The Polarity and Specificity of Antiviral T Lymphocyte Responses Determine Susceptibility to SARS-CoV-2 Infection in Patients with Cancer and Healthy Individuals

Combining SARS-CoV-2 interferon-gamma release assay with humoral response assessment to define immune memory profiles

OBJECTIVES

In the post-SARS-CoV-2 pandemic era, "breakthrough infections" are still documented, due to variants of concerns (VoCs) emergence and waning humoral immunity. Despite widespread utilization, the definition of the anti-Spike (S) immunoglobulin-G (IgG) threshold to define protection has unveiled several limitations. Here, we explore the advantages of incorporating T-cell response assessment to enhance the definition of immune memory profile.

METHODS

SARS-CoV-2 interferon-gamma release assay test (IGRA) was performed on samples collected longitudinally from immunocompetent healthcare workers throughout their immunization by infection and/or vaccination, anti-receptor-binding domain IgG levels were assessed in parallel. The risk of symptomatic infection according to cellular/humoral immune capacities during Omicron BA.1 wave was then estimated.

RESULTS

Close to 40% of our samples were exclusively IGRA-positive, largely due to time elapsed since their last immunization. This suggests that individuals have sustained long-lasting cellular immunity, while they would have been classified as lacking protective immunity based solely on IgG threshold. Moreover, the Cox regression model highlighted that Omicron BA.1 circulation raises the risk of symptomatic infection while increased anti-receptor-binding domain IgG and IGRA levels tended to reduce it.

CONCLUSION

The discrepancy between humoral and cellular responses highlights the significance of assessing the overall adaptive immune response. This integrated approach allows the identification of vulnerable subjects and can be of interest to guide antiviral prophylaxis at an individual level.

Defective Immunity Against SARS-CoV-2 Omicron Variants Despite Full Vaccination in Hematologic Malignancies

SUMMARY

In patients with multiple myeloma, completion of mRNA-based vaccination schemes failed to yield detectable SARS-CoV-2 Omicron-neutralizing antibodies and S1-RBD-specific CD8+ T cells in approximately 60% and 80% of the cases, respectively. Patients who develop breakthrough infections exhibited very low levels of live-virus neutralizing antibodies and the absence of follicular T helper cells. See related article by Azeem et al., p. 106 (9). See related article by Chang et al., p. 1684 (10).

RBD- specific Th1 responses are associated with vaccine-induced protection against SARS-CoV-2 infection in patients with hematological malignancies

The SARS-CoV-2 pandemic still represents a threat for immunosuppressed and hematological malignancy (HM) bearing patients, causing increased morbidity and mortality. Given the low anti-SARSCoV-2 IgG titers post-vaccination, the COVID-19 threat prompted the prophylactic use of engineered anti-SARS-CoV-2 monoclonal antibodies. In addition, potential clinical significance of T cell responses has been overlooked during the first waves of the pandemic, calling for additional in-depth studies. We reported that the polarity and the repertoire of T cell immune responses govern the susceptibility to SARS-CoV-2 infection in health care workers and solid cancer patients. Here, we longitudinally analyzed humoral and cellular immune responses at each BNT162b2 mRNA vaccine injection in 47 HM patients under therapy. Only one-third of HM, mostly multiple myeloma (MM) bearing patients, could mount S1-RBD-specific IgG responses following BNT162b2 mRNA vaccines. This vaccine elicited a S1-RBD-specific Th1 immune response in about 20% patients, mostly in MM and Hodgkin lymphoma, while exacerbating Th2 responses in the 10% cases that presented this recognition pattern at baseline (mostly rituximab-treated patients). Performing a third booster barely improved the percentage of patients developing an S1-RBD-specific Th1 immunity and failed to seroconvert additional HM patients. Finally, 16 patients were infected with SARS-CoV-2, of whom 6 developed a severe infection. Only S1-RBD-specific Th1 responses were associated with protection against SARS-CoV2 infection, while Th2 responses or anti-S1-RBD IgG titers failed to correlate with protection. These findings herald the paramount relevance of vaccine-induced Th1 immune responses in hematological malignancies.

Conserved longitudinal alterations of anti-S-protein IgG subclasses in disease progression in initial ancestral Wuhan and vaccine breakthrough Delta infections

INTRODUCTION

COVID-19 has a wide disease spectrum ranging from asymptomatic to severe. While humoral immune responses are critical in preventing infection, the immune mechanisms leading to severe disease, and the identification of biomarkers of disease progression and/or resolution of the infection remains to be determined.

METHODS

Plasma samples were obtained from infections during the initial wave of ancestral wildtype SARS-CoV-2 and from vaccine breakthrough infections during the wave of Delta variant, up to six months post infection. The spike-specific antibody profiles were compared across different severity groups and timepoints.

RESULTS

We found an association between spike-specific IgM, IgA and IgG and disease severity in unvaccinated infected individuals. In addition to strong IgG1 and IgG3 response, patients with severe disease develop a robust IgG2 and IgG4 response. A comparison of the ratio of IgG1 and IgG3 to IgG2 and IgG4 showed that disease progression is associated with a smaller ratio in both the initial wave of WT and the vaccine breakthrough Delta infections. Time-course analysis revealed that smaller (IgG1 and IgG3)/(IgG2 and IgG4) ratio is associated with disease progression, while the reverse associates with clinical recovery.

DISCUSSION

While each IgG subclass is associated with disease severity, the balance within the four IgG subclasses may affect disease outcome. Acute disease progression or infection resolution is associated with a specific immunological phenotype that is conserved in both the initial wave of WT and the vaccine breakthrough Delta infections.

SARS-CoV-2 in immunocompromised individuals

Immunocompromised individuals and particularly those with hematologic malignancies are at increased risk for SARS-CoV-2-associated morbidity and mortality due to immunologic deficits that limit prevention, treatment, and clearance of the virus. Understanding the natural history of viral infections in people with impaired immunity due to underlying conditions, immunosuppressive therapy, or a combination thereof has emerged as a critical area of investigation during the COVID-19 pandemic. Studies focused on these individuals have provided key insights into aspects of innate and adaptive immunity underlying both the antiviral immune response and excess inflammation in the setting of COVID-19. This review presents what is known about distinct states of immunologic vulnerability to SARS-CoV-2 and how this information can be harnessed to improve prevention and treatment strategies for immunologically high-risk populations.

SARS-CoV-2 pre-exposure prophylaxis: A potential COVID-19 preventive strategy for high-risk populations, including healthcare workers, immunodeficient individuals, and poor vaccine responders

The unprecedented worldwide spread of SARS-CoV-2 has imposed severe challenges on global health care systems. The roll-out and widespread administration of COVID-19 vaccines has been deemed a major milestone in the race to restrict the severity of the infection. Vaccines have as yet not entirely suppressed the relentless progression of the pandemic, due mainly to the emergence of new virus variants, and also secondary to the waning of protective antibody titers over time. Encouragingly, an increasing number of antiviral drugs, such as remdesivir and the newly developed drug combination, Paxlovid® (nirmatrelvir/ritonavir), as well as molnupiravir, have shown significant benefits for COVID-19 patient outcomes. Pre-exposure prophylaxis (PrEP) has been proven to be an effective preventive strategy in high-risk uninfected people exposed to HIV. Building on knowledge from what is already known about the use of PrEP for HIV disease, and from recently gleaned knowledge of antivirals used against COVID-19, we propose that SARS-CoV-2 PrEP, using specific antiviral and adjuvant drugs against SARS-CoV-2, may represent a novel preventive strategy for high-risk populations, including healthcare workers, immunodeficient individuals, and poor vaccine responders. Herein, we critically review the risk factors for severe COVID-19 and discuss PrEP strategies against SARS-CoV-2. In addition, we outline details of candidate anti-SARS-CoV-2 PrEP drugs, thus creating a framework with respect to the development of alternative and/or complementary strategies to prevent COVID-19, and contributing to the global armamentarium that has been developed to limit SARS-CoV-2 infection, severity, and transmission.

Peripheral lymphocyte subset counts predict antibody response after SARS-CoV-2 mRNA-BNT162b2 vaccine in cancer patients: results from the Vax-On-Profile study

Background

The adaptive immune response following COVID-19 vaccination is essential for humoral immunogenicity and clinical protection against symptomatic infections. We present the results of circulating lymphocyte profiling and their correlation with antibody response in cancer patients tested serologically six months after receiving a two-dose schedule of mRNA-BNT162b2 vaccine.

Methods

Absolute counts of lymphocyte subsets were determined using peripheral blood immunophenotyping. We collected samples for flow cytometry analysis alongside quantitative detection of IgG antibodies against the receptor-binding domain (RBD) of the SARS-CoV-2 Spike protein (S1). An IgG titer ≥ 50 AU/mL defined a positive seroconversion response.

Results

311 patients were evaluable for lymphocyte profiling and serologic testing. A preliminary multivariate analysis revealed that cytotoxic chemotherapy was the most consistent factor associated with lower counts of all lymphocyte subpopulations. T helper and B cells were found to be useful in predicting the occurrence of a positive seroconversion response using ROC curve analysis. A significant positive linear correlation was shown when anti-RBD-S1 IgG titers were compared to these lymphocyte subset counts. Univariate analysis indicated that antibody titers and seroconversion rates were significantly improved in the high-level T and B cell subgroups. Multivariate analysis confirmed these significant interactions, as well as the negative predictive value of immunosuppressive corticosteroid therapy.

Conclusions

These findings suggest that simple and widely available peripheral counts of T helper and B cells correlate with humoral response to mRNA-BNT162b2 vaccine in actively treated cancer patients. Upon validation, our results could provide additional insights into the predictive assessment of vaccination efficacy.

Vive la Résistance: T-cell Immunity in the Protection against SARS-CoV-2 Infection

SUMMARY

Fahrner and colleagues investigated the immune response of patients with cancer and cancer-free individuals to SARS-CoV-2 and found that a propensity toward an IL5-predominant Th2/Tc2 response was predictive of susceptibility to infection. The results of this study also suggest that a cellular response against the Spike 1 protein receptor binding domain (S1-RBD) region of the SARS-CoV-2 proteome contributes to protection and that mutations in this region may drive viral evolution and immune escape. See related article by Fahrner et al., p. 958 (8).