Kinetics of cellular and humoral responses to third BNT162B2 COVID-19 vaccine over six months in heart transplant recipients - implications for the omicron variant

BNT162b2-vaccine-induced neutralization responses are immune correlates of clinical protection against SARS-CoV-2 in heart transplant recipients

BACKGROUND

Defining immune correlates of protection against COVID-19 is pivotal for optimizing the use of COVID-19 vaccines, predicting the impact of novel variants on clinical outcomes, and advancing the development of immunotherapies and next-generation vaccines. We aimed to identify vaccine-induced immune correlates of protection against COVID-19-related hospitalizations in a highly vaccinated heart transplant (HT) cohort.

METHODS

In a case-control study of HT recipients vaccinated with the BNT162b2 vaccine, patients were prospectively assessed for vaccine-induced neutralization of the wild-type virus, and the Delta and Omicron BA.1, BA.2, BA.4, and BA.5 variants. Comparative analyses with controls were conducted to identify correlates of protection against COVID-19 hospitalization. ROC analyses were performed. Primary outcomes were COVID-19 hospitalizations and severity of SARS-CoV-2 breakthrough infection.

RESULTS

The study cohort comprised 59 HT recipients aged 58 (49,65) years with breakthrough infections after three or four monovalent BNT162b2 doses; 41 (69.5%) were men. Thirty-six (61%) patients with COVID-19 were hospitalized; most cases were non-severe (58, 98%). For hospitalized (vs. non-hospitalized) COVID-19 patients, vaccine-induced neutralization titers were significantly lower against all SARS-CoV-2 variants (p < .005). Vaccine-induced neutralization of the wild-type virus and delta and omicron BA.1, BA.2, BA.4, and BA.5 variants was associated with a reduced risk for COVID-19-related hospitalization. The optimal neutralization titer thresholds that were predictive of COVID-19 hospitalizations were 96 (wild-type), 48 (delta), 12 (BA.1), 96 (BA.2), 96 (BA.4), and 48 (BA.5).

CONCLUSIONS

BNT162b2-vaccine-induced neutralization responses are immune correlates of protection and confer clinical protection against COVID-19 hospitalizations.

Humoral and T-cell-mediated immunity to SARS-CoV-2 vaccination in patients with liver disease and transplant recipients

BACKGROUND

SARS-CoV-2 vaccination induces a varied immune response among persons with chronic liver disease (CLD) and solid organ transplant recipients (SOTRs). We aimed to evaluate the humoral and T-cell-mediated immune responses to SARS-CoV-2 vaccination in these groups.

METHODS

Blood samples were collected following the completion of a standard SARS-CoV-2 vaccination (2 doses of either BNT162b2 or mRNA-12732), and a subset of patients had a blood sample collected after a single mRNA booster vaccine. Three separate methods were utilized to determine immune responses, including an anti-spike protein antibody titer, neutralizing antibody capacity, and T-cell-mediated immunity.

RESULTS

The cohort included 24 patients with chronic liver disease, 27 SOTRs, and 9 controls. Patients with chronic liver disease had similar immune responses to the wild-type SARS-CoV-2 compared with controls following a standard vaccine regimen and single booster vaccine. SOTRs had significantly lower anti-S1 protein antibodies (p < 0.001), neutralizing capacity (p < 0.001), and T-cell-mediated immunity response (p = 0.021) to the wild-type SARS-CoV-2 compared with controls following a standard vaccine regimen. Following a single booster vaccine, immune responses across groups were not significantly different but numerically lower in SOTRs. The neutralization capacity of the B.1.1.529 Omicron variant was not significantly different between groups after a standard vaccine regimen (p = 0.87) and was significantly lower in the SOTR group when compared with controls after a single booster vaccine (p = 0.048).

CONCLUSION

The immunogenicity of the SARS-CoV-2 vaccine is complex and multifactorial. Ongoing and longitudinal evaluation of SARS-CoV-2 humoral and cellular responses is valuable and necessary to allow frequent re-evaluation of these patient populations.

Effect of a Fourth Dose of mRNA Vaccine and of Immunosuppression in Preventing SARS-CoV-2 Breakthrough Infections in Heart Transplant Patients

Patients with heart transplantation (HT) have an increased risk of COVID-19 disease and the efficacy of vaccines on antibody induction is lower, even after three or four doses. The aim of our study was to assess the efficacy of four doses on infections and their interplay with immunosuppression. We included in this retrospective study all adult HT patients (12/21–11/22) without prior infection receiving a third or fourth dose of mRNA vaccine. The endpoints were infections and the combined incidence of ICU hospitalizations/death after the last dose (6-month survival rate). Among 268 patients, 62 had an infection, and 27.3% received four doses. Following multivariate analysis, three vs. four doses, mycophenolate (MMF) therapy, and HT < 5 years were associated with an increased risk of infection. MMF ≥ 2000 mg/day independently predicted infection, together with the other variables, and was associated with ICU hospitalization/death. Patients on MMF had lower levels of anti-RBD antibodies, and a positive antibody response after the third dose was associated with a lower probability of infection. In HT patients, a fourth dose of vaccine against SARS-CoV-2 reduces the risk of infection at six months. Mycophenolate, particularly at high doses, reduces the clinical effectiveness of the fourth dose and the antibody response to the vaccine.

Humoral and T-Cell Mediated Response after the Third Dose of mRNA Vaccines in Patients with Systemic Lupus Erythematosus on Belimumab

OBJECTIVE

To evaluate humoral and T-cell cellular-mediated immune response after three doses of SARS-CoV-2 mRNA vaccines in patients with systemic lupus erythematosus (SLE) under Belimumab.

PATIENTS AND METHODS

12 patients on Belimumab and 13 age-matched healthy volunteers were recruited. Patients were in remission or in low disease activity, and they were taking no corticosteroids or only low doses. None of the patients and controls had detectable anti-SARS-CoV-2 antibodies due to previous exposure to the virus. All the patients received three doses of mRNA anti-SARS-CoV-2 vaccines and the humoral and cellular-mediated response were tested 4 weeks after the second dose (T0), 6 months after the second dose (T1) and 4 weeks after the third dose (T2). Comparison with the control group was performed at time T0 (i.e., 4 weeks after the second dose). Total anti-SARS-CoV-2 RBD antibodies were analyzed using a diagnostic assay, while cellular-mediated response was evaluated using the interferon-gamma release assay (IGRA).

RESULTS

A humoral response was documented in all the patients at T0 (median 459; IQR 225.25-758.5), but the antibody titer significantly declined from T0 to T1 (median 44.7; IQR: 30.3-202; p = 0.0066). At T2, the antibody titer significantly increased from T1 (median 2500; IQR: 2500-2500), and it was not different from T0 (respectively p < 0.0001, p = 0.66). Cellular-mediated response significantly declined from T0 to T1 (p = 0.003) but not from T0 to T2 (p = 0.3). No differences were found between patients and controls at T0 as regards both humoral and cellular responses (p = 1.0 and p = 0.09 for humoral and cellular responses, respectively).

CONCLUSION

The third dose of mRNA COVID-19 vaccine can restore both humoral and cellular immune response in SLE patients on Belimumab.

Shared 6mer Peptides of Human and Omicron (21K and 21L) at SARS-CoV-2 Mutation Sites

We investigated the short sequences involving Omicron 21K and Omicron 21L variants to reveal any possible molecular mimicry-associated autoimmunity risks and changes in those. We first identified common 6mers of the viral and human protein sequences present for both the mutant (Omicron) and nonmutant (SARS-CoV-2) versions of the same viral sequence and then predicted the binding affinities of those sequences to the HLA supertype representatives. We evaluated change in the potential autoimmunity risk, through comparative assessment of the nonmutant and mutant viral sequences and their similar human peptides with common 6mers and affinities to the same HLA allele. This change is the lost and the new, or de novo, autoimmunity risk, associated with the mutations in the Omicron 21K and Omicron 21L variants. Accordingly, e.g., the affinity of virus-similar sequences of the Ig heavy chain junction regions shifted from the HLA-B*15:01 to the HLA-A*01:01 allele at the mutant sequences. Additionally, peptides of different human proteins sharing 6mers with SARS-CoV-2 proteins at the mutation sites of interest and with affinities to the HLA-B*07:02 allele, such as the respective SARS-CoV-2 sequences, were lost. Among all, any possible molecular mimicry-associated novel risk appeared to be prominent in HLA-A*24:02 and HLA-B*27:05 serotypes upon infection with Omicron 21L. Associated disease, pathway, and tissue expression data supported possible new risks for the HLA-B*27:05 and HLA-A*01:01 serotypes, while the risks for the HLA-B*07:02 serotypes could have been lost or diminished, and those for the HLA-A*03:01 serotypes could have been retained, for the individuals infected with Omicron variants under study. These are likely to affect the complications related to cross-reactions influencing the relevant HLA serotypes upon infection with Omicron 21K and Omicron 21L.