COVID-19 neutralizing antibodies predict disease severity and survival

Immunogenicity Assessment of the SARS-CoV-2 Protein Subunit Recombinant Vaccine (CoV2-IB 0322) in a Substudy of a Phase 3 Trial in Indonesia

BACKGROUND

COVID-19 is one of the most devastating pandemics of the 21st century. Vaccination is one of the most effective prevention methods in combating COVID-19, and one type of vaccine being developed was the protein subunit recombinant vaccine. We evaluated the efficacy of the CoV2-IB 0322 vaccine in Depok, Indonesia.

METHODS

This study aimed to assess the humoral and cellular immune response of the CoV2-IB 0322 vaccine compared to an active control vaccine (COVOVAX™ Vaccine). A total of 120 subjects were enrolled and randomized into two groups, with 60 subjects in each group. Participants received either two doses of the CoV2-IB 0322 vaccine or two doses of the control vaccine with a 28-day interval between doses. Safety assessments were conducted through onsite monitoring and participant-reported adverse events. Immunogenicity was evaluated by measuring IgG anti-RBD SARS-CoV-2 and IgG-neutralizing antibodies. Cellular immunity was assessed by specific T-cell responses. Whole blood samples were collected at baseline, 14 days, 6 months, and 12 months after the second dose for cellular immunity evaluation.

RESULTS

Both vaccines showed high seropositive rates, with neutralizing antibody and IgG titers peaking 14 days after the second dose and declining by 12 months. The seroconversion rate of anti-S IgG was 100% in both groups, but the rate of neutralizing antibody seroconversion was lower in the CoV2-IB 0322 vaccine group at 14 days after the second dose (p = 0.004). The CoV2-IB 0322 vaccine showed higher IgG GMT levels 6 and 12 months after the second dose (p < 0.001 and p = 0.01). T-cell responses, evaluated by IFN-γ, IL-2, and IL-4 production by CD4+ and CD8+ T-cells, showed similar results without significant differences between both groups, except for %IL-2/CD4+ cells 6 months after the second dose (p = 0.038).

CONCLUSION

Both vaccines showed comparable B- and T-cell immunological response that diminish over time.

mRNA vaccine-a desirable therapeutic strategy for surmounting COVID-19 pandemic

As an acute respiratory infectious disease, COVID-19 threatens the safety of global public health. Given the current lack of specific treatment against this disease, research and development of vaccines have become sharp weapons for overcoming the pandemic. mRNA vaccines have become the lead in COVID-19 vaccination strategies due to their advantages, such as rapid industrial production and efficacy. A total of 137 COVID-19 vaccines have entered the clinical trial stage, among which 23 are mRNA vaccines, accounting for 17% of the total vaccines. Herein, we summarize the research and developmental processes of mRNA vaccines as well as the approach for protecting the human body against infection. Focusing on the latest clinical trial data of two COVID-19 mRNA vaccines from Pfizer and Modena, we discuss their effectiveness and safety. Finally, we analyze the challenges and problems that mRNA vaccines face in controlling the COVID-19 pandemic.

Clinical and epidemiological features of patients with COVID-19 reinfection: a systematic review

Recurrent positivity in a patient with COVID-19 may be due to various reasons, not necessarily reinfection. There is concern about the occurrence frequency of reinfection. Five databases and a preprint/preprint repository were searched. All case reports, case series, and observational studies were included. Bias was assessed for each study with the Newcastle-Ottawa Scale tool and reported according to the preferred reporting items for systematic reviews and meta-analyses (PRISMA-2020). After eligibility, 77 studies were included for qualitative synthesis (52 case reports, 21 case series, and four case-controls; 1131 patients included). Of these, 16 studies described a second contact with the SARS-CoV-2 positive case, five studies described healthcare profession-related infection, ten studies described that the source of reinfection was likely to be from the community, one study described travel-related infection, nine studies described vulnerability-related infection due to comorbidity. The mean number of days from discharge or negative test to reinfection ranged from 23.3 to 57.6 days across the different included studies. The risk of bias for all case report/series studies was moderate/high. For observational studies, the risk of bias was low. Reinfection of patients with COVID-19 occurs between the first and second month after the first infection, but beyond, and 90 days have been proposed as a point to begin to consider it. The main factor for reinfection is contact with COVID-19 positive cases.

Immunity to SARS-CoV-2: Lessons Learned

In the year since the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and with understanding of the etiology of the coronavirus disease 2019 (COVID-19) pandemic, it has become clear that most infected individuals achieve some form of immunity against the virus with relatively few reported reinfections. A number of vaccines have already achieved emergency use authorization based on data from large phase 3 field efficacy clinical trials. However, our knowledge about the extent and durability of this immunity, and the breadth of vaccine coverage against SARS-CoV-2 variants is still evolving. In this narrative review, we summarize the latest and rapidly developing understanding of immunity to SARS-CoV-2 infection, including what we have learned about the key antigens of SARS-CoV-2 (i.e., the spike protein and its receptor-binding domain), their importance in vaccine development, the immediate immune response to SARS-CoV-2, breadth of coverage of emerging SARS-CoV-2 variants, contributions of preexisting immunity to related coronaviruses, and duration of immunity. We also discuss lessons from newer approaches, such as systems serology, that provide insights into molecular and cellular immune responses elicited and how they relate to the trajectory of infection, and potentially inform immune correlates of protection. We also briefly examine the limited research literature on immune responses in special populations, such as pregnant women and children.

Functional importance of the D614G mutation in the SARS-CoV-2 spike protein

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an enveloped virus which binds its cellular receptor angiotensin-converting enzyme 2 (ACE2) and enters hosts cells through the action of its spike (S) glycoprotein displayed on the surface of the virion. Compared to the reference strain of SARS-CoV-2, the majority of currently circulating isolates possess an S protein variant characterized by an aspartic acid-to-glycine substitution at amino acid position 614 (D614G). Residue 614 lies outside the receptor binding domain (RBD) and the mutation does not alter the affinity of monomeric S protein for ACE2. However, S(G614), compared to S(D614), mediates more efficient ACE2-mediated transduction of cells by S-pseudotyped vectors and more efficient infection of cells and animals by live SARS-CoV-2. This review summarizes and synthesizes the epidemiological and functional observations of the D614G spike mutation, with focus on the biochemical and cell-biological impact of this mutation and its consequences for S protein function. We further discuss the significance of these recent findings in the context of the current global pandemic.

Enhanced SARS-CoV-2 neutralization by dimeric IgA

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes coronavirus disease 2019 (COVID-19), primarily infects cells at mucosal surfaces. Serum neutralizing antibody responses are variable and generally low in individuals that suffer mild forms of COVID-19. Although potent immunoglobulin G (IgG) antibodies can neutralize the virus, less is known about secretory antibodies such as IgA that might affect the initial viral spread and transmissibility from the mucosa. Here, we characterize the IgA response to SARS-CoV-2 in a cohort of 149 convalescent individuals after diagnosis with COVID-19. IgA responses in plasma generally correlated with IgG responses. Furthermore, clones of IgM-, IgG-, and IgA-producing B cells were derived from common progenitor cells. Plasma IgA monomers specific to SARS-CoV-2 proteins were demonstrated to be twofold less potent than IgG equivalents. However, IgA dimers, the primary form of antibody in the nasopharynx, were, on average, 15 times more potent than IgA monomers against the same target. Thus, dimeric IgA responses may be particularly valuable for protection against SARS-CoV-2 and for vaccine efficacy.

Saliva viral load is a dynamic unifying correlate of COVID-19 severity and mortality

While several clinical and immunological parameters correlate with disease severity and mortality in SARS-CoV-2 infection, work remains in identifying unifying correlates of coronavirus disease 2019 (COVID-19) that can be used to guide clinical practice. Here, we examine saliva and nasopharyngeal (NP) viral load over time and correlate them with patient demographics, and cellular and immune profiling. We found that saliva viral load was significantly higher in those with COVID-19 risk factors; that it correlated with increasing levels of disease severity and showed a superior ability over nasopharyngeal viral load as a predictor of mortality over time (AUC=0.90). A comprehensive analysis of immune factors and cell subsets revealed strong predictors of high and low saliva viral load, which were associated with increased disease severity or better overall outcomes, respectively. Saliva viral load was positively associated with many known COVID-19 inflammatory markers such as IL-6, IL-18, IL-10, and CXCL10, as well as type 1 immune response cytokines. Higher saliva viral loads strongly correlated with the progressive depletion of platelets, lymphocytes, and effector T cell subsets including circulating follicular CD4 T cells (cTfh). Anti-spike (S) and anti-receptor binding domain (RBD) IgG levels were negatively correlated with saliva viral load showing a strong temporal association that could help distinguish severity and mortality in COVID-19. Finally, patients with fatal COVID-19 exhibited higher viral loads, which correlated with the depletion of cTfh cells, and lower production of anti-RBD and anti-S IgG levels. Together these results demonstrated that viral load - as measured by saliva but not nasopharyngeal - is a dynamic unifying correlate of disease presentation, severity, and mortality over time.

Treatment of Severe COVID-19 with Convalescent Plasma in the Bronx, NYC

Convalescent plasma with severe acute respiratory disease coronavirus 2 (SARS-CoV-2) antibodies (CCP) may hold promise as treatment for Coronavirus Disease 2019 (COVID-19). We compared the mortality and clinical outcome of patients with COVID-19 who received 200mL of CCP with a Spike protein IgG titer ≥1:2,430 (median 1:47,385) within 72 hours of admission to propensity score-matched controls cared for at a medical center in the Bronx, between April 13 to May 4, 2020. Matching criteria for controls were age, sex, body mass index, race, ethnicity, comorbidities, week of admission, oxygen requirement, D-dimer, lymphocyte counts, corticosteroids, and anticoagulation use. There was no difference in mortality or oxygenation between CCP recipients and controls at day 28. When stratified by age, compared to matched controls, CCP recipients <65 years had 4-fold lower mortality and 4-fold lower deterioration in oxygenation or mortality at day 28. For CCP recipients, pre-transfusion Spike protein IgG, IgM and IgA titers were associated with mortality at day 28 in univariate analyses. No adverse effects of CCP were observed. Our results suggest CCP may be beneficial for hospitalized patients <65 years, but data from controlled trials is needed to validate this finding and establish the effect of ageing on CCP efficacy.