Humoral response to mRNA vaccines against SARS-CoV-2 in patients with humoral immunodeficiency disease

In vivo antiviral efficacy of LCTG-002, a pooled, purified human milk secretory IgA product, against SARS-CoV-2 in a murine model of COVID-19

Immunoglobulin A (IgA) is the most abundant antibody (Ab) in human mucosae, with secretory form (sIgA) being dominant and uniquely stable. sIgA is challenging to produce recombinantly but is naturally found in human milk, which could be considered a global resource for this biologic, justifying its development as a mucosal therapeutic. Presently, SARS-CoV-2 was utilized as a model mucosal pathogen, and methods were developed to efficiently extract human milk sIgA from donors who were naïve to SARS-CoV-2 or had recovered from infection that elicited high-titer anti-SARS-CoV-2 Spike sIgA in their milk (pooled to make LCTG-002). Mass spectrometry determined that proteins with a relative abundance of 1% or greater were all associated with sIgA. Western blot demonstrated that all batches consisted predominantly of sIgA. Compared to control IgA, LCTG-002 demonstrated significantly higher Spike binding (mean endpoint of 0.87 versus 5.87). LCTG-002 was capable of blocking the Spike receptor-binding domain - angiotensin-converting enzyme 2 (ACE2) interaction with significantly greater potency compared to control (mean LCTG-002 IC50 154ug/mL versus 50% inhibition not achieved for control), and exhibited significant neutralization activity against Spike-pseudotyped virus infection (mean LCTG-002 IC50 49.8ug/mL versus 114.5ug/mL for control). LCTG-002 was tested for its capacity to reduce viral lung burden in K18+hACE2 transgenic mice inoculated with SARS-CoV-2. LCTG-002 significantly reduced SARS-CoV-2 titers compared to control when administered at 0.25 mg/day or 1 mg/day, with a maximum TCID50 reduction of 4.9 logs. This innovative study demonstrates that LCTG-002 is highly pure and efficacious in vivo, supporting further development of milk-derived, polyclonal sIgA therapeutics.

Safety of Nirmatrelvir-Ritonavir Administration in Children With Immunodeficiency and/or Comorbidities With SARS-CoV-2 Infection: A Retrospective Clinical Report

INTRODUCTION

Despite the generally mild course of COVID-19 in children, immunocompromised patients may experience complications or severe infection. This study reports the clinical outcomes of pediatric patients treated with nirmatrelvir and ritonavir (N/R) for SARS-CoV-2 infection.

METHODS

We retrospectively reported the data of children with any immunodeficiency with COVID-19 who received N/R treatment between March 2022 and June 2023 at the Bambino Gesù Children's Hospital. Patients were treated with N/R for 5 days. We compared liver and kidney function before and after treatment with N/R and looked for a relationship between the duration of COVID-19 infection and the time from positivity to administration of N/R administration.

RESULTS

A total of 85 pediatric immunocompromised patients with COVID-19 were included in the study, with a mean age of 10.7 years (SD 4.8), mostly males (60%). We found a significant difference in the viral load before and after N/R administration. Four patients (4.7%) experienced adverse events related to N/R therapy. One of these had to discontinue N/R administration. Three patients (3.5%) experienced negative effects of drug interactions during N/R therapy, namely an increase of sirolimus and ciclosporin serum levels. A significant positive correlation was found between the time from SARS-CoV-2 positivity to N/R administration and the duration of SARS-CoV-2 swab positivity (R = 0.78, P < 0.001), suggesting that the earlier N/R is administered, the shorter the duration of COVID-19 in the study sample.

CONCLUSION

Our experience shows that N/R is reasonably safe in the pediatric population and could favor viral clearance, thus reducing the duration of infection.

mRNA vaccine-induced IgG mediates nasal SARS-CoV-2 clearance in mice

Coronavirus disease 2019 (COVID-19) mRNA vaccines that have contributed to controlling the SARS-CoV-2 pandemic induce specific serum antibodies, which correlate with protection. However, the neutralizing capacity of antibodies for emerging SARS-CoV-2 variants is altered. Suboptimal antibody responses are observed in patients with humoral immunodeficiency diseases, ongoing B cell depletion therapy, and aging. Common experimental mouse models with altered B cell compartments, such as B cell depletion or deficiency, do not fully recapitulate scenarios of declining or suboptimal antibody levels as observed in humans. We report on SARS-CoV-2 immunity in a transgenic mouse model with restricted virus-specific antibodies. Vaccination of C57BL/6-Tg(IghelMD4)4Ccg/J mice with unmodified or N1mΨ-modified mRNA encoding for ancestral spike (S) protein and subsequent challenge with mouse-adapted SARS-CoV-2 provided insights into antibody-independent immunity and the impact of antibody titers on mucosal immunity. Protection against fatal disease was independent of seroconversion following mRNA vaccination, suggesting that virus-specific T cells can compensate for suboptimal antibody levels. In contrast, mRNA-induced IgG in the nasal conchae limited the local viral load and disease progression. Our results indicate that parenteral mRNA immunization can elicit nasal IgG antibodies that effectively suppress local viral replication, highlighting the potential of vaccines in controlling SARS-CoV-2 transmission and epidemiology.

An Overview of the Strategies to Boost SARS-CoV-2-Specific Immunity in People with Inborn Errors of Immunity

The SARS-CoV-2 pandemic has heightened concerns about immunological protection, especially for individuals with inborn errors of immunity (IEI). While COVID-19 vaccines elicit strong immune responses in healthy individuals, their effectiveness in IEI patients remains unclear, particularly against new viral variants and vaccine formulations. This uncertainty has led to anxiety, prolonged self-isolation, and repeated vaccinations with uncertain benefits among IEI patients. Despite some level of immune response from vaccination, the definition of protective immunity in IEI individuals is still unknown. Given their susceptibility to severe COVID-19, strategies such as immunoglobulin replacement therapy (IgRT) and monoclonal antibodies have been employed to provide passive immunity, and protection against both current and emerging variants. This review examines the efficacy of COVID-19 vaccines and antibody-based therapies in IEI patients, their capacity to recognize viral variants, and the necessary advances required for the ongoing protection of people with IEIs.

Characterization of the antispike IgG immune response to COVID-19 vaccines in people with a wide variety of immunodeficiencies

Research on coronavirus disease 2019 vaccination in immune-deficient/disordered people (IDP) has focused on cancer and organ transplantation populations. In a prospective cohort of 195 IDP and 35 healthy volunteers (HV), antispike immunoglobulin G (IgG) was detected in 88% of IDP after dose 2, increasing to 93% by 6 months after dose 3. Despite high seroconversion, median IgG levels for IDP never surpassed one-third that of HV. IgG binding to Omicron BA.1 was lowest among variants. Angiotensin-converting enzyme 2 pseudo-neutralization only modestly correlated with antispike IgG concentration. IgG levels were not significantly altered by receipt of different messenger RNA-based vaccines, immunomodulating treatments, and prior severe acute respiratory syndrome coronavirus 2 infections. While our data show that three doses of coronavirus disease 2019 vaccinations induce antispike IgG in most IDP, additional doses are needed to increase protection. Because of the notably reduced IgG response to Omicron BA.1, the efficacy of additional vaccinations, including bivalent vaccines, should be studied in this population.

Clinical and immunological outcomes of SARS-CoV-2 infection in patients with inborn errors of immunity receiving different brands and doses of COVID-19 vaccines

Introduction

Vaccines against severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) provide successful control of the coronavirus-2019 (COVID-19) pandemic. The safety and immunogenicity studies are encouraging in patients with inborn errors of immunity (IEI); however, data about mortality outcomes and severe disease after vaccination still need to be fully addressed. Therefore, we aimed to determine the clinical and immunological outcomes of SARS-CoV-2 infection in patients with IEI who have received vaccination.

Materials and Methods

Eighty-eight patients with a broad range of molecular etiologies were studied; 45 experienced SARS-CoV-2 infection. Infection outcomes were analyzed in terms of genetic etiology, background clinical characteristics, and immunization history, including the type and number of doses received and the time elapsed since vaccination. In addition, anti-SARS-CoV-2 antibodies were quantified using electrochemiluminescent immunoassay.

Results

Patients were immunized using one of the three regimens: inactivated (Sinovac, Coronavac®), mRNA (BNT162b2, Comirnaty®, Pfizer-Biontech), and a combination. All three regimens induced comparable anti-SARS-CoV-2 IgG levels, with no differences in the adverse events. Among 45 patients with COVID-19, 26 received a full course of vaccination, while 19 were vaccine-naive or received incomplete dosing. No patients died due to COVID-19 infection. The fully immunized group had a lower hospitalization rate (23% vs. 31.5%) and a shorter symptomatic phase than the others. Among the fully vaccinated patients, serum IgM and E levels were significantly lower in hospitalized patients than non-hospitalized patients.

Conclusion

COVID-19 vaccines were well-tolerated by the IEI patients, and a full course of immunization was associated with lower hospitalization rates and a shorter duration of COVID-19 symptoms.

In Vivo Antiviral Efficacy of LCTG-002, a Pooled, Purified Human Milk Secretory IgA product, Against SARS-CoV-2 in a Murine Model of COVID-19

Immunoglobulin A (IgA) is the most abundant antibody (Ab) in human mucosal compartments including the respiratory tract, with the secretory form of IgA (sIgA) being dominant and uniquely stable in these environments. sIgA is naturally found in human milk, which could be considered a global resource for this biologic, justifying the development of human milk sIgA as a dedicated airway therapeutic for respiratory infections such as SARS-CoV-2. In the present study, methods were therefore developed to efficiently extract human milk sIgA from donors who were either immunologically naïve to SARS-CoV-2 (pooled as a control IgA) or had recovered from a PCR-confirmed SARS-CoV-2 infection that elicited high-titer anti-SARS-CoV-2 Spike sIgA Abs in their milk (pooled together to make LCTG-002). Mass spectrometry determined that proteins with a relative abundance of 1.0% or greater were all associated with sIgA. None of the proteins exhibited statistically significant differences between batches. Western blot demonstrated all batches consisted predominantly of sIgA. Compared to control IgA, LCTG-002 demonstrated significantly higher binding to Spike, and was also capable of blocking the Spike - ACE2 interaction in vitro with 6.3x greater potency compared to control IgA (58% inhibition at ∼240ug/mL). LCTG-002 was then tested in vivo for its capacity to reduce viral burden in the lungs of K18+hACE2 transgenic mice inoculated with SARS-CoV-2. LCTG-002 was demonstrated to significantly reduce SARS-CoV-2 titers in the lungs compared to control IgA when administered at either 250ug/day or 1 mg/day, as measured by TCID50, plaque forming units (PFU), and qRT-PCR, with a maximum reduction of 4.9 logs. This innovative study demonstrates that LCTG-002 is highly pure, efficacious, and well tolerated in vivo, supporting further development of milk-derived, polyclonal sIgA therapeutics against SARS-CoV-2 and other mucosal infections.

SARS-CoV-2 Infection and Response to COVID-19 Vaccination in Patients With Primary Immunodeficiencies

Primary immunodeficiencies (PIDs) are heterogeneous, rare disorders that increase susceptibility to infection and/or immune dysregulation. Individuals with certain PIDs are at high risk of severe or fatal outcomes from SARS-CoV-2 infections (the causative agent of COVID-19), either due to the underlying PID and/or due to the presence of comorbidities such as severe lung and liver disease. Vaccination remains the primary strategy to protect individuals with PID from COVID-19. However, populations with PID exhibit variable vaccine seroresponse rates, antibody titers, and neutralization activity depending on the type of PID and/or COVID-19 vaccine, and consequently, are at an elevated risk of severe disease. In this article, we review the COVID-19 burden in patients with PIDs and focus in-depth on findings from patients with predominantly antibody deficiencies or combined immunodeficiencies. We conclude by providing COVID-19 vaccination recommendations for this population.

Response to SARS-CoV-2 initial series and additional dose vaccine in pediatric patients with predominantly antibody deficiency

Data regarding response to SARS-CoV-2 immunization in pediatric patients with predominantly antibody deficiency (PAD) is limited. We evaluated SARS-CoV-2 immunization response by anti-SARS-CoV-2-spike antibody level in 15 pediatric PAD patients. These data were compared to a published cohort of adult PAD patients (n=62) previously analyzed following SARS-CoV-2 immunization at our single center institution. We evaluated demographics, clinical characteristics, immunophenotype, infection history, and past medication use by chart review. Following a two-dose monovalent initial series SARS-CoV-2 immunization, mean anti-SARS-CoV-2-spike antibody levels were significantly higher in pediatric PAD patients compared to adult PAD patients (2,890.7 vs. 140.1 U/mL; p<0.0001). Pediatric PAD patients with low class-switched memory B-cells, defined as <2% of total CD19+ B-cells, had significantly lower mean anti-SARS-CoV-2-spike antibody levels than those without (p=0.02). Following a third-dose monovalent SARS-CoV-2 immunization, the mean anti-SARS-CoV-2-spike antibody levels in pediatric PAD patients significantly increased (2,890.7 to 18,267.2 U/mL; p<0.0001). These data support Centers for Disease Control guidelines regarding three-part SARS-CoV-2 vaccine series, including in the pediatric PAD patient demographic.