Submitted to: American College of Veterinary Pathologists Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 11/15/2003
Publication Date: 11/15/2003
Citation: GRUBOR, B., MEYERHOLZ, D.K., GALLUP, J.M., BROGDEN, K.A., LEHMKUHL, H.D., ACKERMANN, M.R. THE EFFECTS OF BACTERIAL AND VIRAL PNEUMONIA ON SURFACTANT PROTEIN D MRNA EXPRESSION. AMERICAN COLLEGE OF VETERINARY PATHOLOGISTS ABSTRACTS. 2003. E4.
Technical Abstract: Surfactant Protein D (SP-D) is a collagenous calcium-dependent lectin constitutively expressed by type II pneumocytes and Clara cells. Its role in lung innate immunity involves binding to the surface glycoconjugates expressed by a wide variety of microorganisms such as Gram-negative bacteria, Influenza A virus, and various fungi, leading to pathogen inactivation or enhanced neutrophil and macrophage activity. In vivo deficiency of SP-D is associated with increased risk for infection. The purpose of this study was to determine and compare SP-D mRNA expression during the progression of bacterial and viral pneumonia in lambs. The first group of animals, healthy weaned lambs, was inoculated intrabronchially with either pyrogen-free saline (controls) or Mannheimia haemolytica by using a fiberoptic bronchoscope. The animals were subsequently euthanized on day 1, 15, or 45 post-inoculation. The second group, healthy neonatal lambs, received either pyrogen-free saline (controls) or Parainfluenza Type 3 (PI-3) virus intratracheally and intranasally, and the animals were euthanized on day 3, 6, or 17 post-inoculation. The lung tissues were collected and homogenized lung lesions as well as healthy lungs were analyzed by fluorogenic real-time relative quantitative reverse transcriptase PCR (TaqMan). SP-D mRNA levels were not increased or significantly altered by M. haemolytica infection and showed a trend of decreased expression when compared to control animals. In contrast, SP-D mRNA levels were significantly increased in PI-3 virus inoculated lambs at all time points when compared to controls. These results suggest that SP-D expression is not increased by M. haemolytica, which was expected for SP-D, because it is constitutively regulated. The mechanistic basis for increased SP-D expression during PI-3 infection is under investigation.