Reduced lung lesions in pigs challenged 25 weeks after the administration of a single dose of Mycoplasma hyopneumoniae vaccine at approximately 1 week of age

Long-term follow-up of Mycoplasma hyopneumoniae-specific immunity in vaccinated pigs

Mycoplasma hyopneumoniae is the primary agent of enzootic pneumonia in pigs. To minimize the economic losses caused by this disease, M. hyopneumoniae vaccination is commonly practiced. However, the persistence of M. hyopneumoniae vaccine-induced immunity, especially the cell-mediated immunity, till the moment of slaughter has not been investigated yet. Therefore, on two commercial farms, 25 pigs (n = 50) received a commercial bacterin intramuscularly at 16 days of age. Each month, the presence of M. hyopneumoniae-specific serum antibodies was analyzed and the proliferation of and TNF-α, IFN-γ and IL-17A production by different T cell subsets in blood was assessed using recall assays. Natural infection with M. hyopneumoniae was assumed in both farms. However, the studied pigs remained M. hyopneumoniae negative for almost the entire trial. Seroconversion was not observed after vaccination and all pigs became seronegative at two months of age. The kinetics of the T cell subset frequencies was similar on both farms. Mycoplasma hyopneumoniae-specific cytokine-producing CD4⁺CD8⁺ T cells were found in blood of pigs from both farms at one month of age but decreased significantly with increasing age. On the other hand, T cell proliferation after in vitro M. hyopneumoniae stimulation was observed until the end of the fattening period. Furthermore, differences in humoral and cell-mediated immune responses after M. hyopneumoniae vaccination were not seen between pigs with and without maternally derived antibodies. This study documents the long-term M. hyopneumoniae vaccine-induced immune responses in fattening pigs under field conditions. Further research is warranted to investigate the influence of a natural infection on these responses.

Vaccination Failures in Pigs-The Impact of Chosen Factors on the Immunisation Efficacy

Infectious diseases that often lead to economic losses still pose a severe problem in the pig production sector. Because of increasing restrictions on antibiotic usage, vaccines may become one of the major approaches to controlling infectious diseases; much research has proved that they could be very efficient. Nevertheless, during their life, pigs are exposed to various factors that can interfere with vaccination efficacy. Therefore, in the present paper, we reviewed the influence of chosen factors on the pig immunisation process, such as stress, faecal microbiota, host genetics, the presence of MDAs, infections with immunosuppressive pathogens, and treatment with antibiotics and mycotoxins. Many of them turned out to have an adverse impact on vaccine efficacy.

Impact of maternally derived immunity on immune responses elicited by piglet early vaccination against the most common pathogens involved in porcine respiratory disease complex

Background

Newborn piglets can trigger an elementary immune response, but the acquirement of specific antibodies and/or cellular immunity against pathogens before they get infected post-natally is paramount to preserve their health. This is especially important for the pathogens involved in porcine respiratory disease complex (PRDC) as they are widespread, fairly resistant at environment, and genetically variable; moreover, some of them can cause intrauterine/early life infections.

Main body

Piglet protection can be achieved by either passive transfer of maternal derived immunity (MDI) and/or actively through vaccination. However, vaccinating piglets in the presence of remaining MDI might interfere with vaccine efficacy. Hence, the purpose of this work is to critically review the putative interference that MDI may exert on vaccine efficacy against PRDC pathogens. This knowledge is crucial to design a proper vaccination schedule.

Conclusion

MDI transferred from sows to offspring could potentially interfere with the development of an active humoral immune response. However, no conclusive interference has been shown regarding performance parameters based on the existing published literature.

Limited impact of influenza A virus vaccination of piglets in an enzootic infected sow herd

Recent studies have questioned the effect of maternal derived antibodies (MDAs) to protect piglets against infection with influenza A virus (IAV). The lack of protection against IAV infections provided by MDAs has encouraged alternative vaccination strategies targeting young piglets in an attempt to stimulate an early antibody response. There is a lack of studies documenting the efficacy of piglet vaccination. In the present study, we monitored a group of vaccinated and non-vaccinated piglets in a Danish sow herd that initiated piglet vaccination with ¼ dose of an inactivated swine influenza vaccine at the time of castration (day 3-4). A total of 160 piglets from 11 sows were included and either vaccinated with 0.5 mL inactivated swine influenza vaccine or sham-vaccinated. From week 0 until week 6, all included piglets were clinically examined and nasal swapped once per week and weighed at weeks 0, 3 and 6. Blood samples were collected from sows at week 0 and from piglets at week 3. Vaccination of piglets had limited effect on clinical signs, body weight, antibody development and viral shedding, within the first 6 weeks of life. At least 50% of all pigs of each treatment group tested positive for IAV at week 2, and very early onset of IAV shedding was observed. In total, 18 pigs were IAV positive in nasal swabs for more than one consecutive sampling time indicating prolonged shedding and 14 pigs were IAV positive with negative samplings in between indicating re-infection with the same IAV strain.

Use of trachea-bronchial swab qPCR testing to confirm Mycoplasma hyopneumoniae seropositivity in an SPF breeding herd

Background

A dedicated program to monitor for freedom of several economically important diseases is present within most of the breeding companies that currently deliver high health breeding animals to their customers. Serology is therefore the preferential approach in order to screen for most of these diseases, including Mycoplasma hyopneumoniae (M. hyopneumoniae). However, in case of positive serology, further decisions on farm health status and the related consequences should be based on additional confirmation tests.

Case presentation

The current case report demonstrates that tracheo-bronchial swab (TBS) sampling is a suitable alternative to confirm a suspect M. hyopneumoniae-seropositive situation. A Central-European SPF herd was shown positive (90% positive, 10% suspect; n = 10) for M. hyopneumoniae using the conventional ELISA serology (Idexx HerdChek Mhyo ELISA) and a second ELISA test (IDEIA™ Mycoplasma hyopneumoniae EIA kit) did not exclude potential M. hyopneumoniae infection (10% positive, 70% suspect; n = 10). Further follow-up remained inconclusive on both tests. Throughout the entire monitoring period of 6 months, no coughing, necropsy lesions or lesions at slaughter could be detected which could confirm the M. hyopneumoniae health status. TBS sampling was used to confirm the health status for M. hyopneumoniae. In total, 162 samples were collected at different ages (n = 18 per age category): piglets at 3-6-9-12 and 15 wks of age, rearing gilts at 18-21-24 and 27 weeks of age. Collected TBS samples were negative for M. hyopneumoniae until 15 wks of age, but rearing gilts were highly M. hyopneumoniae-positive from 18 wks onwards with 87-100% M. hyopneumoniae-positive animals and PCR Ct-values between 25 and 33.

Conclusions

This case report shows that collection of TBS samples to confirm the M. hyopneumoniae infection status of a breeding herd was able to provide additional information to serology in order to make crucial decisions concerning health management and eradication strategies within the breeding herd.

Field study on the safety and efficacy of intradermal versus intramuscular vaccination against Mycoplasma hyopneumoniae

The present study compares the safety and efficacy of a needle-free, intradermal Mycoplasma hyopneumoniae vaccine to an intramuscular one. 420 piglets (21+3 days of age) were randomly assigned to two vaccination groups (intradermal vaccination V1 (n=138), intramuscular vaccination V2 (n=144)) and one unvaccinated control group (CG, n=138). As safety parameters clinical observations, local injection site reactions (ISR) and rectal temperatures were assessed. Average daily weight gain (ADWG) and pneumonic lung lesions (LL) were measured as efficacy parameters. ISRs were minor in V1. After both vaccinations, no adverse impact on appetite was observed and mean rectal temperatures remained within physiological range. ADWG during the fattening period was significantly higher in vaccinated groups (V1: 913.4 g, V2: 924.5 g) compared with CG (875.6 g). No differences in ADWG were observed between V1 and V2. Vaccinated pigs had a significantly reduced mean extent of LL compared with CG. V1 was superior in reducing the extent and prevalence of LL compared with V2. These results reveal that a needle-free intradermal vaccination is safe and efficacious in reducing both the prevalence and extent of lung lesions, as well as in improving performance parameters, in a farrow-to-finish farm with a late onset of M hyopneumoniae infection.

Assessment of litter prevalence of Mycoplasma hyopneumoniae in preweaned piglets utilizing an antemortem tracheobronchial mucus collection technique and a real-time polymerase chain reaction assay

The swine industry currently lacks validated antemortem methods of detecting baseline herd prevalence of Mycoplasma hyopneumoniae. The focus of our study was to evaluate alternative antemortem detection techniques and to determine baseline litter prevalence in preweaned pig populations utilizing the selected technique and a real-time polymerase chain reaction (qPCR) assay. Preliminary data was analyzed on weaned piglets with evidence of respiratory disease ( n = 32). Five sample types (antemortem nasal swab, tracheobronchial mucus, postmortem deep airway swab, bronchoalveolar lavage, and lung tissue) were collected from each pig. Individual samples were tested for M. hyopneumoniae using qPCR. Compared to nasal swabs, tracheobronchial mucus demonstrated higher test sensitivity ( P < 0.0001). Tracheobronchial mucus was collected from apparently healthy preweaned piglets ( n = 1,759; sow farms 1–3) and preweaned piglets exhibiting signs of respiratory disease ( n = 32; sow farm 4), ranging in age from 12 to 25 days. Samples from sow farms 1–3 were pooled into 2 groups of 5 per litter ( n = 360 pools from 180 litters), and qPCR was utilized to analyze each pool. A qPCR-positive result, threshold cycle <37, from either pool designated the litter positive for M. hyopneumoniae. Two out of 180 litters revealed a positive result (1.1%). Individual qPCR assays were run on the samples collected from sow farm 4. Five out of 30 samples revealed a positive result (16.7%). Tracheobronchial mucus collection in combination with qPCR is a sensitive antemortem sampling technique that can be used to estimate the prevalence of M. hyopneumoniae in preweaned pigs, thus providing insight into the infection dynamics across the entire farrow-to-finish process.

Vaccination inhibits TLR2 transcription via suppression of GR nuclear translocation and binding to TLR2 promoter in porcine lung infected with Mycoplasma hyopneumoniae

Toll-like receptors (TLRs) and glucocorticoid receptor (GR) act respectively as effectors of innate immune and stress responses. The crosstalk between them is critical for the maintenance of homeostasis during the immune response. Vaccination is known to boost adaptive immunity, yet it remains elusive whether vaccination may affect GR/TLR interactions following infection. Duroc×Meishan crossbred piglets were allocated to three groups. The control group (CC) received neither vaccination nor infection; the non-vaccinated infection group (NI) was artificially infected intratracheally with Mycoplasma hyopneumoniae (M. hyopneumoniae); while the vaccinated, infected group (VI) was vaccinated intramuscularly with inactivated M. hyopneumoniae one month before infection. The clinical signs and macroscopic lung lesions were significantly reduced by vaccination. However, vaccination did not affect the concentration of M. hyopneumoniae DNA in the lung. Serum cortisol was significantly decreased in both NI and VI pigs (P<0.01), but only VI pigs demonstrated significantly diminished nuclear GR content. TLRs 1-10 were all expressed in lung, among which TLR2 was the most abundant and was significantly up-regulated (P<0.05) in NI pigs, but not in VI pigs. Accordingly, GR binding to the GR response element on TLR2 promoter was significantly increased (P<0.05) in NI pigs, but not in VI pigs. These results suggest that the inhibition of GR nuclear translocation and binding to the TLR2 promoter, which results in diminished TLR2 expression, is associated with the protective effect of vaccination on M. hyopneumoniae-induced lung lesions in the pig.

Mycoplasma hyopneumoniae: from disease to vaccine development

Mycoplasma hyopneumoniae is the etiological agent of swine enzootic pneumonia (EP), a disease that affects swine production worldwide. Vaccination is the most cost-effective strategy for the control and prevention of the disease. Despite efforts to control M. hyopneumoniae infection, significant economic losses in pig production continue to occur. The results of genome-based research have the potential to help understand the biology and pathogenesis of M. hyopneumoniae, and contribute to the development of more effective vaccines and diagnostic tests. In this review, the characteristics of M. hyopneumoniae related to pathogenesis and control measures will be discussed. Special emphasis will be placed on vaccination strategies that have been proposed with the use of reverse vaccinology approaches.

Vaccination of piglets up to 1 week of age with a single-dose Mycoplasma hyopneumoniae vaccine induces protective immunity within 2 weeks against virulent challenge in the presence of maternally derived antibodies

Enzootic pneumonia, resulting from infection with Mycoplasma hyopneumoniae, is of considerable economic importance to the pig industry and normally is controlled through active vaccination of piglets. We have demonstrated that administration of an inactivated Mycoplasma hyopneumoniae vaccine to piglets less than 1 week old is efficacious under field conditions and reduces the level of lung lesions observed in comparison to that in control pigs. Here, the results of two separate studies, one in piglets with and the second one in piglets without maternal antibodies, conducted to satisfy the requirements of the European Pharmacopoeia (monograph no. 07/2009:2448), are reported. Piglets received either minimal titer Suvaxyn MH-One or saline at less than 1 week of age and were challenged with Mycoplasma hyopneumoniae 2 weeks later. The number of lung lesions was recorded 4 weeks after challenge, and bronchial swab and lung tissue specimens were analyzed for quantification of Mycoplasma hyopneumoniae DNA. In the presence and absence of maternal antibodies, vaccination of piglets at less than 1 week of age was efficacious, with vaccinated piglets having significantly lower percentages of lung with lesions and lower Mycoplasma hyopneumoniae counts detected in bronchial swab and lung tissue specimens at necropsy. In conclusion, the vaccination of piglets at 1 week of age with Suvaxyn MH-One is efficacious in the presence of high levels of maternal antibodies.

Porcine circovirus type 2 and its associated diseases in Korea

This review describes the characterization of porcine circovirus type 2 (PCV2), the field situation of porcine circovirus-associated disease (PCVAD) and the PCV2 vaccine in Korea. PCVAD has been considered the most devastating disease in Korean livestock history since its first outbreak in 1999. Postweaning multisystemic wasting syndrome (PMWS) and porcine respiratory disease complex (PRDC) are the most common clinical forms of PCVAD. Interestingly, only PCV2b strains have been isolated from pigs with PMWS since 2005, but only PCV2a strains were isolated from pigs with PMWS in 2000 to 2001. Clinically, PMWS is divided into two stages: early and late. Early PMWS primarily occurs in pigs between 4 and 8 weeks of age. This form is a typical presentation of PMWS and is characterized clinically by wasting, decreased weight gain, enlarged lymph nodes, and dyspnea. Late PMWS primarily occurs in pigs between 8 and 12 weeks of age. The main clinical manifestation is diarrhea, which is often accompanied by salmonellosis coinfection. In recent years, the PCVAD disease pattern has slightly changed. The occurrence of PMWS has decreased while PRDC cases are increasing in frequency.

Production and characterization of recombinant transmembrane proteins from Mycoplasma hyopneumoniae

Mycoplasma hyopneumoniae is the etiological agent of swine enzootic pneumonia (EP), a chronic respiratory disease which causes significant economic losses to the swine industry worldwide. More efficient strategies for controlling this disease are necessary. In this study, we cloned17 genes coding for transmembrane proteins from M. hyopneumoniae, among which six were successfully expressed in Escherichia coli and had their immunogenic and antigenic properties evaluated. All proteins were immunogenic in mice and sera from naturally infected pigs reacted with the recombinant proteins, suggesting that they are expressed during infection. These antigens may contribute for the development of new recombinant vaccines and diagnostic tests against EP.

Comparative efficacy of commercial Mycoplasma hyopneumoniae and porcine circovirus 2 (PCV2) vaccines in pigs experimentally infected with M. hyopneumoniae and PCV2

The efficacies of two commercial Mycoplasma hyopneumoniae bacterins and porcine circovirus 2 (PCV2) vaccines were compared in conventional pigs immunized at different ages based on humoral response, pathological observation, and growth performance from birth to finishing (175 days of age) using a M. hyopneumoniae and PCV2 co-infection challenge model. One-week-old pigs (n=110) were randomly assigned to five groups: three vaccinated and challenged (VC), and one each of non-vaccinated and challenged (NVC) and negative control. A significant difference was found in the number of genomic copies of M. hyopneumoniae in nasal swabs and PCV2 in serum samples, the average daily weight gain (gram/pig/day) between 63 and 133 dpi, gross and histopathological lung lesion scores, histopathological lymph node lesion scores, and the immunohistochemical analysis of PCV2 among the three VC groups. The single dose schedule for M. hyopneumoniae bacterins and PCV2 vaccines have the advantages of (i) improving daily weight gain (122.4%) and slaughter weight (120.5%), and (ii) reducing the incidence of clinical signs and lung and lymph node lesions.