Generation of the Pathogenic R5-Tropic Simian/Human Immunodeficiency Virus SHIVAD8 by Serial Passaging in Rhesus Macaques▿ †

A new pathogenic R5-tropic simian/human immunodeficiency virus (SHIV) was generated following serial passaging in rhesus macaques. All 13 animals inoculated with SHIVAD8 passaged lineages experienced marked depletions of CD4+ T cells. Ten of these infected monkeys became normal progressors (NPs) and had gradual losses of both memory and naïve CD4+ T lymphocytes, generated antiviral CD4+ and CD8+ T cell responses, and sustained chronic immune activation while maintaining variable levels of plasma viremia (102 to 105 RNA copies/ml for up to 3 years postinfection [p.i.]). To date, five NPs developed AIDS associated with opportunistic infections caused by Pneumocystis carinii, Mycobacterium avium, and Campylobacter coli that required euthanasia between weeks 100 and 199 p.i. Three other NPs have experienced marked depletions of circulating CD4+ T lymphocytes (92 to 154 cells/μl) following 1 to 2 years of infection. When tested for coreceptor usage, the viruses isolated from four NPs at the time of their euthanasia remained R5 tropic. Three of the 13 SHIVAD8-inoculated macaques experienced a rapid-progressor syndrome characterized by sustained plasma viremia of >1 × 107 RNA copies/ml and rapid irreversible loss of memory CD4+ T cells that required euthanasia between weeks 19 and 23 postinfection. The sustained viremia, associated depletion of CD4+ T lymphocytes, and induction of AIDS make the SHIVAD8 lineage of viruses a potentially valuable reagent for vaccine studies

Impacts de la température à court terme sur la respiration hétérotrophe du sol dans des échantillons de sol agricole chaulé.

This study sought to investigate the hourly and daily timescale responses of soil CO2 fluxes to temperature in a limed agricultural soil. Observations from different incubation experiments were compared with the results of a model combining biotic (heterotrophic respiration) and abiotic (carbonate weathering) components. Several samples were pre-incubated for 8-9 days at three temperatures (5, 15 and 25°C) and then submitted to short-term temperature cycles (where the temperature was increased from 5 to 35°C in 10°C stages, with each stage being 3 h long). During the temperature cycles (hourly timescale), the soil CO2 fluxes increased significantly with temperature under all pre-incubation temperature treatments. A hysteresis effect and negative fluxes during cooling phases were also systematically observed. At a given hourly timescale temperature, there was a negative relationship of the CO2 fluxes with the pre-incubation temperature. Using the combined model allowed the experimental results to be clearly described, including the negative fluxes and the hysteresis effect, showing the potentially large contribution of abiotic fluxes to total fluxes in limed soils, after short-term temperature changes. The fairly good agreement between the measured and simulated flux results also suggested that the biotic flux temperature sensitivity was probably unaffected by timescale (hourly or daily) or pre-incubation temperature. The negative relationship of the CO2 fluxes with the pre-incubation temperature probably derived from very labile soil carbon depletion, as shown in the simulations. This was not, however, confirmed by soil carbon measurements, which leaves open the possibility of adaptation within the microbial community.Modélisation de la respiration de sols agricole