Measles Virus Hemagglutinin epitopes immunogenic in natural infection and vaccination are targeted by broad or genotype-specific neutralizing monoclonal antibodies.

Measles virus (MV) remains a leading cause of vaccine-preventable deaths in children. Protection against MV is associated with neutralizing antibodies that preferentially recognize the viral hemagglutinin (MV-H), and to a lesser extent, the fusion protein (MV-F). Although MV is serologically monotypic, 24 genotypes have been identified. Here we report three neutralization epitopes conserved in the more prevalent circulating MV genotypes, two located in the MV-H receptor binding site (RBS) (antigenic site III) and a third in MV-H/MV-F interphase (antigenic site Ia) which are essential for MV multiplication. In contrast, two MV-H neutralization epitopes, showed a genotype-specific neutralization escape due to a single amino acid change, that we mapped in the "noose" antigenic site, or an enhanced neutralization epitope (antigenic site IIa). The monoclonal antibody (mAb) neutralization potency correlated with its binding affinity and was mainly driven by kinetic dissociation rate (koff). We developed an immunoassay for mAb binding to MV-H in its native hetero-oligomeric structure with MV-F on the surface of a MV productive steady-state persistently infected (p.i.) human cell lines, and a competitive-binding assay with serum from individuals with past infection by different MV genotypes. Binding assays revealed that a broad neutralization epitope, in RBS antigenic site, a genotype specific neutralization epitopes, in noose and IIa sites, were immunogenic in natural infection and vaccination and may elicit long-lasting humoral immunity that might contribute to explain MV immunogenic stability. These results support the design of improved measles vaccines, broad-spectrum prophylactic or therapeutic antibodies and MV-used in oncolytic therapies.

Measles virus genetic evolution throughout an imported epidemic outbreak in a highly vaccinated population.

Measles virus circulates endemically in African and Asian large urban populations, causing outbreaks worldwide in populations with up-to-95% immune protection. We studied the natural genetic variability of genotype B3.1 in a population with 95% vaccine coverage throughout an imported six month measles outbreak. From first pass viral isolates of 47 patients we performed direct sequencing of genomic cDNA. Whilst no variation from index case sequence occurred in the Nucleocapsid gene hyper-variable carboxy end, in the Hemagglutinin gene, main target for neutralizing antibodies, we observed gradual nucleotide divergence from index case along the outbreak (0% to 0.380%, average 0.138%) with the emergence of transient and persistent non-synonymous and synonymous mutations. Little or no variation was observed between the index and last outbreak cases in Phosphoprotein, Nucleocapsid, Matrix and Fusion genes. Most of the H non-synonymous mutations were mapped on the protein surface near antigenic and receptors binding sites. We estimated a MV-Hemagglutinin nucleotide substitution rate of 7.28 × 10-6 substitutions/site/day by a Bayesian phylogenetic analysis. The dN/dS analysis did not suggest significant immune or other selective pressures on the H gene during the outbreak. These results emphasize the usefulness of MV-H sequence analysis in measles epidemiological surveillance and elimination programs, and in detection of potentially emergence of measles virus neutralization-resistant mutants.

Syncytial giant cell hepatitis in human immunodeficiency virus-infected patients with chronic hepatitis C: 2 cases and review of the literature.

Syncytial giant cell hepatitis (SGCH) among adult human immunodeficiency virus (HIV)-infected patients has been rarely described. Most cases have been reported in subjects coinfected with the hepatitis C virus (HCV), but its prevalence and outcome remain unknown. We performed a retrospective analysis of all cases of SGCH among 332 liver biopsies from HIV-infected patients seen at a tertiary center in Madrid, Spain, between 1984 and March 2004. Two hundred fifty specimens were obtained from HCV-coinfected patients. There were 2 cases of SGCH, leading to an observed overall prevalence of 0.6% (0.8% when considering only HCV-coinfected patients). In addition to histological changes secondary to chronic hepatitis C, the liver cords were replaced by syncytial giant cells with up to 30 nuclei. There was no histological evidence of measles (among paramyxoviruses) or herpes viruses group infections. In patient 1, there was a progressive clinical worsening after a 3-month course of prednisone, leading to liver failure and death. His postmortem liver biopsy showed more abundant giant hepatocytes accompanied with the development of a histologic pattern of severe fibrosing cholestatic hepatitis. The second patient received a prolonged course of pegylated interferon-alpha-2b and ribavirin with clearance of syncytial giant hepatocytes despite HCV-RNA persistence. SGCH is a rare histological finding among HIV-infected patients with chronic hepatitis C. Specific treatment with pegylated interferon and ribavirin can lead to histological resolution and biochemical improvement, even in the absence of HCV-RNA clearance.