[Antiviral activity of hydroalcoholic extract from Haemanthus albiflos on the Moloney murine leukemia virus and the human immunodeficiency virus]. / Activité antivirale d'un extrait hydro-alcoolique d'Haemanthus albiflos sur le virus de la leucémie murine de Moloney et le virus du syndrome de l'immunodéficience acquise.

We have used a biological test on the microplates of cellular cultures in order to investigate the toxicity and the antiviral properties against different viruses: defective Moloney Murine Leukemia virus (MoMLV) derived from the SVX shuttle and expressing resistance to the G418 antimitotic, and Human Immunodeficiency Virus (HIV) of a hydroalcoholic extract from Haemanthus albiflos (Amaryllidacae). The toxicity was assessed through coloric test evaluation of fixed cells stained with crystal violet. In a population of NIH 3T3 cells (Fibroblasts mouse), the toxicity found with 2, 7, 14 and 28 microliters/ml of lyophilisat extract corresponding at: 0.23, 0.81, 1.62 and 3.24 mg of plant dry, was 32, 50, 63 and 70% respectively. With regards to the antiviral properties, the plant extracts showed an inhibition of 88% on the formation of G418 resistant 3T3 clones. The assay on HIV infected lymphotic cells (P4) showed an IC50 of 4 microliters/ml for this extract plant. Therefore, the toxic effect was similar to the antiviral response.

CAR1, a TNFR-related protein, is a cellular receptor for cytopathic avian leukosis-sarcoma viruses and mediates apoptosis.

Viral envelope (Env)-receptor interactions have been implicated in the cell death associated with infection by subgroups B and D avian leukosis-sarcoma viruses (ALVs). A chicken protein, CAR1, was identified that permitted infection of mammalian cells by these viral subgroups. CAR1 bound to a viral Env fusion protein, comprising an ALV-B surface Env protein and the Fc region of an immunoglobulin, indicating that it is a specific viral receptor. CAR1 contains two extracellular cysteine-rich domains characteristic of the TNFR family and a cytoplasmic region strikingly similar to the death domain of TNFR1 and Fas, implicating this receptor in cell killing. Chicken embryo fibroblasts susceptible to ALV-B infection and transfected quail QT6 cells expressing CAR1 underwent apoptosis in response to the Env-Ig fusion protein, demonstrating that this cytopathic ALV receptor can mediate cell death.