Translational Control of the HIV Unspliced Genomic RNA.

Post-transcriptional control in both HIV-1 and HIV-2 is a highly regulated process that commences in the nucleus of the host infected cell and finishes by the expression of viral proteins in the cytoplasm. Expression of the unspliced genomic RNA is particularly controlled at the level of RNA splicing, export, and translation. It appears increasingly obvious that all these steps are interconnected and they result in the building of a viral ribonucleoprotein complex (RNP) that must be efficiently translated in the cytosolic compartment. This review summarizes our knowledge about the genesis, localization, and expression of this viral RNP.

HIV-2 genomic RNA accumulates in stress granules in the absence of active translation.

During the post-transcriptional events of the HIV-2 replication cycle, the full-length unspliced genomic RNA (gRNA) is first used as an mRNA to synthesize Gag and Gag-Pol proteins and then packaged into progeny virions. However, the mechanisms responsible for the coordinate usage of the gRNA during these two mutually exclusive events are poorly understood. Here, we present evidence showing that HIV-2 expression induces stress granule assembly in cultured cells. This contrasts with HIV-1, which interferes with stress granules assembly even upon induced cellular stress. Moreover, we observed that the RNA-binding protein and stress granules assembly factor TIAR associates with the gRNA to form a TIAR-HIV-2 ribonucleoprotein (TH2RNP) complex localizing diffuse in the cytoplasm or aggregated in stress granules. Although the assembly of TH2RNP in stress granules did not require the binding of the Gag protein to the gRNA, we observed that increased levels of Gag promoted both translational arrest and stress granule assembly. Moreover, HIV-2 Gag also localizes to stress granules in the absence of a 'packageable' gRNA. Our results indicate that the HIV-2 gRNA is compartmentalized in stress granules in the absence of active translation prior to being selected for packaging by the Gag polyprotein.

A genomic and bioinformatics analysis of the integration of HIV in peripheral blood mononuclear cells.

The mechanistic basis of the target-site preference of lentivirus DNA integration is not well understood. In the present in silico study, we describe the integrational profile of simultaneous HIV-1 and HIV-2 infection. A total of 352 genomic DNA sequences from human peripheral blood mononuclear cells (PBMCs) obtained from GenBank and possessing the 5' LTR of HIV were used to characterize the structure and composition of local chromatin associated with high frequency integration sites. These sequences were aligned with the draft human genome (hg18) using BLAST (NCBI) and BLAT (UCSC) in order to derive information about chromosome localization, functional aspects of coding protein genes, CpG island number, and repetitive elements flanking integration sites. No significant differences in the integrational profile between HIV-1 and HIV-2 were found. However, we observed a tendency in both lentiviruses to integrate in the vicinity of protein coding genes. Multiple regression analysis showed a strong correlation between the number of genes and the number of CpG islands in regions with high integration frequency, mainly in chromosome 17 (R = 0.95, p < 0.05). Our results provide strong evidence that HIV-1 and HIV-2 have common genomic environments in the local chromatin regions with high gene density and CpG islands. The understanding of local genomic environments with a high frequency of integration would be the starting point to develop novel antiviral strategies for lentiviral infection.

Current notions of genotype and phenotype vis-à-vis new experimental evidence in molecular biology. A methodological study instigated by the peculiar nature of the HIV-1.

The strict separation of the biological roles of information and function as if they were two mutually exclusive aspects and the absolute identification of the former with nucleic acids and the latter with coded protein machinery has biased biological thinking to the extent that these notions act as very principles in contemporary biology. However, recent discoveries within the realm of RNA-viruses show the traditional application of such notions to be severely limited in conceptual terms.

In vitro HIV infection of primate lymphocytes.

Peripheral blood mononuclear cells (PBMC) obtained from four different primate species were tested for their respective ability to support the "in vitro" replication of the human immunodeficiency viruses, HIV-1, and HIV-2. PBMC of Cebus apella, patas (Erythrocebus patas), green (cercopithecus aethiops sabaeus) and rhesus monkeys (Macaca mulatta) were infected "in vitro" with either HIV-1 or HIV-2. Cultures were assayed weekly for particle-associated reverse transcriptase activity. Both viruses were found to be cytolytic for all these monkey's PBMC. Low levels of HIV-1 and HIV-2 infection were observed in Cebus cells. However, productive infection was only detected in HIV-2 infected rhesus PBMC. The capacity of HIV-2 to replicate in rhesus cells may provide a useful model for evaluating antiviral drugs and vaccines.

In vitro HIV infection of primate lymphocytes

El propósito de este estudio fue el de evaluar la capacidad de los virus del SIDA (VIH-1 y VIH-2) para multiplicarse en las células mononuclearres de la sangre periférica (CMSP) de cuatro especies de primates. CMSP de Cebus apella, patas (Erythrocebus patas), monos verdes (cercopithecus aethiops sabeus) y rhesus (Macaca mulatta) fueron infectados "in vitro" con VIH-1 y con VIH-2. La multiplicación de estos virus se determinó midiendo la actividad de la enzima retrotranscriptasa en los cultivos infectados. Ambos virus produjeron efectos citipáticos en dichos cultivos. Se observó un bajo nivel de multiplicación de los virus VIH-1 y VIH-2 en las células provenientes de monos Cebus. Sin embargo, el virus VIH-2 se multiplicó eficientemente en CMSP de monos rhesus. La capacidad que posee el virus de la inmunodeficiencia humana tipo 2, (VIH-2) de multiplicarse en estas células, podría ser utilizada para en la evaluación "in vivo" de productos antivirales y de vacunas