Ovine pulmonary adenomatosis: Evidence of retroviral immunosuppression

© 2000 Universidad Nacional Mayor de San Marcos. All rights reserved. Monoclonal antibodies have been used to characterize peripheral and pulmonary leukocytes (bronchoalveolar lavage ce lis) derived from naturally affected and experimentally induced sheep pulmonary adenomatosis (SPA, Jaagsiekte, ovine pulmonary carcinoma) cases. Hematological parameters ofperipheral blood from SPA affected animals (n= 1 O) showed marked lymphopenia (2.66± 1.36 × 103 mL-1 , p< 0.05) and neutrophilia (7.96±3.84 × 103 mL-1 , p< 0.05) when compared to non-SPA animals (n=6). The peripheral lymphopenia was characterized by a significant reduction in number and proportions ofCD5+ and major histocompatibility complex (MHC) class-II-restricted (CD4+) T lymphocytes (p<0.05), as well as a significant increase in the proportions of MHC class-I-restricted (CD8+) and B (slgG+, CD45RA+) lymphocytes when compared to non-SPAcases (n=5) (p<0.5). Similar lymphopenia and significant reduction ofCD5+, CD2+ and CD4+ in peripheral blood was also observed in experimentally-induced SPA lambs showing severe SPA lesions 5-1 O weeks post inoculation. The lymphoid alterations observed in these lambs was reflected in significant reduction oflymphoid tissue weight as well as severe lymphoid cellular depletion in the cortical thymus and 2/2 splenic follicles and periarteriolar lymphoid sheath. The affected lambs also slowed evidence of accelerated involutive process of severely affected thymus. Evaluation of BAL samples from SPA affected lungs (n=9), showed a 24-fold increase in total leukocytes and alveolar macrophages, a 185-fold increase in polymorphonuclear cells, andan 11-fold increase in lymphocytes. The influx oflymphoid cells into SPA affected lungs was accompanied by significantly decreased proportions of CD5+ and CD4+, paralleled with an increased proportion ofCD8+ lymphocytes (p< 0.05). Alteration of the CD4+/CD8+ ratio was observed in both peripheral (from 3.9 in non-SPA to 1.4 in SPA) and pulmonary lymphocytes (from 4.9 in non-SPA to 2 in SPA). The vast influx of lymphoid cells into the affected lung tissue may well reflect part ofthe host's immune response against viral infection and/or transformed cells. However, the marked reduction in number and proportion ofMHC class-II-restricted peripheral CD4+ T cells, as well as the increase in the proportions ofMHC class-I- restricted CD8+ T and slgG+ B cells in peripheral lymphocytes, suggests the existence of previously unrecognized immune dysfuntions similar to those reported in retrovirus-induced human and feline immunosuppressive diseases.