Mucosal Transmission of Cell-Associated and Cell-Free Feline Immunodeficiency Virus

Mucosal infection by feline immunodeficiency virus (FIV) was assessed via a single exposure of the vaginal or rectal mucosa to either infectious peripheral blood mononuclear cells (PBMCs), infectious plasma, or cellfree cultured virus. All cats inoculated with cell-free cultured virus (100 or 400 TCID) and 9 of 10 cats inoculated with infected PBMCs (2 x 10⁷ or 2 x 10⁵) became persistently viremic within 3 weeks. Neither cat inoculated with 2 x 10³ PBMCs became viremic. Rectal and vaginal exposure were equally effective routes to induce viremia. CD4⁺ T cells and mitogen-stimulated PBMC proliferation declined in all infected cats. However, a transient PBMC proliferative response to FIV p24 ^gag occurred in most virus-exposed cats, especially those that did not develop detectable infection. FIV was not transmitted by mucosal exposure to infectious virus in plasma (100 TCID), a dose > 10-fold that needed for infection by parental injection. In vitro studies suggested that a plasma heat-stable virus-neutralizing factor may be associated with failure of plasma virus to establish infection via the mucosal route. Mucosal FIV infection provides a new model with which to study early stages of infection and intervention in transmucosal lentivirus infections.