Early appearance of antibodies to simian immunodeficiency virus in saliva and serum of infected macaques

Abstract

Simian immunodeficiency virus (SIV) infection in macaques is an important animal model for human immunodeficiency virus infection in humans. This study evaluated the temporal development of antibodies to SIV in the parotid saliva of macaques inoculated with the virus and compared these findings with the development of antibodies to SIV in the animals' sera. Three animals (ages, 14, 18, and 18 years) were inoculated with the macrophagetropic strain SIVmac239. Prior to inoculation and at consecutive weekly intervals during a four-week period following the initial virus inoculations, parotid saliva and serum were collected from each animal. A fourth animal (age, 9 years) served as a negative control, and the fifth and sixth animals (ages, 2 and 22 years) served as positive controls (6 and 18 months postinoculation, respectively) with SIVmac239. Saliva and serum samples were reacted against SIV antigen in Western blots (immunoblots) prepared in the standard fashion to determine the presence of antibodies. The reactions of these antigen-antibody complexes with biotinylated anti-human immunoglobulin A (IgA), IgM, and IgG and biotinylated anti-human secretory component (SC) determined the class of antibody present or the presence of SC in the original parotid saliva or serum samples. In infected animals, the IgM to SIV was detectable in serum and saliva at 13 days, and antiviral IgA and IgG in serum and saliva were detectable at 20 to 27 days postinoculation. The antibody to SC reacted to saliva from only two animals at 20 and 27 days, and long-term positive controls were positive for SC in saliva, indicating that either secretory IgA or secretory IgM was present in these samples. Antibodies to SIVmac239 antigens have therefore been detected in saliva as early as 13 days postinfection. Saliva may be as useful as serum as a diagnostic specimen and/or disease-monitoring method in this important animal model.