Objective—To develop a reverse transcriptase-polymerase chain reaction (RT-PCR) assay to detect canine melanoma-associated antigens (MAAs) and to use this technique to screen aspirates of lymph nodes (LNs) for evidence of metastatic spread of oral malignant melanoma.
Animals—7 dogs with oral malignant melanoma and 4 dogs with multicentric lymphosarcoma.
Procedures—We prepared cDNA from melanoma tumor biopsies and fine-needle aspirates obtained from submandibular LNs of dogs with oral malignant melanoma or multicentric lymphosarcoma. The RTPCR assay was performed by use of tyrosinase, Melan-A, gp100, tyrosinase-related protein 2 (TRP-2), or melanoma antigen-encoding gene B (MAGE-B)- specific primers.
Results—We detected MAGE-B mRNA in canine testicular tissue but not in melanoma biopsy specimens. Tyrosinase, Melan-A, gp100, and TRP-2 mRNAs were detected in tumor biopsy specimens and in 2 of 5 LN aspirates from dogs with melanoma, suggesting metastatic spread in those 2 dogs. We did not detect MAAs in LN aspirates obtained from dogs with multicentric lymphosarcoma. Sequencing of canine Melan- A and gp100 PCR products confirmed the specificity of the assay for these genes.
Conclusions and Clinical Relevance—Clinical staging of dogs with oral malignant melanoma is useful to assist in designing appropriate treatments. However, results of histologic examination of LN biopsy specimens can be inconclusive and, in humans, can underestimate the number of patients with metastatic disease. Molecular staging of melanomas in dogs can be achieved by screening LN aspirates for MAA mRNA, and this can be performed in combination with cytologic examination to aid in detection of metastatic disease. ( Am J Vet Res 2003;64:544–549)
Objective—To determine whether passive transfer of IgG in neonatal kittens affects plasma opsonic capacity and neutrophil phagocytic and oxidative burst responses to bacteria in vitro.
Animals—22 kittens from 6 specific pathogen-free queens.
Procedure—Kittens were randomized at birth into the following treatment groups: colostrum-fed, colostrum-deprived, or colostrum-deprived supplemented with feline or equine IgG. Blood samples were collected at intervals from birth to 56 days of age. Plasma IgG concentrations were determined by radial immunodiffusion assay. Neutrophil function was assessed by a flow cytometry assay providing simultaneous measurement of bacteria-induced phagocytosis and oxidative burst. The opsonic capacity of kitten plasma was determined in an opsonophagocytosis assay with bacteria incubated in untreated or heat-inactivated plasma.
Results—Among treatment groups, there were no significant differences in neutrophil phagocytic and oxidative burst responses to bacteria or opsonic capacity of plasma. In all samples of plasma, inactivation of complement and other heat-labile opsonins significantly reduced the opsonic capacity. Plasma IgG concentrations in kittens did not correlate with neutrophil function or plasma opsonic capacity before or after inactivation of complement.
Conclusions and Clinical Relevance—The plasma opsonic capacity and neutrophil phagocytic and oxidative burst responses in vitro of kittens receiving passive transfer of IgG via colostrum intake or IgG supplementation and those deprived of colostrum were similar. The alternate complement pathway or other heat-labile opsonins may be more important than IgG in bacterial opsonization and phagocytosis. ( Am J Vet Res 2003;64:538–543)
Objective—To determine the ability of a modified-live virus (MLV) bovine viral diarrhea virus (BVDV) type 1 (BVDV1) vaccine administered to heifers prior to breeding to stimulate protective immunity that would block transmission of virulent heterologous BVDV during gestation, thus preventing persistent infection of a fetus.
Animals—40 crossbred Angus heifers that were 15 to 18 months old and seronegative for BVDV and 36 calves born to those heifers.
Procedure—Heifers were randomly assigned to control (n = 13) or vaccinated (27) groups. The control group was administered a multivalent vaccine wherein the BVDV component had been omitted. The vaccinated heifers were administered a single dose of vaccine (IM or SC) containing MLV BVDV1 (WRL strain). All vaccinated and control heifers were maintained in pastures and exposed to BVDV-negative bulls 21 days later. Thirty-five heifers were confirmed pregnant and were challenge exposed at 55 to 100 days of gestation by IV administration of virulent BVDV1 (7443 strain).
Results—All control heifers were viremic following challenge exposure, and calves born to control heifers were persistently infected with BVDV. Viremia was not detected in the vaccinated heifers, and 92% of calves born to vaccinated heifers were not persistently infected with BVDV.
Conclusions and Clinical Relevance—These results document that vaccination with BVDV1 strain WRL protects fetuses from infection with heterologous virulent BVDV1. (Am J Vet Res 2003;64:530–537)
Objective—To create a stochastic model to quantify the risk that shipments of cattle from regions within the United States would contain animals seropositive for bluetongue virus and to determine shipment-level accuracy of serologic testing by use of a competitive ELISA (c-ELISA).
Sample Population—19,216 shipments containing 528,918 cattle and calves.
Procedure—Data were obtained on number of animals and state of origin of cattle in export shipments originating within the United States between January 1994 and March 2002. Probability distributions for size of export shipments were determined for all states within the United States, and distributions for agar gel immunodiffusion and c-ELISA accuracy (sensitivity and specificity) were determined from expert opinion and review of the literature. The model simulated selection of a shipment and then determined the probability that a threshold number or percentage of cattle within that shipment would have a positive c-ELISA result. Shipment-level sensitivity, specificity, positive-predictive value, and negative-predictive value were calculated.
Results—Substantial differences were evident in the regional probability of a shipment being declared positive, with shipments from northeastern states having the lowest probability and shipments from southwestern states having the highest probability. The c- ELISA had variable predictive values at the shipment level, depending on the threshold used and the prevalence of antibody-positive cattle within the region.
Conclusions and Clinical Relevance—Results from this study will aid importers in making scientifically based decisions regarding risk of importing antibodypositive cattle. ( Am J Vet Res 2003;64:520–529)