This allowed us to determine whether epitope recognition by these MAbs was strain or genotype specific

This allowed us to determine whether epitope recognition by these MAbs was strain or genotype specific. only three MAbs exhibited therapeutic activity against a homologous strain when administered 2 days after infection. Remarkably, no MAb in our panel protected prophylactically against challenge by a strain from a heterologous DENV-3 genotype. Consistent with this, no single MAb neutralized efficiently the nine different DENV-3 strains used in this study, likely because of the sequence variation in DIII within and between genotypes. Our studies suggest that strain diversity may limit the efficacy of MAb therapy or tetravalent vaccines against DENV, as neutralization potency generally correlated with a narrowed genotype specificity. Dengue viruses (DENV) cause the most common arthropod-borne viral infection in humans worldwide, with 50 million to 100 million people infected annually and 2.5 billion people at risk (13,61). Infection by four closely related but Rabbit Polyclonal to NFYC serologically distinct viruses of theFlavivirusgenus (DENV serotypes 1, 2, 3, and 4 [DENV-1 to -4, respectively]) cause dengue fever (DF), an acute, self-limiting, yet severe, febrile illness, or dengue hemorrhagic fever and dengue shock syndrome (DHF/DSS), a potentially fatal syndrome characterized by vascular leakage and a bleeding Nepicastat HCl diathesis. Specific treatment or prevention of dengue disease is supportive, as there is no approved antiviral therapy or vaccine available. DENV has an 11-kb, single-stranded, positive-sense RNA genome that is translated into a polyprotein and is cleaved posttranslationally into three structural (envelope [E], pre/membrane [prM], and capsid [C]) and seven nonstructural (NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5) proteins. The three structural proteins encapsidate a single infectious RNA of the DENV genome, whereas the nonstructural Nepicastat HCl proteins have key enzymatic or regulatory functions that promote replication. Additionally, several DENV proteins are multifunctional and modulate cell-intrinsic and cell-extrinsic host immune responses (10). Most flavivirus-neutralizing antibodies recognize the structural E protein (reviewed in reference40). Based on X-ray crystallographic analysis (32,33), the DENV E protein is divided into three domains: domain I (DI), which is an 8-stranded -barrel, domain II (DII), which consists of 12 -strands, and domain III Nepicastat HCl (DIII), which adopts an immunoglobulin-like fold. Mature DENV virions are covered by 90 antiparallel E protein homodimers, arranged flat along the surface of the virus with quasi-icosahedral symmetry (25). Studies with mouse monoclonal antibodies (MAbs) against DENV-1 and DENV-2 have shown that highly neutralizing anti-DENV antibodies are serotype specific and recognize primarily the lateral-ridge epitope on DIII (15,49,53). Additionally, subcomplex-specific MAbs, which recognize some but not all DENV serotypes, recognize a distinct, adjacent epitope on the A -strand of DIII and also may be inhibitory (16,28,42,53,56). Complex-specific or flavivirus cross-reactive MAbs recognize epitopes in both DII and DIII and are generally less strongly neutralizing (8,53). Beyond having genetic complexity (the E proteins of the four distinct serotypes are 72 to 80% identical at the amino acid level), viruses of each serotype can be further divided into closely related genotypes (43,44,57). DENV-3 is divided into 4 or 5 5 distinct genotypes (depending on the study), with up to 4% amino acid variation between genotypes and up to 2% amino acid variation within a genotype (26,58,62). The individual genotypes of DENV-3 are separated temporally and geographically (1), with genotype I (gI) strains located in Indonesia, gII strains in Thailand, and gIII strains in Sri Lanka and the Americas. Few examples of strains of gIV and gV exist from samples isolated after 1980 (26,62). Infection with one DENV serotype is believed to confer long-term durable immunity against strains of the homologous but not heterologous DENV serotypes due to the specificity of neutralizing antibodies and protective CD8+T cells (45). Indeed, epidemiological studies.