title: Serologically silent, occult equine infectious anemia virus (EIAV) infections in horses.
abstract: 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.
authors.affiliation: Laboratorio de Diagnóstico e Investigaciones Agropecuarias, Sub- Dirección de Ganadería y Sanidad Animal, Ministerio de la Producción de la Provincia de Santa Fe, Boulevard Pellegrini 3100, 3000 Santa Fe, Argentina; Laboratorio de Inmunología, Cátedra de Inmunología. Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Ciudad Universitaria, Paraje El Pozo, 3000 Santa Fe, Argentina.
authors.forename: Sonia
authors.initials: S
authors.lastname: Ricotti
authors.affiliation: Laboratorio de Inmunología, Cátedra de Inmunología. Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Ciudad Universitaria, Paraje El Pozo, 3000 Santa Fe, Argentina.
authors.forename: Maria Inés
authors.initials: MI
authors.lastname: Garcia
authors.affiliation: Laboratorio de Inmunología, Cátedra de Inmunología. Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Ciudad Universitaria, Paraje El Pozo, 3000 Santa Fe, Argentina.
authors.forename: Carolina
authors.initials: C
authors.lastname: Veaute
authors.affiliation: Laboratorio de Inmunología, Cátedra de Inmunología. Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Ciudad Universitaria, Paraje El Pozo, 3000 Santa Fe, Argentina.
authors.forename: Alejandra
authors.initials: A
authors.lastname: Bailat
authors.affiliation: Cátedra de Infectología, Facultad de Ciencias Veterinarias, Universidad Nacional del Litoral, Padre Kredder 2805, 3080 Esperanza, Argentina.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Lucca
authors.affiliation: Department of Veterinary Science, Gluck Equine Research Center, University of Kentucky, Lexington, KY 40546, USA.
authors.forename: R Frank
authors.initials: RF
authors.lastname: Cook
authors.affiliation: Department of Veterinary Science, Gluck Equine Research Center, University of Kentucky, Lexington, KY 40546, USA.
authors.forename: Sheila J
authors.initials: SJ
authors.lastname: Cook
authors.affiliation: Laboratorio de Diagnóstico e Investigaciones Agropecuarias, Sub- Dirección de Ganadería y Sanidad Animal, Ministerio de la Producción de la Provincia de Santa Fe, Boulevard Pellegrini 3100, 3000 Santa Fe, Argentina; Laboratorio de Inmunología, Cátedra de Inmunología. Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Ciudad Universitaria, Paraje El Pozo, 3000 Santa Fe, Argentina. Electronic address: soutullo@fbcb.unl.edu.ar.
authors.forename: Adriana
authors.initials: A
authors.lastname: Soutullo
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D001118:Argentina / Q000453:epidemiology; D001483:Base Sequence; D004279:DNA, Viral / Q000097:blood / Q000235:genetics; D062665:Epidemiological Monitoring / Q000662:veterinary; D004859:Equine Infectious Anemia / Q000097:blood* / Q000453:epidemiology*; D015752:Genes, env / Q000235:genetics; D006736:Horses; D007111:Immunity, Cellular / Q000276:immunology; D004860:Infectious Anemia Virus, Equine / Q000145:classification / Q000235:genetics / Q000276:immunology*; D008655:Mesterolone / Q000097:blood; D008969:Molecular Sequence Data; D010802:Phylogeny; D016415:Sequence Alignment; D014759:Viral Envelope Proteins / Q000235:genetics
chemical_list: D000914:Antibodies, Viral; D004279:DNA, Viral; D014759:Viral Envelope Proteins; C066797:transmembrane envelope glycoprotein gp45, retrovirus; D008655:Mesterolone
keywords: AGID; Absence of seroconversion; Equine infectious anemia virus; Horse; PCR; Western blot