Long-term adaptive response in COVID-19 vaccine recipients and the effect of a booster dose.

We examined the immune response in subjects previously infected with SARS-CoV2 and infection-naïve 9 months after primary 2-dose COVID-19 mRNA vaccination and 3 months after the booster dose in a longitudinal cohort of healthcare workers. Nine months after primary vaccination, previously infected subjects exhibited higher residual antibody levels, with significant neutralizing activity against distinct variants compared to infection-naïve subjects. The higher humoral response was associated with higher levels of receptor binding domain (RBD)-specific IgG+ and IgA+ memory B cells. The booster dose increased neither neutralizing activity, nor the B and T cell frequencies. Conversely, infection-naïve subjects needed the booster to achieve comparable levels of neutralizing antibodies as those found in previously infected subjects after primary vaccination. The neutralizing titer correlated with anti-RBD IFNγ producing T cells, in the face of sustained B cell response. Notably, pre-pandemic samples showed high Omicron cross-reactivity. These data show the importance of the booster dose in reinforcing immunological memory and increasing circulating antibodies in infection-naïve subjects.

Chemokines induced by PEDV infection and chemotactic effects on monocyte, T and B cells.

Porcine epidemic diarrhea virus (PEDV) is a re-emerging pathogen that causes severe economic loss in the pig industry. The host's innate immune system is the first line of defense on virus invasion of the small intestinal epithelial cells. Chemokines, as a part of the innate immune system, play an important role in host immunity against infection, however, and their expression and chemotactic effect on key immune cells in PEDV infection remains unclear. In this study, cDNA microarray was firstly performed to analyzed ileum tissue of piglets on the third day after PEDV infection. The differentially expressed genes mainly involved in multiple biological processes, chemokine signaling pathway and cytokine receptor interaction signaling pathway had the highest enrichment according to GO and KEGG enrichment analysis. The expression levels of chemokines MCP-1, MIP-1ß, IL-8, CXCL9, CXCL10 and CXCL13 in ileum of PEDV- infected piglets were significantly higher than those in the control group. The expression of chemokines in vivo experiment was further verified by RT-qPCR and ELISA using PEDV-infected IPEC-J2 cells. The results showed that the PEDV-infected IPEC-J2 cells had significantly induced protein expression of MCP-1, MIP-1ß, IL-8, CXCL9, CXCL-10 and CXCL13. These results indicated that the changes of chemokines expressed in the ileum of piglets (in vivo) were consistent with those in IPEC-J2 cells (in vitro) after PEDV infection. Finally, the role of chemokines in immune cell migration during PEDV infection was illustrated by siRNA-mediated knock down method and the co-culture model of IPEC-J2 cells with peripheral blood leukocyte cells (PBLCs). The FACS analysis showed that MCP-1 induced by PEDV infection played a chemotactic effect on CD14+ cells, CXCL9 on CD3+CD4-CD8-γδ T, CD3+CD4-CD8+ Tc, CD3+CD4+CD8- Th and CD3+CD4+CD8+ Tm subsets, and CXCL13 on CD19+ B cells. Collectively, our findings first indicate that PEDV-induced chemokines MCP-1, CXCL-9 and CXCL-13 attracted CD14+ cells, T cells and B cells, respectively. These results provide a theoretical basis for studying the mechanism of anti-PEDV infection in piglets.

Developing an Effective Peptide-Based Vaccine for COVID-19: Preliminary Studies in Mice Models.

Coronavirus disease 2019 (COVID-19) has caused massive health and economic disasters worldwide. Although several vaccines have effectively slowed the spread of the virus, their long-term protection and effectiveness against viral variants are still uncertain. To address these potential shortcomings, this study proposes a peptide-based vaccine to prevent COVID-19. A total of 15 B cell epitopes of the wild-type severe acute respiratory coronavirus 2 (SARS-CoV-2) spike (S) protein were selected, and their HLA affinities predicted in silico. Peptides were divided into two groups and tested in C57BL/6 mice with either QS21 or Al(OH)3 as the adjuvant. Our results demonstrated that the peptide-based vaccine stimulated high and durable antibody responses in mice, with the T and B cell responses differing based on the type of adjuvant employed. Using epitope mapping, we showed that our peptide-based vaccine produced antibody patterns similar to those in COVID-19 convalescent individuals. Moreover, plasma from vaccinated mice and recovered COVID-19 humans had the same neutralizing activity when tested with a pseudo particle assay. Our data indicate that this adjuvant peptide-based vaccine can generate sustainable and effective B and T cell responses. Thus, we believe that our peptide-based vaccine can be a safe and effective vaccine against COVID-19, particularly because of the flexibility of including new peptides to prevent emerging SARS-CoV-2 variants and avoiding unwanted autoimmune responses.

SARS-CoV-2-Associated T-Cell Responses in the Presence of Humoral Immunodeficiency.

We report perhaps the most comprehensive study of subsets of CD4+ and CD8+ and subsets of B cells in a mild symptomatic SARS-CoV-2+ immunocompetent patient and a common variable immunodeficiency disease (CVID) patient who had normal absolute lymphocyte counts and remained negative for SARS-CoV-2 IgG antibodies. Naïve (TN), central memory (TCM), effector memory (TEM), and terminally differentiated effector memory (TEMRA) subsets of CD4+ and CD8+ T cells, subsets of T follicular helper cells (cTFH, TFH1, TFH2, TFH17, TFH1/TFH17, and TFR), CD4 Treg, CD8 Treg, mature B cells, transitional B cells, marginal zone B cells, germinal center (GC) B cells, CD21low B cells, antibody-secreting cells (plasmablasts), and Breg cells were examined in patients and age-matched controls with appropriate monoclonal antibodies and isotype controls using multicolor flow cytometry. Different patterns of abnormalities (often contrasting) were observed in the subsets of CD4+ T, CD8+ T, B-cell subsets, and regulatory lymphocytes among the immunocompetent patient and CVID patient as compared to corresponding healthy controls. Furthermore, when data were analyzed between the 2 patients, the immunocompetent patient demonstrated greater changes in various subsets as compared to the CVID patient. These data demonstrate different immunological responses to SARS-CoV-2 infection in an immunocompetent patient and the CVID patient. A marked decrease in GC B cells and plasmablasts may be responsible for failure to make SARS-CoV-2 antibodies. The lack of SARS-CoV-2 antibodies with mild clinical disease suggests an important role of T-cell response in defense against SARS-CoV-2 infection.