Regio- and Enantioselective Construction of Tetrazole Hemiaminal Esters and Related Prodrugs via Biocatalytic Dynamic Kinetic Resolution.

Enzyme-catalyzed dynamic kinetic resolution was applied to the one-pot regio- and enantioselective synthesis of 2,5-disubstituted tetrazole hemiaminal esters, among which 72% of the products were obtained in excellent enantiopurities (99% ees). Tunable stereoselectivity was achieved by using different types of enzymes during the synthesis of a key intermediate for a clinic drug candidate. Successful preparation of tetrazole ester prodrugs and high catalyst recyclability further demonstrated the potential practical application of this protocol.

Enzyme-Catalyzed Dynamic Kinetic Resolution of 2-Formylbenzoic Acids for the Asymmetric Synthesis of Phthalidyl Esters and Related Prodrugs.

An enzyme-catalyzed dynamic kinetic resolution strategy was applied for the asymmetric synthesis of phthalidyl esters in high yields (up to 95%) and enantiomeric purities (up to 99% ee) through a direct one-pot procedure. Preparation of phthalidyl ester prodrugs and a scale-up reaction demonstrated the potential of this method for practical applications.

Rapid detection of porcine circovirus type 2 by a red latex microsphere immunochromatographic strip.

To establish a rapid and specific antigen detection method for porcine circovirus type 2 (PCV2), monoclonal antibodies (mAbs) were produced against the PCV2 epidemic strains and a red latex microsphere immunochromatographic strip was established. A total of eight anti-PCV2b and four anti-PCV2d mAbs were produced, and seven mAbs were confirmed to react with PCV2a, PCV2b, and PCV2d strains using an immunoperoxidase monolayer assay. The results of micro-neutralization tests showed that the mAbs 2C8, 9H4, 10G7, 7B9, and 7C7 had good neutralizing activity, whereas the neutralizing activity of the mAbs 4B3, 4C9, 6H9, and 7E2 was lower than 50%. Three mAbs, 4B3, 7C7, and 9H4, and PCV2 pAb were selected for the establishment of a red latex microsphere immunochromatographic strip, and the combination of mAb 7C7 labeled with red latex microspheres and mAb 9H4 exhibited the greatest detection ability. The immunochromatographic strip had minimum detection limits of 102.5 TCID50/0.1 ml, 100.7 TCID50/0.1 ml, and 101.5 TCID50/0.1 ml for PCV2a/CL, PCV2b/MDJ, and PCV2d/LNHC, respectively. Furthermore, no cross-reactivity was found for African swine fever virus, classical swine fever virus, porcine respiratory and reproductive syndrome virus, porcine parvovirus, porcine pseudorabies virus, porcine circovirus type 1, transmissible gastroenteritis virus, porcine epidemic diarrhea virus, porcine rotavirus, or porcine deltacoronavirus using the immunochromatographic strip. Using PCR as a reference standard, the detection sensitivity, specificity, and overall coincidence rate of the immunochromatographic strip were 81.13%, 100%, and 90.00%. Additionally, the detection ability of the immunochromatographic strip was correlated with that of virus titration. The immunochromatographic strip was used to detect 183 clinical disease samples, and the average positive detection rate was 22.95%. In summary, this method has good sensitivity and specificity and is simple, convenient, and quick to operate. It has high application value for on-site diagnosis of PCV2 and virus quantification. KEY POINTS: • A red latex microsphere immunochromatographic strip for PCV2 detection was developed. • The method was not only simple to operate, but also takes less time. • The method had good sensitivity and specificity.

Development of a performance measurement system for general practitioners' office in China's primary healthcare.

BACKGROUND: General practitioners are the main providers of primary care services. To better strengthen the important role of general practitioners in primary healthcare services, China is promoting the general practitioners' office system. There is a lack of well-accepted methods to measure the performance of general practitioner offices in China. We thus aim to develop a systematic and operable performance measurement system for evaluating the general practitioner's office. METHODS: We establish an index pool of the performance measurement system of general practitioners' offices by a cross-sectional study and the literature research method and adopt the focus group method to establish the preliminary system. The Delphi method is then used to conduct three rounds of consultation to modify indices, which aims to form the final indicator system. We determine the weight of each index by the analytic hierarchy process method, which together with the final indicator system constitutes the final performance measurement system. Finally, we select three offices from three different cities in Sichuan Province, China, as case offices to conduct the case study, aiming to assess its credibility. RESULTS: Our results show that the first office scored 958.5 points, the second scored 768.1 points, and the third scored 947.7 points, which corresponds to the reality of these three offices, meaning that the performance measurement system is effective and manoeuvrable. CONCLUSIONS: Our study provides support for standardizing the functions of China's general practitioner's office, improving the health service quality of generalists, and providing a theoretical basis for the standardization of the general practitioner's office.

Neutralization Mechanism of a Monoclonal Antibody Targeting a Porcine Circovirus Type 2 Cap Protein Conformational Epitope.

Porcine circovirus type 2 (PCV2) is an important pathogen in swine herds, and its infection of pigs has caused severe economic losses to the pig industry worldwide. The capsid protein of PCV2 is the only structural protein that is associated with PCV2 infection and immunity. Here, we report a neutralizing monoclonal antibody (MAb), MAb 3A5, that binds to intact PCV2 virions of the PCV2a, PCV2b, and PCV2d genotypes. MAb 3A5 neutralized PCV2 by blocking viral attachment to PK15 cells. To further explore the neutralization mechanism, we resolved the structure of the PCV2 virion in complex with MAb 3A5 Fab fragments by using cryo-electron microscopy single-particle analysis. The binding sites were located at the topmost edges around 5-fold icosahedral symmetry axes, with each footprint covering amino acids from two adjacent capsid proteins. Most of the epitope residues (15/18 residues) were conserved among 2,273 PCV2 strains. Mutations of some amino acids within the epitope had significant effects on the neutralizing activity of MAb 3A5. This study reveals the molecular and structural bases of this PCV2-neutralizing antibody and provides new and important information for vaccine design and therapeutic antibody development against PCV2 infections.IMPORTANCE PCV2 is associated with several clinical manifestations collectively known as PCV2-associated diseases (PCVADs). Neutralizing antibodies play a crucial role in the prevention of PCVADs. We demonstrated previously that a MAb, MAb 3A5, neutralizes the PCV2a, PCV2b, and PCV2d genotypes with different degrees of efficiency, but the underlying mechanism remains elusive. Here, we report the neutralization mechanism of this MAb and the structure of the PCV2 virion in complex with MAb 3A5 Fabs, showing a binding mode in which one Fab interacted with more than two loops from two adjacent capsid proteins. This binding mode has not been observed previously for PCV2-neutralizing antibodies. Our work provides new and important information for vaccine design and therapeutic antibody development against PCV2 infections.

Host-Seeking Behavior of Aphidius gifuensis (Hymenoptera: Braconidae) Modulated by Chemical Cues Within a Tritrophic Context.

Aphidius gifuensis Ashmaed is a generalist endoparasitoid that parasitizes a variety of aphid species. In China, it is widely used as a biological control agent to protect vegetables and tobaccos in open fields; control efficiency is largely dependent on its host-seeking ability. In this study, a six-choice olfactometer was used to investigate the olfactory responses of A. gifuensis to tobacco plants that had suffered damage (either varying degrees of mechanical damage or from aphid-feeding at different time intervals) and tobacco volatiles with different dosages. Furthermore, the regularity of A. gifuensis females' response toward an aphid/tobacco complex was monitored using a Y-tube olfactometer. Our findings suggest that tobacco plants are significantly attractive to A. gifuensis after they have been punctured with 50 holes, or housed with Myzus persicae (Sulzer) at a density of 400 aphids, except at an infestation time of 12 h. Moreover, aphid density had a more significant effect on the response than the time interval since aphid application. Aphidius gifuensis was found to be active during the daytime and preferred to search for their aphid hosts at 14:00 h. Five EAG-active tobacco volatiles (trans-2-hexenal, methyl salicylate, benzaldehyde, cis-3-hexen-1-ol, and 1-hexanal) were found to significantly attract A. gifuensis females at different concentration ranges. The practical implications of these results are discussed in the framework of the sustainable biological control of pest aphids in agricultural production systems.

Caspase-Dependent Apoptosis Induction via Viral Protein ORF4 of Porcine Circovirus 2 Binding to Mitochondrial Adenine Nucleotide Translocase 3.

Apoptosis is an essential strategy of host defense responses and is used by viruses to maintain their life cycles. However, the apoptotic signals involved in virus replication are poorly known. In the present study, we report the molecular mechanism of apoptotic induction by the viral protein ORF4, a newly identified viral protein of porcine circovirus type 2 (PCV2). Apoptosis detection revealed not only that the activity of caspase-3 and -9 is increased in PCV2-infected and ORF4-transfected cells but also that cytochrome c release from the mitochondria to the cytosol is upregulated. Subsequently, ORF4 protein colocalization with adenine nucleotide translocase 3 (ANT3) was observed using structured illumination microscopy. Moreover, coimmunoprecipitation and pulldown analyses confirmed that the ORF4 protein interacts directly with mitochondrial ANT3 (mtANT3). Binding domain analysis further confirmed that N-terminal residues 1 to 30 of the ORF4 protein, comprising a mitochondrial targeting signal, are essential for the interaction with ANT3. Knockdown of ANT3 markedly inhibited the apoptotic induction of both ORF4 protein and PCV2, indicating that ANT3 plays an important role in ORF4 protein-induced apoptosis during PCV2 infection. Taken together, these data indicate that the ORF4 protein is a mitochondrial targeting protein that induces apoptosis by interacting with ANT3 through the mitochondrial pathway.IMPORTANCE The porcine circovirus type 2 (PCV2) protein ORF4 is a newly identified viral protein; however, little is known about its functions. Apoptosis is an essential strategy of the host defense response and is used by viruses to maintain their life cycles. In the present study, we report the molecular mechanism of the apoptosis induced by the ORF4 protein. The ORF4 protein contains a mitochondrial targeting signal and is an unstable protein that is degraded by the proteasome-dependent pathway. Viral protein ORF4 triggers caspase-3- and -9-dependent cellular apoptosis in mitochondria by directly binding to ANT3. We conclude that the ORF4 protein is a mitochondrial targeting protein and reveal a mechanism whereby circovirus recruits ANT3 to induce apoptosis.

Identification of specific B cell linear epitopes of mycoplasma hyorhinis P37 protein using monoclonal antibodies against baculovirus-expressed P37 protein.

BACKGROUND: Mycoplasma hyorhinis (Mhr) is the etiologic agent of lameness and polyserositis in swine. P37 is a membrane protein of Mhr that may be an important immunogen and is a potential target for diagnostic development. However, there is little information concerning Mhr P37 protein epitopes. A precise analysis of the P37 protein epitopes should extend our understanding of the antigenic composition of the P37 protein and the humoral immune responses to Mhr infection. Investigating the epitopes of Mhr P37 will help to establish a detection method for Mhr in tissue and provide an effective tool for detecting Mhr infection. RESULTS: Western blot and indirect immunofluorescence assays (IFA) confirmed that the expressed P37 protein was recognized by Mhr-positive porcine and mouse sera. Furthermore, the P37 protein was purified using affinity chromatography and used to immunize mice for hybridoma cell fusion. Four monoclonal antibodies (mAbs) found to be positive for Mhr were detected in infected lung tissue. A panel of truncated P37 proteins was used to identify the minimal B cell linear epitopes of the protein based on these mAbs. The core epitope was determined to be 206KIKKAWNDKDWNTFRNF222. CONCLUSIONS: In this study, we identified 17 critical amino acids that determine the epitope of the P37 protein of Mhr. This study identified mAbs that could provide useful tools for investigating the Mhr P37 antigenic core epitope (amino acids 206-222) and detecting Mhr-specific antigens in infected tissue.

The prevalence and genetic diversity of porcine circovirus types 2 and 3 in Northeast China from 2015 to 2018.

A total of 472 samples from domestic pigs collected in China from 2015 to 2018 were tested for the presence of porcine circovirus types 2 and 3 (PCV2 and PCV3, respectively) by conventional polymerase chain reaction analysis. The prevalence of PCV2, PCV3, and PCV2/3 co-infection was 50.0%, 13.3%, and 6.78%, respectively. The complete genomic sequences of 66 PCV2 isolates and four PCV3 isolates were determined. Based phylogenetic analysis, the PCV2 isolates were assigned to three genotypes, PCV2a, PCV2b, and PCV2d, representing 13.6% (9/66), 25.8% (17/66), and 60.6% (40/66) of the total, respectively. All four PCV3 isolates shared a high degree of similarity in their complete nucleotide sequences (98.8-99.8% identity) and ORF2 amino acid sequences (98.6-99.5% identity). These results indicate that all three PCV2 genotypes (PCV2a, PCV2b, and PCV2d) are present on pig farms and that PCV2d has become the predominant genotype. The predicted amino acid sequences of the four PCV3 isolates indicated that PCV3-CN-JL53/PCV3-CN-LN56, PCV3-CN-HLJ3, and PCV3-CN-0710, belonged to the genotypes PCV3a, PCV3b, and PCV3a-IM, respectively. In view of the great harm that PCV2 causes to the pig industry, the epidemic trend of PCV3 should continue to be closely monitored. This study provides information about the prevalence, genetic diversity, and molecular epidemiology of PCV2 and PCV3 in China from 2015 to 2018.

Rescue and characterization of a recombinant HY12 bovine enterovirus carrying a foreign HA epitope in the 3A nonstructural protein.

Full-length infectious cDNA clones for recombinant HY12 bovine enteroviruses designated as rHY12-3A-2-HA, rHY12-3A-3-HA, and rHY12-3A-9-HA were constructed by the insertion of an epitope from influenza virus hemagglutinin (HA) at the N-terminus of the HY12-encoded 3A protein at amino acid positions 2, 3, and 9. The recombinant HY12 viruses expressing the HA epitope were rescued and characterized using immunoperoxidase monolayer assay, western blotting, and electron microscopy. The three rescued recombinant marker viruses showed similar characteristics, such as TCID50 titer, plaque size, and growth properties, to those of parental rHY12 virus. Comparative analysis of the nucleotide sequences demonstrated the three recombinant marker viruses remained stable for 15 passages with no genetic changes. The recombinant viruses remained viable in various permissive cell lines, including BHK-21, Vero, and PK15 cells, suggesting that the insertion of the HA epitope tag had no effect on virus infectivity. Mice infected with the recombinant marker viruses and the parental virus produced anti-HY12-virus antibodies, while the recombinant marker viruses also produced anti-HA-epitope-tag antibodies. Taken together, these results demonstrate that HY12 viruses containing genetic markers may be useful tools for future investigations of the mechanisms of viral pathogenesis and virus replication, as well as for vaccine development.

A broad spectrum monoclonal antibody against porcine circovirus type 2 for antigen and antibody detection.

This study described the production, characterization, and application of monoclonal antibodies (mAbs) against porcine circovirus type 2 (PCV2). Twelve stable hybridomas were produced by immunization with purified PCV2a/LG strain and characterized by immunoperoxidase monolayer assay (IPMA), Western blotting, and neutralization assays. All mAbs could react with the PCV2 Cap protein and neutralize PCV2a/LG strain. One of them, mAb 3A5, reacted to all PCV2 strains from PCV2a, PCV2b, and PCV2d and it could be applied to detect PCV2 antigen and antibodies. It was shown that the mAb 3A5 could be used to locate PCV2 antigen in PK15 cells and the inguinal lymph nodes of PCV2b/YJ stain-infected piglets. Furthermore, this mAb could immunoprecipitate the Cap protein in PCV2-infected PK15 cells. Meanwhile, a capture ELISA based on mAb 3A5 was developed and used to specifically test PCV2 antigen from cultures; a linear relationship was observed between the optical density at 405 nm of the ELISA and viral titers (200-12,800 TCID50/mL), with a correlation coefficient of 0.9999. Finally, a competitive ELISA based on mAb 3A5 was developed to specifically detect antibodies in PCV2-infected and immunized pigs, and its sensitivity was higher than that of the blocking ELISA. This study suggested that the mAb 3A5 could be used in several convenient and efficient methods for PCV2 clinical and pathological studies, as well as surveillance in pigs and seroconversion monitoring in the vaccinated pigs.

Identification of three linear B cell epitopes using monoclonal antibodies against bovine enterovirus VP2 protein.

Bovine enterovirus (BEV) VP2 protein is a structural protein that plays an important role in inducing protective immunity in the host. The function of VP2 has been characterized, but there is little information on its B cell epitopes. Three monoclonal antibodies (mAbs) directed against BEV VP2 were generated and characterized from mice immunized with the recombinant VP2 protein. Three minimal linear epitopes 152FQEAFWLEDG161, 168LIYPHQ173, and 46DATSVD51 reactive to the three mAbs were identified using western blotting analysis. Three-dimensional model of the BEV-E virion and the VP2 monomer showed that epitope 152FQEAFWLEDG161 is exposed on surface of the virion and epitopes 46DATSVD51 and 168LIYPHQ173 are located inside the virion. Alignment of the amino acid sequences corresponding to the regions containing the three minimal linear epitopes in the VP2 proteins and their cross-reactivity with the three mAbs showed that epitope 168LIYPHQ173 is completely conserved in all BEV strains. Epitope 46DATSVD51 is highly conserved among BEV-E strains and partly conserved among BEV-F strains. However, epitope 152FQEAFWLEDG161 is not conserved among BEV-F strains. Using the mAbs of 3H4 and 1E10, we found that VP2 localized in the cytoplasm during viral replication and could be used to monitor the viral antigen in infected tissues using immunohistochemistry. A preliminary 3H4-epitope-based indirect ELISA allowed us to detect anti-BEV-strain-HY12 antibodies in mice. This study indicates that the three mAbs could be useful tools for investigating the structure and function of the viral VP2 protein and the development of serological diagnostic techniques for BEV infection.

Screening and identification of potential protein biomarkers for evaluating the efficacy of intensive therapy in pulmonary tuberculosis.

This research aimed to discover potential biomarkers for evaluating the therapeutic efficacy of intensive therapy in pulmonary tuberculosis (TB). Protein profiles in 2-months intensively treated TB patients, untreated TB patients, and healthy controls were investigated with iTRAQ-2DLC-MS/MS technique. 71 differential proteins were identified in 2-months intensively treated TB patients. Significant differences in complement component C7 (CO7), apolipoprotein A-IV (APOA4), apolipoprotein C-II (APOC2), and angiotensinogen (ANGT) were found by ELISA validation. CO7 and ANGT were also found significantly different in sputum negative patients, compared with sputum positive patients after intensive treatment. Clinical analysis showed that after 2-months intensive treatment several indicators were significantly changed, and the one-year cure rate of sputum negative patients were significantly higher than sputum positive patients. Diagnostic models consisting of APOC2, CO7 and APOA4 were established to distinguish intensively treated TB patients from untreated TB patients and healthy controls with the AUC value of 0.910 and 0.935. Meanwhile, ANGT and CO7 were combined to identify sputum negative and sputum positive TB patients after intensive treatment with 89.36% sensitivity, 71.43% specificity, and the AUC value of 0.853. The results showed that APOC2, CO7, APOA4, and ANGT may be potential biomarkers for evaluating the efficacy of intensive anti-TB therapy.

Nanoparticles Penetrate into the Multicellular Spheroid-on-Chip: Effect of Surface Charge, Protein Corona, and Exterior Flow.

Nanoparticles (NPs) are widely studied as tumor targeted vehicles. The penetration of NPs into the tumor is considered as a major barrier for delivery of NPs into tumor cell and a big challenge to translate NPs from lab to the clinic. The objective of this study is to know how the surface charge of NPs, the protein corona surrounding the NPs, and the fluid flow around the tumor surface affect the penetration and accumulation of NPs into the tumor, through in vitro penetration study based on a spheroid-on-chip system. Surface decorated polystyrene (PS) NPs (100 nm) carrying positive and negative surface charge were loaded to the multicellular spheroids under static and flow conditions, in the presence or absence of serum proteins. NP penetration was investigated by confocal laser microscopy scanning followed with quantitative image analysis. The results reveal that negatively charged NPs are attached more on the spheroid surface and easier to penetrate into the spheroids. Protein corona, which is formed surrounding the NPs in the presence of serum protein, changes the surface properties of the NPs, weakens the NP-cell affinity, and, therefore, results in lower NP concentration on the spheroid surface but might facilitate deeper penetration. The exterior fluid flow enhances the interstitial flow into the spheroid, which benefits the penetration but also strips the NPs (especially the NPs with protein corona) on the spheroid surface, which decreases the penetration flux significantly. The maximal penetration was obtained by applying negatively charged NPs without protein corona under the flow condition. We hope the present study will help to understand the spatiotemporal performance of drug delivery NPs and inform the rational design of NPs with highly defined drug accumulation localized at a target site.

The Comparison of Urinary Stones Between She Minority and Han Nationality in East Fujian, China.

BACKGROUND: The purpose of the study was to compare the incidence of urinary stones of She minority and Han nationality and analyze the composition of urinary stones. METHODS: The study was performed in 381 cases with 181 She minority and 200 Han nationality. The composition of stones was mainly analyzed by infrared absorption spectrum. The incidence of urinary stones at different ages, different gender and different parts was compared between She minority and Han nationality. RESULTS: The urinary stone incidence of males was about twice as high as in women in She minority and Han nationality, and the incidence reached its maximum between the ages of 41 and 60, but the incidence decreased after 60 years of age. The distribution characteristics of urethra stones between She minority and Han nationality showed a significant difference (p < 0.05). The differences of carbonate apatite and struvite in male and female were statistically significant between She minority and Han nationality (p < 0.05). The level of Ca2+ and HPO42- in serum showed significant difference between She minority and Han nationality (p < 0.05). CONCLUSIONS: According to these results, we put forward corresponding preventive measures of urinary stones in She minority.

3D-printed diffractive elements induced accelerating terahertz Airy beam.

We first demonstrate the accelerating terahertz (THz) Airy beam with a 0.3-THz continuous wave. Two diffractive elements are designed and 3D-printed to form the generation system, which cannot only imprint the desired complex phase pattern but also perform the required Fourier transform (FT). We both numerically and experimentally demonstrate the propagation dynamics of the accelerating THz Airy beam and investigate its self-healing property during propagation in the free space. Our observations are in good agreement with the numerical simulations. Such an accelerating THz Airy beam could be able to develop novel THz imaging systems and robust THz communication links.

Discrimination of orbital angular momentum modes of the terahertz vortex beam using a diffractive mode transformer.

We present an efficient method to discriminate orbital angular momentum (OAM) of the terahertz (THz) vortex beam using a diffractive mode transformer. The mode transformer performs a log-polar coordinate transformation of the input THz vortex beam, which consists of two 3D-printed diffractive elements. A following lens separates each transformed OAM mode to a different lateral position in its focal plane. This method enables a simultaneous measurement over multiple OAM modes of the THz vortex beam. We experimentally demonstrate the measurement of seven individual OAM modes and two multiplexed OAM modes, which is in good agreement with simulations.

Function analysis of rs9589207 polymorphism in miR-92a in gastric cancer.

MiR-92a was identified as an essential oncogene by promoting the cell proliferation through FBXW7 in gastric cancer (GC). The function of the single nucleotide polymorphism (SNP) located in the mature region of miR-92a (rs9589207) has not been investigated. We found that rs9589207 in miR-92a was involved in the occurrence of GC by acting as a tumor protective factor and was highly associated with tumor size in GC patients instead of tumor number or metastasis in 554 GC patients and 531 cancer-free controls. Besides, the AA genotype in miR-92a could attenuate the promoting function of miR-92a in cell proliferation with an incapacitation in downregulating the expression of FBXW7. In conclusion, rs9589207 in miR-92a was highly associated with a decreased risk of GC in Chinese Han population and might serve as a novel biomarker for the disease.

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.

The pseudorabies virus DNA polymerase processivity factor UL42 exists as a monomer in vitro and in vivo.

The processivity factors (PFs) of herpesviruses confer processivity to the DNA polymerase. Understanding whether the herpesvirus PFs function as monomers or multimers is important for clarifying the mechanism by which they provide the DNA polymerase with processivity. Herpes simplex virus type 1 UL42 is a monomer, whereas human cytomegalovirus UL44, Epstein-Barr virus BMRF1, and Kaposi's sarcoma-associated herpesvirus PF-8 exist as dimers. However, the oligomeric status of the pseudorabies virus (PRV) DNA polymerase PF UL42 has not been determined. Using fluorescence confocal microscopy and chemical crosslinking, we confirmed that UL42 is a monomer when expressed in vitro. Crosslinking of nuclear extracts from PRV-infected or uninfected PK-15 cells verified that UL42 exists as a monomer in vivo. Our demonstration that UL42 exists as a monomer in vitro and in vivo contributes to the further investigation of the mechanism used by UL42 to achieve processivity.