Submitted by: Patricia Shea, DVM
Am J Vet Res 2019;80:907-911. DOI: 10.2460/ajvr.80.10.907
Effect on urine specific gravity of the addition of glucose to urine samples in dogs and cats
Behrend EN, Botsford AN, et al.
Interpreting urine specific gravity in feline patients with glycosuria can pose a diagnostic dilemma, as dilute urine can be found in cats with diabetes mellitus, hyperthyroidism and other endocrine diseases, chronic kidney disease, pyelonephritis, and hypokalemia, as well as other conditions, any of which can coexist with diabetes mellitus. If the urine is diluted due to osmotic diuresis attributable to glycosuria, is it then still possible to assess renal urine concentrating ability in such a sample?
This laboratory study evaluated the results of addition of glucose to species-specific pooled urine samples with various urine specific gravities (USGs) from 35 cats and 45 dogs, to determine the effects of varying amounts of glucose on USG. Glucose was added to each of the pooled feline urine samples to reach a final concentration of 2,400 mg/mL, and then serial dilutions were performed on the sample.
Addition of any solute to urine, including glucose, will affect the density of the urine, so the addition of glucose to the pooled feline urine samples increased the USGs. In the feline urine pooled samples, glucose was added to produce concentrations of 600, 1,200, and 2,400 mg/dL. In the urine samples that were most concentrated (highest USGs) prior to the addition of glucose, there was little change in the USG. The addition of glucose to the urine samples did not cause clinically important changes in the USG. The USG of a glycosuric urine specimen from a cat or dog still therefore reflects renal urine concentrating ability in that animal.
npj Vaccines. 2018;3:16. DOI: 10.1038/s41541-018-0051-y
FIV vaccine with receptor epitopes results in neutralizing antibodies but does not confer resistance to challenge
Miller C, Emanuelli M, et al.
The search for a safe vaccine that will confer significant protective immunity against the feline immunodeficiency virus (FIV) in cats is motivated by both concern for feline health and welfare, as well as the desire to produce a safe and efficacious vaccine for the human immunodeficiency virus (HIV), which is also a lentivirus with genetic similarities to FIV. Utilizing receptor-mediated entry to cells, both FIV and HIV infect and replicate within CD4+ T cells, ultimately causing depletion of these cells, and result in similar immunopathogenic syndromes in infected individuals.
The currently available commercial FIV vaccine contains inactivated dual subtype (A and D) FIV-infected cells, and its efficacy and usefulness is controversial. Future development of both FIV and HIV vaccines needs to focus on development of protective anti-immunodeficiency virus T cell immunity, rather than anti-immunodeficiency virus antibody.
CD134 is the primary binding receptor for FIV on target cells, and when the virus binds to this receptor, its envelope surface glycoprotein gp95 (SU) alters its conformation so that high affinity binding with the T cell surface entry receptor CXCR4 takes place. A very similar process takes place when HIV infects human T cells. The FIV SU is therefore an important target for induction of neutralizing antibodies. On the T cell surface, autoantibodies to the CD134 receptor have the potential to block infection.
The goal of this study was to determine whether vaccination of cats with CD134-SU complexes would be protective against FIV infection. Fifteen specific pathogen free (SPF) 8-11 week old cats were enrolled in one vaccine protocol (Vaccine Protocol I), while 12 SPF 8-11 week old cats were enrolled in Vaccine Protocol II. In Protocol I, cats were immunized with recombinant FIV-SU protein (derived by expression and purification from Chinese hamster ovary cells) alone, or a complex of recombinant FIV-SU protein with soluble CD134. In Protocol 2, cats were immunized with soluble CD134, recombinant FIV-SU protein derived by expression and purification from human cells, or both together as a complex.
Immunization of the cats proved successful in that the cats produced anti-CD134 and anti-SU antibodies, and these antibodies significantly inhibited FIV infection in vitro. However, when the cats were challenged with actual FIV infection, no vaccine combination was protective, and serum from the vaccinated cats actually enhanced FIV growth in vitro. The investigators concluded that heat-labile factors, including complement, in the serum of vaccinates, may reduce the activity of anti-receptor antibody complexes and enhance viral replication, thereby impacting vaccine efficacy. Also, changes in circulating target cell populations, possibly with enhanced susceptibility to FIV infection, induced by the vaccination itself, may also be a factor in vaccine failure.