Kinetics of immune responses to SARS-CoV-2 proteins in individuals with varying severity of infection and following a single dose of the AZD1222

To characterize the IgG and IgA responses to different SARS-CoV-2 proteins, we investigated the antibody responses to SARS-CoV-2 following natural infection and following a single dose of AZD1222 (Covishield), in Sri Lankan individuals. The IgG and IgA responses were assessed to S1, S2, RBD, and N proteins in patients at 4 weeks and 12 weeks since the onset of illness or following vaccination. Antibodies to the receptor-binding domain of SARS-CoV-2 wild type (WT), α, β, and λ and ACE2 (Angiotensin Converting Enzyme 2) receptor blocking antibodies were also assessed in these cohorts. For those with mild illness and in vaccines, the IgG responses to S1, S2, RBD, and N protein increased from 4 weeks to 12 weeks, while it remained unchanged in those with moderate/severe illness. In the vaccines, IgG antibodies to the S2 subunit had the highest significant rise (P < 0.0001). Vaccines had several-fold lower IgA antibodies to all the SARS-CoV-2 proteins tested than those with natural infection. At 12 weeks, the haemagglutination test (HAT) titres were significantly lower to the α in vaccines and significantly lower in those with mild illness and in vaccines to β and for λ. No such difference was seen in those with moderate/severe illness. Vaccines had significantly less IgA to SARS-CoV-2, but comparable IgG responses those with natural infection. However, following a single dose vaccines had reduced antibody levels to the VOCs, which further declined with time, suggesting the need to reduce the gap between the two doses, in countries experiencing outbreaks due to VOCs

Kinetics of immune responses to the AZD1222/Covishield vaccine with varying dose intervals in Sri Lankan individuals

Background To understand the kinetics of immune responses with different dosing gaps of the AZD1222 vaccine, we compared antibody and T cell responses in two cohorts with two different dosing gaps. Methods Antibodies to the SARS-CoV-2 virus were assessed in 297 individuals with a dosing gap of 12 weeks, sampled 12 weeks post second dose (cohort 1) and in 77 individuals with a median dosing gap of 21.4 weeks (cohort 2) sampled 6 weeks post second dose. ACE2-blocking antibodies (ACE2-blocking Abs), antibodies to the receptor-binding domain (RBD) of variants of concern (VOC), and ex vivo T cell responses were assessed in a subcohort. Results All individuals (100%) had SARS-CoV-2-specific total antibodies and 94.2% of cohort 1 and 97.1% of cohort 2 had ACE2-blocking Abs. There was no difference in antibody titers or positivity rates in different age groups in both cohorts. The ACE2-blocking Abs (p Conclusions Both dosing schedules resulted in high antibody and T cell responses post vaccination, although those with a longer dosing gap had a higher magnitude of responses, possibly as immune responses were measured 6 weeks post second dose compared to 12 weeks post second dose

Comparison of the immunogenicity of five COVID-19 vaccines in Sri Lanka

To determine the antibody responses elicited by different vaccines against SARS-CoV-2, we compared antibody responses in individuals 3 months post-vaccination in those who had received different vaccines in Sri Lanka. Abs to the receptor binding domain (RBD) of the ancestral (wild type) virus (WT) as well as to variants of concern (VoCs), and ACE2 blocking Abs, were assessed in individuals vaccinated with Moderna (n = 225), Sputnik V (n = 128) or Sputnik light (n = 184) and the results were compared with previously reported data on Sinopharm and AZD1222 vaccinees. A total of 99.5% of Moderna, >94% of AZD1222 or Sputnik V and >70% of Sputnik light, >60% of Sinopharm vaccine recipients, had a positive response to ACE2 blocking antibodies. The ACE2 blocking antibody levels were highest to lowest was Moderna > Sputnik V/AZD1222 (had equal levels) > Sputnik light > Sinopharm. All Moderna recipients had antibodies to the RBD of WT, alpha and beta, while positivity rates for delta variant was 80%. The positivity rates for Sputnik V vaccinees for the WT and VoCs were higher than for AZD1222 vaccinees while those who received Sinopharm had the lowest positivity rates (<16.7%). The total antibodies to the RBD were highest for the Sputnik V and AZD1222 vaccinees. The Moderna vaccine elicited the highest ACE2 blocking antibody levels followed by Sputnik V/AZD1222, while those who received Sinopharm had the lowest levels. These findings highlight the need for further studies to understand the effects on clinical outcomes

Comparison of the kinetics and magnitude of antibody responses to different SARS-CoV-2 proteins in Sinopharm/BBIBP-CorV vaccinees following the BNT162b2 booster or natural infection.

The kinetics and magnitude of antibody responses to different proteins of the SARS-CoV-2 virus in Sinopharm/BBIBP-CorV vaccinees has not been previously studied. Therefore, we investigated antibody responses to different SARS-CoV-2 proteins at 2 weeks, 3 months, and 6 months post-second dose in previously infected (n = 20) and uninfected (n = 20) Sinopharm/BBIBP-CorV vaccinees. The IgG antibodies to the S, S1 and S2 and N were several folds higher in those who had natural infection compared to uninfected individuals at all time points. We then compared the persistence of antibody responses and effect of natural omicron infection or BNT162b2 booster in Sinopharm/BBIBP-CorV vaccinees. We measured the total antibodies to the RBD, ACE2 blocking antibodies and antibody responses to different SARS-CoV-2 proteins in Sinopharm vaccinees at 7 months post second dose, including those who remained uninfected and not boosted (n = 21), or those who had previous infection and who did not obtain the booster (n = 17), those who were not infected, but who received a BNT162b2 booster (n = 30), or those who did not receive the booster but were infected with omicron (n = 29). At 7 months post second dose uninfected (no booster) had the lowest antibody levels to the RBD, while omicron infected vaccinees showed significantly higher anti-RBD antibody levels (p = 0.04) than vaccinees who received the booster. Only 3/21 cohort A (14.3%) had ACE2 blocking antibodies, while higher frequencies were observed in naturally infected individuals (100%), those who received the booster (18/21, 85.7%), and omicron infected individuals (100%). Pre-vaccination, naturally infected had the highest antibody levels to the N protein. These data suggest that those previously infected Sinopharm/BBIBP-CorV vaccinees have a robust antibody response, 7 months post vaccination, while vaccinees who were naturally infected with omicron had a similar immune response to those who received the booster. It will be important to investigate implications for subsequent clinical protection

Clinical and laboratory characteristics of patients with acute dengue infection.

<p>Clinical and laboratory characteristics of patients with acute dengue infection.</p

Distribution of SS responses in those who responded to at least one SS peptide of the 4 dengue virus serotype in patients with acute infection.

<p>A indicates, responses to SS peptides during acute infection and C indicated responses to SS during the convalescent period.</p

Effect of IL-10 blockade on antiviral T cell responses.

<p>A: <i>Ex vivo</i> IFNγ responses to DENV-NS3 overlapping peptides and FEC pool of peptides in patients with acute dengue infection, with and without IL-10 blockade (n = 10). The boxes represent the means and the horizontal bars the SEM. B: <i>Ex vivo</i> IFNγ responses to DENV-NS3 overlapping peptides in a patient with acute dengue viral infection, with and without IL-10 blockade. The left two wells are responses to NS3 without IL-10 blockade and the right two wells are responses to NS3 with IL-10 blockade. C: CD107a expression on CD8+ T cells in patients with acute dengue infection in the absence and the presence of IL-10 blockade (n = 6). The cells were gated on CD3+, CD8+ and Propidium Iodide negative cells. The PBMC were stimulated with DENV-NS3 overlapping peptides. The boxes represent the means and the horizontal bars the SEM. D. A dot plot of CD107a expression on CD3+ T cells in a patient with acute dengue infection. The cells were gated on CD3+ and Propidium Iodide negative cells. The PBMC were stimulated with DENV-NS3 overlapping peptide. The left dot-plot shows the responses toNS3 without IL-10 blockade and the right dot-plot is with IL-10 blockade. E: TNFα production by CD8+ T cells in patients with acute dengue infection in the absence and the presence of IL-10 blockade (n = 6). The cells were gated on CD3+ and CD8+ T cells. The PBMC were stimulated with DENV-NS3 overlapping peptides. The boxes represent the means and the horizontal bars the SEM. F: A dot plot of TNFα production in a patient with acute dengue infection. The cells were gated on CD3+ cells. The PBMC were stimulated with DENV-NS3 overlapping peptides. The left dot-plot shows the responses toNS3 without IL-10 blockade and the right dot-plot is with IL-10 blockade.</p

Serum IL-10 levels and DENV-specific immune responses.

<p>A: Serum IL-10 levels in healthy dengue seropositive individuals (n = 12), patients with acute dengue infection who did not respond to any of the SS peptides (n = 16) and patients who made responses to DENV-SS peptides (n = 10). The boxes represent the means and the horizontal bars the SEM. B: <i>Ex vivo</i> IFNγ ELISpot responses to DENV-NS3 overlapping peptides and FEC pool of peptides, in patients who did not respond to any of the SS peptides (n = 16) and patients who made responses to DENV-SS (10) peptides and in patients with DF (n = 10) and DHF (n = 16). The boxes represent the means and the horizontal bars the SEM. C: Correlation of <i>ex vivo</i> IFNγ ELISpot responses to DENV-NS3 overlapping peptides and serum IL-10 levels in patients with acute dengue infection (n = 23). P = 0.03 and Spearmans R = −0.45.</p

Functionality of Dengue Virus Specific Memory T Cell Responses in Individuals Who Were Hospitalized or Who Had Mild or Subclinical Dengue Infection

<div><p>Background</p><p>Although antibody responses to dengue virus (DENV) in naturally infected individuals have been extensively studied, the functionality of DENV specific memory T cell responses in relation to clinical disease severity is incompletely understood.</p><p>Methodology/Principal findings</p><p>Using ex vivo IFNγ ELISpot assays, and by determining cytokines produced in ELISpot supernatants, we investigated the functionality of DENV-specific memory T cell responses in a large cohort of individuals from Sri Lanka (n=338), who were naturally infected and were either hospitalized due to dengue or had mild or sub clinical dengue infection. We found that T cells of individuals with both past mild or sub clinical dengue infection and who were hospitalized produced multiple cytokines when stimulated with DENV-NS3 peptides. However, while DENV-NS3 specific T cells of those with mild/sub clinical dengue infection were more likely to produce only granzyme B (p=0.02), those who were hospitalized were more likely to produce both TNFα and IFNγ (p=0.03) or TNFα alone.</p><p>We have also investigated the usefulness of a novel T cell based assay, which can be used to determine the past infecting DENV serotype. 92.4% of DENV seropositive individuals responded to at least one DENV serotype of this assay and none of the seronegatives responded. Individuals who were seronegative, but had received the Japanese encephalitis vaccine too made no responses, suggesting that the peptides used in this assay did not cross react with the Japanese encephalitis virus.</p><p>Conclusions/significance</p><p>The types of cytokines produced by DENV-specific memory T cells appear to influence the outcome of clinical disease severity. The novel T cell based assay, is likely to be useful in determining the past infecting DENV serotype in immune-epidemiological studies and also in dengue vaccine trials.</p></div