A Double-Blind, Randomized, Placebo-Controlled Phase 1 Study of Ad26.ZIKV.001, an Ad26-Vectored Anti-Zika Virus Vaccine

BACKGROUND

Zika virus (ZIKV) may cause severe congenital disease after maternal-fetal transmission. No vaccine is currently available.

OBJECTIVE

To assess the safety and immunogenicity of Ad26.ZIKV.001, a prophylactic ZIKV vaccine candidate.

DESIGN

Phase 1 randomized, double-blind, placebo-controlled clinical study. (ClinicalTrials.gov: NCT03356561).

SETTING

United States.

PARTICIPANTS

100 healthy adult volunteers.

INTERVENTION

Ad26.ZIKV.001, an adenovirus serotype 26 vector encoding ZIKV M-Env, administered in 1- or 2-dose regimens of 5 × 10¹⁰ or 1 × 10¹¹ viral particles (vp), or placebo.

MEASUREMENTS

Local and systemic adverse events; neutralization titers by microneutralization assay (MN50) and T-cell responses by interferon-γ enzyme-linked immunospot and intracellular cytokine staining; and protectivity of vaccine-induced antibodies in a subset of participants through transfer in an exploratory mouse ZIKV challenge model.

RESULTS

All regimens were well tolerated, with no safety concerns identified. In both 2-dose regimens, ZIKV neutralizing titers peaked 14 days after the second vaccination, with geometric mean MN50 titers (GMTs) of 1065.6 (95% CI, 494.9 to 2294.5) for 5 × 10¹⁰ vp and 956.6 (595.8 to 1535.8) for 1 × 10¹¹ vp. Titers persisted for at least 1 year at a GMT of 68.7 (CI, 26.4-178.9) for 5 × 10¹⁰ vp and 87.0 (CI, 29.3 to 258.6) for 1 × 10¹¹ vp. A 1-dose regimen of 1 × 10¹¹ vp Ad26.ZIKV.001 induced seroconversion in all participants 56 days after the first vaccination (GMT, 103.4 [CI, 52.7 to 202.9]), with titers persisting for at least 1 year (GMT, 90.2 [CI, 38.4 to 212.2]). Env-specific cellular responses were induced. Protection against ZIKV challenge was observed after antibody transfer from participants into mice, and MN50 titers correlated with protection in this model.

LIMITATION

The study was conducted in a nonendemic area, so it did not assess safety and immunogenicity in a flavivirus-exposed population.

CONCLUSION

The safety and immunogenicity profile makes Ad26.ZIKV.001 a promising candidate for further development if the need reemerges.

PRIMARY FUNDING SOURCE

Janssen Vaccines and Infectious Diseases.

A novel flow cytometry-based assay for the quantification of antibody-dependent pneumococcal agglutination

The respiratory pathogen Streptococcus pneumoniae is a major cause of diseases such as otitis media, pneumonia, sepsis and meningitis. The first step towards infection is colonization of the nasopharynx. Recently, it was shown that agglutinating antibodies play an important role in the prevention of mucosal colonization with S. pneumoniae. Here, we present a novel method to quantify antibody-dependent pneumococcal agglutination in a high-throughput manner using flow cytometry. We found that the concentration of agglutinating antibodies against pneumococcal capsule are directly correlated with changes in the size and complexity of bacterial aggregates, as measured by flow cytometry and confirmed by light microscopy. Using the increase in size, we determined the agglutination index. The cutoff value was set by measuring a series of non-agglutinating antibodies. With this method, we show that not only anti-polysaccharide capsule antibodies are able to induce agglutination but that also anti-PspA protein antibodies have agglutinating capabilities. In conclusion, we have described and validated a novel method to quantify pneumococcal agglutination, which can be used to screen sera from murine or human vaccination studies, in a high-throughput manner.

Role of antibodies and IL17-mediated immunity in protection against pneumococcal otitis media

Widespread vaccination against Streptococcus pneumoniae (the pneumococcus) has significantly reduced pneumococcal disease caused by vaccine serotypes. Despite vaccination, overall pneumococcal colonization rates in children have not reduced and otitis media (OM) by non-vaccine serotypes remains one of the most common childhood infections. Pneumococcal surface protein A (PspA) has been shown to be a promising protein antigen to induce broad protection against pneumococcal colonization. However, its ability to protect against OM remains unclear. Using our previously established mouse model of influenza-virus induced pneumococcal OM, we here show that intranasal vaccination of mice with PspA together with the mucosal adjuvant CTB results in a decrease in pneumococcal load in the middle ears. This decrease correlated with the induction of PspA-specific IgA, a balanced IgG1:IgG2a antibody response and the induction of a mucosal Th17 response. Our data suggests that the IL-17 response to PspA is more important for protection against OM, whilst the presence of antibodies may be less important, as determined in mice deficient in IL-17 signaling or antibody production. Together, these results suggest that mucosal vaccination with PspA may not only protect against colonization, but also against the development of virus-induced pneumococcal OM.

A novel quantitative PCR assay for the detection of Streptococcus pneumoniae using the competence regulator gene target comX

Streptococcus pneumoniae is responsible for an estimated 1.6 million deaths worldwide every year. While rapid detection and timely treatment with appropriate antibiotics is preferred, this is often difficult due to the amount of time that detection with blood cultures takes. In this study, a novel quantitative PCR assay for the detection of Streptococcus pneumoniae was developed. To identify novel targets, we analysed the pneumococcal genome for unique, repetitive DNA sequences. This approach identified comX, which is conserved and present in duplicate copies in Streptococcus pneumoniae but not in other bacterial species. Comparison with lytA, the current 'gold standard' for detection by quantitative PCR, demonstrated an analytic specificity of 100% for both assays on a panel of 10 pneumococcal and 18 non-pneumococcal isolates, but a reduction of 3.5 quantitation cycle values (± 0.23 sem), resulting in an increased analytical detection rate of comX. We validated our assay on DNA extracted from the serum of 30 bacteraemic patients who were blood culture positive for Streptococcus pneumoniae and 51 serum samples that were culture positive for other bacteria. This resulted in a similar clinical sensitivity between the comX and lytA assays (47%) and in a diagnostic specificity of 98.2 and 100% for the lytA and comX assays, respectively. In conclusion, we have developed a novel quantitative PCR assay with increased analytical sensitivity for the detection of Streptococcus pneumoniae, which may be used to develop a rapid bedside test for the direct detection of Streptococcus pneumoniae in clinical specimens.

An in vitro model to study immune responses of human peripheral blood mononuclear cells to human respiratory syncytial virus infection

Human respiratory syncytial virus (HRSV) infections present a broad spectrum of disease severity, ranging from mild infections to life-threatening bronchiolitis. An important part of the pathogenesis of severe disease is an enhanced immune response leading to immunopathology. Here, we describe a protocol used to investigate the immune response of human immune cells to an HRSV infection. First, we describe methods used for culturing, purification and quantification of HRSV. Subsequently, we describe a human in vitro model in which peripheral blood mononuclear cells (PBMCs) are stimulated with live HRSV. This model system can be used to study multiple parameters that may contribute to disease severity, including the innate and adaptive immune response. These responses can be measured at the transcriptional and translational level. Moreover, viral infection of cells can easily be measured using flow cytometry. Taken together, stimulation of PBMC with live HRSV provides a fast and reproducible model system to examine mechanisms involved in HRSV-induced disease.

Influenza A virus induced bacterial otitis media is independent of virus tropism for α2,6-linked sialic acid

Background

Otitis media (OM) affects ≥80% of children before the age of three. OM can arise following co-infection with influenza A virus (IAV) and the bacterium Streptococcus pneumoniae. We have previously shown that H3 IAV strains (such as Udorn/72) induced a higher rate of bacterial OM than H1 strains (such as PR8/34). This was associated with more efficient replication of H3 strains in the middle ear.

Findings

Here, we assess if the increased replication of IAV strains such as Udorn/72 in the middle ear is dependent upon the binding of the viral HA to α2,6-linked sialic acid. Using murine and in vitro models, the present study shows that recognition of α2,6-linked sialic acid was not required to facilitate bacterial OM.

Conclusions

Taken together, these data suggest that other features of the HA mediate bacterial OM.

Interactions between Streptococcus pneumoniae and influenza virus: a mutually beneficial relationship?

Historically, most research on infectious diseases has focused on infections with single pathogens. However, infections with pathogens often occur in the context of pre-existing viral and bacterial infections. Clinically, this is of particular relevance for coinfections with Streptococcus pneumoniae and influenza virus, which together are an important cause of global morbidity and mortality. In recent years new evidence has emerged regarding the underlying mechanisms of influenza virus-induced susceptibility to secondary pneumococcal infections, in particular regarding the sustained suppression of innate recognition of S. pneumoniae. Conversely, it is also increasingly being recognized that there is not a unidirectional effect of the virus on S. pneumoniae, but that asymptomatic pneumococcal carriage may also affect subsequent influenza virus infection and the clinical outcome. Here, we will review both aspects of pneumococcal influenza virus infection, with a particular focus on the age-related differences in pneumococcal colonization rates and invasive pneumococcal disease.

Prevalence and distribution of nucleotide sequences typical for pMEA-like accessory genetic elements in the genus Amycolatopsis

The prevalence and distribution of pMEA-like elements in the genus Amycolatopsis was studied. For this purpose, a set of 95 recently isolated Amycolatopsis strains and 16 Amycolatopsis type strains were examined for the presence of two unique pMEA-sequences (repAM and traJ), encoding proteins essential for replication and conjugative transfer. Homologues of repAM and traJ were found in 10 and 26 of 111 investigated strains, respectively, a result which shows that pMEA-like sequences, though not very abundant, can be found in several Amycolatopsis strains. Phylogenetic analysis of the deduced RepAM and TraJ protein sequences revealed clustering with the protein sequences of either pMEA300 or pMEA100. Furthermore, two geographically different populations of pMEA-like elements were distinguished, one originating in Europe and the other in Australia and Asia. Linkage between the distribution of repAM and traJ and the chromosomal identifier, the 16S rRNA gene, indicated that these elements coevolved with their hosts, suggesting that they evolved in an integrated form rather than by horizontal gene transfer of the free replicating form.