The evolution of human immunodeficiency virus type 1 (HIV-1) coreceptor use has been described as the acquisition of CXCR4 use linked to accelerated disease progression. However, CXCR4-using virus can be isolated only from approximately one-half of individuals with progressive HIV-1 disease. The other half continue to yield only CCR5-using viruses (R5 phenotype) throughout the course of disease. In the present work, the use of receptor chimeras between CCR5 and CXCR4 allowed us to study the evolution of HIV-1 with the R5 phenotype, which was not revealed by studies of wild-type coreceptor use. All together, 246 isolates (173 with the R5 phenotype) from 31 individuals were tested for their ability to infect cells through receptor chimeras. R5 narrow virus was able to use only wild-type CCR5, whereas R5 broad(1) to R5 broad(3) viruses were able to use one to three chimeric receptors, respectively. Broad use of chimeric receptors was interpreted as an increased flexibility in the mode of receptor use. R5 broad isolates showed higher infectivity in cells expressing wild-type CCR5 than R5 narrow isolates. Also, the increased flexibility of R5 broad isolates was concomitant with a lower sensitivity to inhibition by the CC chemokine RANTES. Our results indicate a close relationship between HIV-1 phenotypic changes and the pathogenic process, since the mode and efficiency of CCR5 use as well as the decrease in the RANTES sensitivities of isolated viruses are significantly correlated with CD4؉ -T-cell decline in a patient. One possible explanation is that ligand competition at the CCR5 receptor or changed CCR5 availability may shape the outcome of HIV-1 infection.

A translational stop in the hepatitis B virus (HBV) precore codon 28 and specific changes in the core promoter region of the X gene have been suggested to influence the level of circulating HBeAg in patients. We analysed the core promoter region and precore sequences from 59 HBV strains (including 14 from the databank) of different genotypes and from patients with different HBeAg/anti-HBe patterns. The initiator and TATA elements for transcription of precore and pregenomic RNA were highly conserved. The majority of X gene deletions in the core promoter region would lead to translational frame-shifts and stops, truncating the Cterminal end of the X protein. We found significant associations between specific changes in core promoter positions 1762 to 1764, or in precore codon 28, and absence of circulating HBeAg. For the core promoter mutations alone, this association was

No abstract

Adenovirus VA RNA genes have primary sequence constraints due to internal promoter regions and a high degree of secondary structure in the RNA product. To determine the relationships between human and simian adenoviruses, the VA RNA genes of several primate adenoviruses were characterized and compared to those sequences already published. Human adenoviruses of subgenera A, B:2, and F have only one VA RNA gene, whereas human adenoviruses of subgenera B:1, C, D, and E have two. The genomes of 12 monkey adenoviruses were found to have only one VA RNA gene, whereas the genomes of six representative chimpanzee adenoviruses were each found to have two VA RNA genes. Phylogenetic analysis of representative VA RNA gene sequences individually, irrespective of their strain of origin or partnering VA RNA gene, gave the following inferences. (1) The single VA RNA genes of human adenovirus subgenera A and F are most closely related to those of monkey adenoviruses. (2) The VA RNAI genes of human adenoviruses in subgenera B:1, D, and E, and also the single VA RNA genes of subgenus B:2 probably diverged from a common ancestral VA RNA gene. (3) This ancestral gene most likely reduplicated to give the precursor of all VA RNAII genes, the evidence for which has been almost totally lost in subgenus B:2 adenoviruses. (4) The two VA RNA genes of human subgenus C adenoviruses are relatively distant from each other phylogenetically. Since the Ad2 and Ad5 VA RNAI genes have a higher identity to the single VA RNA gene of SAV13 (SV36) than to those of any of the other human adenoviruses, these genes may have entered the human subgenus C adenovirus genome by substitution involving recombination with a simian adenovirus. The results of this study suggest that a renewed appraisal of VA RNA function in adenoviruses other than Ad2 and Ad5 may be necessary.

Early in human immunodeficiency virus 1 (HIV-1) infection CCR5-using (R5) viruses predominate. With disease progression, approximately 50 % of infected individuals develop viruses able to use CXCR4. In the present work, the evolution of the biological properties of HIV-1 was studied in patients who retain viruses with an R5 phenotype despite AIDS onset. A panel of primary R5 HIV-1 isolates sequentially obtained at an asymptomatic stage and after AIDS diagnosis was examined. The viruses were selected based on our previous observation that R5 variants with reduced sensitivity to RANTES inhibition may appear during disease progression. Biological properties of the early and late R5 viruses, including infectivity, replicative capacity, impact of cationic polymer and sensitivity to inhibition by the entry inhibitors T-20 and TAK-779, were evaluated. R5 viruses isolated after AIDS onset displayed elevated replicative capacity and infectivity, and did not benefit from cationic polymer assistance during infection. Late R5 isolates also exhibited reduced sensitivity to inhibition by T-20 and TAK-779, even though the included patients were naïve to treatment with entry inhibitors and the isolates had not acquired mutations within the gp41 HR1 region. In addition, CD4 + T-cell counts at the time of R5 virus isolation correlated with infectivity, replicative capacity and sensitivity to inhibition by entry inhibitors. The results indicate that R5 HIV-1 variants with augmented replicative capacity and reduced sensitivity to entry inhibitors may be selected for during severe immunodeficiency. At a time when the clinical use of entry inhibitors is increasing, this observation could be of importance in the optimal design of such treatments. INTRODUCTIONMany factors, including virus variability, can contribute to the pathogenicity of human immunodeficiency virus type 1 (HIV-1) infection. The high mutation rate and rapid turnover of HIV-1 result in a population of distinct viral variants, in other words a quasispecies, within the infected individual. Antiretroviral drugs and pressure exerted by the immune system of the host are selective forces that can contribute to the emergence of new HIV-1 variants in the viral population (Albert et al., 1990;Mansky, 2002;Mansky et al., 2002;Richman et al., 2003). It has also been suggested that variable expression of viral receptors on target cells serves to select certain HIV-1 variants (van Rij et al., 2000). Upon infection of the target cells, the HIV-1 envelope glycoprotein gp120 interacts with two different cellular receptors. gp120 attaches both to CD4 and to a coreceptor, which ultimately leads to a gp41-mediated fusion of the viral and cell membranes.The coreceptors utilized by HIV-1 include CCR5 and/or CXCR4, which are seven transmembrane chemokine receptors (Feng et al., 1996;Deng et al., 1996;Dragic et al., 1996;Cheng-Mayer et al., 1997;Berger et al., 1999). Early in HIV-1 infection, viruses primarily use CCR5 as a coreceptorThe GenBank/EMBL/DDBJ accession numbers for the sequences...