Symptomless intrauterine transmission of bovine herpesvirus 4 to bovine fetuses László Egyed a, * , Gergely Sassi b , János Tibold c , István Mádl c , Ottó Szenci b a Veterinary Medical Research Institute of the Hungarian Academy of Sciences, P.O. Box 18.1581 Budapest, Hungary b Szent István University, Faculty of Veterinary Science, Clinic for Large Animals, Üll} o, Hungary c Agroprodukt Zrt, Pápa, Hungary article info Article history: Received 18 March 2010 Received in revised form 7 September 2010 Accepted 7 October 2010 Available online 24 February 2011 Keywords: Bovine herpesvirus 4 Intrauterine infection Newborn calves abstract Blood samples of 31 healthy calves and their dams taken immediately after calving before colostrum uptake, and at days 11, 23 and 8 weeks, spleens of seven stillborn calves were analysed in order to determine the source and time of bovine herpesvirus type 4 infection. All the calves were born as seronegatives, while all cattle were seropositives. Viral DNA were amplified by a nested PCR assay from 54.8% of peripheral blood leukocyte samples of newborn calves taken before colostrum uptake, and from all cattle and from their colostrums. Real time PCR detected higher virus level in peripheral blood leukocytes in adult cattle, then in their newborn calves. Bovine semen cells (spermatozoa and leukocyte fractions), spleens of stillborn calves also carried viral genomes. Our results prove, that bovine fetuses can be infected in utero by BoHV-4, but are born as seronegatives. After human examples this is the first report in veterinary virology on intrauterine transmission of a herpesvirus without acute consequences. This phenomenon could explain the low antigenicity of BoHV-4 proteins and lack of neutralizating antibodies. BoHV-4, a gammaherpesvirus, could serve as an animal model for studying inapparent herpesviral infections of human fetuses. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Several families of viruses, including Herpesviridae are able to cause illness and abortion of the fetus, but in the last couple of years reports proved, that viruses may invade fetal cells through different routes without acute consequences [1]. Vertical transplacental transmission of viruses to fetal cells could be established in several ways. Semen cells (spermatozoa, seminal plasma, leukocytes) may transfer viruses into zygotes [2,3]. Viruses were shown to be integrated into chromosomes [4] and transferred to fetal tissues by the regular maternal-fetal transport of maternal cells. Viruses replicate in human trophoblasts and syncytiotrophoblast cells, and transport of immunocomplexes are also suggested. Presence of viruses in fetal tissues, their interaction with fetal immune system might result in post partum consequences (reduced immune response against many virus coded proteins, fetal deple- tion of B cell populations, formation of malignancies, impaired differentiation of virus carrier cells by the micro-RNAs produced or regulated by viral genes). Almost all human herpesviruses have been associated with intrauterine virus transmissions. Human herpesvirus 1 (herpes simplex virus), Human herpesvirus 4 (EpsteineBarr virus, EBV) [5], Human herpesvirus 5 (Human cytomegalovirus) [6], Human herpesviruses 6 and 7 [7]. Human herpesvirus 8 (HHV-8 Kaposi sarcoma virus) were detected from spermatozoa [8], 2% of HHV-6 carrier persons harbor the viral genome in the germ line, and these HHV-6 sequences integrated in their chromosomes might be inherited [4]. Primary EBV infection during pregnancy with apparent trans- placental transmission is rare and only few cases were reported. The main damage was in the heart, eyes and liver. The actual damage to the developing embryo and fetus from maternal EBV seems to be very small. It should be mentioned that the EBV seems to be able to cross the placenta and causes, as described by several investigators, placental infection manifested by deciduitis and vil- litis. These placental pathological changes may increase fetal damage [5]. Some viruses of veterinary interest e.g. Bovine viral diarrhea virus (BVDV), Equine herpesvirus 1 and Bovine herpesvirus 1 [9] are known to infect fetuses and cause acute illnesses or abortions. The intrauterine infections of alphaherpesviruses (EqHV-1 and BoHV-1) frequently resulted in embryonic death, abortion, stillbirth, and usually in clinical signs of the dam. The BVDV is able to infect fetus without causing any clinical signs, but this is not a herpesvirus. * Corresponding author. Tel.: þ36 1 467 4073; fax: þ36 1 252 1069. E-mail address: laci@vmri.hu (L. Egyed). Contents lists available at ScienceDirect Microbial Pathogenesis journal homepage: www.elsevier.com/locate/micpath 0882-4010/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.micpath.2010.10.006 Microbial Pathogenesis 50 (2011) 322e325