María Luisa Celma

Structure of the measles virus hemagglutinin bound to the CD46 receptor

The highly contagious measles virus infects millions of individuals worldwide, causing serious disease in children of developing countries. Infection is initiated by attachment of the measles virus hemagglutinin (MV-H), a glycoprotein anchored to the virus envelope, to the host cell receptors CD46 or signaling lymphocyte activation molecule (SLAM). Here we report the crystal structure of MV-H in complex with a CD46 protein spanning the two N-terminal domains. A unique groove at the side of the MV-H β-propeller domain, which is absent in homologous paramyxovirus attachment proteins, engages residues in both CD46 domains. Key contacts involve a protruding loop in the N-terminal CD46 domain that carries two sequential proline residues (PP motif) and penetrates deeply into a hydrophobic socket in MV-H. We identify a similar PP motif in SLAM, defining a common measles virus recognition epitope in the CD46 and SLAM receptor proteins.

Visceral leishmaniasis as an opportunistic infection in the acquired immunodeficiency syndrome

We describe the case of a woman aged 34 years infected with the human immunodeficiency virus and whose illness was complicated by visceral leishmaniasis that ultimately led to her death.

Measles virus from a long-term persistently infected human T lymphoblastoid cell line, in contrast to the cytocidal parental virus, establishes an immediate persistence in the original cell line.

To investigate the mechanisms of measles virus (MV) establishment and maintenance of persistence in lymphoid cells, we have established a long-term persistent infection with MV, Edmonston strain, in the human T lymphoblastoid cell line MOLT4, which has been in continuous culture for over 8 years. In this culture, designated MOMP1, more than 98% of cells display viral antigens. The MOMP1 culture is immune to superinfection with MV and is not cured by anti-MV antibodies. No evidence of defective interfering particles was obtained. The persistently infected culture releases an infectious virus showing a miniplaque and thermoresistant modified phenotype that, unlike the parental virus Edmonston strain which produces a lytic infection with extensive cell fusion, establishes an immediate persistence in MOLT4 cells with neither significant loss of cell viability nor cell fusion. This suggests that the modification in the virus suffices to maintain the state of persistence without requiring a coevolution of the host cell during the infection, as has been reported in other persistent virus infections.

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.

Measles virus gene expression in lytic and persistent infections of a human lymphoblastoid cell line

MOMP1 is a measles virus (MV) long-term steady-state persistently infected culture of the human T lymphoblastoid cell line MOLT4. The analysis of MV gene expression revealed that in MOMP1 cells, the major MV proteins, haemagglutinin (H), phosphoprotein (P), nucleoprotein, fusion (F) and matrix (M), are present and the fusion precursor (F0) is cleaved into F2 and F1 peptides. H and F2 proteins are glycosylated in both lytic and persistent MOLT4 infections. All major proteins are underexpressed in the persistently infected cultures in comparison to the lytically infected cells. However a relatively greater reduction was observed for H, M and P proteins. Pulse-chase labelling experiments indicated that this underexpression of H, M and P proteins was not due to selective degradation of these proteins in the persistent infection (p.i.). The relative amounts of the major monocistronic and dicistronic mRNAs for MV proteins, with the exception of P mRNA, was not altered in the p.i. with respect to lytically infected MOLT4 cells, suggesting that the defective expression of H and M proteins was not due to a restriction in the transcription of their mRNAs. In contrast, the mRNA for P protein, the most abundant MV mRNA in these lytically infected T lymphoid cells, is markedly underexpressed in the homologous p.i. Thus the underexpression of P protein in p.i. could be due to a decreased availability of P mRNA. This unbalanced underexpression of MV proteins may impair the cell fusion and c.p.e. of MV and facilitate viral persistence in human lymphoid cells.

Epidemiología molecular del virus del sarampión

INTRODUCCION El virus del sarampion (VS) pertenece al genero de los Morbillivirus, que agrupa a los virus del moquillo canino, virus de la peste bovina, virus de los pequenos rumian- tes, morbillivirus de los focidos, y al morbi- llivirus de los delfines. Este genero pertene- ce a la familia de los Paramimviridae, que son virus RNA de una sola cadena de polari- dad negativa (complementaria a los RNA mensajeros) que forma una nucleocapside helicoidal recubierta de membrana de ori- gen celular’. El genoma de los virus salvajes del sa- rampion es una molecula de RNA de 15.984 nucleotidos2, codifica por las proteinas es- tructurales: N (nucleocapsida), P (fosfopro- teina), L (polimerasa), M (matriz), H (hema- glutinina) y F (de fusion) que se incorporan a las particulas viricas, y otras no estructura- les V y C que se encuentran solamente en las celulas infectadas. En la figura 1 se es- quematizan la estructura de virus y sus pro- teinas. El virus de sarampion es un virus de transmision respiratoria que infecta a huma- nos y primates, y del que no se han descrito serotipos.