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The aim of this study was to identify the endogenous retrovirus (ERV) sequences in a bovine genome. We subjected bovine genomic DNA to PCR with degenerate or ovine ERV (OERV) family-specific primers that aimed to amplify the retroviral pro/pol region. Sequence analysis of 113 clones obtained by PCR revealed that 69 were of retroviral origin. On the basis of the OERV classification system, these clones from degenerate PCR could be divided into the ␤3, ␥4, and ␥9 families. PCR with OERV family-specific primers revealed an additional ERV that was classified into the bovine endogenous retrovirus (BERV) ␥7 family. In conclusion, here we report the results of a genome scale study of the BERV. Our study shows that the ERV family expansion in cattle may be somewhat limited, while more diverse family members of ERVs have been reported from other artiodactyls, such as pigs and sheep.The endogenous retroviruses (ERVs) in mammals are classified into the retroviral ␤ (B-/D-type) and ␥ (C-type) genera (3,20). To date, analyses of the ERVs in the genomes of several mammals, including humans, pigs, and sheep, have revealed the presence of multiple different families (1,2,4,5,7,10,11,13,15,16,17,19). For example, in the sheep genome, 12 different ovine ERV (OERV) families were detected. These were classified into three ␤ families (␤1 to ␤3) and nine ␥ families (␥1 to ␥9) (11). However, except for one pro/pol sequence from murine leukemia virus-related retrovirus (MLVRT1-BoEV) (19), no other sequence information regarding ERVs residing in the cattle genome is available.It is known that human ERVs (HERVs) comprise approximately 8% of the human genome (6). Thus, the identification of the ERVs in the bovine genome will be helpful for the annotation of the bovine genome; it will also improve our understanding of ERVs. We searched the bovine genome for the conserved pro/pol nucleotide sequences of ERVs by PCR using degenerate primers, which contain the active site motifs DTGA of protease (PR) protein and YMDD or YVDD of reverse transcriptase (RT) protein (7,10,11,18). Since we found that all ERV clones obtained by degenerate PCR were closely related to three specific OERV families, we also subjected the bovine genome to PCR using OERV family-specific primers.Degenerate PCR amplification of BERV sequences. We isolated the genomic DNA from one Korean Yellow native female cow (Bos taurus) by a simple lysis method (14). The template DNA was subjected to PCR using Taq polymerase and six pairs of degenerate primers previously used for suc-

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Human papillomavirus is known to be the major pathogen of cervical cancer. Here, we report the efficacy of a bivalent human papillomavirus type 16 and 18 DNA vaccine system following repeated dosing in mice and pigs using a recombinant baculovirus bearing human endogenous retrovirus envelope protein (AcHERV) as a vector. The intramuscular administration of AcHERV-based HPV16L1 and HPV18L1 DNA vaccines induced antigen-specific serum IgG, vaginal IgA, and neutralizing antibodies to levels comparable to those achieved using the commercially marketed vaccine Cervarix. Similar to Cervarix, AcHERV-based bivalent vaccinations completely blocked subsequent vaginal challenge with HPV type-specific pseudovirions. However, AcHERV-based bivalent vaccinations induced significantly higher cell-mediated immune responses than Cervarix, promoting 4.5- (HPV16L1) and 3.9-(HPV18L1) fold higher interferon-γ production in splenocytes upon stimulation with antigen type-specific pseudovirions. Repeated dosing did not affect the immunogenicity of AcHERV DNA vaccines. Three sequential immunizations with AcHERV-HP18L1 DNA vaccine followed by three repeated dosing with AcHERV-HP16L1 over 11 weeks induced an initial production of anti-HPV18L1 antibody followed by subsequent induction of anti-HPV16L1 antibody. Finally, AcHERV-based bivalent DNA vaccination induced antigen-specific serum IgG immune responses in pigs. These results support the further development of AcHERV as a bivalent human papillomavirus DNA vaccine system for use in preventing the viral infection as well as treating the infected women by inducing both humoral and cell-mediated immune responses. Moreover, the possibility of repeated dosing indicates the utility of AcHERV system for reusable vectors of other viral pathogen vaccines.