Felipe García-Vallejo

Sequence and phylogenetic analysis of human T cell lymphotropic virus type 1 from Tumaco, Colombia

Human T cell lymphotropic virus type 1 (HTLV-1) is a retrovirus that causes leukemia and the neurological disorder HTLV-1 associated myelopathy or tropical spastic paraparesis (HAM/TSP). Infection with this virus - although it is distributed worldwide - is limited to certain endemic areas of the world. Despite its specific distribution and slow mutation rate, molecular epidemiology on this virus has been useful to follow the movements of human populations and routes of virus spread to different continents. In the present study, we analyzed the genetic variability of a region of the env gene of isolates obtained from individuals of African origin that live on the Pacific coast of Colombia. Sequencing and comparison of the fragment with the same fragment from different HTLV-1 isolates showed a variability ranging from 0.8% to 1.2%. Phylogenetic studies permit us to include these isolates in the transcontinental subgroup A in which samples isolated from Brazil and Chile are also found. Further analyses will be necessary to determine if these isolates were recently introduced into the American continent or if they rather correspond to isolates introduced during the Paleolithic period.

Changes in the topology of gene expression networks by human immunodeficiency virus type 1 (HIV-1) integration in macrophages.

One key step of human immunodeficiency virus type 1 (HIV-1) infection is the integration of its viral cDNA. This process is mediated through complex networks of host-virus interactions that alter several normal cell functions of the host. To study the complexity of disturbances in cell gene expression networks by HIV-1 integration, we constructed a network of human macrophage genes located close to chromatin regions rich in proviruses. To perform the network analysis, we selected 28 genes previously identified as the target of cDNA integration and their transcriptional profiles were obtained from GEO Profiles (NCBI). A total of 2770 interactions among the 28 genes located around the HIV-1 proviruses in human macrophages formed a highly dense main network connected to five sub-networks. The overall network was significantly enriched by genes associated with signal transduction, cellular communication and regulatory processes. To simulate the effects of HIV-1 integration in infected macrophages, five genes with the most number of interaction in the normal network were turned off by putting in zero the correspondent expression values. The HIV-1 infected network showed changes in its topology and alteration in the macrophage functions reflected in a re-programming of biosynthetic and general metabolic process. Understanding the complex virus-host interactions that occur during HIV-1 integration, may provided valuable genomic information to develop new antiviral treatments focusing on the management of some specific gene expression networks associated with viral integration. This is the first gene network which describes the human macrophages genes interactions related with HIV-1 integration.

Caracterización genómica de la integración in vitro del VIH-1 en células mononucleares de sangre periférica, macrófagos y células T de Jurkat

Introduction: Most of the infected host cell genome is available for retroviral integration; however, it has been proposed that this process does not occur at random and depends upon each type of retrovirus. Objective: The objective is to identify and characterize differences in human genome regions of peripheral blood mononuclear cells, macrophages and Jurkat T cells in which integration of HIV-1 occurs. Material and Methods: Three hundred human DNA genome sequences, previously deposited in the GenBank, were selected at random. Using program BLAST, only 264 of them were included in the study because relevant information about chromosomal position, associated genes, repetitive sequences, number of CpG islands and average replication time was available; these sequences were exported to other data bases for analysis. Results: 53% (140/264) of integrations were located on G bands. 70.45% of provirus was located in human genes and the rest was located in repetitive elements. In general the integration site selection was correlated with genomics and structural characteristics of cell chromatin including Alu-Sx and L1 sequences, gene and CpG island densities, remodeling of chromatin, and replication time. All of them would influence the efficient interaction between the pre-integration complex and target cell genomes. Conclusion: It was determined that HIV-1 integration in target cellular genomes would be conditioned by differential characteristics of associated chromatin and by epigenetic processes that would influence the selection of integration sites.

Envelope Sequence Variation and Phylogenetic Relations of Human T Cell Lymphotropic Virus Type 1 from Endemic Areas of Colombia

The HTLV-1 envelope gene of 12 TSP/HAM patients from two endemic areas of southwest Colombia (Tumaco and Buenaventura) was amplified by nested PCR, sequenced, and compared with previously reported HTLV-1 envelope sequences from isolates worldwide. In general, the sequence divergences among all Colombian samples ranged from 0.1 to 1.6%. Some amino acid substitutions, referring to the ATK-1 prototype strain in the surface domain gp46 and in p21, were highly prevalent in southwest Colombia, suggesting a geographical clustering of mutations in the envelope gene. The phylogenetic analysis showed that the Colombian isolates belong to the HTLV-1a lineage with minor subgroups. The genetic distance between Colombian and Japanese isolates ranged from 0.1 to 1.8%; in comparison, the genetic distance between Colombian and Caribbean isolates ranged from 0.4 to 2.2%. Our results strongly suggest that the actual quasispecies populations in southwest Colombia have been generated by separate, differently timed introductions of virus.

Serological and virological evaluation of human T-lymphotropic virus type 1 infection in family groups from Tumaco, Colombia

INTRODUCTION To date there has been no statistical evaluation of the profiles of immunoglobulin classes and viral replication as variables in the study of HTLV-1 infection and circulation among families in virus-endemic areas of Colombia. OBJECTIVE To evaluate the correlation of several immunological and molecular characteristics with the transmission and circulation of HTLV-1 among families in the town of Tumaco. MATERIALS AND METHODS Plasma levels of HTLV-1 specific immunoglobulin classes IgG, IgM and IgA1, as well as IgG and sIgA in oral fluids, were calculated for 32 members of 10 family groups from Tumaco in which the mother and at least one child were infected with the virus. Levels of the different immunoglobulin classes were correlated with viral RNA circulating in plasma or oral fluids and the proviral burden as detected by RT-PCR. RESULTS Significant differences were determined between mothers and carrier children for immunoglobulin levels (p=0.037) and proviral burden (p=0.002). The overall estimate of IgG in plasma and sIgA in oral fluids could be correlated with the circulation of free viral RNA in both fluids and high proviral burden, and associated with HAM/TSP mothers. The detection of anti- tax IgG in plasma revealed differences between HAM/TSP mothers and their offspring. CONCLUSION The study of immunological and molecular variables permitted the analysis of HTLV-1 circulation among families of Tumaco. The strong correlation between levels of IgM specific for the virus and viral RNA circulating in fluids indirectly confirmed the transmission of HTLV-1 among families.

Systemic Approach to the Genome Integration Process of Human Lentivirus

The human genome is one of the most complex molecular structures ever seen in nature. Its extraordinary information content has revealed a surprising mosaicims between coding and non-coding sequences [1-4]. This highly regionalized structure introduces complex patterns for understanding the gene structure and repetitive DNA sequence composition providing a new scenario to study biological process such as Lentivirus cDNA integration into host genome. In the field of genome analysis, bioinformatics provides the key connection between all different forms of data gathered by new high-throughput techniques such as systematic sequencing, expression arrays, and high throughput screenings among others. Although the success of bioinformatics in the genome analysis is undeniable, in some cases has complicated the relationship of computation with experimental biology. There is a need to attend to our pressing needs of bioinformatics applications without forgetting other, perhaps less evident but equally important, aspects of computation in biology.

Epidemiología y bioinformática en el estudio de la Leucemia Linfoma de Células T del Adulto asociada a la infección con VLHT-1

RESUMENObjetivos Establecer la relacion entre el numero de provirus VLHT-1 y lascaracteristicas de la cromatina adyacente en casos de Leucemia Linfoma de CelulasT del Adulto. Metodologia Se realizo una revision sistematica y un metaanalisis de la literaturapublica que considero como variables de estudio los provirus por cromosoma ycaracteristicas estructurales y funcionales de la cromatina adyacente a los sitios deintegracion. La concordancia entre los resultados de la evaluacion que emitierondos expertos fue evaluada con el coeficiente de Spearman Rho. Se evaluo el sesgode publicacion mediante el grafico de embudo y el estadigrafo Egger. De acuerdocon los resultados de la evaluacion de la heterogeneidad se aplico el modelo deefectos fijos para la combinacion de los resultados de las integraciones queocurrieron en: secuencias codificantes y secuencias codificantes de acuerdo consu funcion molecular. Resultados La concordancia entre expertos evaluadores fue de 0,7. No se encontrosesgo de publicacion. Se determino homogeneidad entre los estudiosseleccionados (p>0,05). El provirus VLHT-1 se integro en secuencias en regionestelomericas y subtelomericas. La combinacion de los resultados mostro unaintegracion sitio dirigida hacia regiones codificantes del genoma humano (p<0,05).