BNT162b vaccines protect rhesus macaques from SARS-CoV-2.

A safe and effective vaccine against COVID-19 is urgently needed in quantities that are sufficient to immunize large populations. Here we report the preclinical development of two vaccine candidates (BNT162b1 and BNT162b2) that contain nucleoside-modified messenger RNA that encodes immunogens derived from the spike glycoprotein (S) of SARS-CoV-2, formulated in lipid nanoparticles. BNT162b1 encodes a soluble, secreted trimerized receptor-binding domain (known as the RBD-foldon). BNT162b2 encodes the full-length transmembrane S glycoprotein, locked in its prefusion conformation by the substitution of two residues with proline (S(K986P/V987P); hereafter, S(P2) (also known as P2 S)). The flexibly tethered RBDs of the RBD-foldon bind to human ACE2 with high avidity. Approximately 20% of the S(P2) trimers are in the two-RBD 'down', one-RBD 'up' state. In mice, one intramuscular dose of either candidate vaccine elicits a dose-dependent antibody response with high virus-entry inhibition titres and strong T-helper-1 CD4+ and IFNγ+CD8+ T cell responses. Prime-boost vaccination of rhesus macaques (Macaca mulatta) with the BNT162b candidates elicits SARS-CoV-2-neutralizing geometric mean titres that are 8.2-18.2× that of a panel of SARS-CoV-2-convalescent human sera. The vaccine candidates protect macaques against challenge with SARS-CoV-2; in particular, BNT162b2 protects the lower respiratory tract against the presence of viral RNA and shows no evidence of disease enhancement. Both candidates are being evaluated in phase I trials in Germany and the USA1-3, and BNT162b2 is being evaluated in an ongoing global phase II/III trial (NCT04380701 and NCT04368728).

LC3-associated phagocytosis in microbial pathogenesis.

Phagocytosis is essential for uptake and elimination of pathogenic microorganisms. Autophagy is a highly conserved mechanism for incorporation of cellular constituents to replenish nutrients by degradation. Recently, parts of the autophagy machinery - above all microtubule-associated protein 1 light chain 3 (LC3) - were found to be specifically recruited to phagosomal membranes resulting in phagosome-lysosome fusion and efficient degradation of internalized cargo in a process termed LC3-associated phagocytosis (LAP). Many pathogenic bacterial, fungal and parasitic microorganisms reside within LAP-targeted single-membrane phagosomes or vacuoles after infection of host cells. In this minireview we describe the state of knowledge on the interaction of pathogens with LAP or LAP-like pathways and report on various pathogens that have evolved strategies to circumvent degradation in LAP compartments.

TIP47 is associated with the hepatitis C virus and its interaction with Rab9 is required for release of viral particles.

Hepatitis C virus (HCV) morphogenesis and release are closely linked to lipid metabolism. It has been described recently by our group that TIP47 plays an essential role for the targeting of the NS5A-complexed RNA genome from the replicon complex to the lipid droplet. Moreover, apolipoprotein (apo) E was found to be associated with the viral particle. In light of the fact, that TIP47 harbors an apoE like domain and has a high affinity to lipoproteins, the interaction of TIP47 with the viral particle and the potential relevance for the release of the viral particle were investigated. Coimmunoprecipitations and electron microscopy analysis using immunogold labeling revealed that TIP47 binds to the viral particle and stays associated with the released HCV particle. Silencing of the TIP47 binding partner Rab9 by lentiviral transduction abolishes the viral replication. However, destruction of TIP47-Rab9 interactions by deletion/mutation of the Rab9 binding does not abolish the genome replication domain but prevents the release of HCV particles. The binding of these TIP47 mutants to the viral particle is not affected by destruction of the Rab9 binding domain. Moreover, we found that these TIP47 mutants lacking the binding site for Rab9 misdirect the de novo synthesized viral particles to the autophagosomal/lysosomal compartment where the particles are degraded. From this we conclude that the Rab9-complexed TIP47 plays an essential role for the proper release of hepatitis C viral particles.