing a Th1 response, as evidenced by the proliferation of double-positive CD4+CD8+ T cells, which correlates with an enhanced ability to target the cDC1 subset both in vitro and in vivo.

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PURPOSE: During the COVID-19 pandemic, healthcare workers (HCWs) are at a considerable risk of being infected with SARS-CoV-2; among them, HCWs from ophthalmology departments are more prone to develop severe symptoms. In Mexico City, the prevalence of SARS-CoV-2 infection among HCWs is 30%. The present work aims to describe the seroprevalence among HCWs at an Ophthalmological Reference Centre in Mexico City. METHODS: A self-report questionnaire, RT-PCR test and detection of serum IgG/IgM antibodies against SARS-CoV-2 were performed among HCWs at the Institute of Ophthalmology "Conde de Valenciana". RESULTS: A total of 169 HCWs participated in the study. None of the participants declared severe symptoms, and only 15% showed three or more symptoms. The results showed that 32% of the participants were RT-PCR+ (54/169), and 20% (35/169) presented IgG antibodies against SARS-CoV-2. Thirteen percent of the RT-PCR+ subjects were IgG positive, and 7.6% of the RT-PCR- participants were IgG positive. The presence of three or more symptoms correlated with the presence of IgG antibodies, as well as Ct values of < 32 (p < 0,05). CONCLUSION: Most of the HCW cohort showed mild symptoms, and 69% of the RT-PCR+ participants did not show IgG antibodies against SARS-CoV-2. Seroprevalence was significantly associated with the presentation of COVID-19-associated symptoms.

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Recombinant hybrid antibodies are commonly used in antigen-targeting assays to reduce the immunogenic potential associated with using classic mouse antibodies in other species. The DEC205 receptor has become an attractive target due to its effectiveness in activating the immune response and is considered a promising vaccination target. The aim of this study was to produce a fully chimeric mouse x pig anti-porcine DEC205 recombinant antibody (rAb). Based on a mouse anti-porcine DEC205 monoclonal antibody (mAb), we designed and expressed a chimeric mouse x pig rAb using the Expi293f system. The resulting rAb maintained the recognition capacity of the native mouse mAb toward the porcine DEC205 receptor, as evidenced by western blot analysis. By using flow cytometry, we evaluated the ability of the rAb to recognize DEC205+ dendritic cells. In conclusion, the chimeric mouse x pig anti-DEC205 rAb can be used in antigen-targeting assays as a vaccination strategy in pigs.

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