David J. Evans

Cell receptors for picornaviruses as determinants of cell tropism and pathogenesis

Recent studies have identified at least nine distinct receptors used by the piconaviruses for cell entry. Does the evolution of receptor usage correlate with the different tropisms observed in this group of viruses, and does this influence pathogenesis, or is it the consequence of another selection mechanism that favours virus survival?

Characterization of echoviruses that bind decay accelerating factor (CD55): evidence that some haemagglutinating strains use more than one cellular receptor.

Several echoviruses (EVs) have previously been shown to use decay accelerating factor (DAF) as a cellular receptor. Since DAF is expressed on erythrocytes, EVs that use this receptor cause haemagglutination. Here we show that all EVs that haemagglutinate do so via attachment to DAF and that this interaction can be inhibited by a monoclonal antibody (MAb) specific for DAF domain SCR3. Although the viruses haemagglutinate via DAF some can bind to rhabdomyosarcoma cells from which DAF has been removed and infect in the presence of a MAb against DAF. This suggests that some EVs have the capacity to interact with more than one cellular receptor.

Modelling of poliovirus : HIV-1 antigen chimaeras

We have used laboratory‐based molecular modelling to identify structural features of antigen chimaeras of poliovirus expressing epitopes from human immunodeficiency virus (HIV‐1) that may affect virus viability. Chimaeras were constructed by replacement of antigenic site 1 of VP1 by sequences corresponding to epitopes from HIV‐1. Loop volume, estimated by approximating the loop to an ellipsoid was significantly (P < 0.001) lower in viable (2062.1 Å3 ± 400.2) than in non‐viable (3617 Å3 ± 650.7) constructs. Our results suggest that viable virus will only be formed when antigen chimearas modified at antigenic site of VP1 have a loop occupying a similar volume in space to that occupied by the antigenic site 1 loop. In addition, the modified loop must fit with the peptide bond angles and distances at the top of the β‐barrel of VP1.

A Cassette Vector for the Construction of Antigen Chimaeras of Poliovirus

A cassette vector has been constructed which allows the rapid and extensive modification of one of the neutralizing antigenic sites of the Sabin 1 poliovirus vaccine strain, P1/LSc 2ab. Unique restriction endonuclease sites flanking antigenic site 1 have been engineered into a full-length infectious Sabin 1 cDNA clone with minimal alteration to the coding sequence. This facilitates replacement of this region by oligonucleotides encoding foreign amino acid sequences. Our results indicate that this region is highly flexible in terms of the number and sequence of amino acids which can be accommodated.

Poliovirus antigen chimeras

Poliovirus, the aetiological agent of paralytic poliomyelitis, is arguably the best characterized of all animal viruses. Using recombinant-DNA technology, this information, together with the availability of infectious cDNA clones of the notably safe and efficacious live attenuated Sabin 1 vaccine strains of poliovirus, has enabled the creation of hybrid viruses (chimeras) possessing novel antigenicity. The potential applications of these epitope-presentation systems include their use as immunogens, as antigens for serodiagnosis, and as vaccines.

Global attractivity in a recursive sequence

In this paper, we study the invariant intervals, the globally attractivity of the two equilibrium points, and the oscillatory behavior of the solutions of the difference equationxn=axn-1-bxn-2c+xn-2,n=1,2,...,where a,b,c>0.

Serum albumin inhibits echovirus 7 uncoating

Echoviruses induce a wide spectrum of diseases in man, the most severe being meningitis. In neonates, however, a severe systemic infection can be observed, leading to death. Serum albumin is the most abundant protein in plasma and most interstitial fluids, and its functions include osmoregulation and transport and delivery of hydrophobic molecules such as fatty acids and steroids. The results of cold-synchronized one-step growth analysis of echovirus 7 infection and sucrose-gradient analysis of A-particles suggest that physiological concentrations of albumin block echovirus 7 infection by inhibiting uncoating. The blockage was reversible and was still effective when albumin was added 30 min after virus adsorption. Inhibition of uncoating was confirmed by using rhodanine, a known specific inhibitor of echovirus uncoating. After removal of the albumin blockage, addition of rhodanine perpetuated the inhibition. Serum and interstitial albumin concentrations may limit echovirus infection in vivo and thereby act as an extracellular determinant for echovirus tropism.

Growth and characterization of poliovirus antigen chimeras.

Chapter 22 outlines the construction of engineered, full-length poliovirus cDNAs in which the region encoding a well-characterized antigenic site has been replaced by sequences of choice. This chapter briefly describes the methods used to generate, maintain, and characterize infectious chimeric viruses. These techniques include several developed during the course of poliovirus study that have recently been published (1). This overview describes modifications to these techniques where relevant, but concentrates on methods not detailed by Minor (1). The production and analysis of poliovirus antigen chimeras can be readily subdivided into three discrete areas.

Design and Construction of Poliovirus Epitope Expression Vectors

We have developed the very safe and efficacious live-attenuated Sabin 1 poliovirus vaccine strain as a vehicle for the presentation of defined epitopes from foreign pathogens (1-3). Precise modification of the poliovirus capsid is made possible by the application of recombinant DNA technology to cloned cDNA copies of the viral genome, which are infectious for mammalian cells in culture (4).