The Expression Levels of CD20 as a Prognostic Value in Feline B-Cell Nasal Lymphoma: A Pilot Study

The effect of the semi-quantitative expression of CD20 in the prognosis of feline nasal lymphoma has not been described. This study investigated the prognostic significance of CD20 expression, clinicopathological characterization, and treatment outcomes in cats with nasal lymphoma. Clinical data from cats diagnosed with nasal lymphoma were retrospectively collected, including signalment, clinical signs, clinicopathological variables, treatment outcomes, and survival times. Using ImageJ software, CD20 expression was semi-quantitatively measured based on the proportion of CD20-positive areas. Correlations between laboratory findings, immunohistochemical expressions, and survival outcomes were investigated. All cats included in the study exhibited the B-cell immunophenotype. During treatment, a reduction in PCV was noted in the cats at the second and sixth weeks (p = 0.01 and p = 0.01, respectively). The cats with low CD20 expression exhibited a significantly shorter MST (91 days; 95% CI, 41-141) than those with high CD20 expression (MST, 214 days; 95% CI, 76-351) (p = 0.01). Stage T1 cats displayed a higher MST (143 days; 95% CI, 144-172) than those in other stages > T1 (120 days, 95% CI, 71-169 days) (p = 0.04). Anemia, a common adverse effect in feline nasal lymphoma, did not impact MST. T1 clinical staging and high CD20 expression showed a trend for better MST.

Genetic structure and diversity of green turtle (Chelonia mydas) in the Gulf of Thailand

Background and Aim

The International Union for the Conservation of Nature and Natural Resources lists the green turtle as endangered. Green turtle nesting behavior in the Gulf of Thailand has decreased to <50% of the 1995 level. The population structure of green turtles in the Gulf of Thailand has not yet been studied. This study aimed to characterize the genetic diversity of green turtles in the Gulf of Thailand based on comparisons of mitochondrial DNA (mtDNA) control region with sequences of Indo-Pacific management units (MUs) and rookeries, to investigate population structures, and to explore phylogeographic relationships.

Materials and Methods

Blood samples (1 mL each) from 91 stranded green turtles were collected from four parts of the Gulf of Thailand (eastern, upper, central, and lower). The control mtDNA region was amplified by polymerase chain reaction using LCM15382 and H950 primer. The obtained 384-bp or 770-bp sequences were analyzed for haplotype, clade, and haplotype and nucleotide diversities and were used to construct a phylogenetic tree and haplotype network diagram, respectively. In addition, we analyzed genetic differentiation within and among populations of green turtles in the Gulf of Thailand and between green turtles in the Gulf of Thailand and other Indo-Pacific MUs and rookeries.

Results

In total, 12 (based on 384 bp) or 13 (based on 770 bp) haplotypes and two clades (clades VII and VIII) were identified, with nine or 10 haplotypes belonging to clade VIII and three haplotypes belonging to clade VII. Of the new haplotypes, four or five were identified and classified as clade VII (two haplotypes, for both fragment lengths) and clade VIII (two or three haplotypes, for 384 bp or 770 bp fragments, respectively). The overall haplotype and nucleotide diversity of green turtles in the Gulf of Thailand were high (0.755 ± 0.039 and 0.01146 ± 0.00248, respectively). Based on the analysis of molecular variance, green turtles in the Gulf of Thailand could be divided into two subpopulations (UC-Eastern Gulf of Thailand [UC-EGT] and lower Gulf of Thailand [LGT]). Comparisons with other MUs and rookeries in the Indo-Pacific showed that UC-EGT was not genetically different from the Peninsular Malaysia and Eastern Taiwan (Lanyu) MUs and the Terrangganu and Mersing rookeries, and LGT were not genetically different from Peninsular Malaysia, Sipadan, Brunei Bay, Eastern Taiwan (Lanyu), Scott Reef and Browse Island, and Gulf of Carpentaria MUs and the Perak, Perhentain Island, Redang, Pahang, and Vietnam rookeries.

Conclusion

To the best of our knowledge, this is the first report to identify the haplotypes and clades of green turtles in the Gulf of Thailand and to show that the populations in the Gulf of Thailand not only present high genetic diversity but also have haplotypic endemism. Longer mtDNA fragments (770 bp) increased the resolution of the stock structure. Clade VII is a unique clade not only for Japan but also for Thailand and Malaysia, and CmP82 is a unique haplotype for both the Gulf of Thailand and Malaysia. Conservation and management of these populations are important to preserve the genetic diversity, biological diversity, and evolutionary potential of green turtles in the Gulf of Thailand.

Radiotherapy in combination with exenteration and partial orbitectomy for orbital multilobular tumor of bone in a Cocker Spaniel

Background

Multilobular tumor of bone or multilobular osteochondrosarcoma is a tumor of flat bone in the skull. The treatment of choice for a multilobular tumor of bone is local aggressive surgical excision.

Case Description

A female Cocker Spaniel dog aged 11 years presented with a history of globe displacement of the right eye for 3 months. Ophthalmic examination revealed exophthalmos, third eyelid protrusion, and slightly increased intraocular pressure OD (oculus dexter; right eye). Computed tomography (CT) revealed a mass effect in the right retrobulbar, maxilla, zygomatic, and temporal areas. Right zygomatic and temporal bone lysis were observed. Physical examination, hematology, and blood chemistry results were within normal limits. Exenteration with zygomatic arch removal was performed. During surgery, a firm 2-lobed mass (4.8 × 3.7 and 1.6 × 1.4 cm) adhered to the mandible was found in the retrobulbar area OD. Histopathological findings revealed a multilobular tumor of bone. CT imaging was performed for the remaining tumor and an extended part of the right retrobulbar mass was found. Hypofractioned radiotherapy with 6 fractions of 6 Gy was performed on days 0, 7, 14, 21, 28, and 35. At 1-month and 4-month follow-up inspections, the mass gradually reduced in size. At 8 months and 11 months after radiotherapy, the mass was unremarkable. The dog was alert during all follow-up periods to 1 year and 8 months after hypofractioned radiotherapy combined with exenteration and partial orbitectomy.

Conclusion

Hypofractioned radiotherapy combined with exenteration and partial orbitectomy extended the patient's survival and decreased the size of the remaining tumor for the management of orbital multilobular tumor of bone in this dog for at least 1 year and 8 months.

First report on clinical aspects, blood profiles, bacterial isolation, antimicrobial susceptibility, and histopathology in canine pyometra in Thailand

Background and Aim:

Canine pyometra, either the closed (closed pyometra [CP]) or open (open pyometra [OP]) cervix type, is a frequent uterine disease in intact old age bitches. Therefore, early diagnosis and appropriate medical and surgical treatments are crucial to avoid the life-threatening condition in these bitches. This study aimed to investigate clinical alterations, blood parameters, causative bacteria, antimicrobial susceptibility, and uterine histopathology obtained during aseptic surgical treatment on bitches with pyometra.

Materials and Methods:

Sixty bitches of various breeds and ages with presumptive pyometra diagnoses were included in the study. The diagnoses were based on history, clinical examination, blood parameters, radiography, and ultrasonography. All pyometra bitches were ovariohysterectomized as an emergency surgical treatment. In addition, uterine content and tissues were submitted for bacterial isolation, antimicrobial susceptibility, and uterine histopathological analysis.

Results:

Except for abdominal CP distention, no specific clinical signs were linked to the pyometra type. The mean values of total white blood cell count (WBC) and plasma protein were predominantly raised in pyometra bitches regarding hematological parameters. Leukocytosis was found in both types; however, the WBC in CP was markedly higher than in OP. The mean value of blood urea nitrogen increased in the CP group. Klebsiella pneumoniae and Escherichia coli were the most frequent causative bacteria isolated in CP and OP, respectively. All isolated bacteria were 100% susceptible to imipenem, meropenem, and carbapenem. Marbofloxacin was the second most effective drug against isolated bacteria from both groups. Uncomplicated cystic endometrial hyperplasia (CEH) was not presented in the CP group. CEH and chronic endometritis (type IV), the most severe uterine histopathological changes, were discovered in the CP and OP.

Conclusion:

The CP and OP groups presented leukocytosis, increased plasma protein, and CEH and chronic endometritis. Depression, abdominal distention, and enlarged uterine size were the major characteristics of the CP group. Furthermore, abdominal distension is presented in other abnormalities in clinical practices, providing a differential diagnosis. Drugs in the carbapenem group were the most effective against isolated bacteria; however, they are not routinely used due to bacterial resistance concerns. Thus, marbofloxacin was recommended as an alternative medical treatment because it is convenient to manage by both oral and injection routes.

Expression of the recombinant C-terminal of the S1 domain and N-terminal of the S2 domain of the spike protein of porcine epidemic diarrhea virus

Background and Aim: Porcine epidemic diarrhea virus (PEDV) causes severe diarrhea in suckling piglets, leading to severe economic losses in the swine industry. Commercial vaccines have limited effectiveness against different genogroups of PEDV and the shedding of virus. The C-terminal of the S1 domain and the N-terminal of the S2 domain (S1-2) protein of the spike (S) protein have four neutralizing epitopes. However, research on the expression of the S1-2 segment of the S gene has been limited. In this study, we expressed a recombinant S1-2 protein of the S protein of the PEDV Thai isolate and characterized the immunological properties of the recombinant S1-2 protein. Materials and Methods: The S1-2 segment of the S gene of the PEDV Thai isolate (G2b) was amplified, cloned into the pBAD202/D-TOPO® vector (Invitrogen, Carlsbad, CA, USA), and expressed in Escherichia coli. The optimum concentration of arabinose and the optimum induction time for the expression of the recombinant S1-2 protein were determined using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The immunogenic reactivity of the recombinant S1-2 protein was determined using Western blot analysis with rabbit polyclonal antibodies against the SM98 strain of PEDV (G1a). Results: The recombinant S1-2 segment of the S gene of the PEDV Thai isolate protein was cloned and the recombinant S1-2 protein was successfully expressed. The optimum concentration of arabinose and the optimum induction time for the induction of the recombinant S1-2 protein were 0.2% and 8 h, respectively. The recombinant S1-2 protein reacted specifically with both rabbit anti-histidine polyclonal antibodies and rabbit anti-PEDV polyclonal antibodies. Conclusion: The recombinant S1-2 protein reacted with rabbit anti-PEDV polyclonal antibodies induced by the different PEDV genogroup. Therefore, the recombinant S1-2 protein may be a useful tool for the development of a diagnostic test for PEDV or for a vaccine against PEDV.

Association of bacterial isolates and antimicrobial susceptibility between prostatic fluid and urine samples in canine prostatitis with concurrent cystitis

Most old, intact male dogs usually have prostate disorders, especially benign prostatic hypertrophy and prostatitis with or without abscesses, and concurrent cystitis. The successful treatment of dogs with prostatitis concurrent with cystitis has relied on choosing an appropriate antimicrobial drug based on a bacterial culture and drug sensitivity testing. The objective of the study was to compare the prevalence of bacterial species and results of drug susceptibility testing of bacteria that were isolated from the prostatic fluids and urine samples that were collected from dogs with both prostatitis and cystitis. One hundred and sixty intact male dogs, who presented with both diseases, were recruited for the study. The disease diagnoses were based on clinical history notes, physical examinations, abdominal ultrasonography, prostatic fluid cytology, urinalysis and bacterial cultures from both prostatic fluid and urine samples. The bacterial culture results demonstrated that the major species that were detected in either the prostatic fluid or urine samples were Staphylococcus spp., Escherichia coli, Pseudomonas spp., Streptococcus spp., Proteus mirabilis and Klebsiella pneumoniae. Staphylococcus spp. (26.5 %, 43/162) and Escherichia coli (26.1 %, 12/46) were the most prevalent species from the prostatic fluid and urine samples, respectively. Statistical tests revealed that there were no significantly different prevalence levels among the isolated bacteria between the prostatic fluid and urine samples. Imipenem and gentamicin were the most potent antimicrobial drugs tested against the bacterial isolates in the present study. However, the administration of imipenem to treat prostatitis and cystitis in dogs was of concern. Interestingly, there were no significant differences in the antimicrobial drug susceptibility trends between the prostatic fluid and urine samples. Based on these results, a urine sample might be considered as an optional sample for bacterial cultures and antimicrobial drug susceptibility testing when it is not possible to collect a prostatic fluid sample.

Expression of recombinant 35 kDa fragment of VP2 protein of canine parvovirus using Escherichia coli expression system

Background and Aim:

Canine parvovirus (CPV) is one of the most common viral infections in dogs, causing acute hemorrhagic gastroenteritis and high mortality. Vaccination effectively prevents CPV infection. However, the currently available CPV vaccines have concerns such as maternal immunity interference, shedding of virus vaccine, and false-positive result based on polymerase chain reaction after vaccination. A subunit vaccine can overcome these problems. This study aimed to express the recombinant 35 kDa fragment of the VP2 protein (consisting of epitopes 1-7) and the recombinant full-length VP2 protein (consisting of epitopes 1-10) and to study the ability of these two recombinant proteins to react with rabbit anti-CPV polyclonal antibodies.

Materials and Methods:

The full length and 35 kDa fragment of VP2 gene of CPV were cloned into the pBAD202 Directional TOPO^™ expression vector and expressed in E. coli. The recombinant full-length and the recombinant 35 kDa fragment proteins of VP2 were analyzed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting.

Results:

The recombinant full-length and the recombinant 35 kDa fragment VP2 genes were successfully cloned and expressed. The optimum concentrations of arabinose and induction time for the recombinant full-length and the recombinant 35 kDa fragment VP2 proteins were 0.2% for 6 h and 0.02% for 6 h, respectively. The recombinant full-length and the recombinant 35 kDa fragment VP2 protein molecular weights were approximately 81 and 51 kDa, respectively. The recombinant full-length and the recombinant 35 kDa fragment VP2 proteins specifically interacted with rabbit anti-CPV polyclonal antibodies.

Conclusion:

These results suggest that the recombinant 35 kDa fragment and the recombinant full-length VP2 proteins may be useful in developing a CPV diagnostic test or vaccine.

Detection of specific IgM and IgG antibodies in acute canine monocytic ehrlichiosis that recognize recombinant gp36 antigens

The efficacy of antibody detection tools for all stages of Ehrlichia canis infections and for various genotypes remains unclear. We produced recombinant gp36 (rgp36) antigens from different isolates of Thai E. canis to confirm the immunoreactivities to these recombinant proteins from naturally infected dogs. Sera and blood samples were taken from 21 dogs naturally infected with E. canis and in the clinical stages of acute phase ehrlichiosis. The expression vectors and competent E. coli produced two isolates of rgp36. These two major rgp36s were recognized by the dogs' sera in Western blotting, with both anti-dog IgM and IgG used as secondary antibodies. The two different genotypes of these local recombinant immunoreactive proteins were gp36 subgroup A (isolate 1055) and subgroup B (isolate 533). The Western blot analyses successfully identified both specific IgM and IgG from the dogs' sera. Of all 21 cases, five dogs presented specific IgM, twenty dogs presented specific IgG, and the commercial test used found fifteen seropositive dogs. There were four dogs that presented both specific IgM and IgG. Only one dog presented specific IgM only. This report is the first identification of a specific IgM in dogs in response to acute infections with E. canis. The recombinant gp36 isolates may be useful as potential antigenic material for subsequent serological tests that have a high possibility for differentiating between acute, chronic, primary, and nonprimary infections with E. canis.

Investigation of hemotropic Mycoplasma spp. genotypes in client-owned cats in Thailand

The genetic information for three feline hemoplasmas is limited in Southeast Asia. According to the limited genetic data, this study modified a nested-PCR method targeting the 16S rRNA gene by designing a novel primary forward degenerate primer. Two hundred and thirty-one archived DNA extracts from the blood of client-owned cats with a variety of diseases were used. The modified nested PCR detected feline hemoplasma DNA in 64 of 231 (27.7 %) samples. Sanger DNA sequencing, BLAST, and phylogenetic analyses revealed nine nucleotide sequences of Mycoplasma haemofelis (Mhf) (3.9 %, 9/231), fifty-three nucleotide sequences of Candidatus Mycoplasma haemominutum (CMhm) (22.94 %, 53/231) and two nucleotide sequences of Candidatus Mycoplasma turicensis (CMtc) (0.86 %, 2/231). The phylogenetic analysis demonstrated separate genotypes of 30 DNA sequences of Thai CMhm. In addition, this analysis elucidated distinct genotypes of CMhm in Thai fishing cats (Prionailurus viverrinus). The domestic cat and Thai fishing cat groups were the two major groups separating Thai CMhm genotypes based on the 16S rRNA. One CMhm sequence in Thai fishing cats was also present in domestic cat CMhm genotypes. This result suggests that transmission of CMhm between domestic cats and Thai fishing cats has likely occurred. One Mhf sequence had low genetic identity (82 % similarity). The phylogenetic analysis confirmed that this sequence was still very closely related to Mhf reference sequences. This Mhf-like genotype could be a candidate novel Mhf genotype. This new genetic information for feline hemotropic Mycoplasma provides valuable information for future feline-related clinical studies.

Dynamic evolution of canine parvovirus in Thailand

Background and Aim:

According to the previous study, the circulating canine parvovirus (CPV) in Thailand is 2a and 2b. Nowadays, CPV mutants, including CPV-2c, have been identified in many parts of the world. This study aimed to investigate the genetic diversity of the circulating CPV in Thailand.

Materials and Methods:

Eighty-five CPV-positive fecal samples were obtained from dogs with either acute hemorrhagic diarrhea or diarrhea. The complete VP2 gene of these samples was amplified using VP2 specific primers and polymerase chain reaction (PCR). The obtained full-length VP2 sequences were analyzed and a phylogenetic tree was constructed.

Results:

Sixty and 25 CPV-positive fecal samples were collected in 2010 and 2018, respectively. Thirty-four samples were new CPV-2a and 31 samples were new CPV-2b due to amino acids substitution at position 297 (Ser-Ala). In 2018, 5 new CPV-2a, 19 CPV-2c, and 1 feline panleukopenia virus (FPV) were found, but no new CPV-2b was detected. Moreover, most of the CPV in this study had amino acids mutations at positions 324 and 440. The phylogenetic construction demonstrated the close relationship between the current new CPV-2a with the previous CPV-2a reported from Thailand, China, Uruguay, Vietnam, Singapore, and India. Interestingly, the current new CPV-2b in this study was not closely related to the previous CPV-2b reported in Thailand. The CPV-2c in this study was closer to Asian CPV-2c and further from either European or South America CPV-2c. Interestingly, FPV was identified in a diarrhea dog.

Conclusion:

The evolution of CPV in Thailand is very dynamic. Thus, it is important to monitor for CPV mutants and especially the clinical signs relating to these mutants to conduct surveillance for the emergence of new highly pathogenic CPV in the future.

Identification of uncultured bacteria from abscesses of exotic pet animals using broad-range nested 16S rRNA polymerase chain reaction and Sanger sequencing

Background:

The Sanger sequencing technique has been questioned and challenged by advanced high-throughput sequencing approaches. Sanger sequencing seems to be an obsolete technology. However, there are still research problems that could be answered using the Sanger sequencing technology. Fastidious obligate anaerobic bacteria are mostly associated with abscesses in animals. These bacteria are difficult to isolate from abscesses and are frequently excluded due to the bias of conventional bacterial culturing.

Aim:

This study demonstrated the usefulness of a broad-range polymerase chain reaction (PCR) with Sanger sequencing to identify the majority population of bacteria in abscesses from exotic pet animals.

Materials and Methods:

This study performed a pilot investigation of abscesses from 20 clinical cases (17 rabbits, 2 hedgehogs, and 1 sugar glider) using standard culture methods for both aerobes and anaerobes and broad-range nested PCR targeting the 16S rRNA gene followed by the Sanger sequencing technique.

Results:

The standard culture and PCR techniques detected bacteria in 9 and 17 of 20 samples, respectively. From the 17 sequencings of the 16S rRNA, 10 PCR products were found to be closely related with obligate anaerobes including Bacteroides spp., Fusobacterium spp., Prevotella spp. Phylogenetic analysis using the rpoB gene revealed that the species for the Bacteroides was thetaiotaomicron and for the Fusobacterium was varium and nucleatum. However, the amplification of the rpoB gene for the Prevotella spp. was unsuccessful. Correlations between the standard culture and PCR techniques were found in 9 (6 positive and 3 negative samples) of 20 samples. Eleven samples were discordant between the standard culture and PCR techniques which were composed of eight samples negative by culture but positive by PCR and three samples had different bacteria by the culture and PCR techniques.

Conclusion:

According to this study, broad-range PCR combined with Sanger sequencing might be useful for the detection of dominant anaerobic bacteria in abscesses that were overlooked based on conventional bacterial culture.

Feline panleukopenia virus as the cause of diarrhea in a banded linsang (Prionodon linsang) in Thailand

A banded linsang (Prionodon linsang) presented at our hospital with clinical signs of acute diarrhea. Fecal samples were positive for canine parvovirus (CPV) as determined by polymerase chain reaction with primers specific for both CPV and feline panleukopenia virus (FPV). The full-length VP2 was cloned, sequenced, and compared with sequences of FPV and CPV strains reported in GenBank. The amino acids that determined the host range were similar to those of FPV. Moreover, amino acid analysis of VP2 revealed over 98% homology to FPV. The FPV isolate was closely related with FPV isolates from Japan, South Korea, and China. To the best of our knowledge, this is the first study to report that banded linsang can be infected with FPV.

Association of Ehrlichia canis, Hemotropic Mycoplasma spp. and Anaplasma platys and severe anemia in dogs in Thailand

Canine tick-borne bacteria; Ehrlichia canis, hemotropic Mycoplasma spp. and Anaplasma spp., are organisms transmitted by Rhipicephalus sanguineus ticks. However, only a few clinical studies evaluating dogs infected with these organisms and anemia condition have been published. In this study, the potential tick-borne bacteria linked to anemia were investigated in eighty-one blood samples selected from anemic dogs using a broad range nested-PCR of the 16S rRNA gene. Positive results were shown in 12/81 blood specimens (14.81%). Nucleotide sequences from the PCR products were analyzed using BLAST and resulted in identification of Ehrlichia canis (8), Candidatus Mycoplasma haematoparvum (1) and Anaplasma platys (3). Two other PCR assays were used to detect and identify the positive results of these pathogens including a specific PCR for Ehrlichia canis (gp36) and a specific nested-PCR for hemoplasma species (16S rRNA) and the phylogenetic analyses of E. canis and canine hemoplasmas were performed using these two loci. These specific PCRs revealed co-infection of E. canis and Mycoplasma haemocanis in two cases. These two male dogs had presented with jaundice, severe hemolytic anemia, severe thrombocytopenia, leukocytosis, mild azotemia and hepatitis. Ehrlichia canis was detected in a significantly greater number of severe anemia cases (PCV<15%) than moderate or mild anemia cases (PCV 16-29%) (P<0.05) and these severe anemia cases were 7-fold more at risk of having E. canis infections (odds ratio: 7.11, p=0.020). However, no statistical differences were detected between E. canis detection and degrees of thrombocytopenia or leukopenia. From the results of this study, we conclude that the severity of anemia is associated with E. canis infections rather than the severity of thrombocytopenia.

Variation among Bm86 sequences in Rhipicephalus (Boophilus) microplus ticks collected from cattle across Thailand

Anti-tick vaccines based on recombinant homologues Bm86 and Bm95 have become a more cost-effective and sustainable alternative to chemical pesticides commonly used to control the cattle tick, Rhipicephalus (Boophilus) microplus. However, Bm86 polymorphism among geographically separate ticks is reportedly associated with reduced effectiveness of these vaccines. The purpose of this study was to investigate the variation of Bm86 among cattle ticks collected from Northern, Northeastern, Central and Southern areas across Thailand. Bm86 cDNA and deduced amino acid sequences representing 29 female tick midgut samples were 95.6-97.0 and 91.5-93.5 % identical to the nucleotide and amino acid reference sequences, respectively, of the Australian Yeerongpilly vaccine strain. Multiple sequence analyses of these Bm86 variants indicated geographical relationships and polymorphism among Thai cattle ticks. Two larger groups of cattle tick strains were discernable based on this phylogenetic analysis of Bm86, a Thai group and a Latin American group. Thai female and male cattle ticks (50 pairs) were also subjected to detailed morphological characterization to confirm their identity. The majority of female ticks had morphological features consistent with those described for R. (B.) microplus, whereas, curiously, the majority of male ticks were more consistent with the recently re-instated R. (B.) australis. A number of these ticks had features consistent with both species. Further investigations are warranted to test the efficacies of rBm86-based vaccines to homologous and heterologous challenge infestations with Thai tick strains and for in-depth study of the phylogeny of Thai cattle ticks.

Optimization of one-step real-time reverse transcription-polymerase chain reaction assays for norovirus detection and molecular epidemiology of noroviruses in Thailand

Noroviruses (NoVs) are an important human pathogen associated with acute viral gastroenteritis worldwide. NoVs display a significant amount of genetic heterogeneity, making it difficult to develop comprehensive detection assays. In this study, primer sets and probes were designed for a TaqMan(®)-based real-time reverse transcription-polymerase chain reaction (RT-PCR) for norovirus detection purposes. The assay was optimized and utilized as a multiplex real-time RT-PCR assay for genogroup I (GI) detection, and a singleplex real-time RT-PCR assay for genogroup II (GII) detection. The assays showed high specificity for NoV detection and no cross-reactivity was observed between GI and GII. The detection limit of the assay was as low as 10 and 50 RNA copies per reaction for GI and GII, respectively. The optimized protocol was employed to assess the presence of NoV strains in clinical samples collected throughout Thailand during December 2005 to November 2006. The percentage of NoV infections among children with acute gastroenteritis (case) was 23.8% (119/500) and for children without acute gastroenteritis (control) it was 6.8% (30/441). The frequency of NoV infections varied geographically, with the highest frequency observed in the central region and the lowest frequency in the northern region (P>0.0001). Of the 149 positive case and control specimens, GII was found to be the predominant genogroup (98.6%). Partial capsid sequences were successfully obtained from 67 NoV-positive specimens and a phylogenetic analysis was performed to genotype the viral strains. GII.4 was the most common genotype detected.

Avian and human influenza A virus receptors in trachea and lung of animals

BACKGROUND

Influenza A viruses are capable of crossing the specific barrier between human beings and animals resulting in interspecies transmission. The important factor of potential infectivity of influenza A viruses is the suitability of the receptor binding site of the host and viruses. The affinities of avian and human influenza virus to bind with the receptors and the distributions of receptors in animals are different.

OBJECTIVE

This study aims to investigate the anatomical distribution of avian and human influenza virus receptors using the double staining lectin histochemistry method.

METHODS

Double staining of lectin histochemistry was performed to identify both SA alpha2,3 Gal and SA alpha2,6 Gal receptors in trachea and lung tissue of dogs, cats, tigers, ferret, pigs, ducks and chickens.

RESULTS

We have demonstrated that avian and human influenza virus receptors were abundantly present in trachea, bronchus and bronchiole, but in alveoli of dogs, cats and tigers showed SA alpha2,6 Gal only. Furthermore, endothelial cells in lung tissues showed presence of SA alpha2,3 Gal.

CONCLUSION

The positive sites of both receptors in respiratory tract, especially in the trachea, suggest that all mammalian species studied can be infected with avian influenza virus. These findings suggested that dogs and cats in close contact with humans should be of greater concern as an intermediate host for avian influenza A in which there is the potential for viral adaptation and reassortment.

Molecular characterization of Hepatozoon species in a Leopard Cat (Prionailurus bengalensis) from Thailand

Hepatozoon gamonts were observed by light microscopy in neutrophils of a male, wild-caught Leopard Cat. Complete blood counts at presentation and 6 months later were unremarkable. Serologic tests were negative for both FIV and FeLV. A partial sequence of the 18S rRNA gene from the Hepatozoon found in the cat indicated that, compared with all species examined, the protozoan had the closest relationship (99.2% sequence similarity) with the Hepatozoon of the water python (Stegonotus cucullatus). The cat was clinically healthy at last report. Although Hepatozoon has been found in another wild cat in Thailand, this is the first report in a Leopard Cat. The pathogenicity of Hepatozoon in these cats remains uncertain.

Efficient amplification of light and heavy chain variable regions and construction of a non-immune phage scFv library

Non-immune phage scFv library is one of the most attractive resources for therapeutics, diagnostics and basic research. As a matter of fact, quality of the library is limited by inefficient PCR cloning of antibody genes using degenerated primers. PCR using this type of primers is difficult to optimize conditions for efficient amplification, and therefore causes loss of antibody diversities. To overcome this problem, we described a novel two-step amplification of V(kappa) and V(H) genes with newly designed primer sets. Initially, we amplified V(kappa) and V(H) genes from their signal sequences to the joining region to keep antibody diversity as large as possible. Thereafter, highly degenerated primers were used to amplify the V(kappa) and V(H) genes from the framework region 1 to the joining region. The V(kappa) and V(H) genes from the second PCR then were linked by PCR overlapping extension to generate the scFv library. Fifteen clones from the library were randomly picked and sequenced, and the diversity of full-length scFvs was confirmed. Expression capability of clones in the library was 80% after confirmation using colony hybridization. The results demonstrated the efficiency of this strategy and the primer sets for construction of the scFv library.

Hematologic, cytochemical, ultrastructural, and molecular findings of Hepatozoon-infected flat-headed cats (Prionailurus planiceps)

BACKGROUND

The flat-headed cat (Prionailurus planiceps) is a small wild cat of Southeast Asia and is considered extremely endangered. Little is known about the hematologic values, blood cell morphology, or hemoparasites of this species in relation to other Felidae.

OBJECTIVES

The objective of this study was to report basic hematologic values and describe the light microscopic, cytochemical, and ultrastructural characteristics of blood cells in 2 wild-caught flat-headed cats. In addition, molecular analysis was done of a Hepatozoon organism found in the neutrophils of both cats.

METHODS

Blood samples were collected into EDTA from the cephalic vein. A CBC, manual differential count, manual reticulocyte count, cytochemical stains (Sudan black B [SBB], alpha-naphthyl acetate esterase [ANAE], and beta-glucuronidase), and scanning and transmission electron microscopy were done using standard methods.

RESULTS

HCT was slightly lower and reticulocyte counts and red cell distribution width were higher than the expected values for other species of cats. Hepatozoon organisms were found in the cytoplasm of neutrophils in both cats, but the number of infected neutrophils was very low (1%-2%). Neutrophils stained strongly positive for SBB, but were negative for ANAE and beta-glucuronidase. Hepatozoon-infected neutrophils were negative for SBB, but focally positive for ANAE and beta-glucuronidase. By transmission electron microscopy, gamonts of Hepatozoon sp were observed in neutrophils, and rarely free in plasma. Infected neutrophils had fewer specific granules and more mitochondria compared with noninfected neutrophils. PCR products of partial 18S rRNA revealed that the isolate of Hepatozoon in the flat-headed cats was closely related to that of the frog Hepatozoon sp.

CONCLUSIONS

These results add to our understanding of hematologic values and blood cell morphology in Hepatozoon-infected flat-headed cats as well as the molecular analysis of the Hepatozoon organism, and may be useful for the health management and evaluation of hemoparasitic disease in this species.

Identification of the Actinobacillus pleuropneumoniae serotype using PCR based-apx genes

Actinobacillus pleuropneumoniae (A. pleuropneumoniae) is an important swine respiratory disease pathogen, which has at least 15 serotypes. There are several techniques for the serotyping of A. pleuropneumoniae, however, these techniques are time consuming. In this study, the polymerase chain reaction (PCR) technique was developed for serotyping A. pleuropneumoniae using a set of specific primer designated for the apxI, apxII, apxIII and apxIVA genes. By this PCR typing system, 10 out of the 13 reference strains of A. pleuropneumoniae were differentiated. However, it was not possible to distinguish serotype 2 from 8, serotype 5a from 5b and serotype 9 from 11. Each serotype of A. pleuropneumoniae showed its own products patterns. The PCR typing system was further applied for typing the field isolates of A. pleuropneumoniae and compared to that using the gel immunodiffusion (GID) technique. The results from both PCR and GID techniques were in accordance. Thus, the PCR typing system may provide a rapid and useful tool for typing the serotypes of A. pleuropneumoniae.

Finasteride-induced prostatic involution by apoptosis in dogs with benign prostatic hypertrophy

OBJECTIVE

To determine the effect of finasteride on programmed cell death (apoptosis) of prostatic cells during prostatic involution in dogs with benign prostatic hypertrophy (BPH).

ANIMALS

9 dogs with BPH.

PROCEDURE

Dogs were randomly assigned to treatment or control groups. Treatment dogs (n = 5) were administered finasteride (0.1 to 0.5 mg/kg, PO, q 24 h) for 16 weeks, whereas the 4 control dogs were administered an inert compound. Prostatic cells from the prostatic fluid portion of the ejaculate of treatment and control dogs were obtained before and 1, 2, 3, 4, 8, and 16 weeks after initiation of treatment. Cells were concentrated by use of centrifugation. Prostatic cells were examined for indications of apoptosis by use of a terminal deoxyribonucleotidyl transferase-mediated deoxyuracil triphosphate nick-end labeling technique. After receiving the inert compound for 16 weeks, the 4 control dogs were administered finasteride for 16 weeks, and evaluations were repeated.

RESULTS

Percentage of apoptotic prostatic cells in ejaculated prostatic fluid of treatment dogs increased significantly (from 9% before treatment to 33, 31, 26, and 27% after 1, 2, 3, and 8 weeks of treatment, respectively). There was no significant change in percentage of apoptotic prostatic cells in the ejaculated prostatic fluid of control dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

Finasteride-induced prostatic involution appears to be via apoptosis in dogs with BPH. Finasteride treatment of dogs with BPH causes prostatic involution by apoptosis rather than necrosis.

Double in situ hybridization for simultaneous detection of porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus (PCV)

A double in situ hybridization method for the simultaneous detection of porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus (PCV) genomes in the same tissue section was applied to lung tissues from 9 pigs in which PRRSV and PCV coinfection had been previously demonstrated. Paraffin-embedded tissue sections were simultaneously hybridized with a digoxigenin-labeled antisense RNA probe for PRRSV and a fluorescein-labeled antisense RNA probe for PCV, and hybridization was detected with anti-digoxigenin alkaline phosphatase/fast red and anti-fluorescein peroxidase/diaminobenzidine, respectively. PRRSV and PCV genomes were identified in the same pulmonary cell types as reported previously in all 9 pigs. In all pigs, PCV-positive cells outnumbered PRRSV-positive cells. A small proportion of alveolar macrophages contained both PRRSV and PCV genomes.

Utilization of a rate enhancement hybridization buffer system for rapid in situ hybridization for the detection of porcine circovirus in cell culture and in tissues of pigs with postweaning multisystemic wasting syndrome

A rapid in situ hybridization (ISH) technique for the detection of porcine circovirus (PCV) nucleic acid in cell culture and formalin-fixed paraffin-embedded tissues was developed. A fluorescein-labeled RNA probe was transcribed from a plasmid containing 530 bp of the ORF1 of a PCV isolated from a pig with postweaning multisystemic wasting syndrome (PMWS). Hybridization using standard hybridization buffer was performed at 42 C for 16 hours and was compared to hybridization using rate enhancement hybridization (REH) buffer at 67 C for 2 hours. Hybridization was detected with an alkaline phosphatase-conjugated antifluorescein antibody. In both cultured cells and tissues from pigs with PMWS, the signal intensity and number of labeled cells in sections hybridized with REH buffer were equal to those of sections hybridized with standard hybridization buffer. The total time required for ISH using the REH buffer is 7-8 hours, thus making this protocol suitable for application in routine PCV diagnosis.

Development of probes to differentiate porcine circovirus types 1 and 2 in vitro by in situ hybridization

Porcine circovirus type 1 (PCV1), a PK-15 cell line contaminant, and porcine circovirus type 2 (PCV2), associated with post-weaning multisystemic wasting syndrome (PMWS), are genetically and antigenically related. Several techniques have been developed to detect PCV, including in situ hybridization (ISH). Previously reported probes used for ISH may hybridize with both PCV1 and PCV2 nucleic acids. We attempted to produce probes for ISH that can detect and differentiate PCV2 from PCV1 in PCV-infected cells. Riboprobes were synthesized from the sense and antisense strands of both open reading frames 1 and 2 (ORF1 and ORF2) of PCV2. At 42 and 58 degrees C, the ORF1 antisense probe hybridized with nucleic acid from both PCV1- and PCV2-infected cells. At 58 degrees C, the ORF2 antisense probe hybridized with PCV2 nucleic acid but not with PCV1 nucleic acid. The ORF1 and ORF2 sense probes bound only with PCV2 nucleic acid. Both antisense strand probes produced stronger signals than the sense strand probes. The results showed that the PCV2 ORF1 antisense probe is the most likely probe to detect both PCV types while the ORF2 antisense probe is capable of discriminating between PCV1 and PCV2.

Vascular ultrastructure and DNA fragmentation in swine infected with Shiga toxin-producing Escherichia coli

Shiga toxins (Stx) produced by Escherichia coli cause systemic vascular damage that manifests as edema disease in swine and hemolytic uremic syndrome in humans. In vitro, Stx inhibit protein synthesis and, depending on circumstances, induce necrosis, apoptosis, or both. The mechanism of in vivo Stx-mediated vascular damage is not known. The ability of Stx to cause apoptosis of vasculature in vivo was studied in pigs with edema disease that was produced by oral inoculation with Stx-producing E. coli. Arterioles of ileum and brain were evaluated by terminal dUTP nick-end labeling (TUNEL) assay for DNA fragmentation in myocytes (10 infected pigs, 5 control pigs) and by transmission electron microscopy for ultrastructural changes characteristic of apoptosis (17 infected pigs, 8 control pigs). In comparison with controls, increased numbers of TUNEL-positive arterioles were detected in 6/10 (60%) subclinically affected pigs 14-15 days after inoculation. Ultrastructurally, lesions in myocytes consisted of lysis (necrosis), with cytoplasmic debris and nuclear fragments contained between intact basement membranes. Endothelial cell changes ranged from acute swelling to necrosis and detachment from basement membrane. Subclinically affected pigs (n = 14) tended to have changes predominantly in myocytes, whereas pigs with clinical illness (n = 3) more commonly had changes in endothelial cells. The arteriolar lesions and clinical signs of edema disease are attributed to the effects of Stx on vasculature. Therefore, our findings suggest that the Stx-induced arteriolar lesions seen in this study were primarily necrotic, not apoptotic. We suspect that necrosis was the principal cause of the DNA fragmentation detected.

Ultrastructure and DNA fragmentation analysis of arterioles in swine infected with Shiga toxin-producing Escherichia coli

Shiga toxins (Stx) produced by E. coli are potent cytotoxins that affect the vascular system. In humans, systemic toxemia causes renal glomerular damage manifested as hemolytic uremic syndrome. In swine, Stx-producing E. coli (STEC) cause edema disease that is characterized microscopically by segmental arteriolar smooth muscle cell (SMC) lesions. Our objectives were to characterize ultrastructurally and by TUNEL the type of death (apoptosis or necrosis) that occurs in SMCs during edema disease. Increased DNA fragmentation consistent with apoptosis was detected by TUNEL in arterioles of challenged pigs 14-15 days post inoculation. Ultrastructurally 3 grades of SMC lesions were distinguished: 1) Partial loss of SMCs, intercellular space filled with granular cellular debris admixed with membrane bound vacuoles; 2) Complete loss of SMCs; only granular cellular debris and clear vacuoles remained within basement membrane; 3) Inflammation of media; SMCs replaced by a rim of cellular debris located in the periphery of vessel wall. The most common lesion detected was grade 1 (9 ilea and 4 brains). We did not find apoptotic nuclear changes in SMCs or apoptotic inclusion bodies within resident cells. Our study indicates, that (1) Stx produced during edema disease does not cause SMC apoptosis 14-15 dpi; (2) SMCs undergo an array of changes from degeneration to necrosis.

Prevalence of antibodies to the hepatitis E virus in pigs from countries where hepatitis E is common or is rare in the human population

Hepatitis E virus (HEV) is a very important public health concern in many developing countries where epidemics of hepatitis E are common. Sporadic cases of clinical hepatitis E not only occur in these countries but also occur uncommonly in patients with no known epidemiological exposure to HEV in industrialized countries. The source of infection in industrialized countries is unknown but it has been suggested that animals might serve as a reservoir for HEV in both settings. We recently identified and characterized an HEV strain (swine HEV) that infects large numbers of pigs in the United States. To assess the potential of pigs to serve as a global reservoir of HEV, we measured the prevalence of HEV antibodies in pigs in two countries where hepatitis E is endemic and two countries where it is not. Swine herds in all four countries contained many pigs that were seropositive for IgG anti-HEV, although the percentage of seropositive pigs varied greatly from herd to herd. A very limited number of pig handlers in the two endemic countries were also tested and most of them were found to be seropositive for HEV. The results from this study suggest that hepatitis E is enzootic in pigs regardless of whether HEV is endemic in the respective human population. J. Med. Virol. 59:297-302, 1999. Published 1999 Wiley-Liss, Inc.

A pneumo-virulent United States isolate of porcine reproductive and respiratory syndrome virus induces apoptosis in bystander cells both in vitro and in vivo

Evidence of apoptosis was detected for the United States porcine reproductive and respiratory syndrome virus (PRRSV) in ATCC CRL11171 cells inoculated with strain ATCC VR2385 and in the tissues of pigs infected with the same strain. Apoptosis was detected by agarose gel electrophoresis, transmission electron microscopy and terminal deoxytransferase dUTP nick end labelling (TUNEL) techniques. By electron microscopy and double-labelling techniques, apoptosis was detected primarily in uninfected bystander cells in the continuous cell line rather than the PRRSV-infected cells. In the lungs, the apoptotic cells were predominantly alveolar and pulmonary intravascular macrophages, and mononuclear cells in the alveolar septa. In the lymph nodes, the apoptotic cells were predominantly tingible body macrophages and mononuclear cells. The induction of apoptosis in a large number of mononuclear cells in the lungs and lymph nodes appears to be a mechanism of PRRSV pathogenesis and might be an explanation for a dramatic reduction in the number of alveolar macrophages and circulating lymphocytes and monocytes in PRRSV-infected pigs.

Detection of a novel strain of porcine circovirus in pigs with postweaning multisystemic wasting syndrome

Swine infectious agents, especially viruses, are potential public health risks associated with the use of pig organs for xenotransplantation in humans. Therefore, there is a need for better characterization of swine viruses and for the development of diagnostic tests for their detection. We report here isolation of a novel strain of porcine circovirus (PCV) from pigs with postweaning multisystemic wasting syndrome (PMWS). Affected pigs exhibited severe interstitial pneumonia and lymphoid depletion. The complete nucleotide sequence (1,768 nucleotides) of the genome of the PCV isolate was determined and compared with the sequence of the PCV strain isolated from PK-15 cells. Sequence comparison revealed significant differences between the two PCV strains, with an overall DNA homology of 76%. Two major open reading frames (ORFs) were identified. ORF1 was more conserved between the two strains, with 83% nucleotide homology and 86% amino acid homology. ORF2 was more variable, with nucleotide homology of 67% and amino acid homology of 65%. PCR and in situ hybridization demonstrated abundant viral DNA in various organs of pigs with PMWS. In situ hybridization demonstrated that this strain of PCV targets multiple organs and infects macrophages, lymphocytes, endothelial cells, and epithelial cells.

Transmissible gastroenteritis virus induced apoptosis in swine testes cell cultures

Transmissible gastroenteritis virus (TGEV) is a coronavirus which causes severe gastroenteritis and atrophy of intestinal villous epithelial cells in piglets. However, the mechanism of cell death caused by TGEV is not known. In this study, we report that TGEV induces cell death by apoptosis. TGEV-induced apoptosis was demonstrated by agarose gel electrophoresis, electron microscopy, and terminal deoxytransferase digoxigenin-dUTP nick end labeling (TUNEL). Double labeling experiment confirmed the result from electron microscopy and showed that most of the apoptotic cells were bystander cells as they were negative for TGEV nucleic acids. Results of this study indicate that TGEV induces apoptosis in vitro and that most of the cells undergoing apoptosis are bystander cells, thus amplifying the cytopathic effect of TGEV.

Rapid in situ hybridization technique for the detection of ribonucleic acids in tissues using radiolabelled and fluorescein-labelled riboprobes

In situ hybridization (ISH) is a useful diagnostic and research tool, but is also time consuming. This study was conducted to determine if a rate enhancement hybridization (REH) buffer, developed for membrane hybridization, could be used to decrease hybridization time for ISH. Tissue from swine with an enteric disease produced by a swine coronavirus, transmissible gastroenteritis virus (TGEV), was used as a model to standardize hybridization conditions for a rapid ISH technique. Small intestinal sections from pigs experimentally and naturally infected with TGEV were hybridized for various times at 52 degrees C and 70 degrees C with a radiolabelled or a fluorescein-labelled RNA probe in a standard hybridization or a REH buffer. Viral RNA was detected in intestines from as early as 30 min of hybridization by using both buffers with the radiolabelled probe; however, the signal was stronger with the REH buffer. With the fluorescein-labelled probe, viral RNA was detected in virus-infected cells of the intestines after 30 min of hybridization by using the REH buffer. Signal intensity was greater with the REH buffer than with the standard hybridization buffer when compared at each hybridization time and hybridization temperature using both radiolabelled and fluorescein-labelled probes. With the REH buffer, hybridization signal intensity was greater at 70 degrees C than at 52 degrees C for both probes. The best results were obtained when small intestinal sections were hybridized at 70 degrees C for 2 h using a radiolabelled or a fluorescein-labelled probe diluted in the REH buffer. The fluorescein-labelled RNA probe with REH buffer resulted in a minimal non-specific signal when compared with the radiolabelled probe. These studies demonstrated that the REH buffer can be used to decrease the time of ISH for the detection of viral RNA. This rapid ISH technique should have broad applications in the utilization of probe technology in diagnostics and research for the detection of target ribonucleic acids in situ

Temporal and morphologic characterization of the distribution of porcine reproductive and respiratory syndrome virus (PRRSV) by in situ hybridization in pigs infected with isolates of PRRSV that differ in virulence

Three groups of 5-week-old cesarian-derived, colostrum-deprived pigs were inoculated intranasally with either a high-virulence isolate (VR2385) or a low-virulence isolate (VR2431) of porcine reproductive and respiratory syndrome virus (PRRSV) or with uninfected cell culture and media. Formalin-fixed, paraffin-embedded tissues from pigs euthanatized at 10, 21, and 28 days post-inoculation were examined by in situ hybridization for PRRSV nucleic acid using a digoxigenin-labeled antisense RNA probe approximately 1,000 nucleotides in length. Alveolar macrophages were positive in the lungs of 9/9, 2/2, and 0/2 VR2385-inoculated pigs and 7/9, 1/2, and 2/3 VR2431-inoculated pigs at 10, 21, and 28 days post-inoculation, respectively. More positive cells were detected in lungs from VR2385-inoculated pigs compared to VR2431-inoculated pigs at 10 and 21 days post-inoculation. Positive cells within lymph nodes were tingible body macrophages in germinal centers and macrophages or interdigitating dendritic cells within the paracortical area. VR2385 was detected in the tracheobronchial lymph node (TBLN) and mediastinal lymph node (MLN) of 7/9 and 9/9 pigs at 10 days post-inoculation, but was only detected in the TBLN of 1/2 and 0/2 pigs and in the MLN of 0/2 and 1/2 pigs at 21 and 28 days post-inoculation, respectively. In contrast, VR2431 was detected in teh TBLN and MLN of 5/9 and 2/9 pigs at 10 days post-inoculation and in the TBLN of 0/2 and 1/3 pigs and in the MLN of 0/2 and 0/3 pigs at 21 and 28 days post-inoculation, respectively. There were more positive cells in TBLN and MLN in pigs inoculated with VR2385 at 10 days post-inoculation. Macrophages located at the epithelial-lymphoid interface of tonsilar crypts and within the paracortical areas were positive in tonsils of 9/9, 2/2, and 1/2 VR2385-inoculated pigs and 7/9, 1/2, and 1/3 VR2431-inoculated pigs at 10, 21, and 28 days post-inoculation, respectively. Positive cells in the thymic medulla were multinucleate and were only detected at 10 days post-inoculation in 2/9 VR2385-inoculated pigs and 4/9 VR2431-inoculated pigs. Positive cells within the spleen were few, spindle-shaped, located within smooth muscle trabecula, and only present at 10 days post-inoculation in 3/9 VR2385-inoculated pigs. We conclude that the tissue tropism and distribution of positive cells within tissues is similar for VR2385 and VR2431. However, tissues from more pigs and more cells within tissues were positive in pigs inoculated with VR2385 than VR2431 at 10 and 21 days post-inoculation. These findings indicate that the more virulent isolate VR2385 may replicate better in vivo than the less virulent isolate VR2431. This supports the hypothesis that an increased ability to replicate in vivo contributes to increased virulence of PRRSV.

An overview of immunological and genetic methods for detecting swine coronaviruses, transmissible gastroenteritis virus, and porcine respiratory coronavirus in tissues

Transmissible gastroenteritis (TGE) is an enteric disease of swine caused by a coronavirus, designated as transmissible gastroenteritis virus (TGEV). Commonly used methods for TGEV detection include viral isolation and detection of the viral antigen by indirect immunofluorescence (IFA), immunoperoxidase, and immunogold silver staining. Each of these techniques has some advantages and disadvantages. In general IFA and immunohistochemistry are preferred over viral isolation as TGEV isolation is not very reliable because not all field isolates replicate in cell cultures. The diagnosis of TGEV has become more complicated since the emergence of porcine respiratory coronavirus (PRCV). PRCV is believed to be a TGEV mutant, and can not be easily differentiated from TGEV by immunological tests. Nucleic acid probes and polymerase chain reaction (PCR) have successfully been used to detect and differentiate these viruses. These techniques can detect viral nucleic acids in the specimen but do not provide information on the cell types infected by these viruses. Recently we have developed isotopic and nonisotopic in situ hybridization techniques (ISH) for the detection of these viral nucleic acids in formalin-fixed paraffin-embedded tissues. Furthermore, this procedure can differentiate between TGEV- and PRCV-infected cells. By ISH, TGEV is detected in the mature absorptive enterocytes of tissues infected by TGEV and the crypt epithelial cells are also infected but to a lesser extent. For PRCV, the main infected cells are epithelial cells of the bronchioles, type II pneumocytes, and alveolar and septal macrophages. ISH is an excellent tool for studying molecular pathogenesis of these two viruses especially when used in combination with immunohistochemistry.

In situ hybridization technique for the detection of swine enteric and respiratory coronaviruses, transmissible gastroenteritis virus (TGEV) and porcine respiratory coronavirus (PRCV), in formalin-fixed paraffin-embedded tissues

The in situ hybridization (ISH) technique was developed to detect the swine coronaviruses, transmissible gastroenteritis virus (TGEV) and porcine respiratory coronavirus (PRCV), in cell culture and tissue sections from TGEV-or PRCV-infected pigs. The 35S-labeled RNA probes were generated from two plasmids pPSP.FP1 and pPSP.FP2 containing part of the S gene of TGEV. The procedure was first standardized in cell cultures. The radiolabeled pPSP.FP2 probe detected both TGEV and PRCV in virus-inoculated cell cultures, whereas pPSP.FP1 probe detected TGEV but not PRCV. The probe was then used to detect TGEV or PRCV in tissues of pigs experimentally infected with TGEV or PRCV or naturally infected with TGEV. Again, the probes detected TGEV in intestines of experimentally and naturally infected pigs and PRCV in the lungs of experimentally infected pigs. TGEV RNA was detected mainly within the enterocytes at the tips of villi and, less often, within some crypt epithelial cells. PRCV was shown to replicate mainly in the bronchiolar epithelial cells and in lesser amount in type II pneumocytes, type I pneumocytes, alveolar macrophages and bronchial epithelial cells, respectively. ISH has potential applications as a diagnostic test for the detection and differentiation of TGEV and PRCV in tissues and in studies to gain a better understanding of the mechanism of pathogenesis of enteric and respiratory coronavirus infections.