Development of Next-Generation COVID-19 Vaccines: BARDA Supported Phase 2b Study Designs.

In response to the COVID-19 pandemic, vaccines were quickly and successfully developed and deployed, saving millions of lives globally. While first generation vaccines are safe and effective in preventing disease caused by SARSCoV-2, next-generation vaccines have the potential to improve efficacy and safety. Vaccines delivered by a mucosal route may elicit greater protective immunity at respiratory surfaces thereby reducing transmission. Inclusion of viral antigens in addition to the spike protein may enhance protection against emerging variants of concern. Next-generation vaccine platforms with a new mechanism of action may necessitate efficacy trials to fulfill regulatory requirements. The Biomedical Advanced Research and Development Authority (BARDA) will be supporting Phase 2b clinical trials of candidate next-generation vaccines. The primary endpoint will be improved efficacy in terms of symptomatic disease relative to a currently approved COVID-19 vaccine. In this paper, we discuss the planned endpoints and potential challenges to this complex program.

Duration of Cellular and Humoral Responses after Quadrivalent Human Papillomavirus Vaccination in Healthy Female Adults with or without Prior Type 16 and/or 18 Exposure.

Human papillomavirus virus (HPV) vaccines aim to provide durable protection and are ideal to study the association of cellular with humoral responses. We assessed the duration and characteristics of immune responses provided by the quadrivalent HPV (4vHPV) vaccine in healthy female adults with or without prior exposure with type 16 and 18 HPV. In a prospective cohort, vaccine naïve females received three doses of 4vHPV vaccine and were followed for two years to assess cellular (intracellular cytokine staining, proliferation and B cell ELISpot assays) and humoral (multiplex L1/L2 viral-like particles (VLP) and M4 ELISAs) responses. Frequencies of vaccine-specific CD4+ T cells correlated with antibody responses. Higher HPV antibody titers were found at all time points in participants previously exposed to HPV, except for anti-HPV-18 at Day 187 (one week post the third vaccination). Retrospective cohorts enrolled females who had previously received two or three 4vHPV doses and tested antibody titers by M4 ELISA and pseudovirion neutralization assay along with memory B cells (MBCs). Almost all women enrolled in a retrospective cohort with two prior doses and all women enrolled in a retrospective cohort with three prior doses had sustained antibody and memory responses. Our findings indicate that HPV vaccination induces a long-lasting, robust cellular and humoral immune responses.

Maternal immunization efforts of the National Institutes of Health.

Over the last 35 years, efforts at the National Institutes of Health (NIH) to protect mothers and their infants against infectious diseases have involved a bench-to-bedside approach. Basic and translational research that provided a foundation for clinical trials of vaccines in pregnancy include natural history and vaccine antigen identification studies. Development of laboratory assays and reagents have been funded by NIAID; these are critical for the advancement of vaccine candidates through the preclinical and clinical steps along the maternal immunization research pathway to support vaccine efficacy. Animal models of maternal immunization have been developed to evaluate efficacy of vaccine candidates. Clinical studies required development of maternal immunization protocols to address specific pregnancy related issues, for enrollment and safety assessment of mothers and their infants. NIH has organized and participated in meetings, workshops and other collaborative efforts with partners have advanced maternal immunization efforts. Partners have included many institutes and offices at NIH as well as other Department of Health and Human Services agencies and offices (Food and Drug Administration, Centers for Disease Control and Prevention, National Vaccine Program Office), World Health Organization, academic investigators, Biotech and pharmaceutical companies, and nonprofit organizations such as the Bill and Melinda Gates Foundation. These research and development partnership are essential for advancing maternal immunization. Continued efforts are needed to promote maternal immunization to protect pregnant women and their infants against vaccine-preventable infectious disease, especially in resource-limited settings where the burden of infections is high.

Vaccine monitoring systems: A potential model for medications in pregnancy.

Multiple vaccine safety systems contribute to monitor and assess the safety of vaccines given to pregnant women and their offspring. This article presents a review of the strengths and limitations of several national vaccine safety systems. The review concludes that the present framework of vaccine safety systems offers lessons to be learned toward the design of a system for monitoring and assessing the safety of medications administered to pregnant women in clinical practice and research.

Assessment of safety in newborns of mothers participating in clinical trials of vaccines administered during pregnancy.

A panel of experts convened by the Division of Microbiology and Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, developed proposed guidelines for the evaluation of adverse events in newborns of women participating in clinical trials of maternal immunization in the United States.

Assessment of congenital anomalies in infants born to pregnant women enrolled in clinical trials.

In 2011 and 2012, the Division of Microbiology and Infectious Diseases at the National Institute of Allergy and Infectious Diseases, National Institutes of Health, held a series of meetings to provide guidance to investigators regarding study design of clinical trials of vaccines and antimicrobial medications that enroll pregnant women. Assessment of congenital anomalies among infants born to women enrolled in these trials was recognized as a challenging issue, and a workgroup with expertise in epidemiology, pediatrics, genetics, dysmorphology, clinical trials, and infectious diseases was formed to address this issue. The workgroup considered 3 approaches for congenital anomalies assessment that have been developed for use in other studies: (1) maternal report combined with medical records review, (2) standardized photographic assessment and physical examination by a health professional who has received specific training in congenital anomalies, and (3) standardized physical examination by a trained dysmorphologist (combined with maternal interview and medical records review). The strengths and limitations of these approaches were discussed with regard to their use in clinical trials. None of the approaches was deemed appropriate for use in all clinical trials. Instead, the workgroup acknowledged that decisions regarding the optimal method of assessment of congenital anomalies will likely vary depending on the clinical trial, its setting, and the agent under study; in some cases, a combination of approaches may be appropriate. The workgroup recognized the need for more research on approaches to the assessment of congenital anomalies to better guide investigators in optimal design of clinical trials that enroll pregnant women.

Designing drug trials: considerations for pregnant women.

Clinical pharmacology studies that describe the pharmacokinetics and pharmacodynamics of drugs in pregnant women are critical for informing on the safe and effective use of drugs during pregnancy. That being said, multiple factors have hindered the ability to study drugs in pregnant patients. These include concerns for maternal and fetal safety, ethical considerations, the difficulty in designing appropriate trials to assess the study objectives, and funding limitations. This document summarizes the recommendations of a panel of experts convened by the Division of Microbiology and Infectious Diseases at the National Institute of Allergy and Infectious Diseases, National Institutes of Health. These experts were charged with reviewing the issues related to the development of preclinical and clinical drug studies in pregnant women and to develop strategies for addressing these issues. These findings may also be utilized in the development of future drug studies involving pregnant women and their fetus/neonate.

Research on vaccines during pregnancy: reference values for vital signs and laboratory assessments.

The Division of Microbiology and Infectious Diseases at the National Institute of Allergy and Infectious Diseases, National Institutes of Health organized a series of conferences, "Enrolling Pregnant Women in Clinical Trials of Vaccines and Therapeutics", to discuss enrollment and safety assessments of pregnant women in clinical trials of vaccines. Experts in obstetrics, maternal-fetal medicine, infectious diseases, pediatrics, neonatology, genetics, vaccinology and clinical trial design were charged with identifying normal ranges for vital signs and laboratory assessments in pregnancy. A grading system for adverse events was then developed.

Research on vaccines during pregnancy: protocol design and assessment of safety.

The Division of Microbiology and Infectious Diseases at the National Institute of Allergy and Infectious Diseases, National Institutes of Health organized a series of conferences, entitled "Enrolling Pregnant Women in Clinical Trials of Vaccines and Therapeutics", to discuss study design and the assessment of safety in clinical trials conducted in pregnant women. A panel of experts was charged with developing guiding principles for the design of clinical trials and the assessment of safety of vaccines during pregnancy. Definitions and a grading system to evaluate local and systemic reactogenicity, adverse events, and other events associated with pregnancy and delivery were developed. The purpose of this report is to provide investigators interested in vaccine research in pregnancy with a basic set of tools to design and implement maternal immunization studies which may be conducted more efficiently using consistent definitions and grading of adverse events to allow the comparison of safety reports from different trials. These guidelines and safety assessment tools may be modified to meet the needs of each particular protocol based on evidence collected as investigators use them in clinical trials in different settings and share their findings and expertise.

In vivo capsular switch in Streptococcus pneumoniae--analysis by whole genome sequencing.

Two multidrug resistant strains of Streptococcus pneumoniae - SV35-T23 (capsular type 23F) and SV36-T3 (capsular type 3) were recovered from the nasopharynx of two adult patients during an outbreak of pneumococcal disease in a New York hospital in 1996. Both strains belonged to the pandemic lineage PMEN1 but they differed strikingly in virulence when tested in the mouse model of IP infection: as few as 1000 CFU of SV36 killed all mice within 24 hours after inoculation while SV35-T23 was avirulent.Whole genome sequencing (WGS) of the two isolates was performed (i) to test if these two isolates belonging to the same clonal type and recovered from an identical epidemiological scenario only differed in their capsular genes? and (ii) to test if the vast difference in virulence between the strains was mostly - or exclusively - due to the type III capsule. WGS demonstrated extensive differences between the two isolates including over 2500 single nucleotide polymorphisms in core genes and also differences in 36 genetic determinants: 25 of which were unique to SV35-T23 and 11 unique to strain SV36-T3. Nineteen of these differences were capsular genes and 9 bacteriocin genes.Using genetic transformation in the laboratory, the capsular region of SV35-T23 was replaced by the type 3 capsular genes from SV36-T3 to generate the recombinant SV35-T3* which was as virulent as the parental strain SV36-T3* in the murine model and the type 3 capsule was the major virulence factor in the chinchilla model as well. On the other hand, a careful comparison of strains SV36-T3 and the laboratory constructed SV35-T3* in the chinchilla model suggested that some additional determinants present in SV36 but not in the laboratory recombinant may also contribute to the progression of middle ear disease. The nature of this determinants remains to be identified.

Immunogenicity and efficacy of influenza immunization during pregnancy: recent and ongoing studies.

Pregnant women and young infants are at increased risk from influenza. The World Health Organization and public health guidelines from Australia, Canada, and the United States recommend immunizing pregnant women with trivalent inactivated influenza vaccine. However, there are multiple barriers to the uptake of this recommendation. Additionally, current vaccines are not licensed for infants <6 months of age. Immunizing pregnant women would provide protection to both mothers and infants. The Bill & Melinda Gates Foundation (BMGF) and the National Institute of Allergy and Infectious Diseases (NIAID) are trying to address some of the issues associated with maternal immunization, which could be an effective intervention in both high- and low-resource settings to combat the significant maternal and infant morbidity and mortality due to influenza. BMGF and NIAID efforts are complementary to each other, focusing on evaluating the immunogenicity, efficacy, and safety of influenza vaccines during pregnancy; and the potential effect of maternal immunization on outcomes in infants in low-resource populations.

Maternal and neonatal characteristics associated with neonatal neutropenia in hypertensive pregnancies.

The purpose of this study was to identify maternal and neonatal characteristics affecting marked neonatal neutropenia in pregnancies complicated by hypertension. A single institution retrospective chart review over 2 years of singleton and multifetal pregnancies with hypertensive disorders meeting American College of Obstetricians and Gynecologists criteria was performed. Neutropenia and sepsis occurring within the first 16 days of life (DOL) were studied. Neutropenia was defined as an absolute neutrophil count of <1500/microL and sepsis as any positive blood, cerebrospinal fluid, or urine culture. The study group contained neonates with neutropenia. From all other hypertensive pregnancies, a presumed nonneutropenic control group was randomly generated with a 4:1 ratio; these neonates may or may not have had a complete blood count (CBC) performed because they were clinically stable. Multiple gestations were separately analyzed and compared with hypertensive multifetal neonates with confirmed CBCs showing no neutropenia. Chi-square, Mann-Whitney U, and regression analyses were performed. Five hundred forty-three hypertensive pregnancies representing 633 births, 173 (27.3%) of which were from multiple gestations, were studied. There were 32 (5.9%) cases of neutropenia, with 22 (68.8%) from multiple gestations. Of premature multiple gestations, 45.2% born between 24 and 34 weeks' gestation developed neutropenia. The median time to diagnosis of neutropenia was 1.2 hours with 80.6% detected on the first DOL. Resolution of neutropenia occurred within 7 days in 84.4% of surviving neonates. Univariate analysis showed significant associations of neutropenia with gestational age at delivery, multiple gestations, birth weight, severe preeclampsia, and development of neonatal sepsis. When multiple gestations were analyzed, linear regression showed only sepsis to be significantly associated with neutropenia (p = 0.027). Hypertensive disorders of pregnancy and premature delivery are common in multiple gestations and are associated with neutropenia (12.7% versus 2.2% neutropenia in singletons (p < 0.001). Furthermore, multiple gestations with neutropenia had a higher incidence of sepsis than singletons with neutropenia.

Phase 1/2 double-blind, placebo-controlled, dose escalation, safety, and pharmacokinetic study of pagibaximab (BSYX-A110), an antistaphylococcal monoclonal antibody for the prevention of staphylococcal bloodstream infections, in very-low-birth-weight neonates.

Staphylococcal sepsis is a major cause of morbidity and mortality in very-low-birth-weight (VLBW) infants. A human chimeric monoclonal antibody, pagibaximab, was developed against staphylococcal lipoteichoic acid. We evaluated the safety, tolerability, and pharmacokinetics of pagibaximab in VLBW neonates. A phase 1/2, randomized, double-blind, placebo-controlled, dose escalation study was conducted in VLBW infants (700 to 1,300 g) 3 to 7 days old. Patients received two doses 14 days apart of intravenous pagibaximab (10, 30, 60, or 90 mg/kg of body weight) or placebo in a 2:1 ratio. Blood and urine samples were obtained pre- and postinfusion for analysis of safety and pharmacokinetics, and data on adverse events were gathered. Staphylococcal organisms causing sepsis were collected and evaluated. Fifty-three patients received at least one dose of pagibaximab or placebo. The average gestational age was 27.6 weeks; the average birth weight was 1,003 g. All serious adverse events were deemed unrelated or probably not drug related. Morbidity and mortality were similar across treatment groups. No evidence of immunogenicity of pagibaximab was detected. Pagibaximab pharmacokinetics was linear. The mean clearance (CL), volume of distribution, and elimination half-life of pagibaximab were independent of dose. The serum half-life was 20.5 +/- 6.8 days. Pagibaximab enhanced serum opsonophagocytic activity. All staphylococci causing sepsis were opsonizable by pagibaximab. Two infusions of pagibaximab, administered 2 weeks apart to high-risk neonates appeared safe and tolerable, and pharmacokinetics were linear. Evaluation of more frequent doses, at the highest doses tested, in neonates at high-risk of staphylococcal sepsis, is warranted.

Neonatal cord blood subsets and cytokine response to bacterial antigens.

We compared lymphocyte subsets and cytokine responses to bacteria among term, preterm infants, and adults. Lymphocyte subset percentages in cord blood (22 preterm, 27 term neonates) and peripheral blood from 21 adults and cytokine/chemokine interleukin (IL)-6, IL-8, IL-10, IL-12, interferon gamma (IFN gamma) responses to Escherichia coli, group B Streptococcus (GBS), Staphylococcus epidermidis, and Lactobacillus plantarum (Lp299v) were assessed by flow cytometry. Preterm compared with term infants had increased CD8 (+) T cells (p = 0.02) and reduced naïve CD4 (+) T cells (p < 0.0001). Memory T and natural killer (NK) T cells were reduced (p < 0.001) in neonates; NK and CD56 (+)161 (+) NK cells were increased (p < 0.001). CD56 (+)CD8 (+) NK cells were higher in preterm compared with term infants. Despite individual exceptions, cytokine responses in neonates were weaker than adults except for IL-8 response to E. coli in preterm and IL-12 response to Lp299v in term infants. IL-10 responses were weaker in preterm (p = 0.01) and term (p = 0.005) infants to S. epidermidis and to E. coli (p = 0.03 for both) compared with adults. Differences in regulatory subpopulations of NK and T cells between neonates and adults and term compared with preterm infants were observed. These differences rather than intrinsic functional deficiency may account for neonatal cytokine responses to bacteria.

Cytokine expression in response to bacterial antigens in preterm and term infant cord blood monocytes.

BACKGROUND: Neonatal susceptibility to bacterial infection is associated with an immature immune system, but the role of different bacterial antigens in specific responses is largely unknown. OBJECTIVE: To evaluate differences in intracellular cytokine response to physiologically relevant bacterial antigens in term and preterm infants as compared with adults. METHODS: Cord blood samples from preterm and term neonates and adult peripheral blood samples were cultured ex vivo with and without whole heat-killed bacteria. Intracellular leukocyte production of interleukin (IL)-6, IL-10, IL-12, and IL-8 responses was assessed by flow cytometry. RESULTS: Monocytes were the primary producers of all mediators. Escherichia coli was the most potent stimulant. Lactobacillus plantarum 299v activated fewer monocytes as compared with E. coli for all responses (p < 0.05), except for IL-12 in term neonates. IL-6 response to Staphylococcus epidermidis was lower in both groups of neonates as compared with adults (p = 0.023 and p = 0.001). IL-8 response to S. epidermidis was lower in term as compared with preterm neonates and adults (p = 0.003). IL-10 response to group B streptococci was lower in term neonates as compared with adults and higher in preterm as compared with term neonates (p = 0.015). CONCLUSIONS: Monocytes from term neonates compared to preterm neonates show a downregulated anti-inflammatory response to specific bacteria. High neonatal response to pathogenic E. coli in the preterm infant could cause uncontrolled inflammatory response, while lower IL-6 response to S. epidermidis in neonates may indicate a basis for vulnerability to S. epidermidis infection.

Levels of pro-inflammatory cytokines produced from cord blood in-vitro are pathogen dependent and increased in comparison to adult controls.

BACKGROUND: Overproduction of pro-inflammatory cytokines may play a role in increased morbidity and mortality from neonatal sepsis. Objective of this study was to compare secretion of pro-inflammatory cytokines by the cord blood cells of healthy term neonates to the venous blood cells of healthy adults in vitro after stimulation with common neonatal pathogens. METHOD: Blood samples were cultured in the presence of heat-killed group B beta-hemolytic streptococci (GBS), Escherichia coli (E. coli) and Staphylococcus epidermidis (S. epi). Concentrations of secreted cytokines (interleukine-6, IL-6, tumor necrosis factor-alpha, TNF-alpha, interleukine-1 beta, IL-1beta and interleukine-8, IL-8) were measured after 0, 1, 2 and 4 h of incubation using chemiluminescent immunometric automated assay. RESULTS: Blood samples from 22 neonates and 16 adults were compared. After stimulation by GBS and E. coli, cord blood cells secreted significantly higher levels of IL-6 and IL-8 than blood cells of healthy adults. In cord blood, E. coli induced secretion of higher concentration of IL-6, TNF-alpha, IL-1beta and IL-8 than S. epi, and more IL-6 than GBS; GBS induced more IL-1beta than S.epi. CONCLUSIONS: Response of cord blood to microbial activators is different from that of adult controls. Each isolate of heat-killed bacteria induced different amount of pro-inflammatory cytokines in vitro. This may represent a useful in vitro virulence test.