alpha-Melanocyte-stimulating hormone binding and biological activity in a human melanoma cell line.

Synthetic alpha-melanocyte-stimulating hormone (alpha-MSH) was found to bind to the plasma membrane of the HM6A human melanoma cell line, using an immunocytochemical method. When treated with 10(-7) to 10(-9) M alpha-MSH, melanoma cells exhibited an increase of intracellular cyclic adenosine 3':5'-monophosphate, followed by stimulation of tyrosinase activity. Significant inhibition of DNA synthesis measured by [3H]thymidine uptake and inhibition of cell growth was found. A retrovirus expression was detected in the supernatant of HM6A cells as assayed by the KC cell syncytium-forming test. In he presence of 10(-7) M alpha-MSH, the number of syncytium-forming units was increased 15-fold. These results demonstrate that alpha-MSH modulates human melanoma differentiation and virus expression in vitro.

HIV-1 infectivity and host range modification by cathepsin D present in human vaginal secretions.

OBJECTIVE: To investigate HIV-1 infectivity in the natural environment of vaginal secretions. DESIGN: Vaginal wash samples collected from 14 healthy women were incubated in vitro with various HIV-1 strains for 10 min at 37 degrees C and then assayed for infectivity on primary lymphocyte cultures, or on CEM cells, or on CD4- ME180 cells derived from vaginal epithelium. METHODS: HIV-1 infectivity was measured by early virus growth in the various host cells tested using a quantitative p24 assay and by the Karber procedure. RESULTS: Preincubation of HIV-1(IIIB) with vaginal wash samples or 2 microg/ml cathepsin D increased the ability of the virus to grow in lymphocyte cultures. The vaginal wash effect was abolished by 5 microg/ml pepstatin A, an inhibitor of aspartyl proteases. Presence of precursor and mature forms of cathepsin D in vaginal wash was demonstrated after passage through a pepstatin A-agarose column. Median tissue culture infective doses of HIV-1(IIIB) and HIV-1(JRFL) strains were increased 14.4-fold and 18-fold, respectively, after preincubation in vaginal wash sample, and were increased by pretreatment with 2 microg/ml cathepsin D. When CD4 receptors of CEMss cells were blocked by OKT4a monoclonal antibody, the cells lost susceptibility to HIV-1 (IIIB), but supported the growth of virus pretreated with vaginal wash sample or cathepsin D. These treated viruses were able to initiate infection of CD4-ME180 epithelial cells, which were not receptive to untreated virus. ME180 cells were shown to possess the messenger of CXC-chemokine receptor-4. CONCLUSIONS: Vaginal secretions may help HIV-1 transmission to women by increasing infectivity for CD4+ cells and allowing entrance into some CD4-epithelial cells.

[Formation of pseudotypes of VSV after culture in a human melanoma]. / Formation de pseudotypes de VSV après culture dans un mélanome humain.

Electron microscope studies showed a high production of melanosomes and viral particles budding into the cisternae of the endoplasmic reticulum in cells derived from a subcutaneous metastasis. The history of this subline (HM6B-A) has been summarized elsewhere. An amelanotic subline (provided by the same patient) did not show similar virus particles. When infected with a vesicular stomatitis virus (VSV) thermolabile mutant (tl), these cells produced a VSV pseudotype in which a thermosensitive antigen was modified. Modification of surface VSV antigens was also detected by neutralisation tests. Using these tests, the VSV-pseudotype particles could be used as a tool to detect one or more antigens to a "putative" human melanomavirus, which might be only partially expressed.

Inhibition of HIV infectivity by lactoperoxidase-produced hypothiocyanite.

HIV aliquots, from a supernatant of ARV-4 cell line, were mixed with an equal volume of a OSCN.generating glucose-glucose oxidase + thiocyanate-lacteroperoxidase solution, and then pre-incubated at 37 degrees C for periods of 30 secs to one hour. These mixtures were then inoculated into cultures of phytohaemagglutinin-stimulated lymphocytes. Viral growth was monitored with an ELISA quantitating the specific p24 protein either in the culture cells or in the supernatant. In control experiments, the virus produced both intra- and extra-cellular p24. In the controls, concentration of p24 per 10(6) lymphocytes grew rapidly. By contrast, HIV that was pretreated with the OSCN generating system for 30 sec., produced very little p24, and no detectable amount of this protein could be found after 2 min. pre-treatment.

A human milk factor susceptible to cathepsin D inhibitors enhances human immunodeficiency virus type 1 infectivity and allows virus entry into a mammary epithelial cell line.

Human immunodeficiency virus type 1 (HIV-1) growth in lymphocyte cultures was increased when the virus inoculum was incubated in breast milk. The enhancing effect of milk was abolished by anti-cathepsin D antibody or by pepstatin A, a cathepsin D inhibitor. The cathepsin D-producing CD4-negative MCF7 mammary cells supported the growth of some HIV-1 isolates. An MCF7 line chronically producing HIV-1 IIIb was obtained. Cathepsin D may induce conformational modification of viral gp120, allowing direct interaction with a coreceptor. We demonstrated the presence of CXCR4 mRNA in MCF7 cells.