Immunohistochemical Detection of Porcine Rotavirus Using Immunogold Silver Staining (IGSS)

Immunogold silver staining (IGSS) was applied for the detection of porcine group A rotavirus in formalin-fixed paraffin-embedded tissue sections of small intestine. Prior to the application of IGSS, the reactivity of protein A-gold as a marker was tested with group-specific antiserum in immunogold electron microscopy. Immune aggregates were intensely and specifically labeled with the gold complex. Application of IGSS to tissue sections resulted in specific dark staining of villous enterocytes infected by group A rotavirus. This method also proved effective for the detection of rotaviral antigen in infected cultured cells. The IGSS method may be suitable for routine diagnostic detection of rotaviral infections and may have application for detection of other viral pathogens of veterinary importance.

Detection rates of porcine reproductive and respiratory syndrome virus, porcine circovirus type 2, and swine influenza virus in porcine proliferative and necrotizing pneumonia

A retrospective study on pig lung tissues from 60 cases of proliferative and necrotizing pneumonia (PNP) was performed to determine the presence of porcine reproductive and respiratory syndrome virus (PRRSV), swine influenza virus (SIV), and porcine circovirus type 2 (PCV2) in these lesions. Cases selected included 30 cases diagnosed between 1988 and 1992 and 30 cases diagnosed between 1997 and 2001. In each group of 30 cases, 10 were from suckling piglets, whereas the other 20 were from postweaned animals representing either nursery or grower-finisher pigs. Immunohistochemistry using a monoclonal antibody to influenza virus type A was used to determine the presence of SIV, and in situ hybridization was used for the detection of PRRSV and PCV2 nucleic acids. PRRSV was detected in 55 of the 60 cases examined (92%), PCV2 in 25 cases (42%), and SIV in only 1 case (2%). In 30 cases (50%), PRRSV was the only virus detected, whereas in 25 other cases (42%), a combination of PRRSV and PCV2 could be detected in the lungs with PNP lesions. PCV2 could not be detected in the lungs of suckling pigs with PNP. All PCV2-positive cases were found in postweaned pigs and were always in combination with PRRSV. In this latter age group, PCV2 was detected in 63% of the cases (25/40). Data from our study indicate that SIV is rarely identified in PNP and that PCV2 infection is not essential for the development of PNP lesions. The results of the present study demonstrate that PRRSV is consistently and predominantly associated with PNP and should be considered the key etiologic agent for the condition.

Infectious agents identified in pigs with multifocal interstitial nephritis at slaughter

One kidney was taken from each of 100 pigs at slaughter; 50 had gross lesions of multifocal interstitial nephritis and 50 had no gross lesions. Forty-nine of the affected kidneys had lesions that were characterised by the presence of either a few randomly distributed or numerous widely disseminated pale foci, 1 to 3 mm in diameter, on the cortical surface (white-dotted kidneys). Microscopically, these focal inflammatory lesions often had a distinct lymphofollicular pattern (follicular nephritis). Lesions of chronic vasculitis were observed in 21 of the affected kidneys. Histologically, the control kidneys had only small and sparse inflammatory foci. Standard bacterial cultures of kidneys of both groups were not significant, and cultures for the isolation of leptospires were all negative. Virological examination of the kidney homogenates by PCR did not reveal any porcine reproductive and respiratory syndrome virus and only a few cases were positive for the porcine circovirus type 1. However, porcine parvovirus (PPV) and porcine circovirus type 2 (PCV-2) were detected in many kidneys of both groups but in a significantly higher proportion of the kidneys with interstitial nephritis. There was a significant association between the lesions and the presence of PPV and PCV-2 with odds ratios of 7.5 (P<0.0001) and 3.4 (P=0.0074), respectively, and the odds ratio increased to 22.7 (P<0.0001) when both viruses were identified in the same kidney. However, a subsample of kidneys taken from both groups were negative by immunohistochemistry for the presence of PPV and PCV-2 antigens.

Pharmacotherapies for attention-deficit/hyperactivity disorder: expected-cost analysis

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) is a common childhood neurobehavioral disorder characterized by inattention, hyperactivity, and impulsivity. Prevalence estimates in elementary school children generally range from 3% to 8%. ADHD is frequently treated with psychostimulant medications, which have been shown to improve both cognitive and behavioral outcomes for most children.

OBJECTIVE

The goal of this study was to estimate the total expected costs for the treatment and management of school-age children with ADHD using 6 commonly prescribed pharmacotherapies: methylphenidate immediate-release/extended-release (MPH IR/ER), methylphenidate immediate-release (MPH IR), Metadate CD (branded MPH IR/ER), Concerta (branded MPH ER), Ritalin (branded MPH IR), and Adderall (a combination of dextroamphetamine and amphetamine salts).

METHODS

A literature review and clinical assessment using a 27-question survey instrument were used to capture information on the clinical characteristics of ADHD, including common treatment regimens, clinical management of patients, pathways of care, and components of care. A meta-analysis provided response rates for 3 commonly used pharmacotherapies: Metadate CD, MPH IR, and Adderall. Information from the clinical assessment and the meta-analysis were used to populate a decision-analytic model to compute total expected cost for each comparator.

RESULTS

The average total annual expected cost per patient was $1,487 for Metadate CD, $1,631 for Concerta. $1,792 for MPH IR/ER, $1,845 for MPH IR, $2,080 for Ritalin, and $2,232 for Adderall.

CONCLUSIONS

Metadate CD had the lowest total expected cost and Adderall had the highest total expected cost among the ADHD pharmacotherapies evaluated. The differences were attributable to differences in drug-acquisition costs and the need for in-school dosing of twice-daily and thrice-daily medications.

Polyclonal activation of B cells occurs in lymphoid organs from porcine reproductive and respiratory syndrome virus (PRRSV)-infected pigs

Porcine reproductive and respiratory syndrome virus (PRRSV) induces a persistent viral infection associated with an inefficient humoral immune response. A study of lymphoid B cells and specific humoral immune response was performed in blood and several lymphoid organs collected from PRRSV experimentally-infected pigs. Groups of specific pathogen-free (SPF) pigs were infected with the LHVA-93-3 isolate of PRRSV, and blood, tonsils, spleen and mediastinal lymph nodes (MLN) were collected at various times postinfection (p.i.) (3-60 days). Lymphoid cells were isolated, immunolabeled for cytofluorometric determination of B cell percentages, used for counting specific anti-PRRSV antibody secreting B cells by an ELISPOT assay, or cultured for metabolic activity. The presence of anti-PRRSV antibodies in the serum of infected pigs was determined using a commercial ELISA assay. Virus detection was performed in all tissues, including lungs, by virus isolation and RT-PCR. The results show that percentages of B cells increased in tonsils as soon as 3 days until 17 days p.i. in PRRSV-infected pigs while they increased in spleen at 3 days p.i. only, due to an increase of larger Ig(high)-producing B cells. Metabolic activity of lymphoid cells from blood and spleen increased at 3 days p.i. only while lymphoid cells from tonsils and MLN transiently decreased at that time and increased thereafter up to 60 days p.i. Anti-PRRSV antibody-secreting B cells occurred in tonsils after 10 days p.i. and strongly increased up to 60 days p.i. However, specific anti-PRRSV-secreting B cells were detected in blood and spleen after 17 days p.i and in MLN only after 45 days p.i. Specific antibodies were detectable in serum at 10 days p.i., reached the maximum level at 45 days and remained high up to 60 days p.i. Infectious virus was detected in lungs and MLN as soon as 3 days p.i., and remained detectable up to 45 days p.i. in tonsils of one pig while viral RNA was detected in most organs up to 60 days p.i. In vitro experiments revealed that inactivated virus induced a stimulation of lymphoid cells isolated from PRRSV-infected pigs while it was cytotoxic for lymphoid cells from control pigs. Taken together, these results indicate that viral infection induced simultaneously a polyclonal activation of B cells, mainly in tonsils, and an exaggerated and prolonged specific humoral immune response due to persistent viral infection in lymphoid organs.

Clinical and economic impact of new trends in glaucoma treatment

CONTEXT

Glaucoma is a chronic ophthalmic condition affecting approximately 15 million people. Several therapies are currently available (eg, beta-blockers, sympathomimetics, carbonic anhydrase inhibitors) but have side effects that may limit use. Over the last few years, new medications with improved efficacy and side-effect profiles have become available. This analysis evaluates 2 therapies, brimonidine and betaxolol, based on head-to-head clinical trial data to determine clinical consequences and their related expected costs.

OBJECTIVE

To calculate comparative costs and the cost-effectiveness of brimonidine 0.2% and betaxolol 0.25% as first-line therapy for patients with primary open-angle glaucoma.

DESIGN

Safety, efficacy, effectiveness, and quality-of-life data were collected in a multicenter, randomized, double-blind, head-to-head comparative effectiveness study, with a drug switch possibility. A disease-intervention model (decision tree) was developed with clinicians, academicians, and health economists. Components of care for each pathway in the model were identified and evaluated; their costs were applied at appropriate points throughout the tree. Expected outcomes and costs were computed and compared.

PATIENTS

Participants were men (n = 76) and women (n = 112), 21 years of age or older, with newly diagnosed or currently untreated ocular hypertension or open-angle glaucoma.

RESULTS

The clinical success rates of first-line brimonidine 0.2% and betaxolol 0.25% are 73.9% and 56.2%, respectively, as determined in a head-to-head comparative effectiveness trial. Total expected costs for patients receiving brimonidine and betaxolol as a primary therapy are $301.37 and $328.19, respectively, based on the model. Dividing costs by outcomes, the cost-effectiveness ratios for brimonidine and betaxolol are $407.81 ($301.37/0.739) and $583.97 ($328.19/0.562), respectively, representing the cost/unit outcome, or the cost to achieve clinical success.

CONCLUSIONS

Brimonidine 0.2% is less costly and more cost-effective than betaxolol 0.25% when used as initial monotherapy with and without subsequent add-on therapies, including laser treatments and/or surgery, as needed.

PCR detection and evidence of shedding of porcine circovirus type 2 in boar semen

An experimental study was conducted to evaluate the potential presence of porcine circovirus type 2 (PCV2) in the semen of infected boars. Four mature boars were inoculated intranasally with PCV2 isolate LHVA-V53 propagated on PK15 cells. Two boars inoculated with the supernatant of noninfected PK15 cells were kept as controls. Serum samples were collected from all boars at 4, 7, 11, 13, 18, 21, 25, 28, 35, and 55 days postinoculation (dpi) and from the four PCV2-infected boars at 90 dpi. Samples were tested for the presence of antibodies to PCV2 by an indirect immunofluorescence assay and for the presence of PCV2 DNA by PCR and nested PCR. Semen samples were collected from all six boars at 5, 8, 11, 13, 18, 21, 25, 28, 33, and 47 dpi and tested for the presence of PCV2 DNA by a nested PCR assay. Antibodies to PCV2 could be detected as early as 11 dpi in one boar, and all four infected boars were found positive for PCV2 antibodies by 18 dpi. Thereafter all infected boars remained positive for antibodies to PCV2 until 90 dpi. Analysis of serum samples by nested PCR demonstrated the presence of PCV2 DNA as early as 4 dpi in three of four infected boars. Serum samples from all infected boars were positive for PCV2 DNA from 11 dpi until 35 dpi but were negative at 90 dpi. PCV2 DNA was detected as soon as 5 dpi in the semen of two infected boars and intermittently thereafter in the semen of all four infected boars. The semen of two infected boars was positive for PCV2 DNA at 47 dpi. Following infection, PCV2 DNA can be detected in semen concurrently with the presence of PCV2 DNA and antibodies in the serum. The present study suggests that PCV2 may be shed intermittently in the semen of infected boars.

Duration of effect of botulinum toxin type A in adult patients with cervical dystonia: a retrospective chart review

BACKGROUND

Clinical trials have established the efficacy and safety of botulinum toxin type A (BTX-A) in patients with cervical dystonia. To maintain the clinical benefits of BTX-A, injections need to be repeated whenever patients' symptoms begin to recur.

OBJECTIVE

The purpose of this study was to determine, in clinical practice settings, the mean duration of effect of BTX-A in the treatment of adult patients with cervical dystonia.

METHODS

A retrospective chart review was undertaken at an academic center and a private neurology practice. At each site, > or =50 patients being treated for cervical dystonia were identified and randomized for chart review. Patients had to have received the first assessable injection of BTX-A between January 1, 1998, and March 31, 1998, to coincide with the clinical availability of the most current formulation of the neurotoxin. A chart was eligible for review if the patient was aged > or =18 years, had a documented diagnosis of idiopathic cervical dystonia, was being treated with BTX-A, and had been under the continuous care of investigators from January 1, 1998, to August 31, 1999. Of the 102 patients initially identified, the first 30 from each site who met the study inclusion criteria were assessed for (1) age and sex; (2) severity of dystonia; (3) years of BTX-A use; (4) dates of first, second, third, and fourth BTX-A injections; (5) drug dose; (6) use of electromyography; (7) use of other prescribed therapies; (8) laboratory tests; and (9) adverse events. The mean interval between each visit and mean per-patient duration of effect were calculated and stratified by patient characteristics.

RESULTS

The mean age of the patients was 56.4 years. Two thirds of the patients were women. Forty-one of the 60 patients (68.3%) had either moderate or severe disease, and 48 (80.0%) had experienced cervical dystonia for >5 years. The mean per-patient duration of effect across the 4 visits was 15.5 weeks (range, 12.2-24.3 weeks). The duration of effect did not differ significantly between study sites despite the differences in disease severity, drug dose, and use of adjunctive therapy.

CONCLUSION

BTX-A the controls symptoms of cervical dystonia for 12 to 24 weeks, with a mean duration of effect per patient of 15.5 weeks.

Experimental transmission of porcine circovirus type 2 (PCV2) in weaned pigs: a sequential study

Weaned specific pathogen-free pigs were inoculated intranasally with porcine circovirus type 2 (PCV2) and killed in groups of two or three animals at 6, 13, 20, 27 and 34 days post-inoculation (dpi), together with appropriate uninfected controls, for examination by histopathological, immunohistochemical (immunogold silver staining; IGSS), polymerase chain reaction (PCR) and viral isolation techniques. Serum samples were also collected for detection of antibodies. No major clinical signs were observed in infected pigs, and gross lesions were essentially limited to the lungs and lymph nodes of some of the animals. Histologically, no lesions were seen at 6 dpi, but bronchointerstitial pneumonia was invariably noted from 13 dpi onwards. Granulomatous inflammation, with or without intracytoplasmic inclusions, was present in lymphoid tissues (e.g. lymph nodes, thymus, spleen and tonsil) from day 20 onwards, being most severe at days 20 and 27 dpi. Liver inflammation was present at days 13, 20 and 27 dpi. Virus was demonstrated in the tissues by isolation and PCR methods throughout the experiment. PCV2 antigens were detected by IGSS in bronchial and bronchiolar epithelial cells, in mononuclear cells and multinucleated giant cells within inflammatory lesions, and in mononuclear cells of apparently normal tissues (e.glamina propria of the small intestine and the bronchus-associated lymphoid tissue). The lesions were consistent with those of postweaning multisystemic wasting syndrome (PMWS), although not all previously reported PMWS lesions were seen. PCV2 antibodies were detected in infected pigs from day 13 onwards. The results demonstrated widespread distribution of PCV2 after infection and persistence of the virus in vivo for at least 34 days. It would appear that PCV2 can induce PMWS lesions in weaned pigs in the absence of porcine parvovirus and other common swine pathogens.

Retrospective serological survey of antibodies to porcine circovirus type 1 and type 2

A retrospective serological survey was performed to determine the presence of antibodies to porcine circovirus type 1 (PCV1) and porcine circovirus type 2 (PCV2) in serum samples collected from sows at slaughterhouses in Canada in 1985, 1989, and 1997. Each serum sample was tested by indirect immunofluorescence on PCV-free PK15 cells, on PCV1-infected PK15 cells and on PCV2-infected PK15 cells. For the 3 years studied, sera positive to PCV1 and PCV2 were identified and the number of sera positive for PCV2 was greater than the number of sera positive for PCV1. The results indicated 1) that PCV2 appears to be the main PCV type circulating in the Canadian pig population, 2) that PCV2 had been circulating in the Canadian pig population at least 10 years before the postweaning multisystemic wasting syndrome (PMWS) was reported, and 3) that serological evaluation using PCV1 underestimates the seroprevalence of PCV2.

Management of patients with Bacilli Calmette-Guérin-refractory carcinoma in situ of the urinary bladder: cost implications of a clinical trial for valrubicin

OBJECTIVE

This study was undertaken to identify the expected first- and second-year clinical costs associated with intravesical valrubicin therapy, using a decision analytic model, for patients with Bacilli Calmette-Guérin (BCG)-refractory carcinoma in situ (CIS) of the urinary bladder.

BACKGROUND

Cancer of the urinary bladder is the fourth most common malignancy in men and the sixth most common noncutaneous carcinoma overall. One histopathologic stage of bladder cancer is CIS, for which BCG intravesical immunotherapy is the first-line therapy. Radical cystectomy has been recommended for patients with CIS who do not respond to or become refractory to therapy with BCG. Surgery, however, may not be appropriate for all patients, especially those who are ineligible for the lengthy procedure because of advanced age or comorbidities and those who prefer alternative nonsurgical management. For these groups, intravesical valrubicin therapy is a plausible alternative.

METHODS

Models were developed and populated with data from 1 open-label study of 90 patients, information from the medical literature, and input from clinical experts. The analysis was conducted from the payor perspective for direct costs only.

RESULTS

Our data indicate that first- and second-year expected costs for valrubicin therapy are $19,912 and $23,496, respectively. Expected cost for radical cystectomy was also evaluated, since some patients may have no other option if drug therapy fails.

CONCLUSION

Our cost-consequence analysis and clinical data provide decision-makers with tools to aid in global budgetary projections of fractional and total expected health care costs associated with the management BCG-refractory CIS of the urinary bladder.

Typing of porcine circovirus in clinical specimens by multiplex PCR

A multiplex PCR assay was developed to detect and differentiate between the porcine circovirus (PCV) infecting persistently the PK 15 cell line (PCV type I) and the PCV associated with postweaning multisystemic wasting syndrome (PMWS) (PCV type II). DNA products with unique sizes characteristic of each type of PCV were obtained. Sequencing of these products demonstrated that the nucleotide sequences were type-specific. Tissue samples from a total of 42 field cases from Québec were studied, among which 41 were collected in 1997-1998 and one which had been previously collected in 1994. These 42 cases found previously to be PCV-positive by PCR were tested in the present study by a multiplex PCR assay to determine the type of PCV in each case. From these 42 field cases, 40 cases were PCV type II-positive, one case was PCV type I-positive and one case was positive for both PCV types I and II. PCV type II was identified in typical PMWS field cases, but also in field cases submitted for various clinical histories, some of which were not suggestive of PMWS. In the field case where PCV type I was detected, there was no clinical evidence nor histological lesions suggestive of PMWS. The demonstration of PCV type II in a total of 41/42 field cases in the present study suggests that PCV type II may be the main type of PCV circulating in pigs. Furthermore the detection of PCV type II in a field case dating back to 1994 indicates that this PCV type was circulating in pigs in Québec several years before the report of clinical PMWS in this province.

Impact of palivizumab on expected costs of respiratory syncytial virus infection in preterm infants: potential for savings

In its clinical assessment of the respiratory syncytial virus (RSV)-specific monoclonal antibody palivizumab, the IMpact-RSV Study Group demonstrated a reduction in hospitalizations for RSV-related lower respiratory tract infection in infants who received prophylaxis compared with infants who did not receive prophylaxis. An assessment of the RSV-related expenses for managing both groups of infants is needed to provide insight into the value of prophylaxis. The present study was conducted to identify and compare RSV-related health care expenditures incurred by infants who did not receive prophylaxis throughout one RSV season and after. Using a decision-analytic model populated with data from the contemporary medical literature, a pharmacoeconomic study was conducted from the perspective of the payer. Probabilities for RSV-related hospitalizations of infants who did and did not receive prophylaxis were abstracted from several published studies. Components of inpatient and outpatient care were identified through examination of hospital records, reviews of the published literature, and consultation with expert clinicians. Charges related to prophylaxis and medical management of infection were abstracted from hospital billing records and published data. Appropriate charges were applied to decision-tree branches and multiplied by in-line probabilities for outcomes. Products at terminal nodes were summed to establish total expected charges for both groups of infants. Widespread clinical use of prophylactic palivizumab would result in incremental expenses < or =$3459 per infant or cost savings < or =$39,107 per infant. The variability in value of prophylaxis derives from the rate of RSV-related hospitalizations in the community and the total health care expense of managing infected infants.

Cutaneous and systemic necrotizing vasculitis in swine

A systemic vasculitis involving particularly the skin and kidneys has been recently described in swine under the name dermatitis/nephropathy syndrome. Twelve pigs with gross cutaneous lesions typical of this condition were necropsied, and morphologic, immunohistochemical, microbiologic, and epidemiologic characteristics were studied. The pigs were divided into three groups comprising eight pigs with acute lesions, two with chronic lesions, and two with acute lesions kept for sequential skin biopsies. Acute skin lesions consisted of round to irregular, red to purple macules and papules that often coalesced to form large, irregular patches and plaques. With time, the lesions became covered by crusts and faded gradually, sometimes leaving scars. Characteristic distribution included the perineal area of the hindquarters, limbs, dependent parts of the abdomen and thorax, and margins of the ears. In the acute phase of the disease, necrotizing and leucocytoclastic vasculitis of small-caliber blood vessels were observed within the dermis and panniculus and in various extracutaneous locations such as the renal pelvis and synovial membranes. All pigs had macroscopic evidence of pneumonia and generalized lymphadenopathy. Microscopically, they had interstitial pneumonia and perivascular cuffing of mononuclear cells in various tissues including skin. The presence of immunoglobulins and complement was demonstrated by immunofluorescence in and around necrotic vessels of the skin in the early stages. Porcine reproductive and respiratory syndrome (PRRS) virus (PRRSV) antigens were detected by immunohistochemistry in macrophages located around vessels of the tissues examined (skin and kidneys) in acute and chronic cases. PRRSV RNA was demonstrated by reverse transcription-polymerase chain reaction in lung and spleen homogenates from all pigs. The PRRSV was isolated in cell culture from 11 of the pigs. These findings suggest that PRRSV infection may play a role in the pathogenesis of this systemic vascular disease of swine.

Differentiation of North American and European porcine reproductive and respiratory syndrome virus genotypes by in situ hybridization

Non-radioactive probes that can detect specifically North American and European isolates of porcine reproductive and respiratory syndrome virus (PRRSV) in formalin-fixed paraffin-embedded tissues by in situ hybridization were developed. These probes allow the differentiation between North American and European genotypes of the PRRS virus as well as the detection of both genotypes. Two amplified cDNA products generated by polymerase chain reaction (PCR), one from the cDNA of the Canadian PRRSV LHVA-93-3 isolate and the second one from the European Lelystad isolate, and labelled with digoxigenin were utilized as probes. The LHVA-93-3 derived probe was found to detect Canadian and USA PRRSV isolates in infected cells, while the Lelystad derived probe hybridized only with European isolates. The specificity of both probes was also demonstrated on formalin-fixed tissues collected from PRRSV infected pigs. Furthermore, by combining the LHVA-93-3 (North American) probe and the Lelystad (European) probe, successful detection of both PRRSV genotypes in fixed tissues could be achieved.

Evaluation of the presence of porcine reproductive and respiratory syndrome virus in packaged pig meat using virus isolation and polymerase chain reaction (PCR) method

An investigation was carried out to assess the potential presence of porcine reproductive and respiratory syndrome virus (PRRSV) in packaged pig meat. Samples of meat were collected at the processing plants and were sent to the laboratory for testing by virus isolation and reverse transcription-polymerase chain reaction (RT-PCR). Samples collected at four plants were randomly selected from lots of packaged pig meat from different slaughtering days and were sent frozen to the laboratory. Homogenates of meat were prepared and were inoculated onto MARC-145 cells and after two passages the presence of PRRSV was monitored by indirect immunofluorescence staining using PRRSV specific monoclonal antibody. All pig meat samples (six pools of meat samples from 73 different lots = 438 total homogenates) tested were found negative by virus isolation. Primers from open reading frames 6 and 7 were designed and a RT-PCR assay was developed and was demonstrated to detect both North American and European PRRSV isolates. Using this assay virus was detected at a concentration as low as 0.355 infectious virions per ml in supernatant of PRRSV infected cells. This RT-PCR assay could detect PRRS viral nucleic acid from various tissue samples of experimentally infected pigs including muscle tissue, thus demonstrating its applicability on tissue samples. All meat sample homogenates tested by RT-PCR (one sample pool from the 73 lots) were also found negative for PRRS viral nucleic acid. The results suggest that pig meat does not retain detectable amounts of PRRSV and further support that the transmission of PRRSV through pig meat is unlikely.

Performance of ELISA antigens prepared from 8 isolates of porcine reproductive and respiratory syndrome virus with homologous and heterologous antisera

Porcine reproductive and respiratory syndrome virus (PRRSV) ELISA antigens of high quality were produced using 8 different isolates of PRRSV: the European Lelystad virus (LV), the U.S. MN-1b, 89-46448, 93-44927, and 93-24025B, and the Canadian LHVA-93-3, PA-8 and GH-6 virus isolates. The performance of each of these 8 antigens and a commercial PRRSV antibody test kit (Idexx's HerdChek) were measured against antisera raised in 5 groups of 6 piglets inoculated with either LV, MN-1b, 89-46448, 93-44927, or 93-24025B. Among the 8 isolates, the 89-46448 isolate produced the broadest spectrum of antigen and resulted in earlier detection of antibodies to various North American PRRSV isolates, followed by MN-1b as the 2nd best ELISA antigen for the detection of North American PRRSV antibodies. The GH-6 and PA-8 viral antigens exhibited restricted detection of PRRSV antibodies. The LV and 89-46448 combined antigens produced the best performance for the detection of antibodies against both European and North American antigenic types of PRRSV. Using 173 panel samples collected at 11 to 60 d after intranasal inoculation with 1 of the 5 PRRSV isolates, the sensitivities of the indirect ELISA used were 73.4%, 98.3%, 90.8%, 98.3%, 83.2%, 93.1%, 77.1%, 64.2%, 98.8% and 95.9% for LV, MN-1b, LHVA-93-3, 89-46448, 93-44927, 93-24025B, PA-8, GH-6 antigens, 89-46448-LV combined antigens and Idexx's PRRSV antibody test kit, respectively. All 8 antigens gave negative results with preinfection porcine sera (n = 30); high background or nonspecific reactions were not observed with the antigens.

Comparative study of serological methods for the detection of antibodies to porcine reproductive and respiratory syndrome virus

A comparison was made of serological diagnostic methods used for the detection of antibodies against porcine reproductive and respiratory syndrome (PRRS) virus. In the "phase I" PRRS test panel comparison, a panel of sera collected from 135 pigs of various ages, from North American herds with and without PRRS histories, were sent to 4 different laboratories and tested by an indirect immunofluorescent assay (IFA), an immunoperoxidase monolayer assay (IPMA) and an indirect enzyme-linked immunosorbent assay (iELISA). In the "phase II" PRRS test panel comparison, a panel of 382 sera collected from pigs of various ages, PRRS histories, and from various locations in North America and France, were divided into 2 panels (A & B) and sent to 3 Canadian laboratories and tested by the IFA and iELISA. In the phase I comparison, agreement between the IFA of laboratory 4 and the iELISA and IPMA of laboratory 3 was excellent (kappa values of 95% and 98%, respectively). This contrasted with the poor agreement between these laboratories and the IFA results of laboratories 1 and 2 in the phase I trial. In the phase II comparison, the results demonstrated good agreement between various tests both within and between laboratories. The overall performance of the iELISA was superior in the combination of sensitivity (96.1%) and specificity (100%) relative to the reference classification of the serum samples and repeatability (kappa value 98%). The iELISA is technically superior to IFA and IPMA, time efficient, cost effective and suitable for testing of a large number of samples over a short period of time. Thus, the iELISA may be a better alternative to IFA or IPMA for routine detection of PRRS viral antibodies in swine sera.

Antigenic variability of porcine reproductive and respiratory syndrome (PRRS) virus isolates. Influence of virus passage in pig

In order to study the antigenic variability of porcine reproductive and respiratory syndrome virus (PRRSV), 18 European and Canadian field isolates were analysed with a panel of 15 monoclonal antibodies (MAbs) raised against five different European and one Canadian PRRSV isolates. The antigenic pattern of these isolates was used to infer their phylogenetic relationships. Isolates which had the same reactivity pattern were gathered together so that five antigenic profiles were analysed. The pairwise distances between these groups were defined based on antigenic pattern differences. Two main antigenic groups were obtained, discriminating between the European and the Canadian populations, as illustrated by the great distance observed between European and Canadian isolates (D = 0.5619 +/- 0.0625) compared to the distance between European isolates (D = 0.1524 +/- 0.0735). The distance matrix allowed also the construction of a tree diagram. Bootstrap analysis was performed to test the confidence in the branching. The tree diagram confirmed the distinction between the European and the Canadian PRRSV populations. Antigenic variability between an isolate and its progeny recovered after one or two passages in vivo was examined on six isolates. It was restricted to the GP3 protein of the virus.

Detection of porcine reproductive and respiratory syndrome virus in paraffin-embedded tissues: comparison of immunohistochemistry and in situ hybridization

A non-radioactive in situ hybridization (ISH) method developed recently and an immunohistochemical method, the immunogold silver staining (IGSS), were compared for the detection of porcine reproductive and respiratory syndrome virus (PRRSV) in formalin-fixed paraffin-embedded tissues. Serial sections from 98 tissues, representing different organs from PRRSV experimentally infected pigs, and serial sections from 46 lung tissues from field cases were tested by both methods. Results obtained on tissues from experimentally infected pigs and tissues from field cases demonstrated that ISH was more sensitive than immunohistochemistry. More tissues were positive by ISH compared to IGSS and also a greater number of labelled cells and a stronger signal in stained cells were observed in ISH-treated sections. The ISH method described, using a 254 bp digoxigenin-labelled cDNA probe, is a rapid, highly specific and sensitive detection method which can be used for the diagnosis of PRRSV in routinely fixed and processed tissues.

Typing of porcine reproductive and respiratory syndrome viruses by a multiplex PCR assay

A rapid multiplex PCR assay was developed to distinguish between North American and European genotypes of porcine reproductive and respiratory syndrome (PRRS) virus after a portion of the polymerase gene (open reading frame 1b) was sequenced for two North American PRRS virus strains. DNA products with unique sizes characteristic of each genotype were obtained.

Differential reactivity of a monoclonal antibody directed to the membrane protein of porcine reproductive and respiratory syndrome virus

A monoclonal antibody (2C12) against the 19 kDa membrane (M) protein of a Canadian isolate of porcine reproductive and respiratory syndrome (PRRS) virus was produced. By indirect immunofluorescence (IIF) cytoplasmic fluorescence was observed in infected cells, but the pattern of fluorescence was generally different and intensity was weaker than that observed using the nucleocapsid protein-directed monoclonal antibody SDOW17. When tested by IIF towards a total of 26 PRRS virus isolates from Canada, 122 isolates from the US and 13 isolates from Europe the 2C12 MAb reacted with all the North American isolates tested including the VR-2332 isolate and the vaccine (RespPRRS) isolate. However no reactivity was observed towards the European isolates tested including the Lelystad virus. This reactivity pattern suggests that the epitope recognized by this MAb on the M protein of PRRS virus appears highly conserved among North American isolates but absent or weakly expressed on European isolates of PRRS virus.

A pharmacoeconomic evaluation of intravenous fosphenytoin (Cerebyx) versus intravenous phenytoin (Dilantin) in hospital emergency departments

The cost of emergency department services has become a major concern for patients, providers, and payers. Solid economic information is needed to provide a rationale for the selection of therapeutic options and the provision of care that is both clinically and financially prudent. To assess the full cost of care for patients with seizures who are treated in an acute care setting, a modified activity-based cost-accounting model was developed. The model was populated with data from a double-masked, parallel-group, single-dose, multicenter clinical trial designed to investigate the safety and tolerability of phenytoin (Dilantin) and fosphenytoin (Cerebyx) given intravenously in equivalent loading doses according to established recommendations. A total of 52 patients were enrolled in the trial; 13 were given phenytoin and 39 were given fosphenytoin. Salaries and benefits of emergency medical services personnel, drug acquisition costs, and direct and indirect overhead expenditures common to a large hospital emergency department comprised the total costs to treat enrolled patients and manage adverse events. The average cost to treat patients with fosphenytoin was lower than the cost to treat similar patients with phenytoin based on the frequency of adverse events associated with each comparator and the resources (human and material) consumed in the management of those events.

Detection of porcine reproductive and respiratory syndrome virus in cell cultures and formalin-fixed tissues by in situ hybridization using a digoxigenin-labeled probe

A nonradioactive in situ hybridization method is described for the detection of porcine reproductive and respiratory syndrome virus (PRRSV) in cell cultures and in formalin-fixed paraffin-embedded tissue sections originating from experimentally infected pigs and from 1 field case. A 174 bp cDNA probe targeting the viral RNA encoding the nucleocapsid protein of a Canadian PRRSV isolate was generated by polymerase chain reaction. The cDNA probe was labeled by random priming with digoxigenin-dUTP using a commercially available kit. The ability of the digoxigenin-labeled probe to specifically detect PRRSV RNA was tested on cultured cells infected with 6 Canadian PRRSV isolates, a US PRRSV isolate and the European Lelystad isolate. The probe detected all Canadian PRRSV isolates tested as well as the US PRRSV isolate but did not detect the Lelystad isolate. In addition, when tested on formalin-fixed paraffin-embedded tissue sections from pigs experimentally infected with several Canadian isolates and from a field case, a strong signal without background staining was obtained. Our results indicate that nonradioactive in situ hybridization could represent a useful tool for the detection of PRRSV in routinely fixed and processed tissues. In situ hybridization could also be used to differentiate infection by North American and European Lelystad-like PRRSV isolates.

Evaluation of the persistence of porcine reproductive and respiratory syndrome virus in pig carcases

The presence of porcine reproductive and respiratory syndrome (PRRS) virus in pig meat was assessed in samples collected from experimentally infected pigs and from the carcases of pigs from infected herds at an abattoir. In the experimental study, pigs approximately six months old were inoculated with two isolates of PRRS virus and tissue samples were collected seven and 14 days after inoculation. At seven days, PRRS virus was recovered from lungs, tonsils, lymph nodes and muscle tissues, and viral antigens were detected by immunogold silver staining (IGSS) in formalin-fixed lungs, tonsils and scattered cells in muscle tissues. Neither PRRS virus nor antigens were detected in muscle tissue samples collected 14 days after inoculation. In the abattoir pigs, attempts were made to isolate PRRS virus from a total of 44 samples of muscle tissue, collected as pools, from the carcases of 44 pigs originating from seropositive herds. No PRRS virus could be isolated on porcine alveolar macrophages from these 44 muscle tissue samples and no PRRS virus antigens could be detected by IGSS in the formalin-fixed tissue samples. Although the results of experimental infections indicated that PRRS virus may be recovered from muscle tissues early after infection with the virus, the presence of PRRS virus in muscle tissues from carcases of slaughter pigs previously exposed to the PRRS virus could not be demonstrated.

Antigenic comparison of Canadian and US isolates of porcine reproductive and respiratory syndrome virus using monoclonal antibodies to the nucleocapsid protein

Fifteen Canadian field isolates of porcine reproductive and respiratory syndrome (PRRS) virus from Quebec and Ontario were compared with 5 US PRRS virus (PRRSV) isolates and with the European Lelystad isolate using monoclonal antibodies (MAbs) SDOW17, EP147, and VO17 directed to the 15-kDa nucleocapsid protein of PRRSV. All Canadian and US isolates tested by indirect immunofluorescence were recognized by the 3 MAbs, and individual titers of MAbs towards Canadian and US PRRSV isolates were similar as well. In contrast, the Lelystad virus isolate reacted only with the SDOW17 MAb and showed no reactivity with either EP147 or VO17. The reactivity pattern with these MAbs suggests that the Canadian isolates of PRRSV tested are antigenically similar to US isolates of PRRSV, and that these North American isolates share highly conserved epitopes on the 15-kDa nucleocapsid protein that clearly differentiate them from the European Lelystad virus isolate.

Isolation and experimental oral transmission in pigs of a porcine reproductive and respiratory syndrome virus isolate

A virus inducing a cytopathic effect on porcine alveolar macrophages was isolated from the lungs of a pig with respiratory problems and lesions of proliferative and necrotizing pneumonia. The isolate was found to react with porcine reproductive and respiratory syndrome virus (PRRSV) monoclonal antibodies by indirect immunofluorescence and was designated LHVA-93-3. The virus could also be propagated on the MARC-145 cell line. The LHVA-93-3 macrophage-passaged isolate was inoculated orally or intranasally in four-week-old specific pathogen-free pigs. Histologically, focal to multifocal lesions of proliferative, necrotizing and interstitial pneumonia could be observed in the lungs of pigs inoculated orally or intranasally, 6 and 10 days post-inoculation. Virus could be reisolated from essentially the same tissues including serum following both routes of infection. The distribution of PRRSV antigens in fixed tissues as determined by immunogold silver staining (IGSS) was similar in orally or intranasally inoculated pigs. The results of this experimental transmission study indicate that pigs may become infected by PRRSV following oral as well as intranasal exposure.

Immunohistochemical detection of porcine reproductive and respiratory syndrome virus using colloidal gold

Two cytopathic agents were isolated on porcine alveolar macrophages following inoculation with homogenates of lung tissues from pigs showing respiratory problems. These isolates were identified as porcine reproductive and respiratory syndrome (PRRS) virus isolates by indirect immunofluorescence using a PRRS virus (PRRSV) specific monoclonal antibody (MAb) and were designated as LHVA-92-1 and LHVA-92-2. Immunogold electron microscopy using a porcine PRRS positive serum pool and protein A-gold resulted in an intense labelling of aggregates of viral particles. Dark specific cytoplasmic staining of porcine alveolar macrophages infected with both virus isolates could be observed by immunogold silver staining (IGSS) using the specific MAb. This method proved effective in detecting PRRSV antigens in several ethanol-fixed tissues of piglets intranasally inoculated with the supernatants of macrophages infected with each isolate. Immunogold silver staining was also successfully used for the detection of PRRSV antigens on sections of formalin-fixed paraffin-embedded lung tissues and on frozen sections of lungs. The present results indicate that colloidal gold may be useful for the identification and immunohistochemical detection of PRRSV in tissues.

The application of immunogold silver staining (IGSS) for the detection of transmissible gastroenteritis virus in fixed tissues

Protein A-gold (PAG) and a primary porcine antiserum were used in immunogold silver staining (IGSS) for the detection of transmissible gastroenteritis virus (TGEV) in formalin-fixed paraffin-embedded tissue sections of small intestine originating from infected pigs. Immunogold electron microscopy was used to evaluate the reactivity of the prepared PAG marker with the specific porcine TGEV antiserum. Gold particles were closely associated with single virions and immune aggregates of TGEV. When IGSS, using PAG as the marker, was applied to tissue sections, dark staining of TGEV-infected villous enterocytes was observed. Background was low, allowing good visualization by light microscopy of the distribution of viral antigen. Two other gold conjugates, protein A/G-gold (PA/GG) and protein G-gold (PGG), were tested in IGSS. The labeling with PA/GG was comparable to that obtained with PAG. However, no staining was observed when PGG was used. The use of IGSS and PAG offers advantages and may represent a useful technique for the detection of other viral pathogens.

Identification of atypical rotaviruses in outbreaks of preweaning and postweaning diarrhea in Québec swine herds

Intestinal contents of diarrheic pigs from 120 outbreaks of diarrhea were examined for the presence of atypical rotaviruses. Pigs involved in these outbreaks were aged two days to five weeks and samples collected over a period of one year originated from different regions of the province of Québec. Samples were analyzed by polyacrylamide gel electrophoresis (PAGE) for the presence of viral RNA and genome profiles were compared to those of porcine rotavirus A/OSU, B/Ohio and C/Cowden. Based on electropherotypes both typical (group A) and atypical (groups B and C) rotaviruses were identified. Rotaviruses could be demonstrated in 25.8% of outbreaks and together atypical rotaviruses accounted for 46.7% of rotavirus-positive outbreaks. Other common enteropathogens were often present in conjunction with rotaviruses in the preweaning and postweaning outbreaks studied.

Porcine group C rotavirus as a cause of neonatal diarrhea in a Quebec swine herd

A porcine group C rotavirus was found to be the unique cause of a problem of enzootic neonatal diarrhea in a minimal disease herd composed of 190 sows on a continuous farrowing program. During the outbreaks of diarrhea, 10 to 80% of the litters were affected with a morbidity rate of 100% and case fatality rates of 5 to 10%. Clinical signs began 24 to 48 h after birth and were characterized by a profuse yellow diarrhea lasting a few days. Piglets from different outbreaks of diarrhea were necropsied. They had multifocal villous atrophy in the small intestine, especially in the ileum. Group C rotavirus was demonstrated by direct immunofluorescent staining of frozen intestinal sections and by polyacrylamide gel electrophoresis of viral RNA extracted from the intestinal contents of diarrheic piglets. The infection with clinical illness and lesions was reproduced experimentally in newborn piglets by oral inoculation of a suspension prepared from a pool of intestinal contents from diarrheic piglets.

Bovine viral diarrhea virus proteins: heterogeneity of cytopathogenic and non-cytopathogenic strains and evidence of a 53K glycoprotein neutralization epitope

Intracellular virus-induced polypeptides from 3 cytopathogenic and 2 non-cytopathogenic bovine viral diarrhea (BVD) virus reference strains were analyzed by radioimmunoprecipitation and polyacrylamide gel electrophoresis, using a specific bovine multivalent antiserum and a neutralizing BVD-virus monoclonal antibody. Electrophoretic patterns of major proteins demonstrate extensive variation between strains. Most notably, a major 80,000 (80K) polypeptide was present in all cytopathogenic strains but absent in both non-cytopathogenic strains. Furthermore, a neutralizing monoclonal antibody produced against the NADL strain immunoprecipitated a 53K glycoprotein indicating that this protein carries an important neutralization epitope that is not present in all strains tested.

Typing of cytopathic and noncytopathic bovine viral diarrhea virus reference and Canadian field strains using a neutralizing monoclonal antibody

Cytopathic and noncytopathic reference strains as well as Canadian field isolates of bovine viral diarrhea virus were analyzed by neutralization and immunofluorescence tests using a bovine viral diarrhea virus-specific neutralizing monoclonal antibody. Results on reference strains indicated three major antigenic groups: I) NADL-like, II) New York 1-like and III) Oregon C24V-like. Field isolates could be segregated into groups I and II and none could be typed into the group III. It appears that most bovine viral diarrhea virus strains share a common antigen which carries a major neutralization epitope. These characteristics would make this monoclonal antibody a useful reagent for taxonomic and epizootiological studies.

Comparison of methods for concentration and purification of bovine viral diarrhea virus

The NADL strain of bovine viral diarrhea virus (BVDV) was concentrated by hollow fiber ultrafiltration or polyethylene glycol and purified by centrifugation through sucrose or potassium tartrate gradients. The protein content of polyethylene glycol concentrates was much lower than that of ultrafiltration concentrates. Conversely, recoveries of infectivity were greater using polyethylene glycol (100%) as compared to ultrafiltration (50%). Sucrose or potassium tartrate density gradients appeared comparable in purification of BVD virus. Peak infectivity fractions in both gradients corresponded quite well, having densities of 1.12-1.14 g/cm3, and showed a 150-fold reduction of protein when compared to crude viral supernate. Further examination by negative stain electron microscopy revealed integral pleomorphic, roughly spherical particles in both purified virus preparations. Small knob-like projections could be seen on viral particles.

Cell-protective monoclonal antibodies to bovine enterovirus-3 and partial or no activity against other serotypes

Preparation of monoclonal antibodies to bovine virus diarrhea virus (BVDV) yielded some hybridoma cells that secreted monoclonal antibodies against the Madin-Darby bovine kidney cells. The anti-cellular monoclonal antibodies reacted with other bovine cells (bovine turbinate and testicle) but not with cell lines derived from other animal species. Subclones derived from one hybridoma partially blocked the infectivity of BVDV, possibly through the binding of the monoclonal antibodies with an epitope close to the receptor site of BVDV and not by way of steric hindrance. Unexpectedly, these same subclones completely blocked the infectivity of bovine enterovirus-3 (BEV-3) strain 240A and partially blocked the infectivity of BEV-2 and BEV-3 (ATCC strain) but not that of other serotypes. Other subclones derived from two other hybridomas, although cell membrane specific, did not have a protective activity against BEV or BVDV.

Bovine viral diarrhea virus-infected MDBK monolayer as antigen in enzyme-linked immunosorbent assay (ELISA) for the measurement of antibodies in bovine sera

A specific ELISA for the detection of IgG antibodies against bovine viral diarrhea virus (BVDV) has been developed and was compared with the seroneutralization (SN) titers for a total of 60 bovine serum samples. A BVDV-infected Madin-Darby Bovine Kidney (MDBK) cell monolayer served as test antigen. The following results were obtained: a coefficient of correlation (r) of 0.63 (P less than 0.01) between BVDV-ELISA and SN titer in BVDV-seroconverted animals and 0.71 for all sera, including that from BVDV vaccinated animals; a sensitivity of 92%, a specificity of 91%, a concordance of 92%; and a demonstration of a parallel increase in BVDV-ELISA and SN titers in animals with seroconversion. The BVDV-ELISA permits a more complete evaluation of the humoral immune response to BVDV.