Maternal COVID-19 Vaccination and Prevention of Symptomatic Infection in Infants

BACKGROUND AND OBJECTIVES

Maternal vaccination may prevent infant coronavirus disease 2019 (COVID-19). We aimed to quantify protection against infection from maternally derived vaccine-induced antibodies in the first 6 months of an infant's life.

METHODS

Infants born to mothers vaccinated during pregnancy with 2 or 3 doses of a messenger RNA COVID-19 vaccine (nonboosted or boosted, respectively) had full-length spike (Spike) immunoglobulin G (IgG), pseudovirus 614D, and live virus D614G, and omicron BA.1 and BA.5 neutralizing antibody (nAb) titers measured at delivery. Infant severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection was determined by verified maternal-report and laboratory confirmation through prospective follow-up to 6 months of age between December 2021 and July 2022. The risk reduction for infection by dose group and antibody titer level was estimated in separate models.

RESULTS

Infants of boosted mothers (n = 204) had significantly higher Spike IgG, pseudovirus, and live nAb titers at delivery than infants of nonboosted mothers (n = 271), and were 56% less likely to acquire infection in the first 6 months (P = .03). Irrespective of boost, for each 10-fold increase in Spike IgG titer at delivery, the infant's risk of acquiring infection was reduced by 47% (95% confidence interval 8%-70%; P = .02). Similarly, a 10-fold increase in pseudovirus titers against Wuhan Spike, and live virus nAb titers against D614G, and omicron BA.1 and BA.5 at delivery were associated with a 30%, 46%, 56%, and 60% risk reduction, respectively.

CONCLUSIONS

Higher transplacental binding and nAb titers substantially reduced the risk of SARS-CoV-2 infection in infants, and a booster dose amplified protection during a period of omicron predominance. Until infants are age-eligible for vaccination, maternal vaccination provides passive protection against symptomatic infection during early infancy.

World Tuberculosis Day 2023 theme "Yes! We Can End TB!"

Intro

Viruses, including SARS-CoV-2, which causes COVID-19, are constantly changing. These genetic changes (aka mutations) occur over time and can lead to the emergence of new variants that may have different characteristics. After the first SARS-CoV-2 genome was published in early 2020, scientists all over the world soon realized the immediate need to obtain as much genetic information from as many strains as possible. However, understanding the functional significance of the mutations harbored by a variant is important to assess its impact on transmissibility, disease severity, immune escape, and the effectiveness of vaccines and therapeutics.

Methods

Here in Canada, we have developed an interactive framework for visualizing and reporting mutations in SARS-CoV-2 variants. This framework is composed of three stand-alone yet connected components; an interactive visualization (COVID-MVP), a manually curated functional annotation database (pokay), and a genomic analysis workflow (nf-ncov-voc). Findings: COVID-MVP provides (i) an interactive heatmap to visualize and compare mutations in SARS-CoV-2 lineages classified across different VOCs, VOIs, and VUMs; (ii) mutation profiles including the type, impact, and contextual information; (iii) annotation of biological impacts for mutations where functional data is available in the literature; (iv) summarized information for each variant and/or lineage in the form of a surveillance report; and (v) the ability to upload raw genomic sequence(s) for rapid processing and annotating for real-time classification.

Discussion

This comprehensive comparison allows microbiologists and public health practitioners to better predict how the mutations in emerging variants will impact factors such as infection severity, vaccine resistance, hospitalization rates, etc.

Conclusion

This framework is cloud-compatible & standalone, which makes it easier to integrate into other genomic surveillance tools as well. COVID-MVP is integrated into the Canadian VirusSeq data portal (https://virusseqdataportal.ca ) - a national data hub for SARS-COV-2 genomic data. COVID-MVP is also used by the CanCOGeN and CoVaRR networks in national COVID-19 genomic surveillance.

COVID-19 booster vaccination during pregnancy enhances maternal binding and neutralizing antibody responses and transplacental antibody transfer to the newborn (DMID 21-0004)

IMPORTANCE

COVID-19 vaccination is recommended during pregnancy for the protection of the mother. Little is known about the immune response to booster vaccinations during pregnancy.

OBJECTIVE

To measure immune responses to COVID-19 primary and booster mRNA vaccination during pregnancy and transplacental antibody transfer to the newborn.

DESIGN

Prospective cohort study of pregnant participants enrolled from July 2021 to January 2022, with follow up through and up to 12 months after delivery.

SETTING

Multicenter study conducted at 9 academic sites.

PARTICIPANTS

Pregnant participants who received COVID-19 vaccination during pregnancy and their newborns.

EXPOSURES

Primary or booster COVID-19 mRNA vaccination during pregnancy.

MAIN OUTCOMES AND MEASURES

SARS-CoV-2 binding and neutralizing antibody (nAb) titers after primary or booster COVID-19 mRNA vaccination during pregnancy and antibody transfer to the newborn. Immune responses were compared between primary and booster vaccine recipients in maternal sera at delivery and in cord blood, after adjusting for days since last vaccination.

RESULTS

In this interim analysis, 167 participants received a primary 2-dose series and 73 received a booster dose of mRNA vaccine during pregnancy. Booster vaccination resulted in significantly higher binding and nAb titers, including to the Omicron BA.1 variant, in maternal serum at delivery and cord blood compared to a primary 2-dose series (range 0.55 to 0.88 log ₁₀ higher, p<0.0001 for all comparisons). Although levels were significantly lower than to the prototypical D614G variant, nAb to Omicron were present at delivery in 9% (GMT ID50 12.7) of Pfizer and 22% (GMT ID50 14.7) of Moderna recipients, and in 73% (GMT ID50 60.2) of boosted participants (p<0.0001). Transplacental antibody transfer was efficient regardless of vaccination regimen (median transfer ratio range: 1.55-1.77 for binding IgG and 1.00-1.78 for nAb).

CONCLUSIONS AND RELEVANCE

COVID-19 mRNA vaccination during pregnancy elicited robust immune responses in mothers and efficient transplacental antibody transfer to the newborn. A booster dose during pregnancy significantly increased maternal and cord blood antibody levels, including against Omicron.Findings support continued use of COVID-19 vaccines during pregnancy, including booster doses.

TRIAL REGISTRATION

clinical trials.gov; Registration Number: NCT05031468 ; https://clinicaltrials.gov/ct2/show/NCT05031468.

KEY POINTS

Question: What is the immune response after COVID-19 booster vaccination during pregnancy and how does receipt of a booster dose impact transplacental antibody transfer to the newborn?Findings: Receipt of COVID-19 mRNA vaccines during pregnancy elicited robust binding and neutralizing antibody responses in the mother and in the newborn. Booster vaccination during pregnancy elicited significantly higher antibody levels in mothers at delivery and cord blood than 2-dose vaccination, including against the Omicron BA.1 variant.Meaning: COVID-19 vaccines, especially booster doses, should continue to be strongly recommended during pregnancy.

Safety and Immunogenicity of a Third Dose of SARS-CoV-2 mRNA Vaccine - An Interim Analysis

Waning immunity after two SARS-CoV-2 mRNA vaccinations and the emergence of variants precipitated the need for a third dose of vaccine. We evaluated early safety and immunogenicity after a third mRNA vaccination in adults who received the mRNA-1273 primary series in the Phase 1 trial approximately 9 to 10 months earlier. The booster vaccine formulations included 100 mcg of mRNA-1273, 50 mcg of mRNA-1273.351 that encodes Beta variant spike protein, and bivalent vaccine of 25 mcg each of mRNA-1273 and mRNA-1273.351. A third dose of mRNA vaccine appeared safe with acceptable reactogenicity. Vaccination induced rapid increases in binding and neutralizing antibody titers to D614G, Beta, and Delta variants that were similar or greater than peak responses after the second dose. Spike-specific CD4+ and CD8+ T cells increased to similar levels as after the second dose. A third mRNA vaccination was well tolerated and generated robust humoral and T cell responses. ClinicalTrials.gov numbers NCT04283461 (mRNA-1273 Phase 1) and NCT04785144 (mRNA-1273.351 Phase 1).

Overcoming Steric Restrictions of VRC01 HIV-1 Neutralizing Antibodies through Immunization

Broadly HIV-1 neutralizing VRC01 class antibodies target the CD4-binding site of Env. They are derived from VH1-2∗02 antibody heavy chains paired with rare light chains expressing 5-amino acid-long CDRL3s. They have been isolated from infected subjects but have not yet been elicited by immunization. Env-derived immunogens capable of binding the germline forms of VRC01 B cell receptors on naive B cells have been designed and evaluated in knockin mice. However, the elicited antibodies cannot bypass glycans present on the conserved position N276 of Env, which restricts access to the CD4-binding site. Efforts to guide the appropriate maturation of these antibodies by sequential immunization have not yet been successful. Here, we report on a two-step immunization scheme that leads to the maturation of VRC01-like antibodies capable of accommodating the N276 glycan and displaying autologous tier 2 neutralizing activities. Our results are relevant to clinical trials aiming to elicit VRC01 antibodies.

Memory CD4+ T cells guide memory B cell adaptability to drifting influenza vaccination

Influenza A annually infects 5–10% of the world’s human population resulting in an estimated one million deaths. Unlike other infectious agents, where either infection or vaccination against the disease confers long-term immunity, influenza causes annual epidemics and re-infects previously exposed individuals as a result of antigenic drift in the surface glycoprotein hemagglutinin (HA). Due to antigenic drift, the human immune system is simultaneously exposed to both novel and conserved parts of the influenza virus through vaccination and/or infection multiple times throughout life. Preexisting immunity by infection or vaccination influences subsequent neutralizing antibody responses, the correlate of protection for influenza. To understand how preexisting immunity augments future responses to drifted influenza immunization, we established mouse models, sequentially infecting mice with a H1N1 strain and then immunizing with a second drifted H1N1 strain. Mice previously infected with A/CA have increased neutralizing antibody response (nAb) to A/PR upon immunization with A/PR HA. This increase in nAbs was dependent on CD4+ T cell and memory B cell, correlating with CD4+ T cell reactivity conserved across both influenza HA’s. We also found increased germinal center PR8-specific B and T follicular helper cells post vaccination in the draining lymph node. These results suggest conserved MHC Class II restricted epitopes within HA are critical for B cells to adapt to drifting influenza and could be leveraged to boost out subsequent neutralizing antibody responses. Understanding the mechanism by which preexisting immune responses shape future responses is essential to optimize and leverage vaccination strategies.

Overcoming the Neonatal Limitations of Inducing Germinal Centers through Liposome-Based Adjuvants Including C-Type Lectin Agonists Trehalose Dibehenate or Curdlan

Neonates and infants are more vulnerable to infections and show reduced responses to vaccination. Consequently, repeated immunizations are required to induce protection and early life vaccines against major pathogens such as influenza are yet unavailable. Formulating antigens with potent adjuvants, including immunostimulators and delivery systems, is a demonstrated approach to enhance vaccine efficacy. Yet, adjuvants effective in adults may not meet the specific requirements for activating the early life immune system. Here, we assessed the neonatal adjuvanticity of three novel adjuvants including TLR4 (glucopyranosyl lipid adjuvant-squalene emulsion), TLR9 (IC31^®), and Mincle (CAF01) agonists, which all induce germinal centers (GCs) and potent antibody responses to influenza hemagglutinin (HA) in adult mice. In neonates, a single dose of HA formulated into each adjuvant induced T follicular helper (T_FH) cells. However, only HA/CAF01 elicited significantly higher and sustained antibody responses, engaging neonatal B cells to differentiate into GCs already after a single dose. Although antibody titers remained lower than in adults, HA-specific responses induced by a single neonatal dose of HA/CAF01 were sufficient to confer protection against influenza viral challenge. Postulating that the neonatal adjuvanticity of CAF01 may result from the functionality of the C-type lectin receptor (CLR) Mincle in early life we asked whether other C-type lectin agonists would show a similar neonatal adjuvanticity. Replacing the Mincle agonist trehalose 6,6′-dibehenate by Curdlan, which binds to Dectin-1, enhanced antibody responses through the induction of similar levels of T_FH, GCs and bone marrow high-affinity plasma cells. Thus, specific requirements of early life B cells may already be met after a single vaccine dose using CLR-activating agonists, identified here as promising B cell immunostimulators for early life vaccines when included into cationic liposomes.

Comparative Systems Analyses Reveal Molecular Signatures of Clinically tested Vaccine Adjuvants

A better understanding of the mechanisms of action of human adjuvants could inform a rational development of next generation vaccines for human use. Here, we exploited a genome wide transcriptomics analysis combined with a systems biology approach to determine the molecular signatures induced by four clinically tested vaccine adjuvants, namely CAF01, IC31, GLA-SE and Alum in mice. We report signature molecules, pathways, gene modules and networks, which are shared by or otherwise exclusive to these clinical-grade adjuvants in whole blood and draining lymph nodes of mice. Intriguingly, co-expression analysis revealed blood gene modules highly enriched for molecules with documented roles in T follicular helper (TFH) and germinal center (GC) responses. We could show that all adjuvants enhanced, although with different magnitude and kinetics, TFH and GC B cell responses in draining lymph nodes. These results represent, to our knowledge, the first comparative systems analysis of clinically tested vaccine adjuvants that may provide new insights into the mechanisms of action of human adjuvants.

Recombinant polymorphic membrane protein D in combination with a novel, second-generation lipid adjuvant protects against intra-vaginal Chlamydia trachomatis infection in mice

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rPmpD in combination with SLA elicits significant protection against intra-vaginal Ct challenge.

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Antibodies induced by immunisation with rPmpD recognise Ct elementary bodies.

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SLA is a novel adjuvant class that may be widely used in future preclinical Ct vaccine development.

The development of a chlamydial vaccine that elicits protective mucosal immunity is of paramount importance in combatting the global spread of sexually transmitted Chlamydia trachomatis (Ct) infections. While the identification and prioritization of chlamydial antigens is a crucial prerequisite for efficacious vaccine design, it is likely that novel adjuvant development and selection will also play a pivotal role in the translational potential of preclinical Ct vaccines. Although the molecular nature of the immuno-modulatory component is of primary importance, adjuvant formulation and delivery systems may also govern vaccine efficacy and potency. Our study provides the first preclinical evaluation of recombinant Ct polymorphic membrane protein D (rPmpD) in combination with three different formulations of a novel second-generation lipid adjuvant (SLA). SLA was rationally designed in silico by modification of glucopyranosyl lipid adjuvant (GLA), a TLR4 agonistic precursor molecule currently in Phase II clinical development. We demonstrate robust protection against intra-vaginal Ct challenge in mice, evidenced by significantly enhanced resistance to infection and reduction in mean bacterial load. Strikingly, protection was found to correlate with the presence of robust anti-rPmpD serum and cervico-vaginal IgG titres, even in the absence of adjuvant-induced Th1-type cellular immune responses elicited by each SLA formulation, and we further show that anti-rPmpD antibodies recognize Ct EBs. These findings highlight the utility of SLA and rational molecular design of adjuvants in preclinical Ct vaccine development, but also suggest an important role for anti-rPmpD antibodies in protection against urogenital Ct infection.

Chitin microneedles for an easy-to-use tuberculosis skin test

An easy-to-use tuberculosis skin test is developed with chitin microneedles that deliver purified protein derivative at the correct skin depth and result in a positive test in BCG-immunized guinea pigs.

Modulation of protection against Mycobacterium tuberculosis by adjuvants that elicit different T cell responses. (166.18)

The use of an adjuvant within a vaccine can influence and direct the immune response to enable a desired outcome. A T helper 1 (Th1) response, including antigen-specific production of interferon-gamma (IFN-γ), is needed to protect against Mycobacterium tuberculosis. A successful subunit vaccine should include not only an appropriate antigen but also a proper adjuvant to ensure that a Th1 mediated cellular response is induced. Only a few adjuvants have been approved for use in human vaccines such as Alum and oil-in-water (o/w) based emulsions, including MF59 (Novartis), AS03 (GSK Biologics), AF03 (Sanofi) and liposomes (Crucell). These adjuvants primarily induce humoral responses. A new adjuvant in approved products is AS04, which combines the TLR-4 agonist monophosphoryl lipid A (MPL) with Alum. In this study we combine our candidate TB vaccine, ID93, with a synthetic TLR-4 agonist, glucopyranosyl lipid adjuvant (GLA) mixed with a stable o/w emulsion (SE). Both SE and GLA-SE induce potent cellular responses when combined with ID93 in mice. ID93/GLA-SE induced multifunctional CD4+ Th1 cell responses (IFN-γ, TNF-α, IL-2) in mice and protected both mice and guinea pigs against M. tuberculosis. In contrast, ID93/SE in the absence of GLA induced IL-5 and provided no protection, as assessed by bacterial burden, survival, and pathology. These results demonstrate the importance of properly formulating subunit vaccines with effective adjuvants for use against TB.

Dissecting mechanisms of immunodominance to the common tuberculosis antigens ESAT-6, CFP10, Rv2031c (hspX), Rv2654c (TB7.7), and Rv1038c (EsxJ)

Diagnosis of tuberculosis often relies on the ex vivo IFN-γ release assays QuantiFERON-TB Gold In-Tube and T-SPOT.TB. However, understanding of the immunological mechanisms underlying their diagnostic use is still incomplete. Accordingly, we investigated T cell responses for the TB Ags included in the these assays and other commonly studied Ags: early secreted antigenic target 6 kDa, culture filtrate protein 10 kDa, Rv2031c, Rv2654c, and Rv1038c. PBMC from latently infected individuals were tested in ex vivo ELISPOT assays with overlapping peptides spanning the entirety of these Ags. We found striking variations in prevalence and magnitude of ex vivo reactivity, with culture filtrate protein 10 kDa being most dominant, followed by early secreted antigenic target 6 kDa and Rv2654c being virtually inactive. Rv2031c and Rv1038c were associated with intermediate patterns of reactivity. Further studies showed that low reactivity was not due to lack of HLA binding peptides, and high reactivity was associated with recognition of a few discrete dominant antigenic regions. Different donors recognized the same core sequence in a given epitope. In some cases, the identified epitopes were restricted by a single specific common HLA molecule (selective restriction), whereas in other cases, promiscuous restriction of the same epitope by multiple HLA molecules was apparent. Definition of the specific restricting HLA allowed to produce tetrameric reagents and showed that epitope-specific T cells recognizing either selectively or promiscuously restricted epitopes were predominantly T effector memory. In conclusion, these results highlight the feasibility of more clearly defined TB diagnostic reagent.

Expression cloning of an immunodominant family of Mycobacterium tuberculosis antigens using human CD4(+) T cells

Development of a subunit vaccine for Mycobacterium tuberculosis (Mtb) is likely to be dependent on the identification of T cell antigens that induce strong proliferation and interferon gamma production from healthy purified protein derivative (PPD)(+) donors. We have developed a sensitive and rapid technique for screening an Mtb genomic library expressed in Escherichia coli using Mtb-specific CD4(+) T cells. Using this technique, we identified a family of highly related Mtb antigens. The gene of one family member encodes a 9.9-kD antigen, termed Mtb9.9A. Recombinant Mtb9.9A protein, expressed and purified from E. coli, elicited strong T cell proliferation and IFN-gamma production by peripheral blood mononuclear cells from PPD(+) but not PPD(-) individuals. Southern blot analysis and examination of the Mtb genome sequence revealed a family of highly related genes. A T cell line from a PPD(+) donor that failed to react with recombinant Mtb9.9A recognized one of the other family members, Mtb9.9C. Synthetic peptides were used to map the T cell epitope recognized by this line, and revealed a single amino acid substitution in this region when compared with Mtb9.9A. The direct identification of antigens using T cells from immune donors will undoubtedly be critical for the development of vaccines to several intracellular pathogens.

Molecular characterization and human T-cell responses to a member of a novel Mycobacterium tuberculosis mtb39 gene family

We have used expression screening of a genomic Mycobacterium tuberculosis library with tuberculosis (TB) patient sera to identify novel genes that may be used diagnostically or in the development of a TB vaccine. Using this strategy, we have cloned a novel gene, termed mtb39a, that encodes a 39-kDa protein. Molecular characterization revealed that mtb39a is a member of a family of three highly related genes that are conserved among strains of M. tuberculosis and Mycobacterium bovis BCG but not in other mycobacterial species tested. Immunoblot analysis demonstrated the presence of Mtb39A in M. tuberculosis lysate but not in culture filtrate proteins (CFP), indicating that it is not a secreted antigen. This conclusion is strengthened by the observation that a human T-cell clone specific for purified recombinant Mtb39A protein recognized autologous dendritic cells infected with TB or pulsed with purified protein derivative (PPD) but did not respond to M. tuberculosis CFP. Purified recombinant Mtb39A elicited strong T-cell proliferative and gamma interferon responses in peripheral blood mononuclear cells from 9 of 12 PPD-positive individuals tested, and overlapping peptides were used to identify a minimum of 10 distinct T-cell epitopes. Additionally, mice immunized with mtb39a DNA have shown increased protection from M. tuberculosis challenge, as indicated by a reduction of bacterial load. The human T-cell responses and initial animal studies provide support for further evaluation of this antigen as a possible component of a subunit vaccine for M.tuberculosis.