Primary HIV-1 infection of human CD4+ T cells passaged into SCID mice leads to selection of chronically infected cells through a massive fas-mediated autocrine suicide of uninfected cells

We have recently shown that a human CD4+ T cell line (CEM-SS) acquires the permissiveness to M-tropic strains and primary isolates of HIV-1 after transplantation into SCID mice. This permissiveness was associated with the acquisition of a memory (CD45RO+) phenotype as well as of a functional CCR5 coreceptor. In this study, we have used this model for invest-igating in vivo the relationships between HIV-1 infection, apoptosis and T cell differentiation. When an in vivo HIV-1 infection was performed, the CEM cell tumors grew to a lower extent than the uninfected controls. CEM cells explanted from uninfected SCID mice (ex vivo CEM) underwent a significant level of spontaneous apoptosis and proved to be CD45RO+, Fas+ and Fas-L+, while Bcl-2 expression was significantly reduced as compared to the parental cells. Acute HIV-1 infection markedly increased apoptosis of uninfected ex vivo CEM cells, through a Fas/Fas-L-mediated autocrine suicide/fratricide, while parental cells did not undergo apoptosis following viral infection. The susceptibility to apoptosis of ex vivo CEM cells infected with the NSI strain of HIV-1, was progressively lost during culture, in parallel with the loss of Fas-L and marked changes in the Bcl-2 cellular distribution. On the whole, these results are strongly reminiscent of a series of events possibly occurring during HIV-1 infection. After an initial depletion of bystander CD4+ memory T cells during acute infection, latently or chronically infected CD4+ T lymphocytes are progressively selected and are protected against spontaneous apoptosis through the development of an efficient survival program. Studies with human cells passaged into SCID mice may offer new opportunities for an in vivo investigation of the mechanisms involved in HIV-1 infection and CD4+ T cell depletion.     

Systemic alkalinisation delays prostate cancer cell progression in TRAMP mice

The microenvironment of solid tumours is extremely acidic and this condition arises since the precancerous stage. This acidic milieu could therefore provide a useful target for both prophylactic and therapeutic approaches. In TRAMP transgenic mice, an in vivo model of prostate adenocarcinoma (AC), oral administration of alkaline water was devoid of unwanted side effects, and when started from an early age was as effective as NaHCO₃ in significantly delaying tumour progression, while when started when prostate tumours were already present, a nonstatistically significant trend in the same direction was detected. These findings indicate that the use of alkalinizing drugs should be considered for chemoprevention and, in association with standard chemotherapy, for treatment of human prostate AC.     

New halogenated phenylcoumarins as tyrosinase inhibitors

With the aim to find out structural features for the tyrosinase inhibitory activity, in the present communication we report the synthesis and pharmacological evaluation of a new series of phenylcoumarin derivatives with different number of hydroxyl or ether groups and bromo substituent in the scaffold. The synthesized compounds 5-12 were evaluated as mushroom tyrosinase inhibitors showing, two of them, lower IC₅₀ than the umbelliferone. Compound 12 (IC₅₀ = 215 μM) is the best tyrosinase inhibitor of this series.     

The centriolar rim. The structure that maintains the configuration of centrioles and basal bodies in the absence of their microtubules

Preparations of centrioles from bovine spleen were incubated in solutions of NaCl, MgCl2, HCl, NaOH, EDTA and heparin. Their effects on the centrioles were studied by electron microscopy of ultrathin sections. It was found that the microtubules of centriolar cylinders gradually disintegrate at a higher than physiological ionic strength and at a pH value lower than 3.5 and higher than 8.5. After microtubule extraction, a closely apposed rim or sheath of dense centriolar matrix remains which has the same dimensions of length and width as the original centriole. Some other centriolar structures, including the pericentriolar satellites and certain structures in the cylinders (hub) are also preserved. The basal bodies of fish spermatozoa revealed similar structures, including the centriolar rim and hub, after microtubule extraction. Thus, the microtubule triplets are not involved in maintaining the structure of the centriolar cylinder; this role is rather carried out by amorphous material--the matrix, surrounding the microtubules.     

Human Lymphoblastoid CD4+ T Cells Become Permissive to Macrophage-Tropic Strains of Human Immunodeficiency Virus Type 1 after Passage into Severe Combined Immunodeficient Mice through In Vivo Upregulation of CCR5: In Vivo Dynamics of CD4+ T-Cell Differentiation in Pathogenesis of AIDS

In this article, we show that passage in SCID mice rendered a human CD4⁺ T-cell line (CEM cells) highly susceptible to infection by macrophage-tropic (M-tropic) strains and primary clinical isolates of human immunodeficiency virus type 1 (HIV-1). This in vivo-acquired permissiveness of CEM cells was associated with the induction of a CD45RO⁺ phenotype as well as of some β-chemokine receptors. Regulated upon activation, normal T-cell expressed and secreted chemokine entirely inhibited the ability of M-tropic HIV-1 strains to infect these cells. These findings may lead to new approaches in investigating in vivo the capacity of different HIV strains to exploit chemokine receptors in relation to the dynamics of the activation and/or differentiation state of human CD4⁺ T cells.     

Study of peripheral chromatin granules--anchorosomes

The granular particles of chromatin peripheral layer, were isolated together, with the nuclear envelope by treatment of nuclei with nuclease. These particles differ from total chromatin by a decreased content of histone H1, a specific set of minor acid-soluble proteins and a low DNA methylation level. Taking account of the fact that these particles facilitate chromatin interaction with the nuclear envelope, the latter were termed as "anchorosomes". Using UV-induced cross-linking of DNA to the proteins, it was found that all anchorosome-specific acid-soluble proteins can directly interact with anchorosomal DNA. Treatment of anchorosomes with staphylococcal nuclease and electron microscopic data showed that anchorosomes have a nucleosomal organization. Five to ten per cent of anchorosomal DNA appear to be firmly bound to nuclear lamina. This DNA cannot be separated from the lamina by treatment with 2 M NaCl, 1% SDS or heparin (1 mg/ml). The bulk of DNA in the laminal fraction after treatment with the above reagents is protected from hydrolysis with DNAase I by anchorosomal proteins and thus has a high molecular weight (10,000-30,000 base pairs). After treatment of anchorosomes with 0.6 M or 2 M NaCl, DNAase I splits this DNA, predominantly to minor fragments.     

Human cytomegalovirus regulates surface expression of the viral protein UL18 by means of two motifs present in the cytoplasmic tail

UL18 is a trans-membrane viral protein expressed on human cytomegalovirus (HCMV)-infected cells, and its surface expression determines the interaction of infected cells with lymphocytes expressing the CD85j (LIR-1/ILT2) receptor. We previously showed that the UL18-CD85j interaction elicits activation of T lymphocytes. However, in in vitro cell models UL18 displays mostly undetectable surface expression. Thus, we asked how surface expression of UL18 is regulated. Domain-swapping experiments and construction of specific mutants demonstrated that two motifs on its cytoplasmic tail, homologous to YXXPhi and KKXX consensus sequences, respectively, are responsible for impairing UL18 surface expression. However, the presence of the whole HCMV genome, granted by HCMV infection of human fibroblasts, restored surface expression of either UL18 or chimeric proteins carrying the UL18 cytoplasmic tail, starting from the third day after infection. It is of note that the two motifs responsible for cytoplasmic retention are identical in all 17 HCMV strains examined. We disclosed a control mechanism used by the HCMV to regulate the availability of UL18 on the infected-cell surface to allow interaction with its ligand on T and NK cells.     

Whale (Balaenoptera physalus) haemoglobin: primary structure,functional characterisation and computer modelling studies

The functional properties of haemoglobin from the Mediterranean whale Balaenoptera physalus have been studied as functions of heterotropic effector concentration and temperature. Particular attention has been given to the effect of carbon dioxide and lactate since the animal is specialised for prolonged dives often in cold water. The molecular basis of the functional behaviour and in particular of the weak interaction with 2,3-diphosphoglycerate is discussed in the light of the primary structure and of computer modelling. On these bases, it is suggested that the A2 (Pro-->Ala) substitution observed in the beta chains of whale haemoglobin may be responsible for the displacement of the A helix known to be a key structural feature in haemoglobins that display an altered interaction with 2,3-diphosphoglycerate as compared with human haemoglobin. The functional and structural results, discussed in the light of a previous study on the haemoglobin from the Arctic whale Balaenoptera acutorostrata, give further insights into the regulatory mechanisms of the interactive effects of temperature, carbon dioxide and lactate.