The complexities of CD28 and CTLA-4 signalling: PI3K and beyond

A successful immune response requires a set of non-cognate cell-cell interactions which provide the second "costimulatory" signal to the T cells. The best characterized costimulatory receptor expressed on resting T cells is CD28 which provides poorly-defined cyclosporin-resistant biochemical signal(s) that promote expression of several cytokines/chemokines. Another major effect of CD28 ligation is the promotion of cell survival which is thought to occur via the up-regulation of Bcl-xL expression, CD28 shares its ligands B7.1 and B7.2 with the related CTLA-4, which plays an inhibitory role in T cell activation. Manipulation of CD28/CTLA-4 interactions with their natural ligands has provided exciting results in transplantation and tumor therapy settings and also has potential in the treatment of several diseases such as arthritis and multiple sclerosis, asthma and protection against HIV infection. The biochemical basis for the different functional outcomes of CD28 and CTLA-4 ligation has been the subject of intense investigation over the past few years. This review will focus on our current understanding of the biochemical signals that may be involved in regulating the different functional outcomes of CD28 and CTLA-4, with particular emphasis on the role played by the PI3K-dependent signalling cascade.     

Watermelon mosaic virus-Morocco is a distinct potyvirus

Summary The relationship of the Morocco isolate of watermelon mosaic virus (WMV) to WMV 2, soybean mosaic virus (a virus closely related to WMV 2) and the W strain of papaya ringspot virus (PRSV-W), formerly WMV 1, was examined by comparing tryptic peptide profiles using high performance liquid chromatography. The profiles indicated that the coat protein sequence of WMV-Morocco differed substantially from those of the other potyviruses. This conclusion was supported by sequence data from five tryptic peptides from the coat protein of WMV-Morocco, which showed only 61–68% identity to equivalent sequences in PRSV-W, WMV 2 and zucchini yellow mosaic, another potyvirus infecting cucurbits. Based on the above data, and on known correlations between coat protein sequence similarities and potyvirus relationship, it is concluded that WMV-Morocco should be regarded as a distinct potyvirus.     

Angiotensin-1-converting enzyme (ACE) plasma concentration is influenced by multiple ACE-linked quantitative trait nucleotides

Circulating angiotensin-1-converting enzyme (ACE) is a highly heritable trait, and a major component of the genetic variance maps to the region of the ACE gene. The strong effect of the locus, and the interest in ACE as a candidate gene for cardiovascular disorders, has led to extensive investigation of its relationship to the ACE phenotype, providing one of the most complete examples of quantitative trait locus (QTL) analysis in humans. Resequencing of ACE followed by haplotype analysis in families of British and French origin has shown that the genetic variants that are primarily associated with the ACE trait map to an 18 kb interval flanked by two intragenic, ancestral recombination breakpoints. This critical interval contains dozens of ACE-associated variants in Caucasians, but identification of which of these directly influence ACE concentration is ambiguous because of the almost complete linkage disequilibrium in European populations. In a complementary sequencing and genotyping study of individuals from West African families, we show that this population has much greater haplotype diversity across the gene. Through analysis of the contrasting relationships of the trait phenotype with haplotypes that carry different allelic combinations from those observed in Caucasians, we demonstrate that (at least) two major intragenic sites within the critical interval and (at least) one minor promoter site are associated with the ACE quantitative trait through additive effects. These results point to the importance of analysing diverse populations with different gene genealogies in gene-association studies.     

Gain of 1q and loss of 22 are the most common changes detected by comparative genomic hybridisation in paediatric ependymoma

Ependymomas are the third most common brain tumour in the paediatric population. Although cytogenetic and molecular analyses have pinpointed deletions of chromosomes 6q, 17, and 22 in a subset of tumours, definitive patterns of genetic aberrations have not been determined. In the present study, we analysed 40 ependymomas from paediatric patients for genomic loss or gain using comparative genomic hybridisation (CGH). Eighteen of the tumours (45%) had no detectable regions of imbalance. In the remaining cases, the most common copy number aberrations were loss of 22 (25% of tumours) and gain of 1q (20%). Three regions of high copy number amplification were noted at 1q24-31 (three cases), 8q21-23 (two cases), and 9p (one case). Although there was no association with the loss or gain of any chromosome arm or with benign versus anaplastic histologic characteristics, the incidence of gain of 7q and 9p and loss of 17 and 22 was significantly higher in recurrent versus primary tumours. This study has identified a number of chromosomal regions that may contain candidate genes involved in the development of different subgroups of ependymoma.     

An attempt to treat rabies encephalitis in monkeys with intrathecal live rabies virus RV 675

Summary A highly attenuated rabies virus, RV 675, proved innocuous but immunogenic when injected intrathecally into monkeys by the lumbar route. Attempts to use this virus to modify the course of fatal rabies encephalitis in monkeys were inconclusive possibly because of the brief encephalitic illness. Further studies are indicated to investigate RV 675 as a candidate therapeutic agent for rabies encephalitis.     

Coat protein of potyviruses 7. Amino acid sequence of peanut stripe virus

Summary The amino acid sequence of the 287-residue coat protein of peanut stripe virus (PStV) was determined from the sequences of overlapping peptide fragments. Results indicated that the amino terminus was blocked by an acetyl group, as has previously been found for the coat protein of Johnsongrass mosaic potyvirus. Comparison of the PStV sequence with coat proteins of 20 distinct potyviruses gave sequence identities of 47–57%, except for zucchini yellow mosaic virus (ZYMV), passionfruit woodiness virus (PWV), and the related strains watermelon mosaic virus 2 (WMV 2) and soybean mosaic virus-N, which showed sequence identities of 70–76%. Several amino acid residues which were common to the core sequences of these coat proteins were at positions previously found to be invariant among potyvirus coat proteins. The degree of these similarities suggests that although PStV, WMV 2, ZYMV, and PWV are distinct potyviruses, they share a common ancestor in their evolutionary development.     

"Acadian" and "classical" forms of Friedreich ataxia are most probably caused by mutations at the same locus

"Acadian ataxia" is a form of Friedreich ataxia found in individuals of Acadian ancestry. It was described by Barbeau (in Sobue I (ed): Spinocerebellar Degeneration; Tokyo: Univ. Tokyo Press, pp 121-142, 1980) as having a slower course of degeneration and less severe secondary symptoms than "classical" Friedreich ataxia. He suggested that these 2 forms of the disease may be distinct. The mutation causing "classical" Friedreich ataxia has recently been mapped to chromosome 9 through genetic linkage studies, and here we show that the locus causing Friedreich ataxia in Acadian families from southwestern Louisiana is tightly linked to the same DNA marker, D9S15. Thus, these 2 disorders, which may be differentiated clinically, are most probably due to mutation(s) at the same locus on chromosome 9.     

Chemical and antigenic characterization of the carbohydrate side chains of an Asian (N2) influenza virus neuraminidase

The Pronase-released neuraminidase heads from the Asian influenza virus A/Tokyo/3/67 contain four oligosaccharide units attached at asparagine residues 86, 146, 200, and 234. Chemical analysis of the isolated tryptic, chymotryptic, or thermolytic glycopeptides shows that the oligosaccharide side chains attached at residues 86 and 200 are essentially of the oligomannoside (simple or Type II) variety containing two residues of N-acetylglucosamine, five residues of mannose, and less than molar ratios of galactose and fucose. The carbohydrate side chains attached at residues 146 and 234 are of the N-acetyllactosamine (complex or Type I) type and contain N-acetylglucosamine, mannose, galactose, and fucose. The complex oligosaccharide unit at residue 146 is unusual in that it also contains N-acetylgalactosamine, a sugar residue rarely found in N-glycosidically linked carbohydrates. Antigenic analysis of these four isolated glycopeptides showed that only the N-acetyllactosamine oligosaccharide unit at asparagine residue 146 was capable of binding to antibodies raised against uninfected chick chorioallantoic membranes and is hence antigenically related to chick embryo host antigen.     

Efficiency of human rotavirus propagation in cell culture.

This study was designed to find methods to reproducibly propagate human rotaviruses from fecal specimens and to determine the relationship between particle numbers and infectivity. Growth of virus was initially compared in primary and continuous lines of monkey kidney cells. Primary cells (African green and cynomolgus monkey kidney) supported virus growth directly from fecal specimens much more efficiently than did continuous lines of African green (CV-1) or rhesus (MA104) monkey kidney cells. Rotaviruses were grown in primary cells from 14 of 14 fecal specimens of different individuals collected over a 3-year period. Although rotaviruses in fecal samples could not always be grown in the continuous cell lines, two passages in primary cells appeared to fully adapt the viruses for propagation in the continuous cell line tested (MA104). The efficiency of rotavirus growth was quantified with five of the fecal isolates. It was calculated that, on the average, 1 out of every 46,000 particles in fecal specimens infected monkey kidney cells. After three passages in primary cells, an average of 1 out of every 6,600 progeny virus particles appeared to be infectious. Thus, rotaviruses in fecal specimens were consistently grown in primary cells, and passage in these cells both increased virus infectivity and adapted the viruses for growth in continuous cell lines.