RESUMO
The establishment of anterior-posterior (AP) regional identity is an essential step in the appropriate development of the vertebrate central nervous system. An important aspect of AP neural axis formation is the inherent plasticity that allows developing cells to respond to and recover from the various perturbations that embryos continually face during the course of development. While the mechanisms governing the regionalization of the nervous system have been extensively studied, relatively less is known about the nature and limits of early neural plasticity of the anterior-posterior neural axis. This study aims to characterize the degree of neural axis plasticity in Xenopus laevis by investigating the response of embryos to a 180-degree rotation of their AP neural axis during gastrula stages by assessing the expression of regional marker genes using in situ hybridization. Our results reveal the presence of a narrow window of time between the mid- and late gastrula stage, during which embryos are able undergo significant recovery following a 180-degree rotation of their neural axis and eventually express appropriate regional marker genes including Otx, Engrailed, and Krox. By the late gastrula stage, embryos show misregulation of regional marker genes following neural axis rotation, suggesting that this profound axial plasticity is a transient phenomenon that is lost by late gastrula stages.
RESUMO
BACKGROUNDTo understand the features of a replicating vaccine that might drive potent and durable immune responses to transgene-encoded antigens, we tested a replication-competent adenovirus type 4 encoding influenza virus H5 HA (Ad4-H5-Vtn) administered as an oral capsule or via tonsillar swab or nasal spray.METHODSViral shedding from the nose, mouth, and rectum was measured by PCR and culturing. H5-specific IgG and IgA antibodies were measured by bead array binding assays. Serum antibodies were measured by a pseudovirus entry inhibition, microneutralization, and HA inhibition assays.RESULTSAd4-H5-Vtn DNA was shed from most upper respiratory tract-immunized (URT-immunized) volunteers for 2 to 4 weeks, but cultured from only 60% of participants, with a median duration of 1 day. Ad4-H5-Vtn vaccination induced increases in H5-specific CD4+ and CD8+ T cells in the peripheral blood as well as increases in IgG and IgA in nasal, cervical, and rectal secretions. URT immunizations induced high levels of serum neutralizing antibodies (NAbs) against H5 that remained stable out to week 26. The duration of viral shedding correlated with the magnitude of the NAb response at week 26. Adverse events (AEs) were mild, and peak NAb titers were associated with overall AE frequency and duration. Serum NAb titers could be boosted to very high levels 2 to 5 years after Ad4-H5-Vtn vaccination with recombinant H5 or inactivated split H5N1 vaccine.CONCLUSIONReplicating Ad4 delivered to the URT caused prolonged exposure to antigen, drove durable systemic and mucosal immunity, and proved to be a promising platform for the induction of immunity against viral surface glycoprotein targets.TRIAL REGISTRATIONClinicalTrials.gov NCT01443936 and NCT01806909.FUNDINGIntramural and Extramural Research Programs of the NIAID, NIH (U19 AI109946) and the Centers of Excellence for Influenza Research and Surveillance (CEIRS), NIAID, NIH (contract HHSN272201400008C).
Assuntos
Adenovírus Humanos/genética , Vetores Genéticos , Vacinas contra Influenza/administração & dosagem , Vacinas contra Influenza/imunologia , Adenovírus Humanos/imunologia , Adenovírus Humanos/fisiologia , Administração Oral , Adolescente , Adulto , Anticorpos Neutralizantes/sangue , Anticorpos Antivirais/sangue , Antígenos Virais/genética , Feminino , Glicoproteínas de Hemaglutininação de Vírus da Influenza/genética , Glicoproteínas de Hemaglutininação de Vírus da Influenza/imunologia , Humanos , Imunidade Celular , Imunidade Humoral , Imunidade nas Mucosas , Virus da Influenza A Subtipo H5N1/genética , Virus da Influenza A Subtipo H5N1/imunologia , Vacinas contra Influenza/genética , Influenza Humana/imunologia , Influenza Humana/prevenção & controle , Masculino , Sprays Nasais , Tonsila Palatina , Replicação Viral , Eliminação de Partículas Virais , Adulto JovemRESUMO
Induction of an antibody response capable of recognizing highly diverse strains is a major obstacle to the development of vaccines for viruses such as HIV and influenza. Here, we report the dynamics of B cell expansion and evolution at the single-cell level after vaccination with a replication-competent adenovirus type 4 recombinant virus expressing influenza H5 hemagglutinin. Fluorescent H1 or H5 probes were used to quantitate and isolate peripheral blood B cells and their antigen receptors. We observed increases in H5-specific antibody somatic hypermutation and potency for several months beyond the period of active viral replication that was not detectable at the serum level. Individual broad and potent antibodies could be isolated, including one stem-specific antibody that is part of a new multidonor class. These results demonstrate prolonged evolution of the B cell response for months after vaccination and should be considered in efforts to evaluate or boost vaccine-induced immunity.