The SARS‐CoV‐2 virus was detected for the first time in December 2019 in Wuhan, China. Currently, this virus has spread around the world, and new variants have emerged. This new pandemic virus provoked the rapid development of diagnostic tools, therapies and vaccines to control this new disease called COVID‐19. Antibody detection by ELISA has been broadly used to recognize the number of persons infected with this virus or to evaluate the response of vaccinated individuals. As the pandemic spread, new questions arose, such as the prevalence of antibodies after natural infection and the response induced by the different vaccines. In Mexico, as in other countries, mRNA and viral‐vectored vaccines have been widely used among the population. In this work, we developed an indirect ELISA test to evaluate S1 antibodies in convalescent and vaccinated individuals. By using this test, we showed that IgG antibodies against the S1 protein of SARS‐CoV‐2 were detected up to 42 weeks after the onset of the symptoms, in contrast to IgA and IgM, which decreased 14 weeks after the onset of symptoms. The evaluation of the antibody response in individuals vaccinated with Pfizer‐BioNTech and CanSinoBio vaccines showed no differences 2 weeks after vaccination. However, after completing the two doses of Pfizer‐BioNTech and the one dose of CanSinoBio, a significantly higher response of IgG antibodies was observed in persons vaccinated with Pfizer‐BioNTech than in those vaccinated with CanSinoBio. In conclusion, these results confirm that after natural infection with SARS‐CoV‐2, it is possible to detect antibodies for up to 10 months. Additionally, our results showed that one dose of the CanSinoBio vaccine induces a lower response of IgG antibodies than that induced by the complete scheme of the Pfizer‐BioNTech vaccine.

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.

No abstract

Introduction: The current coronavirus disease- 2019 (COVID-19) pandemic has caused a sudden increase in pneumonia cases, with a case-fatality rate of 10.9% in Mexico. Two inpatient groups have been defined, with different clinical evolution: cases of severe pneumonia and those with life-threatening disease (Acute respiratory distress syndrome [ARDS], invasive mechanical ventilation [IMV] requirement, and multiorgan involvement). Currently, there is no effective treatment. Convalescent plasma (CP) has been used to treat another viral infections and outbreaks since the last century. The rationale is that neutralizing antibodies contained in CP suppress viremia and produce immunoregulation. However, an established therapeutic dose during this pandemic is lacking. Aim: To evaluate in a phase I trial the minimum effective dose of CP in severe and life-threatening disease patients and then carry out a phase II study to establish the effectiveness (overall survival at 30 days) comparing it with a non-randomized control group. Methods and design. Our study is an open-label, multicenter, non-randomized and started in May, 2020 and was approved by the ethics committee at HGE & HCN Pemex; respectively. CP donor selection: pre-donors who were infected by SARS-CoV-2 were evaluated on +30 day by serum titration (≥1:320 IgG antibody); then connected to apheresis machine to obtain 600 ml of CP that were fractionated in 200 ml bags and stored. Patients: Two groups were formed: severe and life-threating disease. CP was offered to patients who were admitted on two hospitals. Patients should meet the following criteria: SARS-CoV-2 positive for qRT- PCR, respiratory rate> 30 per minute or Kirby index <300 or IMV requirement; be older than 18 years; and sign the informed consent. Statistics: For demographic variables, the differences were evaluated with parametric or non-parametric analysis. For survival, Kaplan Meier curves were assessed for each group. A p value <0.05 was considered significant. Outcomes: A total of 110 CP bags have been transfused. The median serum IgG antibody titers were 1: 960. Dosing, phase 1. Severe group (n=14): 71% received two CP bags (400 ml) and 29% three CP bags (600 mL). Life-threatening disease group (n=10): 60% received 4 CP bags (800 ml) and 40% 3 CP bags (600 ml). Dose was established at 400 ml for the severe group and 800 ml for the life-threatening group. Security: CP infusions were well tolerated, with only 3 adverse events (2.72%) reported: one case of transfusion associated circulatory overload (TACO) that resolved with the use of loop diuretics as a serious adverse event; one fever episode (grade 1) and one case of rash (grade 1) after CP infusion. Phase II: The calculated n to be included in each arm (severe vs. life-threatening disease) is 68 and 52 patients, respectively. So far, we have included a total of 42 patients treated with CP. This entire cohort was compared with a historic group of COVID-19 patients who received other treatment strategies. Clinical characteristics on both plasma (PG) and control group (CG) are presented in table 1. We observed statistically significant differences on smoking habit, D-Dimer levels and ARDS severity between groups. The median overall follow- up was 24 days [PG 28 days vs. CG 21.5 days]. Overall Survival (OS) between PG and CG was 74% vs. 54% at 30-days respectively [HR=0.43 (C.I.95%=0.23 to 0.91, p=0.021); figure 1]. We analyzed OS by group stratification: COVID-19 severity (severe disease vs. life-threatening disease) and ARDS severity. We found no difference in OS between severe disease-PG and severe disease-CG; but we observed an OS difference between life-threatening-PG and life-threatening-CG [32% vs. 5.8% at 30-days; p=0.003]. ARDS-PG vs. ARDS-CG showed OS differences in moderate [59% vs. 25% at 30 days; p=0.01, respectively] and severe ARDS [63% vs. 0%; p=0.001, respectively]; however, there was not statistically significant difference between mild ARDS-PG and CG groups [89% vs. 86%; p=0.85, respectively]. Conclusion: This is the first phase I trial aiming to establish an effective CP dose for COVID-19 patients, at least in México. For severe and life-threatening disease, 2 and 4 CP bags were suggested. This treatment was secure, with <3% of adverse events reported. OS could be modified using certain doses based on disease severity and pa02/Fi02 index. We will continue to include patients until the calculated n is reached. Disclosures Villela: Roche: Other: advisory board, Speakers Bureau; amgen: Speakers Bureau.

The SARS-CoV-2 virus was detected for the first time in December 2019 in Wuhan, China. Currently, this virus has spread around the world, and new variants have emerged. This new pandemic virus provoked the rapid development of diagnostic tools, therapies and vaccines to control this new disease called COVID-19. Antibody detection by ELISA has been broadly used to recognize the number of persons infected with this virus or to evaluate the response of vaccinated individuals. As the pandemic spread, new questions arose, such as the prevalence of antibodies after natural infection and the response induced by the different vaccines. In Mexico, as in other countries, mRNA and viral-vectored vaccines have been widely used among the population. In this work, we developed an indirect ELISA test to evaluate S1 antibodies in convalescent and vaccinated individuals. By using this test, we showed that IgG antibodies against the S1 protein of SARS-CoV-2 were detected up to 42 weeks after the onset of the symptoms, in contrast to IgA and IgM, which decreased 14 weeks after the onset of symptoms. The evaluation of the antibody response in individuals vaccinated with Pfizer-BioNTech and CanSinoBio vaccines showed no differences two weeks after vaccination. However, after completing the two doses of Pfizer-BioNTech and the one dose of CanSinoBio, a significantly higher response of IgG antibodies was observed in persons vaccinated with Pfizer-BioNTech than in those vaccinated with CanSinoBio. In conclusion, these results confirm that after natural infection with SARS-CoV-2, it is possible to detect antibodies for up to ten months. Additionally, our results showed that one dose of the CanSinoBio vaccine induces a lower response of IgG antibodies than that induced by the complete scheme of the Pfizer-BioNTech vaccine.