Efficacy and adverse effects of the antiviral compound plerixafor in feline immunodeficiency virus-infected cats

BACKGROUND

Bicyclam derivatives inhibit feline immunodeficiency virus (FIV) replication through selective blockage of chemokine receptor CXCR4.

HYPOTHESIS/OBJECTIVES

CXCR4 antagonist plerixafor (AMD3100, 1,1'-bis-1,4,8,11-tetraazacyclotetradekan) alone or combination with adefovir (PMEA, 9-(2-phosphonylmethoxyethyl)adenine) safe and effective for treating FIV-infected cats.

ANIMALS

Forty naturally FIV-infected, privately owned cats.

MATERIALS AND METHODS

Prospective, placebo-controlled, double-blind clinical trial. Cats randomly classified into 4 treatment groups. Received AMD3100, PMEA, AMD3100 in combination with PMEA, or placebo for 6 weeks. Clinical and laboratory parameters, including CD4(+) and CD8(+) cell counts, FIV proviral and viral load measured by quantitative polymerase chain reaction (qPCR) evaluated. Additionally, FIV isolates from cats treated with AMD3100 tested for drug resistance.

RESULTS

FIV-infected cats treated with AMD3100 caused significant decrease in proviral load compared to placebo group (2.3 ± 3.8% to 1.9 ± 3.1%, of blood lymphocytes P < .05), but did not lead to improvement of clinical or immunological variables; it caused a decrease in serum magnesium concentration without clinical signs. No development of resistance of FIV isolates to AMD3100 found during treatment period. PMEA administration improved stomatitis (stomatitis score [degree 1 - 100] PMEA group: 23 ± 19 to 11 ± 10, P < .001; AMD3100 + PMEA group: 12 ± 17 to 3 ± 5, P < .05), but did not decrease proviral or viral load and caused anemia (RBC [× 10(6) /μL] PMEA group: 9.07 ± 1.60 to 6.22 ± 2.16, P < .05; AMD3100 ± PMEA group: 8.80 ± 1.23 to 5.84 ± 1.58, P < .001).

CONCLUSIONS AND CLINICAL IMPORTANCE

Administration of CXCR4 antagonists, as AMD3100, can induce reduction of proviral load and may represent viable treatment of FIV-infected cats. Combination treatment with PMEA not recommended.

[Receptors for animal retroviruses]

Diseases caused by animal retroviruses have been recognized since 19th century in veterinary field. Most livestock and companion animals have own retroviruses. To disclose the receptors for these retroviruses will be useful for understanding retroviral pathogenesis, developments of anti-retroviral drugs and vectors for human and animal gene therapies. Of retroviruses in veterinary field, receptors for the following viruses have been identified; equine infectious anemia virus, feline immunodeficiency virus, feline leukemia virus subgroups A, B, C, and T, Jaagsiekte sheep retrovirus, enzootic nasal tumor virus, avian leukosis virus subgroups A, B, C, D, E, and J, reticuloendotheliosis virus, RD-114 virus (a feline endogenous retrovirus), and porcine endogenous retrovirus subgroup A. Primate lentiviruses require two molecules (CD4 and chemokine receptors such as CXCR4) as receptors. Likewise, feline immunodeficiency virus also requires two molecules, i.e., CD134 (an activation marker of CD4 T cells) and CXCR4 in infection. Gammaretroviruses utilize multi-spanning transmembrane proteins, most of which are transporters of amino acids, vitamins and inorganic ions. Betaretroviruses and alpharetroviruses utilize transmembrane and/or GPI-anchored proteins as receptors. In this review, I overviewed receptors for animal retroviruses in veterinary field.

Design and synthesis of membrane fusion inhibitors against the feline immunodeficiency virus

Feline immunodeficiency virus (FIV) is a pathogenic virus that causes an AIDS-like syndrome in the domestic cats. For viral entry and infection, fusion between the virus and the cell membrane is the critical process and this process is mediated by an envelope glycoprotein gp40. We have identified fusion inhibitory peptides from the heptad repeat-2 (HR2) of gp40. Remodeling of the original sequences using alpha-helix-inducible motifs revealed the interactive residues of gp40. Comparative analysis of HR2 peptides derived from four FIV strains demonstrated that the interactive surface of the Shizuoka strain-derived HR2 peptides provides the highest affinity of all the FIV strains examined.