A comprehensive assessment of long-term SARS-CoV-2-specific adaptive immune memory in convalescent COVID-19 Solid Organ Transplant recipients

mRNA-based COVID-19 vaccination of lung transplant recipients with prior SARS-CoV-2 infection induces durable SARS-CoV-2-specific antibodies and T cells

Lung transplant recipients (LTRs) are particularly at risk of developing severe coronavirus disease-2019 (COVID-19), but are also difficult to protect by vaccination due to their immunocompromised state. Here, we investigated the immunogenicity of mRNA-based COVID-19 vaccines in LTRs who had a prior natural SARS-CoV-2 infection. At a median of 184 days after SARS-CoV-2 infection, LTRs were vaccinated twice with the mRNA-1273 COVID-19 vaccine, with a 28-day interval. Blood samples were obtained pre-vaccination, 28 days after the first dose, and 28 days and 6 months after the second dose. Spike (S-) and nucleocapsid (N-) specific antibodies were measured, as well as neutralization of the ancestral and Omicron BA.5 variant. S-specific T cell responses were evaluated using IFN-γ ELISpot，IGRA, and activation markers by flow cytometry. Phenotyping of T cells was performed by using high-resolution spectral flow cytometry. Most LTRs with prior infection had detectable S-specific antibodies and T cells at baseline. After the first vaccination, S-specific antibody levels increased significantly; an additional increase was observed after the second vaccination. N-specific antibodies decreased during the study period, indicative of the fact that no further breakthrough infections occurred. An increase in IFN-γ producing T cells was observed after the first vaccination, but no additional boost could be detected after the second vaccination. Antibody levels and virus-specific T cell responses remained significantly higher compared to pre-vaccination levels at 6 months post-vaccination, indicating an additive and durable effect of vaccination after infection in LTRs. Neutralizing antibodies were detected against the ancestral strain and retained cross-reactivity with Omicron BA.5, albeit at lower levels. Moreover, the quantity and phenotype of SARS-CoV-2 spike-specific T cells were similar in LTRs compared to controls with hybrid immunity. In conclusion, mRNA-based COVID-19 vaccines are immunogenic in LTRs with prior immunity, and antibody and T cell responses are durable up to 6 months post-vaccination.

Role of SARS-CoV-2-specific memory B cells promoting immune protection after booster vaccination in solid organ transplantation

Introduction

Solid organ transplant (SOT) recipients display weak seroconversion and neutralizing antibody (NAb) responses after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination and remain at risk of severe coronavirus disease 2019 (COVID-19). While B-cell memory is the hallmark of serological immunity, its role in driving successful vaccine responses and providing immune protection in SOT patients remains unclear.

Methods

We investigated the function and interplay of SARS-CoV-2-specific memory B cells (mBc), different cytokineproducing T cells, and cross-reactive NAb in driving seroconversion and protection against COVID-19 in two cohorts. First, we studied a large cohort of 148 SOT recipients and 32 immunocompetent individuals who underwent several vaccinations. Subsequently, we assessed 25 SOT patients participating in a randomized controlled trial to compare two different immunosuppressive strategies for allowing successful seroconversion and memory-cell responses after booster vaccination.

Results

We corroborate previous findings that B- and T-cell memory responses are weaker and more delayed in SOT patients than in immunocompetent (IC) individuals; however, within the SOT cohort, we found that these responses are relatively stronger and more robust in patients not receiving mycophenolate mofetil (MMF)-based therapies. Anti- spike IgG titers strongly correlated with RBD-specific IgG-producing mBc, with both displaying broad viral cross reactivity. Prebooster SARS-CoV-2-specific mBc and IL-2- producing T cells accurately predicted Nab seroconversion (AUC, 0.828) and protection against severe COVID-19. While switching unresponsive SOT patients from calcineurin inhibitors (CNI)/MMF to a low-exposure CNI/mTOR-i regimen favored wider SARS-CoV-2-specific immune responses after a fourth booster vaccination, preformed RBD-specific mBc predicted NAb seroconversion.

Discussion

Our study adds new insights into the pathobiology of immune memory and highlights the pivotal role of SARS-CoV-2-specific mBc in promoting immune protection inSOT patients.

Characterization of the Antibody Response to SARS-CoV-2 Infection in COVID-19 Transplant versus Nontransplant Recipients by Ig-MS

Solid organ transplant recipients with immunosuppressant regimens to prevent rejection are less able to mount effective immune responses to pathogenic infection. Here, we apply a recently reported mass spectrometry-based serological approach known as Ig-MS to characterize immune responses against infection with SARS-CoV-2 in cohorts of transplant recipients and immunocompetent controls, both at a single early time point following COVID-19 diagnosis as well as over the course of one-month postdiagnosis. We found that the antibody repertoires generated by transplant recipients against SARS-CoV-2 do not differ significantly compared to immunocompetent individuals with regard to repertoire titer, clonality, or glycan composition. Importantly, our study is the first to characterize the evolution of antibody glycan profiles in transplant recipients with COVID-19 disease, presenting evidence that the evolution of glycan composition in these immunocompromised individuals is similar to that in immunocompetent people.

Hybrid immunity protection against SARS-CoV-2 and severe COVID-19 in kidney transplantation: A retrospective, comparative cohort study

Hybrid immunity, resulting from a combination of SARS-CoV-2 infection and vaccination, offers robust protection against COVID-19 in the general population. However, its impact on immunocompromised patients remains unexplored. We investigated the effect of hybrid immunity against the Omicron variant in a population of kidney transplant recipients receiving the fourth dose mRNA monovalent vaccination. By extracting data from the clinical records and performing individual interviews, participants were categorized into the hybrid cohort (previously infected and vaccinated individuals) and the vaccine cohort (vaccinated-only individuals). The study comprised 1114 participants, 442 in the hybrid and 672 in the vaccine cohorts. From April 2022 to August 2023, 286 infections, 38 hospitalizations and 9 deaths were reported. The cumulative incidence of infection was 12.1% (95% confidence interval [CI], 9.03-16.03) for the hybrid cohort and 36.54% (95% CI, 32.81-40.54) for the vaccine cohort after 300 days of follow-up. Hybrid immunity was associated to a 72% lower risk of infection (adjusted hazard ratio, 0.28; 95% CI, 0.21-0.38) and a 96% lower risk of hospitalization (adjusted hazard ratio, 0.04; 95% CI, 0.01-0.32). No deaths occurred in the hybrid cohort. Hybrid immunity was associated with a lower incidence of SARS-CoV-2 infection and severe COVID-19, underscoring its importance for risk stratification in this vulnerable patient population.

Evaluation of T Cell Response to SARS-CoV-2 in Kidney Transplant Recipients Receiving Monoclonal Antibody Prophylaxis and the Utility of a Bivalent mRNA Vaccine Booster Dose

Monoclonal antibodies have been administered to kidney transplant recipients (KTRs) with a poor or non-responder status to SARS-CoV-2 vaccination. The cellular response to SARS-CoV-2 has been poorly studied in this context. We assessed the T cell response to SARS-CoV-2 in 97 patients on the day of the injection of tixagevimab/cilgavimab using an IFNγ enzyme-linked immunospot assay (ELISPOT). Among the 97 patients, 34 (35%) developed COVID-19 before the injection. Twenty-nine (85.3%) had an ELISPOT compatible with a SARS-CoV-2 infection. There was no difference between KTRs under belatacept or tacrolimus treatment. Sixty-three patients (64.9%) had no known COVID-19 prior to the ELISPOT, but nine (14.3%) had a positive ELISPOT. In 21 KTRs with a positive ELISPOT who received a booster dose of a bivalent mRNA vaccine, median antibody titers and spike-reactive T cells increased significantly in patients under tacrolimus but not belatacept. Our study emphasizes the potential usefulness of the exploration of immune cellular response to SARS-CoV-2 by ELISPOT. In KTRs with a positive ELISPOT and under CNI therapy, a booster dose of mRNA vaccine seems effective in inducing an immune response to SARS-CoV-2.

An Overview of Liver Transplantation: Current Status, Recent Techniques, and Challenges-Perspectives From a Center in China

Liver transplantation is the best way to treat end-stage liver disease.With benefits from enhanced techniques, refined management, and advanced medications, liver transplant boasts a commendable 5-year survival rate for recipients. Nevertheless, acquiring the perioperative management and surgical skills essential for liver transplant is a time-consuming process for new surgeons. In addition, COVID-19 has also affected the field. Based on our actual situation in China, we have provided an overview of donor evaluation,recipient selection,transplant procedures, postoperative complications and management, longterm management, and pandemic strategies to guide new clinical surgeons in the field.

The Importance of Measuring SARS-CoV-2-Specific T-Cell Responses in an Ongoing Pandemic

Neutralizing antibodies are considered a correlate of protection against SARS-CoV-2 infection and severe COVID-19, although they are not the only contributing factor to immunity: T-cell responses are considered important in protecting against severe COVID-19 and contributing to the success of vaccination effort. T-cell responses after vaccination largely mirror those of natural infection in magnitude and functional capacity, but not in breadth, as T-cells induced by vaccination exclusively target the surface spike glycoprotein. T-cell responses offer a long-lived line of defense and, unlike humoral responses, largely retain reactivity against the SARS-CoV-2 variants. Given the increasingly recognized role of T-cell responses in protection against severe COVID-19, the circulation of SARS-CoV-2 variants, and the potential implementation of novel vaccines, it becomes imperative to continuously monitor T-cell responses. In addition to "classical" T-cell assays requiring the isolation of peripheral blood mononuclear cells, simple whole-blood-based interferon-γ release assays have a potential role in routine T-cell response monitoring. These assays could be particularly useful for immunocompromised people and other clinically vulnerable populations, where interactions between cellular and humoral immunity are complex. As we continue to live alongside COVID-19, the importance of considering immunity as a whole, incorporating both humoral and cellular responses, is crucial.

Evaluation of the Humoral and Cellular Immune Response Post COVID-19 Infection in Kidney Transplant Recipients

Kidney transplantation is a major risk factor for severe forms of coronavirus disease 2019 (COVID-19). The dynamics and the persistence of the immune response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in this immunocompromised population remain largely unknown. This study aimed to evaluate the persistence of humoral and cellular immune response in kidney transplant recipients (KTRs) and to establish whether immunosuppressive therapy influenced long-term immunity in this population. We report here the analysis of anti-SARS-CoV-2 antibodies and T cell-mediated immune responses in 36 KTRs compared to a control group who recovered from mild COVID-19. After a mean time of 5.22 ± 0.96 months post symptom onset for kidney transplant recipients, 97.22% of patients and 100% of the control group displayed anti-S1 immunoglobulin G SARS-CoV-2 antibodies (p > 0.05). No significant difference was reported in the median of neutralizing antibodies between the groups (97.50 [55.25-99] in KTRs vs. 84 [60-98] in control group, p = 0.35). A significant difference in SARS-CoV-2-specific T cell reactivity was found in the KTRs compared to the healthy controls. The levels of IFNγ release after stimulation by Ag1, Ag2 and Ag3 were higher in the control group compared to the kidney transplant group (p = 0.007, p = 0.025 and p = 0.008, respectively). No statistically significant correlation between humoral and cellular immunity was found in the KTRs. Our findings indicated that humoral immunity persisted similarly for up to 4 to 6 months post symptom onset in both the KTRs and the control group; however, T cell response was significantly higher in the healthy population compared to the immunocompromised patients.

Serologic response to COVID-19 infection or vaccination in pediatric kidney transplant recipients compared to healthy children

BACKGROUND

Differences in serologic response to COVID-19 infection or vaccination were reported in adult kidney transplant recipients (KTR) compared to non-immunocompromised patients. This study aims to compare the serologic response of naturally infected or vaccinated pediatric KTR to that of controls.

METHODS

Thirty-eight KTR and 42 healthy children were included; aged ≤18 years, with a previously confirmed COVID-19 infection or post COVID-19 vaccination. Serological response was measured by anti-spike protein IgG antibody titers. Response post third vaccine was additionally assessed in KTR.

RESULTS

Fourteen children in each group had previously confirmed infection. KTR were significantly older and developed a 2-fold higher antibody titer post-infection compared to controls [median (interquartile range [IQR]) age: 14.9 (7.8, 17.5) vs. 6.3 (4.5, 11.5) years, p = 0.02; median (IQR) titer: 1695 (982, 3520) vs. 716 (368, 976) AU/mL, p = 0.03]. Twenty-four KTR and 28 controls were vaccinated. Antibody titer was lower in KTR than in controls [median (IQR): 803 (206, 1744) vs. 8023 (3032, 30,052) AU/mL, p < 0.001]. Fourteen KTR received third vaccine. Antibody titer post booster in KTR reached similar levels to those of controls post two doses [median (IQR) 5923 (2295, 12,278) vs. 8023 (3034, 30,052) AU/mL, p = 0.37] and to KTR post natural infection [5282 AU/mL (2583, 13,257) p = 0.8].

CONCLUSION

Serologic response to COVID-19 infection was significantly higher in KTR than in controls. Antibody level in KTR was higher in response to infection vs. vaccination, contrary to reports in the general population. Response to vaccination in KTR reached levels comparable to controls only after third vaccine.

Long term SARS-CoV-2-specific cellular immunity after COVID-19 in liver transplant recipients

PURPOSE

Long-term immunity after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in immunosuppressed patients is not well characterized. We aimed to explore the long-term natural immunity against SARS-CoV-2 in liver transplant (LT) recipients compared to the non-transplanted population (control group).

METHODS

Fifteen LT recipients and 15 controls matched according to variables associated with disease severity were included at 12 months following the coronavirus disease 2019 (COVID-19) onset. Peripheral blood mononuclear cells were stimulated with peptide pools covering spike (S), nucleocapside (N), and membrane (M) proteins. Reactive CD4+ and CD8+ T cells were identified using flow cytometry, and cytokine production was evaluated in the culture supernatants using cytometric bead array. Serum anti-N and anti-S IgG antibodies were detected with chemiluminescence.

RESULTS

The percentage of patients with a positive response in both CD4+ and CD8+ T cells against each viral protein and IL2, IL10, TNF-α, and IFN-γ levels was similar between LT recipients and controls. IFN-γ levels were positively correlated with the percentage of reactive CD4+ (p = 0.022) and CD8+ (p = 0.043) T cells to a mixture of M + N + S peptide pools. The prevalence and levels of anti-N and anti-S IgG antibodies were slightly lower in the LT recipients, but the difference was not statistically significant.

CONCLUSION

LT recipients exhibited a similar T cell response compared to non-transplanted individuals one year after COVID-19 diagnosis.

SARS-CoV-2-Specific T Cell Responses in Immunocompromised Individuals with Cancer, HIV or Solid Organ Transplants

Adaptive immune responses play an important role in the clinical course of SARS-CoV-2 infection. While evaluations of the virus-specific defense often focus on the humoral response, cellular immunity is crucial for the successful control of infection, with the early development of cytotoxic T cells being linked to efficient viral clearance. Vaccination against SARS-CoV-2 induces both CD4+ and CD8+ T cell responses and permits protection from severe COVID-19, including infection with the currently circulating variants of concern. Nevertheless, in immunocompromised individuals, first data imply significantly impaired SARS-CoV-2-specific immune responses after both natural infection and vaccination. Hence, these high-risk groups require particular consideration, not only in routine clinical practice, but also in the development of future vaccination strategies. In order to assist physicians in the guidance of immunocompromised patients, concerning the management of infection or the benefit of (booster) vaccinations, this review aims to provide a concise overview of the current knowledge about SARS-CoV-2-specific cellular immune responses in the vulnerable cohorts of cancer patients, people living with HIV (PLWH), and solid organ transplant recipients (SOT). Recent findings regarding the virus-specific cellular immunity in these differently immunocompromised populations might influence clinical decision-making in the future.

Major Update 2: Antibody Response and Risk for Reinfection After SARS-CoV-2 Infection-Final Update of a Living, Rapid Review

BACKGROUND

The durability of the antibody response after SARS-CoV-2 infection and the role of antibodies in protection against reinfection are unclear.

PURPOSE

To synthesize evidence on the SARS-CoV-2 antibody response and reinfection risk with a focus on gaps identified in our prior reports.

DATA SOURCES

MEDLINE (Ovid), EMBASE, CINAHL, World Health Organization Research Database, and reference lists from 16 December 2021 through 8 July 2022, with surveillance through 22 August 2022.

STUDY SELECTION

English-language, cohort studies evaluating IgG antibody duration at least 12 months after SARS-CoV-2 infection, the antibody response among immunocompromised adults, predictors of nonseroconversion, and reinfection risk.

DATA EXTRACTION

Two investigators sequentially extracted study data and rated quality.

DATA SYNTHESIS

Most adults had IgG antibodies after SARS-CoV-2 infection at time points greater than 12 months (low strength of evidence [SoE]). Although most immunocompromised adults develop antibodies, the overall proportion with antibodies is lower compared with immunocompetent adults (moderate SoE for organ transplant patients and low SoE for patients with cancer or HIV). Prior infection provided substantial, sustained protection against symptomatic reinfection with the Delta variant (high SoE) and reduced the risk for severe disease due to Omicron variants (moderate SoE). Prior infection was less protective against reinfection with Omicron overall (moderate SoE), but protection from earlier variants waned rapidly (low SoE).

LIMITATION

Single review for abstract screening and sequential review for study selection, data abstraction, and quality assessment.

CONCLUSION

Evidence for a sustained antibody response to SARS-CoV-2 infection is considerable for both Delta and Omicron variants. Prior infection protected against reinfection with both variants, but, for Omicron, protection was weaker and waned rapidly. This information may have limited clinical applicability as new variants emerge.

PRIMARY FUNDING SOURCE

Agency for Healthcare Research and Quality. (PROSPERO: CRD42020207098).

Immune responses to SARS-CoV-2 in dialysis and kidney transplantation

Despite progressive improvements in the management of patients with coronavirus disease 2019 (COVID-19), individuals with end-stage kidney disease (ESKD) are still at high risk of infection-related complications. Although the risk of infection in these patients is comparable to that of the general population, their lower rate of response to vaccination is a matter of concern. When prevention strategies fail, infection is often severe. Comorbidities affecting patients on maintenance dialysis and kidney transplant recipients clearly account for the increased risk of severe COVID-19, while the role of uremia and chronic immunosuppression is less clear. Immune monitoring studies have identified differences in the innate and adaptive immune response against the virus that could contribute to the increased disease severity. In particular, individuals on dialysis show signs of T cell exhaustion that may impair antiviral response. Similar to kidney transplant recipients, antibody production in these patients occurs, but with delayed kinetics compared with the general population, leaving them more exposed to viral expansion during the early phases of infection. Overall, unique features of the immune response during COVID-19 in individuals with ESKD may occur with severe comorbidities affecting these individuals in explaining their poor outcomes.

Long-lasting adaptive Immune memory specific to SARS-CoV-2 in convalescent COVID-19 Stable People living with HIV

OBJECTIVE

While the course of natural immunization specific to SARS-CoV-2 has been described among convalescent coronavirus disease 2019 (COVID-19) people without HIV (PWOH), a thorough evaluation of long-term serological and functional T- and B-cell immune memory among people with HIV (PWH) has not been reported.

METHODS

Eleven stable PWH developing mild (n = 5) and severe (n = 6) COVID-19 and 39 matched PWOH individuals with mild (MILD) (n = 20) and severe (SEV) (n = 19) COVID-19 infection were assessed and compared at 3 and 6 months after infection for SARS-CoV-2-specific serology, polyfunctional cytokine (interferon-γ [IFN-γ], interleukin 2 [IL-2], IFN-γ/IL-2, IL-21) producing T-cell frequencies against four main immunogenic antigens and for circulating SARS-CoV-2-specific immunoglobulin G (IgG)-producing memory B-cell (mBc).

RESULTS

In all time points, all SARS-COV-2-specific adaptive immune responses were highly driven by the clinical severity of COVID-19 infection, irrespective of HIV disease. Notably, while a higher proportion of mild PWH showed a higher decay on serological detection between the two time points as compared to PWOH, persistently detectable IgG-producing mBc were still detectable in most patients (4/4 (100%) for SEV PWH, 4/5 (80%) for MILD PWH, 10/13 (76.92%) for SEV PWOH and 15/18 (83.33%) for MILD PWOH). Likewise, SARS-CoV-2-specific IFN-γ-producing T-cell frequencies were detected in both PWH and PWOH, although significantly more pronounced among severe COVID-19 (6/6 (100%) for SEV PWH, 3/5 (60%) for MILD PWH, 18/19 (94.74%) for SEV PWOH and 14/19 (73.68%) for MILD PWOH).

CONCLUSIONS

PWH develop a comparable short and long-term natural functional cellular and humoral immune response than PWOH convalescent patients, which are highly influenced by the clinical severity of the COVID-19 infection.