Western immunoblot analysis of the antigens of Haemobartonella felis with sera from experimentally infected cats.

Cats were experimentally infected with a Florida isolate of Haemobartonella felis in order to collect organisms and evaluate the immune response to H. felis. Cryopreserved organisms were thawed and injected intravenously into nonsplenectomized and splenectomized cats. Splenectomized animals were given 10 mg of methylprednisolone per ml at the time of inoculation. Blood films were evaluated daily for 1 week prior to infection and for up to 60 days postinfection (p. i.). Blood for H. felis purification was repeatedly collected from splenectomized animals at periods of peak parasitemias. Organisms were purified from infected blood by differential centrifugation, separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and transferred to nitrocellulose membranes for immunoblot analysis. Serum was collected from nonsplenectomized animals prior to and for up to 60 days p.i. and was used on immunoblots to identify antigens. The combination of splenectomy and corticosteroid treatment resulted in marked, cyclic parasitemias without concurrent severe anemia, providing an opportunity to harvest organisms in a manner that was not lethal to the animals. Several antigens (150, 52, 47, 45, and 14 kDa) were identified. An antigen with a molecular mass of approximately 14 kDa appeared to be one of the most immunodominant and was consistently recognized by immune sera collected at various times during the course of infection. These data suggest that one or more of these antigens might be useful for the serologic diagnosis of H. felis infections in cats.

Characterization of phosphofructokinase-deficient canine erythrocytes.

Dogs homozygously affected with muscle-type phosphofructokinase (PFK) deficiency had about 20% of normal erythrocyte PFK activity and exhibited a compensated haemolytic anaemia. Erythrocyte glucose-6-phosphate and fructose-6-phosphate concentrations were increased and dihydroxyacetone phosphate and 2,3-bisphosphoglycerate values were below normal in affected dogs. Other intermediates distal to the PFK step were not significantly below normal and fructose-1,6-bisphosphate was even above normal. Erythrocyte ATP was higher than normal in affected dogs owing to the reticulocytes present. Abnormal adenylate metabolism was demonstrated by low ATP/AMP and ADP/AMP ratios and the inability to maintain ATP content when affected erythrocytes were incubated with cyanide. Glucose-1,6-bisphosphate content was normal, and fructose-2,6-bisphosphate content in affected canine erythrocytes was higher than normal. Studies of erythrocyte PFK isozymes revealed altered enzyme kinetic properties in affected dogs which appeared to be due to the loss of the M-type subunit.

Effect of 2,3-diphosphoglycerate concentration on the alkaline fragility of phosphofructokinase-deficient canine erythrocytes.

1. Erythrocytes in whole blood samples from dogs with phosphofructokinase (PFK) deficiency had lower 2,3-diphosphoglycerate (2,3-DPG) concentrations, higher ATP concentrations, and were more alkaline fragile than normal canine erythrocytes. 2. Reticulocytes from a PFK-deficient dog contained nearly three times the ATP concentration of normal canine erythrocytes, and had 2,3-DPG concentrations similar to normal canine erythrocytes. 3. PFK-deficient reticulocytes are not alkaline fragile. 4. The erythrocyte 2,3-DPG concentration in whole blood samples from PFK-deficient dogs was increased to normal by in vitro incubation with dihydroxyacetone, pyruvate and phosphate. This incubation resulted in only a slight increase in ATP concentration. 5. The alkaline fragility of these 2,3-DPG replenished PFK-deficient erythrocytes was normal. 6. Findings in this study indicate that the increased alkaline fragility of canine PFK-deficient erythrocytes is the result of decreased intracellular 2,3-DPG concentration.