Serologically silent, occult equine infectious anemia virus (EIAV) infections in horses.

Molecular and serological techniques for Equine Infectious Anemia Virus (EIAV) diagnosis were compared using samples from 59 clinically normal horses stabled on five farms in the Santa Fe Province of Argentina. Of these 26 (44.1%) were positive in official AGID tests and/or gp45/gp90-based ELISA. Surprisingly 18 of the 33 seronegative horses were positive in a PCR against viral sequences encoding gp45 (PCR-positive/AGID-negative) with all but one remaining EIAV-antibody negative throughout a two year observation period. The gp45 PCR results are supported by fact that 7/18 of these horses were positive in the Office International des Epizooties (OIE) recommended EIAV gag gene specific PCR plus 2 of this 7 also reacted in a PCR directed predominantly against the 5' untranslated region of the viral genome. Furthermore sufficient quantities of serum were available from 8 of these horses to verify their seronegative status in sensitive Western Blot tests and demonstrate by ELISA the absence of EIAV-specific antibodies was not attributable to abnormalities in total IgG concentration. Studies involving 7 of the PCR-positive/AGID-negative horses to measure lymphocyte proliferation in the presence of PHA showed no significant differences between this group and control animals. In addition, lymphocytes from 2 of these 7 horses responded to peptides derived from gp90 and gp45. Together these results demonstrate that apparently clinically normal horses with no gross signs of immunodeficiency in terms of total IgG concentration or T helper-cell function can remain seronegative for at least 24 months while harboring EIAV specific nucleic acid sequences.

Determination of 17 beta-hydroxy-1 alpha-methyl-17 alpha-propyl-5-alpha-androstan-3-one in plasma by gas chromatography-mass spectrometry with single-ion detection.

The topical anti-androgen 17 beta-hydroxy-1 alpha-methyl-17 alpha-propyl-5 alpha-androstan-3-one is determined in plasma samples by extracting with ether and subsequent mass fragmentography with single-ion detection at m/z 303. 17 beta-Hydroxy-1 alpha-methyl-17 alpha-pentyl-5 alpha-androstan-3-one, added to the samples before extraction, is used as the internal standard. Reproducibility was calculated to be +/- 5.9% at the 5-ng/mL level and 0.4% at the 20-ng/mL level. The limit of detection is approximately 1 ng/mL. Total gas chromatography-mass spectrometry analysis time is approximately 10 min/sample.