Clonació del gen de l'envolta de vih en el plàsmid pnl Δenv-Ren per la obtenció de recombinants

Estudi elaborat a partir d’una estada al Laboratori de Inmunopatología del SIDA del Dr Alcamí a l’Instituto de Salud Carlos III-Centro Nacional de Microbiologia, entre finals de desembre de 2006 i març de 2007. L’objectiu ha estat millorar la caracterització de l’envolta del VIH-1 mitjançant l’obtenció de virus recombinants, ja que això permet estudiar l’envolta viral tant genètica com fenotípicament. En aquest cas, s’ha estudiat l'envolta viral dels pacients sotmesos a vacunació terapèutica amb cèl•lules dendrítiques polsades amb virus autòlegs. Durant aquesta estada es realitza un aprenentatge profund de les tècniques adequades per a l'amplificació i clonatge del gen complet de l'envolta del VIH-1 (env), així com de l’obtenció de virus recombinants amb l’envolta del pacient i els corresponents assaigs de tropisme viral i neutralització sèrica. Aquesta metodologia empra el virus quimèric pNL4.3 delta_env Renilla, construït a partir del virus de referència NL4.3 i que té dues característiques importants: la primera és que conté un gen marcador Renilla, que a l’interior de les cèl•lules infectades té activitat luciferasa. La utilització del virus pNL4.3 delta_env Renilla en assaigs de neutralització presenta diversos avantatges front altres assaigs més convencionals, tant a nivell de sensibilitat i especificitat com d’estalvi de temps.

Recent studies on Schistosoma intercalatum: taxonomic status, puzzling distribution and transmission foci revisited

Schistosoma intercalatum, which causes human rectal schistosomiasis in Africa, still presents a great interest for its imprecise taxonomic status and its puzzling distribution in Africa. Two geographically isolated strains of S. intercalatum are recognized, the Lower Guinea strain and the Congo strain, which differ from each other in a number of morphological, biological and biochemical characteristics. Recent molecular data using RAPD markers indicate high divergence between the two strains, with values of Nei and Li's similarity indice allowing recognition of two genetically distinct taxa: experiments on pre- and post-isolating mechanisms are in progress in order to re-evaluate the taxonomic status of this polytypic species. With regard to its geographical distribution, S. intercalatum is characterized by the existence of two stable endemic areas (localized in Lower Guinea and North East of Democratic Republic of Congo) which correspond to the historical areas of species discovery, and the emergence during the last 15 years of new foci of the Lower Guinea strain outside previously known endemic areas. The absence of local adaptation of the Lower Guinea strain to its intermediate host, supported by experimental studies, may help to facilitate the spread of this strain. Nevertheless, the present restricted distribution of this species remains puzzling, because its potential snail hosts (bulinids) are widely distributed throughout much of Africa. Recent experimental and epidemiological studies suggest that interspecific sexual interactions between human schistosomes could have a role in limiting the distribution of S. intercalatum: the competitive sexual processes acting among human schistosomes show that S. haematobium and S. mansoni are always competitively dominant over S. intercalatum. These epidemiological observations lead the authors to distinguish three kinds of transmission foci for S. intercalatum.

Genetic characterization of St. Louis encephalitis virus isolated from human in São Paulo, Brazil

The molecular characterization of SPH253157, a new strain of St. Louis encephalitis virus (SLEV), isolated in 2004 from the first case of human infection recognized in the state of São Paulo, Brazil, is reported. The patient, presenting a febrile illness without neurological involvement, was hospitalized as a probable case of dengue fever. Genomic RNA was isolated from the supernatant of C6/36 cells infected with acute phase-serum specimen of the patient and the envelope gene was amplified by reverse-transcription-polymerase chain reaction. The complete nucleotide sequence of the envelope gene of this isolate was directly sequenced from the amplified products and compared with other Brazilian and American SLEV strains. Phylogenetic analyses were carried out under maximum likelihood criterion with outgroups both included and excluded. Outgroups comprised four flavivirus of the Japanese encephalitis group. Phylogeny also included Bayesian analysis. The results indicated that the new SLEV isolate belongs to lineage III, being closely related to an Argentinean strain recovered from Culex sp. in 1979. It is concluded that there are at least 3 lineages of SLEV in Brazil.