Basic aspects of acquired immunity: Dendritic cells and T cells in motion

UBL - phd migration 201

A live attenuated RSV vaccine, process development studies

Respiratory Syncytial Virus (RSV) is the leading cause of lower respiratory tract disease in infants and young children. A vaccine to prevent the high burden of disease caused by RSV is urgently needed, but not available. A live attenuated respiratory syncytial virus (RSV) vaccine for intranasal delivery is currently under development at Intravacc. The vaccine concept comprises a live Glycoprotein-complemented RSVΔG virus. This G-RSVΔG virus is generated by proliferation of an RSVΔG on G-expressing Vero cells. The vaccine thus contains virus particles that have the G-protein on their surface but not in their RNA genomes. This recombinant virus is highly attenuated compared to wild type RSV and therefore presents a live attenuated vaccine candidate for RSV infection. A vaccine production process has been setup for the production of Phase I clinical lots. In short, the production process steps are: cell and virus culture, clarification, continuous flow density gradient ultracentrifugation, ultra/diafiltration, filling and lyophilization. An example of process development is the design of the cell and virus culture method. Using the statistical design of experiment approach the virus culture has been optimized to both virus yield and harvest quality. As RSV is a filamentous virus, the optimization of harvest quality with respect to purification opportunities is pivotal. This DoE was done at lab-scale bioreactors (2-L) and the chosen conditions were successfully scaled-up to 50-L single use bioreactors. Preparation of preclinical and clinical lots is done at this scale. The pre-clinical studies were successful. In the cotton rat model, the G-RSVΔG vaccine is safe, immunogenic and protects against challenge with wild type RSV. The following step, a clinical Phase I study, is planned

Maturation of monocyte-derived dendritic cells with Toll-like receptor 3 and 7/8 ligands combined with prostaglandin E2 results in high interleukin-12 production and cell migration

Dendritic cells (DC) are professional antigen-presenting cells of the immune system that play a key role in regulating T cell-based immunity. In vivo, the capacity of DC to activate T cells depends on their ability to migrate to the T cell areas of lymph nodes as well as on their maturation state. Depending on their cytokine-secreting profile, DC are able to skew the immune response in a specific direction. In particular, IL-12p70 producing DC drive T cells towards a T helper 1 type response. A serious disadvantage of current clinical grade ex vivo generated monocyte-derived DC is the poor IL-12p70 production. We have investigated the effects of Toll-like receptor (TLR)-mediated maturation on ex vivo generated human monocyte-derived DC. We demonstrate that in contrast to cytokine-matured DC, DC matured with poly(I:C) (TLR3 ligand) and/or R848 (TLR7/8 ligand) are able to produce vast amounts of IL-12p70, but exhibit a reduced migratory capacity. The addition of prostaglandin E2 (PGE2) improved the migratory capacity of TLR-ligand matured DC while maintaining their IL-12p70 production upon T cell encounter. We propose a novel clinical grade maturation protocol in which TLR ligands poly(I:C) and R848 are combined with PGE2 to generate DC with both high migratory capacity and IL-12p70 production upon T cell encounter

Maximizing dendritic cell migration in cancer immunotherapy

The success of dendritic cell (DC)-based immunotherapy in inducing cellular immunity against tumors is highly dependent on accurate delivery and trafficking of the DC to T-cell-rich areas of secondary lymphoid tissues. To provide an overview of DC migration in vivo and how migration to peripheral lymph nodes might be improved to optimize DC therapy. We focused on DC migration in preclinical models and human skin explants and on clinical vaccination trials studying migration of in vitro-generated DC. DC migration requires an intricate interplay between the cell and its environment. To maximize migration for cellular therapy, it is important to optimize the generation of migratory DC as well as treatment strategie

Prevalent levels of RSV serum neutralizing antibodies in healthy adults outside the RSV-season

One of the main challenges in early clinical research with respiratory syncytial virus (RSV) live-attenuated vaccines (LAVs) is to assess immunogenicity in healthy adults. Healthy adults will have preexisting levels of serum neutralizing antibodies that could prematurely neutralize the LAV and underestimate the potential effect of the vaccine on the immune system. Data on prevalence and distribution of virus neutralizing titers (VNTs) in healthy adults is limited and there is no absolute threshold for protection against RSV-infection that can serve as an eligibility criterion in early phase trials. We assessed the RSV-specific serum VNT in healthy adults outside the Dutch RSV-Season in two clinical studies performed in 2017 (exploratory study, n = 100) and 2018 (first-in-human LAV-study, n = 190) using the same neutralizing assay. Our findings show that the prevalence and distribution of serum VNT was overall consistent in the two clinical studies. Log2 VNTs were normally distributed, distributions of VNTs were similar and there was no statistical difference in mean log2 VNT for both studies (p = .3). Serum VNTs were comparable during the 6 months of screening in the FIH LAV-study. Our findings will help to determine a cutoff serum VNT to be used as an eligibility criterion in future early phase clinical trials

A lack of Birbeck granules in Langerhans cells is associated with a naturally occurring point mutation in the human Langerin gene.

Item does not contain fulltextA heterozygous mutation in the Langerin gene corresponding to position 837 in the Langerin mRNA was identified in a person deficient in Birbeck granules (BG). This mutation results in an amino acid replacement of tryptophan by arginine at position 264 in the carbohydrate recognition domain of the Langerine protein. Expression of mutated Langerin in human fibroblasts induces tubular-like structures that are negative for BG-specific antibodies and do not resemble the characteristic structural features of BG

First-in-human administration of a live-attenuated RSV vaccine lacking the G-protein assessing safety, tolerability, shedding and immunogenicity: a randomized controlled trial

BACKGROUND: Human respiratory syncytial virus (RSV) is a major cause of lower respiratory tract infections in early infancy and in elderly. A pediatric vaccine against RSV would not only prevent morbidity and mortality amongst infants and young children but could also reduce transmission to elderly. The RSVΔG vaccine consists of a live-attenuated RSV that lacks the G attachment protein. RSVΔG is severely impaired in binding to host cells and exhibits reduced infectivity in preclinical studies. Intranasal immunization of cotton rats with RSVΔG vaccine protected against replication of wildtype RSV, without inducing enhanced disease. METHODS: We performed a first-in-human trial with primary objective to evaluate safety and shedding of RSVΔG (6.5 log10 CCID50) after intranasal administration. Healthy adults aged between 18 and 50, with RSV neutralizing serum titers below 9.6 log2, received a single dose of either vaccine or placebo (n = 48, ratio 3:1). In addition to safety and tolerability, nasal viral load, and systemic and humoral immune responses were assessed at selected time points until 4 weeks after immunization. RESULTS: Intranasal administration of RSVΔG was well tolerated with no findings of clinical concern. No infectious virus was detected in nasal wash samples. Similar to other live-attenuated RSV vaccines, neutralizing antibody response following inoculation was limited in seropositive adults. CONCLUSIONS: A single dose of 6.5 log10 CCID50 of RSVΔG was safe and well-tolerated in seropositive healthy adults. RSVΔG was sufficiently attenuated but there were no signs of induction of antibodies. Safety and immunogenicity can now be explored in children and eventually in seronegative infants. Clinical trial register: NTR7173/EudraCT number 2016-002437-30

Maximizing dendritic cell migration in cancer immunotherapy.

Item does not contain fulltextBACKGROUND: The success of dendritic cell (DC)-based immunotherapy in inducing cellular immunity against tumors is highly dependent on accurate delivery and trafficking of the DC to T-cell-rich areas of secondary lymphoid tissues. OBJECTIVE: To provide an overview of DC migration in vivo and how migration to peripheral lymph nodes might be improved to optimize DC therapy. METHODS: We focused on DC migration in preclinical models and human skin explants and on clinical vaccination trials studying migration of in vitro-generated DC. RESULTS/CONCLUSIONS: DC migration requires an intricate interplay between the cell and its environment. To maximize migration for cellular therapy, it is important to optimize the generation of migratory DC as well as treatment strategies