OBJECTIVES

To investigate the presence of anti-histone antinuclear antibodies in dogs with natural leishmania infection and to assess its correlation with several clinical signs.

MATERIALS

A total of 92 sera from leishmania infected dogs were included in the study. Clinical signs most commonly associated with immune complex deposition and positive antinuclear antibody titers such as glomerulonephritis, skin lesions, uveitis and arthritis were assessed during physical examination. Hemogram, serum biochemistry and urinalysis were also performed in all dogs.

Anti-histone antibodies were determined by an ELISA method using purified bovine histones directly absorbed onto micro-ELISA plates. All sera were tested in duplicate. Sera from 20 healthy dogs were used as negative controls. Optical density readings after background subtraction were divided by 2 SD above mean values obtained with the healthy controls to obtain ELISA units. Reactions < 1 unit were considered negative. Positive reactions were graded as weak (1-1.5 units); moderate (1.6-2.5 units) and strong (> 2.5 units).

RESULTS

Thirty-four dogs (37%) had elevated anti-histone IgG antibodies. More than half of the positive reactions were classified as weak-positives (N= 22); however, 11 dogs (12%) produced moderate reactions and one dog yielded a strong reaction. When ELISA results were compared with clinical findings, a direct relationship between main clinical manifestations and anti-histone antibodies could not be made, due to the low number of moderate and strong positive dogs and to the fact than many positive dogs showed multi-organ involvement, specially skin lesions, uveitis and proteinuria. The dog with a strong anti-histone antibodies reaction showed skin lesions and proteinuria with normal serum creatinine and BUN levels. There was no correlation between OD and creatinine levels of the dogs with moderate (N=11) and strong (N=1) anti-histone reactions.

CONCLUSION

Cationic histones can bind to the negatively charged glomerular basement membrane and act as planted antigens for antibody binding. This mechanism has been proposed to explain the high incidence of renal lesions in canine SLE. Although the presence of elevated concentrations of IgG anti-histone antibodies in dogs with leishmaniasis could not be related to the development of glomerulonephritis, the high proportion of positive dogs (37%) must be taken into consideration when explaining the pathogeny of type III hypersensitivity reaction clinical signs found in canine leishmaniasis.