Hyperglobulinemia and lymphocyte subset changes in naturally infected, inapparent carriers of equine infectious anemia virus.

OBJECTIVE

To determine blood protein concentration, immunoglobulin concentration, and lymphocyte profiles in equine infectious anemia virus (EIAV) seropositive, naturally infected horses without clinical signs of disease.

ANIMALS

26 clinically normal seropositive horses, 6 febrile ponies with experimentally induced EIA, and 52 clinically normal seronegative horses and ponies.

PROCEDURE

Serum and EDTA-anticoagulated blood were obtained from all horses and ponies, and total serum protein and albumin concentrations, immunoglobulin concentrations, and blood lymphocyte subset counts were determined.

RESULTS

Compared with seronegative horses, EIAV seropositive inapparent carrier horses had no significant difference in serum reverse transcriptase activity, PCV, or platelet count. Inapparent carrier horses had increased plasma total solids and serum globulin concentrations and decreased serum albumin concentration and albumin-to-globulin ratio. Total serum immunoglobulin and serum IgM concentrations were increased. Inapparent carrier horses had significantly decreased percentages of CD5+ and CD4+ blood lymphocytes.

CONCLUSIONS

Serum protein and lymphocyte subset changes in EIAV-infected inapparent carrier horses are consistent with immune activation or chronic inflammation, both of which may, in part, be the result of virus-induced polyclonal B-cell activation.

CLINICAL RELEVANCE

EIAV seropositive horses have immune-related abnormalities consistent with ongoing viral activity regardless of the duration they have been infected, even when the usual signs of disease (anemia, fever, weight loss) are not apparent.