Histologic lesions in cynomolgus monkeys (Macaca fascicularis) naturally infected with simian retrovirus type D: comparison of seropositive, virus-positive, and uninfected animals.

Simian retrovirus (SRV) type D is a common cause of simian acquired immunodeficiency syndrome (SAIDS), a usually fatal immunosuppressive disease of macaques. Associated gross and histologic lesions have been well described for the rhesus macaque (Macaca mulatta) in experimental and natural infections. However, morphologic changes induced by this virus at the gross and light-microscopic level have not been documented in the cynomolgus macaque (Macaca fascicularis). In 1996, sporadic cases of anemia, weight loss, and diarrhea were noted in a colony of cynomolgus macaques in our research facility. Out of 28 animals, 24 tested positive for SRV by serology or virus isolation. Animals could mainly be classified into 1 of 2 categories: 1) positive for virus isolation but negative for SRV antibody and 2) negative for virus isolation but antibody positive. During the process of eliminating the virus from the colony, a complete postmortem examination was performed on the 24 infected animals that had to be culled. Twelve SRV-negative animals were available as controls. Minimal to mild follicular lymphoid infiltrates were seen in various organ systems in 75% of the negative animals, compared with moderate to marked infiltrates in 83% of infected animals. Lymphoid infiltrates were more common in the brain, bone marrow, and salivary gland of viremic animals and were rare to nonexistent in seropositive or negative animals. Lymphoid hyperplasia was present in 38% of the infected animals, whereas lymphoid depletion was seen in 47% of the infected animals. Overall, lesions were of greater severity in viremic animals than in virus-negative or seropositive animals. Overall, infected animals had lower, statistically significant hematocrit and lymphocyte values. Viremic animals had significantly lower hematocrit, white blood cell, lymphocyte, and neutrophil values than did controls. Only 1 out of 24 infected animals had clinical signs that were consistent with the definition of SAIDS, and none had evidence of opportunistic infections. Lesions were similar to those already reported in other species of macaques, but the absence of severe illness that was consistent with SAIDS in most viremic animals suggests that there may be a different manifestation of disease in the cynomolgus.

Effects of nitric oxide synthase inhibition on the pathophysiology observed in a model of chronic granulomatous colitis.

The objective of this study was to assess the role that nitric oxide (NO) may play in mediating the colonic inflammation observed in a model of chronic granulomatous colitis using two pharmacologically different inhibitors of nitric oxide synthase (NOS). The NOS inhibitors NG-nitro-L-arginine methyl ester (L-NAME; 15 mumol/kg/day) and aminoguanidine (AG; 15 mumol/kg/day) were administered to rats in their drinking water, beginning 3 days before the induction of colitis and continuing for the entire 3-week period. We found that chronic NOS inhibition by L-NAME or AG significantly attenuated the peptidoglycan/polysacchride (PG/PS)-induced increases in macroscopic colonic inflammation scores and colonic MPO activity. Only AG, and not L-NAME, attenuated the PG/PS-induced increases in colon dry weight. Both L-NAME and AG significantly attenuated the PG/PS-induced increases in spleen inflammation, whereas neither drug significantly attenuated the PG/PS-induced liver inflammation. Although both L-NAME and AG inhibited NO production in vivo, as measured by decreases in plasma nitrite and nitrate levels, only AG was found to attenuate these values significantly (38 +/- 3 vs. 83 +/- 8 microM, respectively; P < .05). Finally, administration of L-NAME, but not of AG, significantly increased mean arterial pressure from 83 mm Hg in colitic animals to 105 mm Hg in the PG/PS+L-NAME-treated animals (P < .05). We conclude that NO may play an important role in mediating some of the pathophysiology associated with this model of chronic granulomatous colitis.

Toxin production by Pasteurella multocida isolated from rabbits with atrophic rhinitis.

Naturally acquired turbinate atrophy in rabbits was associated with Pasteurella multocida infection. Several in vitro and in vivo studies were conducted to document toxin production from P multocida isolates and to determine the relation of toxin to atrophic rhinitis in rabbits. Ten isolates of P multocida serotype A:12 were obtained from adult New Zealand White rabbits with noninduced atrophic rhinitis. Specific-pathogen-free rabbits inoculated intranasally with isolates of P multocida developed rhinitis and turbinate atrophy. However, inoculation with filtrates of the same bacteria failed to induce turbinate atrophy. Cytotoxicity was observed in assays, using bovine embryonic turbinate cell cultures with extracts of P multocida, but not in agar overlay cytotoxicity assays, using bovine embryonic turbinate, bovine embryonic lung, or Vero cell cultures, or in a sandwich ELISA, using monoclonal antibodies to purified P multocida toxin. Thus, turbinate atrophy was experimentally reproduced in rabbits with isolates of P multocida, but toxin was only detected in vitro by cell culture assay of P multocida extracts.

Polypeptides associated with Pasteurella multocida infection in rabbits.

Polypeptides from whole cell preparations of Pasteurella multocida serotypes A:12 and A:3 were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and transferred to nitrocellulose paper. Antigens were detected by immunoblot analysis, using sera from 3 groups of rabbits. Sera were obtained from rabbits inoculated intranasally with P multocida serotype A:12 or A:3, from rabbits maintained in a rabbitry with enzootic P multocida A:12 infection, and from rabbits maintained in a rabbitry with enzootic P multocida A:3 infection. Immunoblot analyses of pre- and postinoculation sera from experimentally infected rabbits, using serotype A:12 antigen, revealed 3 polypeptides with approximate molecular mass of 28, 30, and 37 kDa that consistently detected antibodies after P multocida-induced infection. Sera from rabbits naturally infected with either serotype, tested against serotype A:12 and A:3 antigens, detected the same polypeptides in both serotypes. Thus, immunologic reactivity to these polypeptides may be useful for serologic detection of P multocida infection.