Currently no vaccine exists for hepatitis C virus (HCV), a major pathogen thought to infect 170 million people globally. Many studies suggest that host T cell responses are critical for spontaneous resolution of disease, and preclinical studies have indicated a requirement for T cells in protection against challenge. We aimed to elicit HCV-specific T cells with the potential for protection using a recombinant adenoviral vector strategy in a Phase I study of healthy human volunteers. Two adenoviral vectors expressing NS proteins from HCV genotype 1B were constructed based on rare serotypes (Human Adenovirus 6 (Ad6) and Chimpanzee Adenovirus 3 (ChAd3)). Both vectors primed T cell responses against HCV proteins; these T cell responses targeted multiple proteins and were capable of recognizing heterologous strains (genotypes 1A and 3A). HCV-specific T cells consisted of both CD4+ and CD8+ T cells subsets, secreted IL-2, IFNγ, and TNFα, and could be sustained for at least a year after boosting with the heterologous adenoviral vector. Studies using MHC peptide tetramers revealed long-lived central and effector memory pools that retained polyfunctionality and proliferative capacity. These data indicate that an adenoviral vector strategy can induce sustained T cell responses of a magnitude and quality associated with protective immunity, and open the way for studies of prophylactic and therapeutic vaccines for HCV.

Replication defective Adenovirus vectors based on the human serotype 5 (Ad5) have been shown to induce protective immune responses against diverse pathogens and cancer in animal models and to elicit robust and sustained cellular immunity in humans. However, most humans have anti-Ad5 neutralising antibodies that can impair the immunological potency of such vaccines. Here we show that most other human Adenoviruses from rare serotypes are far less potent as vaccine vectors than Ad5 in mice and non-human primates, casting doubt on their potential efficacy in humans. To identify novel vaccine carriers suitable for vaccine delivery in humans we isolated and sequenced over a thousand Adenovirus strains from chimpanzees (ChAd). Replication-defective vectors were generated from different ChAd serotypes and were screened for neutralization by human sera and for ability to grow in human cell lines already approved for clinical studies. Most importantly, we devised a screening strategy to rank the ChAd vectors by immunological potency in mice which predicts their immunogenicity in non-human primates and humans. The vectors studied varied by up to a thousand-fold in potency for CD8 T cell induction in mice. Two of the Europe PMC Funders Group

Protein-in-adjuvant formulations and viral-vectored vaccines encoding blood-stage malaria Ags have shown efficacy in rodent malaria models and in vitro assays against Plasmodium falciparum. Abs and CD4+ T cell responses are associated with protective efficacy against blood-stage malaria, whereas CD8+ T cells against some classical blood-stage Ags can also have a protective effect against liver-stage parasites. No subunit vaccine strategy alone has generated demonstrable high-level efficacy against blood-stage infection in clinical trials. The induction of high-level Ab responses, as well as potent T and B cell effector and memory populations, is likely to be essential to achieve immediate and sustained protective efficacy in humans. This study describes in detail the immunogenicity of vaccines against P. falciparum apical membrane Ag 1 in rhesus macaques (Macaca mulatta), including the chimpanzee adenovirus 63 (AdCh63), the poxvirus modified vaccinia virus Ankara (MVA), and protein vaccines formulated in Alhydrogel or CoVaccine HT adjuvants. AdCh63-MVA heterologous prime-boost immunization induces strong and long-lasting multifunctional CD8+ and CD4+ T cell responses that exhibit a central memory-like phenotype. Three-shot (AdCh63-MVA-protein) or two-shot (AdCh63-protein) regimens induce memory B cells and high-titer functional IgG responses that inhibit the growth of two divergent strains of P. falciparum in vitro. Prior immunization with adenoviral vectors of alternative human or simian serotype does not affect the immunogenicity of the AdCh63 apical membrane Ag 1 vaccine. These data encourage the further clinical development and coadministration of protein and viral vector vaccine platforms in an attempt to induce broad cellular and humoral immune responses against blood-stage malaria Ags in humans.

No abstract

Under physiological salt conditions double-stranded (ds) RNA is resistant to the action of most mammalian extracellular ribonucleases (RNases). However, some pancreatic-type RNases are able to degrade dsRNA under conditions in which the activity of bovine RNase A, the prototype of the RNase superfamily, is essentially undetectable. Human pancreatic ribonuclease (HP-RNase) is the most powerful enzyme to degrade dsRNA within the tetrapod RNase superfamily, being 500-fold more active than the orthologous bovine enzyme on this substrate. HP-RNase has basic amino acids at positions where RNase A shows instead neutral residues. We found by modeling that some of these basic charges are located on the periphery of the substrate binding site. To verify the role of these residues in the cleavage of dsRNA, we prepared four variants of HP-RNase: R4A, G38D, K102A, and the triple mutant R4A/G38D/K102A. The overall structure and active site conformation of the variants were not significantly affected by the amino acid substitutions, as deduced from CD spectra and activity on single-stranded RNA substrates. The kinetic parameters of the mutants with double-helical poly(A).poly(U) as a substrate were determined, as well as their helix-destabilizing action on a synthetic DNA substrate. The results obtained indicate that the potent activity of HP-RNase on dsRNA is related to the presence of noncatalytic basic residues which cooperatively contribute to the binding and destabilization of the double-helical RNA molecule. These data and the wide distribution of the enzyme in different organs and body fluids suggest that HP-RNase has evolved to perform both digestive and nondigestive physiological functions.