PCV2 Antibody Research Articles

Development and application of a blocking ELISA based on a N protein monoclonal antibody for the antibody detection against porcine reproductive and respiratory syndrome virus 2

Porcine reproductive and respiratory syndrome (PRRS) is one of the most widespread illnesses in the world's swine business. To detect the antibodies against PRRSV-2, a blocking enzyme-linked immunosorbent assay (B-ELISA) was developed, utilizing a PRRSV-2 N protein monoclonal antibody as the detection antibody. A checkerboard titration test was used to determine the optimal detection antibody dilution, tested pig serum dilution and purified PRRSV coated antigen concentration. After analyzing 174 negative pig sera and 451 positive pig sera, a cutoff value of 40 % was selected to distinguish between positive and negative sera using receiver operating characteristic curve analysis. The specificity and sensitivity of the assay were evaluated to equal 99.8 % and 96 %, respectively. The method had no cross-reaction with PCV2, PRV, PPV, CSFV, PEDV, TGEV, and PRRSV-1 serum antibodies, and the coefficients of variation of intra-batch and inter-batch repeatability experiments were both <10 %. A total of 215 clinical serum samples were tested, and the relative coincidence rate with commercial ELISA kit was 99.06 %, and the kappa value was 0.989, indicating that these two detection results exhibited high consistency. Overall, the B-ELISA should serve as an ideal method for large-scale serological investigation of PRRSV-2 antibodies in domestic pigs.

Phylogenetic Analysis and Serological Investigation of Porcine Circovirus Indicates Frequent Infection with Various Subtypes.

Porcine circoviruses (PCVs) are notorious for triggering severe diseases in pigs and causing serious economic losses to the swine industry. In the present study, we undertook a comprehensive approach for the investigation of PCV prevalence, including the phylogenetic analysis of obtained PCV sequences, the determination of major circulating genotypes and serological screening based on different recombinant Cap proteins with specific immunoreactivity. Epidemiological surveillance data indicate that PCV2d and PCV3a are widely distributed in Southwest China, while PCV4 has only sporadic circulation. Meanwhile, serological investigations showed high PCV2 antibody positivity in collected serum samples (>50%), followed by PCV4 (nearly 50%) and PCV3 (30-35%). The analysis supports different circulation patterns of PCV2, PCV3 and PCV4 and illustrates the PCV2/PCV3 genetic evolution characteristics on a nationwide basis. Taken together, our findings add up to the current understanding of PCV epidemiology and provide new tools and insight for PCV antiviral intervention.

Production of virus-like particles of porcine circovirus 2 in baculovirus expression system and its application for antibody detection

BackgroundPorcine circovirus 2 (PCV-2) is one of the pathogens that leads to a growing and persistent threat in pigs. Thus, the development of serological detection methods for PCV-2 is of great necessity for clinical diagnosis as well as epidemiological investigations. This study aimed to establish an indirect enzyme-linked immunosorbent assay (ELISA) to examine antibodies against PCV-2 based on virus-like particles (VLPs).ResultsRecombinant PCV-2 Cap protein was expressed in the baculovirus-insect cells system and PCV-2 VLPs were observed over transmission electron microscopy (TEM). The PCV-2 VLPs were shown to have good immunogenicity in mice and stimulated a high level of PCV-2 antibody titers. Using PCV-2 VLPs as coating antigen, the indirect ELISA can detect PCV-2 antibodies in animals with diagnostic sensitivity and specificity of 98.33% and 93.33% compared to immunofluorescence assay (IFA), respectively. The intra- and inter-assay coefficient variations (CVs) were < 10% in a batch, and < 15% in different batches, indicating good repeatability. There was no cross-reaction of this ELISA with antibodies against other porcine viruses. A total of 170 serum samples collected from different pig farms in China were tested for PCV-2 antibodies, and 151 (88.8%) samples were PCV-2 antibody positive.ConclusionOur findings suggest that this ELISA was rapid, specific, and reproducible and can be used for large-scale serological investigations of PCV-2 antibodies in pigs.

Synergistic pathogenicity by coinfection and sequential infection with JXA1-like HP-PRRSV and PCV2d in PCV2 antibody-positive post-weaned pigs

Porcine reproductive and respiratory syndrome virus (PRRSV) and Porcine circovirus (PCV) are two important pathogens, which caused respiratory disease in pigs. PRRSV and PCV2 had caused great economic losses to the pig industry. Pigs coinfection with PCV2 and PRRSV were common in the clinic, PCV2 antibodies can be detected in most of the pigs. PCV2d and HP-PRRSV(JXA1-like) were two major viruses circulating in the pigs in China. In this study, HP-PRRSV (JXA1-like) and PCV2d were used to coinfect and (or) sequential infect 5-week-old weaned PCV2-antibody positive pigs and the clinical indications, pathological, virus load, and specific antibodies of the challenged post-weaned piglets were evaluated. Thirty 5-week-old post-weaned pigs were divided into six groups infected with PBS, PCV2, PRRSV, PCV2-PRRSV, PRRSV-PCV2, and Co-PRRSV-PCV2 according to the PCV2 specific antibodies. Pigs infected with PRRSV can experience diarrhea, increased body temperature, weight loss, and even death. The pigs in the PRRSV infected group and PRRSV-PCV2 infected group showed severe clinical symptoms, high mortality, and low average daily gain. The main pathological changes were widening of the lung interstitium, lung adhesion, and so on. The PRRSV-PCV2 infected group showed high levels of TNF-α and IL-2. In conclusion, PRRSV and PRRSV-PCV2 sequential infected pigs showed most pathogenic signs, and PCV2-PRRSV sequential infected pigs showed less pathogenicity than pigs of PCV2 and PRRSV coinfection and PRRSV monoinfection from day 10–14, partially suppressing the cytokine storm produced by PRRSV.

Association between Head-to-Chest Circumference Ratio and Intrauterine Growth-Retardation Related Outcomes during Preweaning and Postweaning.

Simple SummaryLarge litter size might cause significant variation in piglet intrauterine development and growth. Piglets affected by intrauterine growth-retardation (IUGR) have abnormal head shapes and body conformations, as well as lower survival, growth, and meat quality. Therefore, methods for discriminating lower growth and performance piglets that will support the management of IUGR at the individual and farm levels are needed. We hypothesize that piglets with lower birth weight, colostrum intake, average daily gain, and immune response against PCV-2 have differential head-to-chest circumference ratios (HCRs) at birth. We observed that greater HCRs were associated with lower birth weight, colostrum intake, and weight gain. Additionally, piglets with greater HCRs had higher PCV-2 antibodies. The HCR was associated with outcomes linked to IUGR. Thus, HCR might be used as an objective, low-invasive, and inexpensive tool to assess newborn piglets and assist in neonatal and nursery management.The objective of this study is to evaluate the association between the head-to-chest circumference ratio (HCR) and birth weight (BW), colostrum intake, and average daily weight gain (ADG) at preweaning and postweaning periods. Additionally, associations between HCR and PCV-2 serum antibody titers and the PCV-2 seroconversion ratio (SCR) were assessed. Head and chest circumferences were measured at birth, and HCR was calculated from 110 piglets born from 8 pregnant sows randomly selected from maternity pens. Linear mixed models were used to test whether changes in HCR were associated with fluctuations of BW, colostrum intake, and ADG. In addition, HCR least-square means were compared between piglets classified as lower or greater BW, colostrum intake, and ADG. Finally, receiving operating characteristic curve analyses were performed to estimate HCR thresholds for discriminating between lower and greater performance piglets during preweaning and postweaning periods. Increments in HCR were associated with lower BW, colostrum intake, and ADG. An HCR threshold of 0.82 maximized sensibility and specificity for the classification of lower and greater performance piglets regarding BW, colostrum intake, and ADG during the periods of 0 to 7 and 0 to 69 days of life. When piglets were categorized into HCR ≤ 0.82 and HCR > 0.82 groups, piglets with HCR ≤ 0.82 had lower (log10) PCV-2 serum antibody titers at 26 days of life compared with piglets with HCR > 0.82 (3.30 ± 0.05 vs. 3.47 ± 0.05 g/dL). On the other hand, piglets that showed low SCR between 26 and 69 days of life had greater HCRs compared with piglets with high SCRs (0.83 ± 0.008 vs. 0.8 ± 0.008). The use of HCRs allowed us to identify piglets with lower performance and impaired immune response against PCV-2. The HCR indicator could be used as a selection criterion for preventive management for piglets showing delayed performance potentially associated with IUGR.

Evidence of transboundary transmission of viral pathogens through pigs transported from Myanmar to Mizoram, India

In Mizoram, pigs used to migrate through the porous international border from Myanmar. It is speculated that the migrated animals may act as potential carriers of various microbial pathogens. But so far no scientific evidence is available in this aspect. The present study was conducted on the detection of serum antibodies and molecular detection of classical swine fever virus (CSFV), porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus 2 (PCV2) and rotavirus in the pigs. A total of 204 blood and 209 rectal swabs were collected from apparently healthy pigs of Champhai district of Mizoram transported from Myanmar. All the serum samples were subjected to ELISA based detection of antibodies against CSFV, PRRSV and PCV2. The whole blood/serum/feces were processed for extraction of viral nucleic acids and subjected to PCR/RT-PCR for detection of CSFV, PRRSV, PCV2 and rotavirus. A total of 105 (51.47%), 12(5.88%) and 36 (17.65%) serum samples were found to be positive for antibodies against CSFV, PRRSV and PCV2, respectively. In addition, 17 (8.33%) sera were recorded positive for both CSFV and PCV-2 antibodies and 9 (4.41%) sera were positive for CSFV, PCV-2 and PRRSV antibodies. By specific PCR, group A rotavirus was found to be most prevalent (8.33%) followed by PCV-2 (7.84%), CSFV (4.41%) and PRRSV (0.9%). All the rotaviruses were detected as Group A only. Of the 204 animals, 2 (0.98%) pigs showed co-infection with all the four viruses under the study. A total of 5 (2.45%) pigs were positive for co-infection with CSFV and PCV-2 and 4 (1.96%) pigs were positive for co-infection with PCV-2 and rotavirus. The present study provided laboratory based evidence on transmission of porcine viral pathogens from Myanmar to Mizoram.

Porcine circovirus type 2a or 2b based experimental vaccines provide protection against PCV2d/porcine parvovirus 2 co-challenge

With the discovery of Porcine circovirus type 2d (PCV2d) in the USA in 2012 and subsequent genotype shift from the previously predominant PCV2b to PCV2d in the face of widespread PCV2a vaccination, concerns over PCV2 vaccine efficacy were raised. The objective of this study was to evaluate the efficacy of two similarly produced PCV2 vaccines, one containing the PCV2a capsid and the other one containing the PCV2b capsid, in the conventional pig model against PCV2d/porcine parvovirus 2 (PPV2) co-challenge. A co-challenge was added since there is evidence that PPV2 may exacerbate PCV2 infection and since PCV2 only rarely causes disease in experimentally infected pigs, hence vaccine efficacy can be difficult to assess. In brief, sixty 3-week-old-pigs from a PCV2 seropositive farm without evidence of active virus replication (no PCV2 viremia, low antibody titers with no evidence of increase after two consecutive bleedings) were blocked by PCV2 antibody titer and then randomly divided into three groups with 20 pigs each, a non-vaccinated group (challenge control), a PCV2a vaccinated group (VAC2a) and a PCV2b vaccinated group (VAC2b). Vaccinations were done at 4 and again at 6 weeks of age. At 8 weeks of age, all pigs were challenged with a PCV2d strain via intranasal and intramuscular routes of inoculation followed by intramuscular administration of PPV2 one day later. PCV2 vaccination, regardless of PCV2 genotype, resulted in significantly higher humoral and cellular immunity compared to non-vaccinated challenge control pigs as evidenced by increased numbers of interferon (IFN) γ secreting cells after PCV2d stimulation of peripheral blood mononuclear cells collected prior to challenge. Furthermore, PCV2a and PCV2b vaccinations both reduced PCV2d viremia and PCV2-associated pathological lesions. Under the study conditions, the PCV2a and PCV2b vaccine preparations each induced immune responses and clinical protection against a heterologous PCV2d/PPV2 co-challenge.

Reservoirs of Porcine Circoviruses: A Mini Review.

Porcine circovirus (PCV) is one of the smallest known DNA viruses in mammals. At present, PCVs are divided into three species, PCV1, PCV2, and PCV3. PCV1 and PCV2 were found in the 1970s and the 1990s, respectively, whereas PCV3 was discovered recently in 2016. PCV1 does not cause diseases in pigs. However, PCV3, similar to PCV2, is reported to be associated with several swine diseases, including porcine dermatitis and nephropathy syndrome (PDNS) and reproductive failure. PCVs are very common in domestic pigs as well as wild boars. However, PCVs have been occasionally isolated from non-porcine animals, including ruminants (such as cattle, goats, wild chamois, and roe deers), rodents (such as NMRI mice, BALB/c mice, Black C57 mice, ICR mice, Mus musculus, and Rattus rattus), canines (such as dogs, minks, foxes, and raccoon dogs), insects (such as flies, mosquitoes, and ticks), and shellfish. Moreover, PCVs are frequently reported in biological products, including human vaccines, animal vaccines, porcine-derived commercial pepsin products, and many cell lines. PCVs are also abundant in the environment, including water samples and air samples. Interestingly, PCV1 and/or PCV2 antibody or antigen has also been detected in sera, stool samples and respiratory swab samples of human, revealing zoonotic potential of PCVs. Thus, PCVs inhabit many types of reservoirs. In this review, we summarize the reservoirs of PCVs, and this information would be helpful in understanding the natural circulating status and possible cross-species transmission of PCVs.

Seroprevalence of Porcine Circovirus-2 in Domestic Pigs (Sus Scrofa Domestica) in Latvia

Abstract Porcine circovirus-2 (PCV2) is the primary agent of Postweaning Multisystemic Wasting Syndrome (PMWS), and is associated with Porcine Circovirus Associated Disease, which causes great economic losses in pig breeding. PCV2 infection is distributed worldwide throughout the domestic pig population. There have not been any investigations on the distribution of PCV2 sero-prevalence in the population of pigs in Latvia. However PCV2 is one of main differential infections for many diseases, and therefore it is very variable in clinical presentation of PMWS and other diseases associated with PCV2. The objective of this study was to investigate the seroprevalence of PCV2 in pigs of different-scale farms located in different regions of Latvia. Blood samples of 963 pigs from 58 different-scale farms were examined for the PCV2 antibody from 2006 to 2016. It can be suggested that PCV2 is widespread within the territory of Latvia. Farms with pig number of up to 10 and farms with more than 5000 animals have different levels of biosafety, housing conditions and herd management. Nevertheless, the study showed that the number of PCV2-seropositive animals is similar in all farms (from 70.0% to 79.7%).

The emergence of porcine circovirus 2 infections in the Northeastern part of India: A retrospective study from 2011 to 2017

Porcine circovirus (PCV) infection has emerged as an alarming threat to the pig population of India, especially in the Northeastern region (NER) over the last 10years. The present study is a comprehensive report of the seroepidemiology of PCV2 and its incidences in the pig population from organized and unorganized farms of the entire NER of India from 2011 to 2017. A total of 5697 serum samples were screened by ELISA and the mean positivity of PCV2 antibodies in suspected sera was 31.27%. A total of 22 confirmed cases of PCV2 infection were recorded during the years 2014-2017. Seroprevalence of PCV2 infection in sows causing reproductive disorders in NER suggested its higher incidence in organized farms (65.7%) as compared to unorganized farms (17.6%). A detailed pathological and histopathological examination of the tissue samples collected from the affected animals indicated the presence of PCV2. Molecular characterization and phylogenetic analysis of four PCV2 isolates depicted the circulation of PCV2d genotype in the states of Meghalaya and Assam.

Estimation of the diagnostic performance of two ELISAs to detect PCV2 antibodies in pig sera using a Bayesian method

This study was designed to assess the diagnostic characteristics of two PCV2 ELISAs without a gold standard. Four hundred and sixty-five serum samples from finishing pigs (25 herds) not vaccinated against PCV2 were used. Samples were tested by two ELISAs: an in-house ELISA (I-ELISA) and the commercial SERELISA®PCV2 Ab Mono Blocking kit (S-ELISA). A ROC curve was used to assess the S-ELISA’s optimal threshold by taking the I-ELISA as a reference and using the cut-off previously determined by comparison to an cccmonolayer assay (IPMA). This led to an S-ELISA result ≥170 being considered as positive. The sensitivity (Se) and specificity (Sp) of each ELISA were then estimated without a gold standard using a Bayesian approach. The mean Se and Sp values of the I-ELISA were slightly higher than those of the S-ELISA (mean Se I-ELISA=0.90 vs. mean Se S-ELISA=0.86; mean Sp I-ELISA=0.92 vs. mean Sp S-ELISA=0.85). However, the 95% credibility intervals (CI95%) overlapped (Se I-ELISA CI95%=0.85–0.95 vs. Se S-ELISA CI95%=0.82–0.90; Sp I-ELISA CI95%=0.82–0.98 vs. Sp S-ELISA CI95%=0.75–0.94). Both ELISAs appeared to be valuable tools for detecting PCV2 antibodies.

Comparative efficacy of experimental inactivated and live-attenuated chimeric porcine circovirus (PCV) 1-2b vaccines derived from PCV1 and PCV2b isolates originated in China

BackgroundPorcine circovirus type-2b (PCV2b) is recognized as the etiological agent of the various clinical manifestations of porcine circovirus-associated disease (PCVAD). Previous studies have demonstrated effectiveness of chimeric PCV1-2 vaccines against PCV2b challenge. In this study, the efficacy of inactivated and live-attenuated (2 × 103.5 or 2 × 104.0 50 % tissue culture infective dose [TCID50] dose) chimeric PCV1-2b vaccines was compared side-by-side in conventional pigs.MethodsTwenty-seven non-PCV2 viremic pigs without PCV2-specific antibody were randomly divided into six groups, including four vaccinated and challenged groups, a nonvaccinated challenged group, and a mock group. All pigs except those in the mock group were challenged at 28 days post vaccination (DPV) using PCV2b.ResultsBoth inactivated and live-attenuated chimeric PCV1-2b vaccines induced a robust antibody responses, and significantly decreased microscopic lesion and lower viral loads in serum or superficial inguinal lymph nodes (SILN) compared with that in the nonvaccinated challenged group. PCV2 antibody titers decreased after 7 days post challenge (DPC) in pigs administered the inactivated PCV1-2b vaccine and they were lower than those in pigs inoculated with live-attenuated PCV1-2b on the day of necropsy. Moreover, no viremia was present in pigs inoculated with live-attenuated PCV1-2b vaccine at 21 DPC regardless of the dose difference.ConclusionsThe results demonstrated that both inactivated and live-attenuated chimeric PCV1-2b vaccines were effective to induce protective immunity against PCV2b infection.

Virological and serological characterization of vaccinated and non-vaccinated piglet subpopulations coming from vaccinated and non-vaccinated sows

The present study describes the virological and serological profiles of PCV2 vaccinated (V) and non-vaccinated (NV) piglet subpopulations coming from V and NV sows in a PCV2 subclinically infected farm. Four hundred seventy-six piglets born from V or NV sows were further subdivided in a total of four groups: NV sows–NV pigs (NV–NV), NV sows–V pigs (NV–V); V sows–NV pigs (V–NV) and V sows–V pigs (V–V). Seventy-five pigs were randomly selected at the beginning of the trial from each group and they were bled at 4, 8, 12, 16, 21 and 25 weeks of age. All animals included in the trial were weighed at 4 and 25 weeks of age and their average daily weight gain (ADWG) was calculated. Serum samples obtained at different time points were used to assess PCV2 infection (viremia) and the level of antibodies by means of immunoperoxidase monolayer assay (IPMA) against this pathogen. IPMA titers (classified in high, medium or low) and PCR results (positive or negative) were analyzed using a multiple correspondence and K-means cluster analysis. According to these tests, animals included in the study were classified into the following four clusters: (1) 93 piglets that were viremic mainly from 12 to 25 weeks of age and with PCV2 antibody titers increasing over time; (2) 75 piglets with late PCV2 infection and seroconversion (later than 16 weeks of age); (3) 26 piglets with high but decreasing PCV2 antibody titers and low percentages of PCV2 PCR positive serum samples; and (4) 105 piglets with medium and high IPMA titers throughout the trial and sporadic PCR positive samples. The defined subpopulations of piglets were observed in all experimental groups (NV–NV, NV–V, V–NV and V–V) although in variable percentages. Thus, animals from clusters 1 and 2 belonged mainly to the NV–NV and V–NV groups and animals from clusters 3 and 4 were distributed mainly into the NV–V and V–V groups. Finally, the ADWG of pigs belonging to clusters 3 and 4 was significantly higher (p=0.02) than that of pigs belonging to clusters 1 and 2. Within each cluster, no statistically significant differences were found in ADWG between treatment groups.

Serological Survey of Porcine circovirus-2 in Captive Wild Boars (Sus scrofa) from Registered Farms of South and South-east Regions of Brazil.

This study aimed to survey captive wild boars for antibodies against Porcine circovirus-2 (PCV-2) in registered farms. Serum samples (n=1305) were collected from 90-day-old wild boars from 118 farms of the Brazilian South-east region, including the states of Minas Gerais and São Paulo, and South region, including the states of Paraná, Rio Grande do Sul and Santa Catarina. All herds (100%) presented reactive animals, in varying numbers and from low-to-high antibody titres, with the occurrence ranging from 82 to 89%. Considering farms, the average prevalence was of 84.9% (P<0.05) and ranged from 54.1 to 94.95%. Regarding the geographic regions studied, the prevalence was of 100%, with PCV2 antibodies detected in wild boars of all regions. This study provides the first evidence of PCV2 antibodies in captive wild boars in Brazil.

Specific and non‐specific immunity of piglets from sows fed diets containing specific fatty acids in field conditions

The transfer of passive immunity from sows to piglets is important and it is the first immune protection of the new born piglet. Improving sows immunity by adding immuno-stimulating product in sows diet can positively affect colostrum composition and transfer of immune molecules to piglets. The aim of the current study is to evaluate the benefit of a different solution, made of specific fatty acids from marine origin that have been used in human medicine for decades, for sows and piglets. Two trials were conducted in commercial farm, involving 240 sows at different periods of the year. Sows were divided in a control group, without supplementation, and a test group, supplemented with the feed additive from the 90th day of gestation to weaning. Sows body condition, piglets viability and growth were recorded. Milk immunoglobulin content was measured, as well as Aujeszky antibodies in sows and piglets blood as marker of specific immunity, and blood bactericidal activity, complement activity and lysozyme as markers of non specific immunity. No effect of the product was observed on piglets zootechnical criteria and specific immunity parameters but significant improvement of piglet non specific immunity, was observed. No difference was observed neither in the piglets blood PRRSV and PCV2 antibodies and viruses nor in Aujeszky antibodies. Blood complement activity seems to be an accurate indicator of immuno-stimulating additive efficiency. Giving alkyl-glycerol fatty acids to sows in late gestation and lactation can improve the passive immunity transfer to piglets.

Effect of porcine circovirus type 2a or 2b on infection kinetics and pathogenicity of two genetically divergent strains of porcine reproductive and respiratory syndrome virus in the conventional pig model

To determine differences in infection kinetics of two temporally and genetically different type 2 porcine reproductive and respiratory syndrome virus (PRRSV) isolates in vivo with and without concurrent porcine circovirus (PCV) type 2a or 2b infection, 62 pigs were randomly assigned to one of seven groups: negative controls (n=8); pigs coinfected with a 1992 PRRSV strain (VR-2385) and PCV2a (CoI-92-2a; n=9), pigs coinfected with VR-2385 and PCV2b (CoI-92-2b; n=9), pigs coinfected with a 2006 PRRSV strain (NC16845b) and PCV2a (CoI-06-2a; n=9), pigs coinfected with NC16845b and PCV2b (CoI-06-2b; n=9), pigs infected with VR-2385 (n=9), and pigs infected with NC16845b (n=9). Blood samples were collected before inoculation and at day post-inoculation (dpi) 3, 6, 9 and 12 and tested for the presence of PRRSV antibody and RNA, PCV2 antibody and DNA, complete blood counts, and interferon gamma (IFN-γ) levels. Regardless of concurrent PCV2 infection, VR-2385 initially replicated at higher levels and reached peak replication levels at dpi 6. Pigs infected with VR-2385 had significantly higher amounts of viral RNA in serum on both dpi 3 and dpi 6, compared to pigs infected with NC16845b. The peak of NC16845b virus replication occurred between dpi 9 and dpi 12 and was associated with a delayed anti-PRRSV antibody response in these pigs. PCV2 coinfection resulted in significantly more severe macroscopic and microscopic lung lesions and a stronger anti-PRRSV IgG response compared to pigs infected with PRRSV alone. This work further emphasizes in vivo replication differences among PRRSV strains and the importance of coinfecting pathogens.

Prolonged Detection of PCV2 and Anti-PCV2 Antibody in Oral Fluids Following Experimental Inoculation

The onset, level and duration of PCV2 and anti-PCV2 antibody in oral fluid were evaluated using samples collected from experimentally inoculated pigs for 98 days post-inoculation (DPI). Pigs (n = 24) were obtained at 3 weeks of age and randomly allocated to 4 treatment pens of 6 pigs each: (i) negative control group; (ii) inoculated with PCV2a (strain ISU 40895) on DPI 0; (iii) inoculated with PCV2a (strain ISU-40895) on DPI 0 and re-challenged at DPIs 35 and 70; (iv) inoculated with PCV2a (ISU-40895), PCV2b (PVG4072) and PCV2a (ISU-4838) on DPIs 0, 35 and 70, respectively. Serum was collected from each animal, and one oral fluid sample was collected from each pen (group) every other day from DPI 2 through DPI 14 and weekly through 98 DPI. Oral fluid samples were assayed for the presence of PCV2 by quantitative polymerase chain reaction (qPCR) and anti-PCV2 IgG, IgA and IgM antibody isotypes by enzyme-linked immunosorbant assay (ELISA). Serum was assayed for anti-PCV2 IgG by ELISA. Anti-PCV2 antibodies (IgG, IgM and IgA) were detected in oral fluid from experimentally inoculated pigs from DPI 14 with IgG and IgA clearly present at 98 DPI. PCV2 was detected in oral fluid samples from all pens of inoculated pigs at 2 DPI. Thereafter, PCV2 was detected in oral fluid throughout 98 DPI. Overall, the data indicated that PCV2 infection in swine is prolonged, persists in the face of an active antibody response and can be efficiently monitored using oral fluid specimens.

Immune response to type-2 porcine circovirus in weaned pigs

Sixteen crossbred barrows (Duroc × Landrace × Yorkshire) weaned at 28 days with an initial body weight of 5.12-8.64 kg and no antibodies to PCV2 were used in a 5-week trial to evaluate the immune response after intranasal inoculation with type-2 porcine circovirus. The percentage of peripheral blood ANAE+ T cells, PCV2 antibody titer, immunoglobulins, and serum IFN-\gamma, IL-2, and sIL-2R levels were determined. The results show that the percentage of peripheral blood ANAE+ T cells was notably higher in inoculated pigs 5 days post-inoculation (dpi) and significantly lower 21 dpi than in the control group. The anti-PCV2 titer in the inoculated group was significantly higher than that in the control group 14 dpi. The immunoglobulin profile of the 2 groups also differed. The IFN-\gamma level in the inoculated group decreased significantly from 7 to 28 dpi, as compared with the control group. The results suggest that PCV2 challenge results in an immune system response.

Genetic background influences pig growth rate responses to porcine circovirus type 2 (pcv2) vaccines (2008)

Pigs were identified as potential test pigs at birth and ear tagged for identification. Characteristics including litter, genetic background, gender, and birth weight were recorded and used in allotting PCV2 vaccine treatment groups. Pigs were vaccinated according to label dose with a 2-dose commercial PCV2 vaccine (Circumvent PCV, Intervet Inc., Millsboro, DE) at weaning (d 0) and again 14 d later. Vaccinated and control pigs were comingled within the same pen for the duration of the study. Pigs were individually weighed on d 0, 40, and 130 to measure growth rate. Backfat and loin depth were measured on d 130 by using real-time ultrasound. Blood was collected on d 0, 40, and 130 for indirect fluorescent antibody measurement of PCV2 antibodies and polymerase chain reaction (PCR) analysis for determination of PCV2 virus load. By d 130, vaccinates were heavier (P < 0.01) than controls. However, the magnitude of the weight difference between control and vaccinates was almost 4 times greater in the A×A pigs than in the B×B pigs (P < 0.05). On the basis of growth performance, the different genetic backgrounds responded differently to the PCV2 vaccination even though they were comingled in the same pen. In the 2 pure-line populations, even the best performing portion of the population appeared to benefit from vaccination, suggesting that growth performance of most pigs is being affected by PCV2 infection.

Porcine circovirus type 2 antibody detection in backyard pigs from Mexico City

PCV2 antibodies have been found in pigs from all continents. However, this finding has been mainly studied in domestic swine reared under intensive production conditions. Mexico City, with a human population over 19 million in 2005, has both urban and rural areas. The pig production in its rural area is based on small family backyard farms. Taking into account this rather unique form of rearing pigs, the objective of this study was to determine the seroprevalence in backyard pigs from the rural area of Mexico City. A total of 695 backyard pig serum samples from 108 small family farms belonging to seven municipal areas were studied by immunoperoxidase monolayer assay technique. One hundred six out of the 108 family farms (98.14%) had at least one positive serum sample. On the other hand, 136 (19.57%), 264 (37.99%) and 248 (34.82%) pigs had low, intermediate and high titres to PCV2, respectively. Only 53 samples (7.63%) were negative for PCV2 antibodies. No apparent differences in antibody titre groups were observed among backyard pigs from the different municipal areas. In conclusion, the present study, the first one performed in this kind of extensively produced pigs, indicates that PCV2 is ubiquitous in backyard pigs from Mexico City.