Dose-dependent systemic human immunodeficiency virus infection of SCID-hu mice after intraperitoneal virus injection.

SCID mice were engrafted with human foetal liver, thymus and lung. Human cells were subsequently detected among peripheral blood leukocytes for 81% of tested animals and in tissue implants for 100% of tested animals. SCID-hu mice received intraperitoneal injections of human immunodeficiency virus type 1 (HIV1) at from 20 up to 20,000 median tissue culture infectious doses (TCID5). HIV1 infection was detected by means of cell culture and polymerase chain reaction both in blood and implants, up to 58 days after infection. The rate of infection was dependent upon the inoculated dose: the frequency of thymus infection ranged from 14% with 20-500 TCID50 up to 100% with 20,000 TCID50. HIV1 infection was detected less frequently in blood leukocytes than in thymus. Thymus virus load ranged from 40 to 50,000 HIV1 provirus copies per million cells and was not correlated with either infectious dose or viraemia. Thymus T-cell depletion was observed mainly in the CD1+4+8+ immature thymocyte compartment. The same rate of SCID-hu mouse infection was obtained using three different primary HIV1 isolates, suggesting that infection was not restricted to a few particular virus strains. The systemic infection of SCID-hu mice following intraperitoneal virus injection mimics some traits of human HIV infection and provides a promising, novel approach for future investigations in this field.