Strikingly, analysis performed on a large number of culture supernatants showed that this fraction of DIII- and DI/DII-cross-reactive antibodies was considerably higher in secondary infections

Strikingly, analysis performed on a large number of culture supernatants showed that this fraction of DIII- and DI/DII-cross-reactive antibodies was considerably higher in secondary infections. and Vaughn, 2002), with an economic burden rivaling that of malaria. A primary infection is believed to provide effective, durable and possibly life-long protection against re-infection with the same serotype, but only short-term protection against other serotypes (Rothman, 2004). Classical epidemiologic studies suggested that immunity to one of the four DENV serotypes can increase disease severity upon subsequent challenge with a different serotype leading, in some cases, to severe dengue, a disease characterized by plasma leakage and hemorrhagic manifestations Xipamide (Halstead, 1970). Poorly neutralizing cross-reactive antibodies raised in response to a previous serotype are believed to contribute to pathogenesis of severe dengue by promoting computer virus entry via Fc receptors (FcR) and contamination of myeloid cells (Halstead, 2003), leading to antibody-dependent enhancement (ADE) of contamination. The role of antibodies in severe dengue is S5mt supported by epidemiological studies showing that infants with waning levels of maternal antibodies (age 69 months) are most vulnerable to severe DENV disease (Halstead et al., 2002;Nguyen et al., 2004), and that serum from these infants enhances DENV infectionin vitro(Chau et al., 2008;Kliks et al., 1988). The difficulty of balancing immunity to the four serotypes and minimizing incomplete response and the risk of ADE are major hurdles in the development of a tetravalent vaccine against DENV (Whitehead et al., 2007). The 10.7 Kb RNA genome of DENV encodes three structural proteins, the capsid protein (C), a membrane-associated protein (prM), and an envelope protein (E), and seven non-structural proteins (NS1, NS2A, Xipamide NS2B, Xipamide NS3, NS4A, NS4B, NS5). The E protein is usually structurally conserved among flaviviruses and consists of three distinct domains. Domain name I (DI) participates in the conformational changes required for viral entry and nucleocapsid escape from the endosomal compartment, domain Xipamide name II (DII) contains the fusion loop, and domain name III (DIII) has been suggested to bind cellular receptors (Bhardwaj et al., 2001;Chin et al., 2007;Chu et al., 2005;Rey et al., 1995). Partially mature virions also express varying levels of prM protein on their surface, which is normally cleaved by a furin-like cellular protease to generate the mature virion (Stadler et al., 1997). The most potent neutralizing antibodies against DENV, or other flaviviruses such as West Nile Computer virus (WNV), bind to DIII and have been shown in some cases to be effective as passive prophylaxis or therapy in rodents (Beasley and Barrett, 2002;Goncalvez et Xipamide al., 2008;Gromowski et al., 2008;Kaufman et al., 1987;Oliphant et al., 2005;Sanchez et al., 2005;Shrestha et al., 2010;Sukupolvi-Petty et al., 2007). DIII-reactive antibodies produced by mice immunized with computer virus and boosted with recombinant E protein are largely serotype-specific and do not neutralize all the genotypes within a given serotype (Shrestha et al., 2010). The role of antibodies to DI/DII is usually less clear as they tend to be more cross-reactive and less potent in neutralization (Crill and Chang, 2004;Goncalvez et al., 2004;Oliphant et al., 2006). Antibodies to prM generally have poor neutralizing and enhancing activity (Falconar, 1999;Huang et al., 2006), although recent studies suggest that some anti-prM mAbs can augment infectivity of poorly infectious immature virions (Rodenhuis-Zybert et al., 2010). Antibodies against NS1, a secreted non-structural glycoprotein that is absent from the virion but expressed around the cell surface, can also protect against infectionin vivo, through FcR-dependent and -impartial mechanisms (Chung et al., 2006), or possibly contribute to pathogenesis (Falconar, 2007;Lin et al., 2008). Our current knowledge of the human antibody response to DENV is mostly based on serological studies. In this study, we used an improved method of memory B cell immortalization (Traggiai et al., 2004) combined with a broad screening approach to isolate a large panel of DENV-reactive mAbs from human donors..