Equine Arteritis Virus Elicits a Mucosal Antibody Response in the Reproductive Tract of Persistently Infected Stallions

Abstract

Equine arteritis virus (EAV) has the ability to establish persistent infection in the reproductive tract of the stallion (carrier) and is continuously shed in its semen. We have recently demonstrated that EAV persists within stromal cells and a subset of lymphocytes in the stallion accessory sex glands in the presence of a significant local inflammatory response. In the present study, we demonstrated that EAV elicits a mucosal antibody response in the reproductive tract during persistent infection with homing of plasma cells into accessory sex glands. The EAV-specific immunoglobulin isotypes in seminal plasma included IgA, IgG1, IgG3/5, and IgG4/7. Interestingly, seminal plasma IgG1 and IgG4/7 possessed virus-neutralizing activity, while seminal plasma IgA and IgG3/5 did not. However, virus-neutralizing IgG1 and IgG4/7 in seminal plasma were not effective in preventing viral infectivity. In addition, the serological response was primarily mediated by virus-specific IgM and IgG1, while virus-specific serum IgA, IgG3/5, IgG4/7, and IgG6 isotype responses were not detected. This is the first report characterizing the immunoglobulin isotypes in equine serum and seminal plasma in response to EAV infection. The findings presented herein suggest that while a broader immunoglobulin isotype diversity is elicited in seminal plasma, EAV has the ability to persist in the reproductive tract, in spite of local mucosal antibody and inflammatory responses. This study provides further evidence that EAV employs complex immune evasion mechanisms during persistence in the reproductive tract that warrant further investigation.

Downregulation of MicroRNA eca-mir-128 in Seminal Exosomes and Enhanced Expression of CXCL16 in the Stallion Reproductive Tract Are Associated with Long-Term Persistence of Equine Arteritis Virus

“…We have demonstrated that long-term persistent infection in the stallion is associated with host genetic factors, specifically with the presence of a specific allele encoding the chemokine CXCL16 (CXCL16S) (30,31). Furthermore, EAV has the ability to persist despite the induction of a strong systemic immune response and local inflammatory and mucosal antibody responses at the site of persistence (26,27). Clearly, EAV employs complex strategies to evade host immunity, and the immunopathogenesis of viral persistence remains to be further elucidated ( Fig.…”

“…Semen samples. Collection of equine semen samples from stallions that were experimentally infected with EAV (n ϭ 7) has been described elsewhere (19,26,27). In addition, archived semen samples from long-term EAV carrier stallions that were naturally infected with EAV were included in the study.…”

Intrahost Selection Pressure Drives Equine Arteritis Virus Evolution during Persistent Infection in the Stallion Reproductive Tract

“…EAV has been demonstrated in a variety of host cells within the ampullae (primary site of persistent infection) and other accessory sex glands of stallions (47). These sites of virus persistence are not immunologically privileged and are characterized by the presence of moderate to severe inflammatory cell infiltration (81). These observations suggest that infection of various cells in the reproductive tract, including the local inflammatory and immune cells, is the driving force for the selection and reduction of the initial viral variant population at the site of viral persistence.…”

“…About 10% to 70% of sexually mature stallions develop persistent infection and become carriers after natural infection (5,20,87). This occurs in the presence of high levels of virus neutralizing antibodies in serum that effectively eliminates systemic infection in body tissues, with the exception of the stallion reproductive tract (5,16,20,81,88,89). While previous studies have shown that natural transmission of EAV can occur by aerosolized respiratory secretions or through insemination with infective semen, the diversity observed during persistent infection contrasts with the relative genetic stability during horizontal transmission in a disease outbreak (30).…”

Host Factors that Contribute to Equine Arteritis Virus Persistence in the Stallion: an Update

“…Some of our ongoing studies are focused on identifying the tissue and cellular localization sites of EAV during persistent infection in the reproductive tract of the stallion with the long-term goal of determining the underlying mechanism(s) by which EAV can establish and maintain persistent infection. Specifically, we have used archived tissues from long-term carrier stallions, stallions that were infected with EAV but had stopped shedding detectable virus in semen, and uninfected control animals[46]. The specific sites of EAV persistence in the reproductive tract were determined by virus isolation and single and dual immunohistochemistry (IHC).…”