Identification of two new antigen epitopes on the putative capsid protein encoded by torque teno sus virus type 1 ORF1

Torque teno viruses in health and disease

Torque teno viruses (TTVs) are small, ubiquitous, viruses with a highly diverse, single-stranded, negative sense DNA genome and wide host range. They are detected at high rates in both healthy and diseased individuals and are considered a significant part of the mammalian virome. Similar to human TTVs, swine TTVs (TTSuVs) are epidemiologically linked to several coinfections including porcine circovirus types 2 and 3 and the porcine reproductive and respiratory disease syndrome virus. Experimental infection of gnotobiotic pigs with TTSuVs resulted in lesions in multiple organs and exacerbation of coinfections, making TTSuVs the only members of the Anelloviridae family with experimental evidence for pathogenicity. However, due to the lack of reliable cell culture and animal models, mechanistic studies on viral immunity and pathogenesis are limited. The objective of this review is to summarize the current status of knowledge regarding the biology, detection, pathogenesis and public health significance of TTSuVs, while identifying gaps in knowledge which limit the field.

Neutralization of genotype 2 porcine epidemic diarrhea virus strains by a novel monoclonal antibody

Porcine epidemic diarrhea virus (PEDV) has two genotypes, G1 and G2. To research the immunogenicity differences of PEDV G1 and G2 genotype strains and obtain a neutralizing monoclonal antibody (mAb), we inoculated specific-pathogen-free BALB/c mice with a newly emerged strain, PEDV-LNCT2. After immunizations, cells from the spleen of the mice were fused with SP2/0 myeloma cells. Following culturing and subcloning, a strain, 1B9, secreting neutralizing antibody, was obtained. The 1B9 mAb neutralized new variant genotype 2 PEDV strains (LNCT2, LNSY, and Hjms), but it did not neutralize a genotype 1 PEDV strain (CV777), in vitro. Results showed that the epitope recognized by the 1B9 mAb lies in the spike protein, and that it is a conformational epitope. These findings confirm that allelic differences in the PEDV S gene between the G1 and G2 genotype strains led to changes in the S protein and, thus, differences in its immunogenicity.

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The mAb of 1B9 could neutralize PEDV new variant strains from genotype 2.

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The mAb of 1B9 could not neutralize PEDV strain from genotype 1.

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The antiviral strategy of mAb 1B9 work by combination with the S protein of PEDV.

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The epitope recognized by mAb 1B9 is a conformational epitope.

Functional characterization of a new promoter isolated from torque teno sus virus 1

Torque teno sus virus 1 (TTSuV1) has a non-enveloped, single-stranded, negative-sense circular DNA genome, and it is widely distributed in pigs. Open reading frame 1 (ORF1) of TTSuV1 can be transcribed into mRNA and then translated into protein; however, its promoter has not yet been identified. We used a dual-luciferase reporter system, involving pGL3-Basic and pRL-TK, to identify the promoter of TTSuV1 ORF1. Our results revealed that the sequence between nucleotides 196 and 525 promoted the transcription of the firefly luciferase gene. The core sequence of the promoter was between nucleotides 250 and 400. A comparison of the identified TTSuV1 ORF1 promoter with that from cytomegalovirus (CMV) suggested that the two promoters were similar in strength. Our findings provide new information regarding the molecular biology of TTSuV1 and have revealed a new promoter that can be used in plasmids for numerous applications.

Identification of three antigen epitopes on the nucleocapsid protein of the genotype C of bovine parainfluenza virus type 3

Bovine parainfluenza virus type 3 (BPIV3) is an important respiratory tract pathogen for both young and adult cattle. So far, three genotypes A, B and C of BPIV3 have been described on the basis of genetic and phylogenetic analysis. But fine mapping of epitopes of BPIV3 is scant and the antigenic variations among the three genotypes of BPIV3 have not been reported. Nucleocapsid protein (NP) is the most abundant protein in the virion and highly conserved in BPIV3, which is crucial for the induction of protective immunity in host. To identify antigenic determinants of BPIV3 NP, a panel of monoclonal antibodies (mAbs) was tested against a series of overlapping recombinant NP fragments expressed in Escherichia coli. Firstly, six monoclonal antibodies (mAbs) against NP of the genotype C of BPIV3 (BPIV3c) were generated by using the purified BPIV3c strain SD0835 as immunogen and the recombinant NP of SD0835 as screening antigen. Then three antigen epitopes were identified with the six mAbs. One epitope (91)GNNADVKYVIYM(102) was recognized by mAb 5E5. The mAbs 7G5, 7G8, 7G9, and 7H5 were reactive with another epitope (407)FYKPTGG(413). The third epitope (428)ESRGDQDQ(435) was reactive with mAb 6F8. Further analysis showed that the epitope (91-102 amino acids [aa]) was the most conserved and reactive with mAb 5E5 for all three genotypes of BPIV3 and HPIV3. The epitope (407-413 aa) was relatively conserved and reactive with mAbs 7G5, 7G8, 7G9, and 7H5 for BPIV3a, BPIV3c and HPIV3, but not reactive with BPIV3b. The epitope (428-435 aa) was less conserved and was reactive only with mAb 6F8 for BPIV3a and BPIV3c. These results suggested that there were evident antigenic variations among the three genotypes of BPIV3 and HPIV3. The mAb 6F8 could be used to detect BPIV3a and BPIV3c. The mAbs 7G5, 7G8, 7G9, and 7H5 might be used for differentiate BPIV3a, BPIV3c and HPIV3 from BPIV3b. The mAb 5E5 might be used for detecting all three types of BPIV3 and HPIV3. The results in this study would have potential applications in the development of suitable diagnostic techniques for BPIV3, which was prevalent in China.