Virus isolation, genetic characterization and seroprevalence of Toscana virus in Algeria.

Toscana virus (TOSV; Bunyaviridae, Phlebovirus) is transmitted by sandflies of the genus Phlebotomus in the Mediterranean area. One strain of TOSV was isolated from a total of almost 23 000 sandflies collected in Kabylia, Algeria. The complete genome was sequenced, and phylogenetic studies indicated that it was most closely related with TOSV strain from Tunisia within lineage A, which also includes Italian, French and Turkish strains. A seroprevalence study performed on 370 sera collected from people living in the same area showed that almost 50% possessed neutralizing antibodies against TOSV, a rate much higher than that observed in Southern Europe. Sandfly species distribution in the study area suggests that the vector of TOSV in this region belongs to the subgenus Larroussius. These data support the rapid implementation of the diagnosis of TOSV in clinical microbiology laboratories to estimate the burden in patients presenting with neuroinvasive infections and febrile illness.

Arthropods as a source of new RNA viruses.

The discovery and development of methods for isolation, characterisation and taxonomy of viruses represents an important milestone in the study, treatment and control of virus diseases during the 20th century. Indeed, by the late-1950s, it was becoming common belief that most human and veterinary pathogenic viruses had been discovered. However, at that time, knowledge of the impact of improved commercial transportation, urbanisation and deforestation, on disease emergence, was in its infancy. From the late 1960s onwards viruses, such as hepatitis virus (A, B and C) hantavirus, HIV, Marburg virus, Ebola virus and many others began to emerge and it became apparent that the world was changing, at least in terms of virus epidemiology, largely due to the influence of anthropological activities. Subsequently, with the improvement of molecular biotechnologies, for amplification of viral RNA, genome sequencing and proteomic analysis the arsenal of available tools for virus discovery and genetic characterization opened up new and exciting possibilities for virological discovery. Many recently identified but "unclassified" viruses are now being allocated to existing genera or families based on whole genome sequencing, bioinformatic and phylogenetic analysis. New species, genera and families are also being created following the guidelines of the International Committee for the Taxonomy of Viruses. Many of these newly discovered viruses are vectored by arthropods (arboviruses) and possess an RNA genome. This brief review will focus largely on the discovery of new arthropod-borne viruses.

New insights into centromere organization and evolution from the white-cheeked gibbon and marmoset.

The evolutionary history of alpha-satellite DNA, the major component of primate centromeres, is hardly defined because of the difficulty in its sequence assembly and its rapid evolution when compared with most genomic sequences. By using several approaches, we have cloned, sequenced, and characterized alpha-satellite sequences from two species representing critical nodes in the primate phylogeny: the white-cheeked gibbon, a lesser ape, and marmoset, a New World monkey. Sequence analyses demonstrate that white-cheeked gibbon and marmoset alpha-satellite sequences are formed by units of approximately 171 and approximately 342 bp, respectively, and they both lack the high-order structure found in humans and great apes. Fluorescent in situ hybridization characterization shows a broad dispersal of alpha-satellite in the white-cheeked gibbon genome including centromeric, telomeric, and chromosomal interstitial localizations. On the other hand, centromeres in marmoset appear organized in highly divergent dimers roughly of 342 bp that show a similarity between monomers much lower than previously reported dimers, thus representing an ancient dimeric structure. All these data shed light on the evolution of the centromeric sequences in Primates. Our results suggest radical differences in the structure, organization, and evolution of alpha-satellite DNA among different primate species, supporting the notion that 1) all the centromeric sequence in Primates evolved by genomic amplification, unequal crossover, and sequence homogenization using a 171 bp monomer as the basic seeding unit and 2) centromeric function is linked to relatively short repeated elements, more than higher-order structure. Moreover, our data indicate that complex higher-order repeat structures are a peculiarity of the hominid lineage, showing the more complex organization in humans.

Divergent origins and concerted expansion of two segmental duplications on chromosome 16.

An unexpected finding of the human genome was the large fraction of the genome organized as blocks of interspersed duplicated sequence. We provide a comparative and phylogenetic analysis of a highly duplicated region of 16p12.2, which is composed of at least four different segmental duplications spanning in excess of 160 kb. We contrast the dispersal of two different segmental duplications (LCR16a and LCR16u). LCR16a, a 20 kb low-copy repeat sequence A from chromosome 16, was shown previously to contain a rapidly evolving novel hominoid gene family (morpheus) that had expanded within the last 10 million years of great ape/human evolution. We compare the dispersal of this genomic segment with a second adjacent duplication called LCR16u. The duplication contains a second putative gene family (KIAA0220/SMG1) that is represented approximately eight times within the human genome. A high degree of sequence identity (approximately 98%) was observed among the various copies of LCR16u. Comparative analyses with Old World monkey species show that LCR16a and LCR16u originated from two distinct ancestral loci. Within the human genome, at least 70% of the LCR16u copies were duplicated in concert with the LCR16a duplication. In contrast, only 30% of the chimpanzee loci show an association between LCR16a and LCR16u duplications. The data suggest that the two copies of genomic sequence were brought together during the chimpanzee/human divergence and were subsequently duplicated as a larger cassette specifically within the human lineage. The evolutionary history of these two chromosome-specific duplications supports a model of rapid expansion and evolutionary turnover among the genomes of man and the great apes.