In this classification system, NoVs are divided into five genogroups and 29 clusters with eight clusters in genogroup I (GI), 17 in GII, two in GIII, and one each in GIV and GV (Table 8.1) . plant expression systems as a novel production platform for VLP-based NoV vaccines are discussed in light of their cost-effectiveness, production speed, and scalability. Recent Sodium orthovanadate achievements from the first successful demonstration of NoV VLP production in plant expression system under the current Good Manufacture Practice (cGMP) regulation by the US Food and Drug Administration (FDA) are detailed. Moreover, results of human clinical trials demonstrating the safety and efficacy of insect and plant-derived NoV VLPs are also presented. Due to the diversity of capsid protein among different NoV strains and its rapid antigenic drift, we speculate that vaccine development should focus on multivalent VLP vaccines derived from capsid proteins of the most prevalent strains. With the very recent approval of Sodium orthovanadate the first plant-made biologics by the FDA, we also speculate that plant-based production systems will play an important role in manufacturing such multivalent VLP-based NoV vaccines. in the family [4, 5]. They were first discovered and characterized in their prototype virus, the Norwalk virus (NV) in 1972 [6, 7]. Studies of NV revealed that NoVs are non-enveloped viruses with an RNA genome surrounded by a round capsid protein shell approximately 38 nm in diameter . Classification of NoVs, however, has proved difficult and controversial until the recent development of molecular biology tools. Since there is no culture system available to grow these viruses in vitro, accurate serotyping based on neutralization is not possible . Instead, classification of NoV had to rely on cross-challenge studies in volunteers and immune cross-reactivity analysis with electron microscopy [10C13], which lacks accuracy and reproducibility due to the cross-reactivity of antibodies . Recent development of sophisticated molecular methods including reverse transcription polymerase chain reaction (RT-PCR) has allowed a more reliable NoV classification based on the amino acid sequence of the major capsid protein . In this classification system, NoVs are divided into five genogroups and 29 clusters with eight clusters in genogroup I (GI), 17 in GII, two in GIII, and one each in GIV and GV (Table 8.1) . Within the five genotypes, GI and GIV strains are found to infect humans exclusively, and GII Rabbit Polyclonal to MOS are found in both humans and pigs, while GIII and GV strains are animal viruses that infect cattle and murine species, Sodium orthovanadate respectively [15, 16]. Currently, strains in cluster 4 of GII (GII.4) are the most prevalent NoVs in human population [17, 18]. Table 8.1 Classification of noroviruses heat-liable toxin LTR192G) elicited anti-NVCP titers equivalent to that of two dosages of 200 g orally delivered adjuvanted VLPs . In addition to intestinal IgA in fecal samples, a strong anti-NVCP IgA response was also detected in vaginal washes. Furthermore, these mucosal IgA responses were long lasting and could be detected a year after the IN immunization . These data not only demonstrate that NVCP VLP is a potent mucosal antigen in stimulating systemic and local mucosal antibody responses, but also indicate its ability Sodium orthovanadate in eliciting antibody response at distal mucosa. These findings clearly demonstrated the ability of insect cell-derived NVCP VLPs in eliciting systemic and mucosal B-cell responses to potentially neutralize NV and inhibit its infection and also suggest Sodium orthovanadate their application as carriers of heterologous epitopes to combat sexually transmitted infections (STI). For example, chimeric NVCP VLPs that are decorated with epitopes of STI pathogens can potentially induce the production of neutralizing IgAs in the reproductive mucosa. Mammalian cell-VEE Replicon Produced NoV VLPs VEE, an alphavirus, has been developed as a replicon vaccine vector. To express a specific vaccine, the coding sequence for the antigen of interest is cloned in place of the VEE structural gene just downstream from the 26S promoter in VEE replicon cDNA to drive its high expression levels . Cotransfection of the cDNA replicon construct with another construct carrying VEE structural genes into mammalian cells will allow the recombinant viral RNA to pack in the VEE viral capsid to form virus replicon particles (VRPs) [57, 105, 115]. These VEE VRPs can infect mammalian cells.