Comparison between DNA Detection in Trigeminal Nerve Ganglia and Serology to Detect Cattle Infected with Bovine Herpesviruses Types 1 and 5

Abstract

Bovine herpesviruses (BoHVs) types 1 (BoHV-1) and 5 (BoHV-5) are alphaherpesviruses of major importance to the bovine production chain. Such viruses are capable of establishing latent infections in neuronal tissues. Infected animals tend to develop a serological response to infection; however, such response—usually investigated by antibody assays in serum—may eventually not be detected in laboratory assays. Nevertheless, serological tests such as virus neutralization (VN) and various enzyme-linked immunosorbent assays (ELISAs) are widely employed to check individual or herd status of BoHV infections. The correlation between detection of antibodies and the presence of viral nucleic acids as indicatives of infection in infected cattle has not been deeply examined. In order to investigate such correlation, 248 bovine serum samples were tested by VN to BoHV-1 and BoHV-5, as well as in a widely employed (though not type-differential) gB ELISA (IDEXX IBR gB X2 Ab Test) in search for antibodies to BoHVs. Immediately after blood withdrawal, cattle were slaughtered and trigeminal ganglia (TG) excised for DNA extraction and viral nucleic acid detection (NAD) by nested PCR. Neutralizing antibodies to BoHV-1 and/or BoHV-5 were detected in 44.8% (111/248) of sera, whereas the gB ELISA detected antibodies in 51.2% (127/248) of the samples. However, genomes of either BoHV-1, BoHV-5, or both, were detected in TGs of 85.9% (213/248) of the animals. These findings reveal that the assays designed to detect antibodies to BoHV-1 and/or BoHV-5 employed here may fail to detect a significant number of latently infected animals (in this study, 35.7%). From such data, it is clear that antibody assays are poorly correlated with detection of viral genomes in BoHV-1 and BoHV-5-infected animals.

Impairment on nuclear maturation rate in oocytes from cows naturally infected by bovine herpesvirus 1 (BoHV-1)

“…The nested PCR method enabled the identification of the genomes of BoHV-1, BoHV-5, or both in 85.9% (213/248) of the animals, whereas the seroneutralization method identified only 44.8% (111/248), and the ELISA method identified 51.2% (127/248) (Puentes et al 2016). Puentes et al (2016) emphasized that the detection of latently infected animals still depends on the postmortem identification of viral DNA in the trigeminal ganglion.…”

“…The nested PCR method enabled the identification of the genomes of BoHV-1, BoHV-5, or both in 85.9% (213/248) of the animals, whereas the seroneutralization method identified only 44.8% (111/248), and the ELISA method identified 51.2% (127/248) (Puentes et al 2016). Puentes et al (2016) emphasized that the detection of latently infected animals still depends on the postmortem identification of viral DNA in the trigeminal ganglion. Thus, the non-detection of viral DNA in the blood in this study can be explained by the brief period of acute disease manifestation in naturally infected animals or by the viral latency state in the sensorial and autonomic ganglia -a typical mechanism of the subfamily Alphaherpesvirinae (Spear 2004).…”

Latent <i>bovine herpesvirus</i> 1 and 5 in milk from naturally infected dairy cattle

“…The possible reasons for samples presenting a positive VNT/negative N-PCR and negative VNT/positive N-PCR analysis might be the low viral load, which cannot be detected by the N-PCR assay and low antibody level that cannot be detected by the VNT, respectively. Correspondingly, a previous study also showed a low Kappa index (k=0.13) when working with the VNT and nucleic acid detection in the trigeminal ganglia ( post mortem analysis) [ 14 ]. In our study, we provide an in vivo analysis.…”

“…Furthermore, because of the low viral load (shown below), the detection of anti-BoHV-1 and/or BoHV-5 antibodies, and the absence of clinical signs of herpesvirus infection in the animals, it is clear that there was latent infection. In this case, the detection of antibodies against herpesviruses indicates that the animals had latent infection, meaning that there was antibody production during an acute infection at some time in the past [ 14 ].…”

“…Even though VNT is the test of choice for antibody detection against BoHV according to the OIE [ 12 ], it is not designed, by itself, to detect latently infected animals. It is necessary to develop more sensitive serological methods and standardization of the molecular assay, which has higher sensitivity [ 14 ] and would also be important to detect the latent infection. In order to diagnose BoHV latent infection in vivo , molecular assays should be performed on tissues such as peripheral blood leukocytes, which are non-neural sites of latent infection maintenance and can be collected from blood and milk [ 2 ].…”