Dynamics of Humoral and Cellular Responses in Renal Transplant Recipients Receiving 3 Doses of SARS-CoV-2 mRNA Vaccine

Measures to Increase Immunogenicity of SARS-CoV-2 Vaccines in Solid Organ Transplant Recipients: A Narrative Review

Purpose of review: To review the data on the immunogenicity of COVID-19 vaccines, administered by different strategies, in solid organ transplant recipients (SOTRs). Recent findings: COVID-19 booster vaccines were given to SOTRs as a widespread practice in many transplant centers, mostly as the third and/or fourth dose in an extended vaccine series, with a significantly improved humoral response compared with the initial two-dose scheme. However, one-third of SOTRs remained unresponsive, despite these boosters. Next steps: Vaccination with standard dosing remains the most feasible strategy for attaining protection against COVID-19. Additional booster doses and temporarily holding or reducing mycophenolate mofetil/mycophenolic acid may provide immunogenicity to vaccines, according to recent studies demonstrating some efficacy with these measures. Preexposure prophylaxis with monoclonal antibodies showed benefit in immunocompromised patients but is no longer recommended by the National Institutes of Health (NIH) due to diminished efficacy against Omicron and recent variants. Screening for the presence and titers of SARS-CoV-2-specific antibodies in SOTRs is not recommended in most clinical settings. T cell-based techniques are needed to evaluate vaccine efficacy and risk of infection. As SARS-CoV-2 continues to evolve, new vaccines based on conservative protein component/complexes of the COVID virus, in addition to its spike protein, are warranted to offer prolonged protection.

Cellular immune response of SARS-CoV-2 vaccination in kidney transplant recipients: a systematic review and meta-analysis

Background

Evidence has demonstrated inferior humoral immune responses after SARS-CoV-2 vaccination in kidney transplant recipients compared to the general population. However, data on cellular immune responses in this population have not been established.

Methods

We searched the MEDLINE, Scopus, and Cochrane databases and included studies reporting cellular immune response rates in kidney transplant recipients after receiving SARS-CoV-2 vaccines. Studies that reported factors associated with cellular immune responders or non-responders were also included (PROSPERO: CRD42022375544).

Results

From a total of 1,494 articles searched, 53 articles were included in the meta-analysis. In all, 21 studies assessed cellular immune response by interferon-γ enzyme-linked immunosorbent spot (IFN-γ ELISPOT), 22 studies used interferon-γ release assay (IGRA), and 10 studies used flow cytometric analysis. The pooled response rate after two doses (standard regimen) and three doses of vaccination was 47.5% (95%CI 38.4-56.7%) and 69.1% (95%CI 56.3-80.6%) from IFN-γ ELISPOT, 25.8% (95%CI 19.7-32.4%) and 14.7% (95%CI 8.5-22.2%) from IGRA, and 73.7% (95%CI 55.2-88.8%) and 86.5% (95%CI 75.3-94.9%) from flow cytometry, respectively. Recipients with seroconversion were associated with a higher chance of having cellular immune response (OR 2.58; 95%CI 1.89-3.54). Cellular immune response in kidney transplant recipients was lower than in dialysis patients (OR 0.24; 95%CI 0.16-0.34) and the general population (OR 0.10; 95%CI 0.07-0.14). Age and immunosuppressants containing tacrolimus or corticosteroid were associated with inferior cellular immune response.

Conclusion

Cellular immune response after SARS-CoV-2 vaccination in kidney transplant recipients was lower than in dialysis patients and the general population. Age, tacrolimus, and corticosteroid were associated with poor response. Cellular immune response should also be prioritized in vaccination studies.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42022375544.

Case Report: Kinetics and durability of humoral and cellular response of SARS-CoV-2 messenger RNA vaccine in a lung and kidney transplant recipient

We present a case report of a 63-year-old female health care worker who is 15 years status post double lung transplant and six years status post living related donor kidney transplant who is healthy on a chronic immunosuppression regimen including prednisone, mycophenolate, and tacrolimus who received the SARS-CoV-2 mRNA vaccine (Pfizer-BioNTech BNT162b2) primary series and had poor initial humoral response to the COVID-19 mRNA vaccine, then demonstrated a robust, sustained immune response against S1 and S2 antigens for over seven months after receiving the recommended vaccine doses, including booster dose, without developing COVID-19 or other serious adverse events. Her immune response to vaccination indicates effective formation of anti-spike T cell memory despite chronic immunosuppression. This case report provides a comprehensive characterization of her immune response to this SARS-CoV-2 vaccination series. As vaccine effectiveness data is updated, and as better understanding of immune response including hybrid immunity emerges, these findings may reassure that recipients of SOTs may be capable of durable immune responses to emerging variants of SARS-CoV-2.

Kinetics of humoral immune response and severity of infection after three doses of SARS-CoV-2 mRNA vaccine in a large cohort of kidney transplant recipients

BACKGROUND

COVID-19 in kidney transplant recipients is associated with high morbidity and mortality. In this study we aimed to evaluate: (i) the seroconversion rate after BNT162b2 (Pfizer-BioNTech) SARS-CoV-2 vaccine, (ii) factors associated with humoral response, (iii) clinical outcome of COVID-19 in kidney transplanted patients.

METHODS

We enrolled a cohort of 743 kidney transplant recipients followed up from March 2020 until April 2022. A subset of 336 patients, who received three-doses of SARS-CoV-2 vaccine, was analyzed in terms of kinetics of humoral immune response and compared to a control group of 94 healthcare workers. Antibody response was tested before vaccination (T₀), 15 and 90 days after the second dose (T₁ and T₂), on the day of the third dose (T₃) and one month after the third dose (T₄).

RESULTS

We observed that 66 out of 743 subjects had COVID-19 infection pre-vaccination: 65.2% had severe symptoms, 27.3% were hospitalized (9 deaths), none were asymptomatic. After three doses, 51 patients had COVID-19 infection, 60.8% were asymptomatic, 27.5% reported mild symptoms, 3.9% showed severe symptoms, 7.8% were hospitalized (2 deaths). In the subset of 336 vaccinated patients, an antibody level > 0.8 U/ml was detected at T₁, that increased at T₂ and T_3, peaking at T₄. Independent factors associated with a negative antibody titer at T₄ were decreasing estimated glomerular filtration rate, time from transplantation, and antimetabolites (all p < 0.001) and age (p = 0.007).

CONCLUSIONS

The kinetics of humoral response after three doses of vaccine in kidney transplant patients is characterized by a late but effective immune response against SARS-CoV-2, reducing morbidity and mortality.