Immunohistochemical localization of feline immunodeficiency virus using native species antibodies

Area of Science:

• Veterinary Virology
• Immunology
• Pathology

Background:

• Feline immunodeficiency virus (FIV) is a significant pathogen in cats, analogous to human immunodeficiency virus (HIV).
• Understanding early FIV target cells is crucial for developing effective treatments and vaccines.
• Existing antibody detection methods for FIV in feline tissues lack sensitivity and specificity.

Purpose of the Study:

• To identify early in vivo target cells of FIV (clades B and C) in infected cats.
• To develop and validate a novel immunohistochemical protocol for detecting FIV antigens in feline tissues.

Main Methods:

• Developed a sensitive immunohistochemical protocol using native species anti-FIV antibodies from chronically infected cats.
• Employed biotinylated protein A and tyramide signal amplification for enhanced detection.
• Labeled tissues for FIV antigen and cell phenotype (T lymphocytes, macrophages, dendritic cells).

Main Results:

• Identified numerous productively infected cells in bone marrow, lymph nodes, thymus, MALT, and spleen.
• Detected few infected cells in the liver and none in the kidney or brain at 3 weeks post-infection.
• Antigen-bearing cells were primarily T lymphocytes, with some macrophages and dendritic cells.

Conclusions:

• FIV rapidly expands in T cells and targets long-lived immune cell populations.
• FIV replication is quiescent in the brain early in infection.
• Native species antibody-based immunohistochemistry offers a superior method for detecting FIV and has broader applications.