Preliminary evidence of age-dependent clinical signs associated with porcine circovirus 2b in experimentally infected CH3/Rockefeller mice

Effects of liraglutide on sperm characteristics and fertilization potential following experimentally induced diabetes in mice

The current study was conducted to analyze the dose-dependent effects of liraglutide against the diabetes-induced detrimental impact on sperm parameters and fertilization potential. For this purpose, 42 adult male mice were randomly divided into control (with no intervention) and experimental groups. Next, the experimental group was subdivided into diabetic, 1.20 mg kg^-1 liraglutide-received diabetic, 1.80 mg kg^-1 liraglutide-received diabetic, 1.20 mg kg^-1 liraglutide-received non-diabetic and 1.80 mg kg^-1 liraglutide-received non-diabetic groups. All chemicals were administrated subcutaneously. Following 42 days, the animals were euthanized, and sperm samples were collected. The sperm count, motility, viability, DNA integrity, and maturity were analyzed and compared between groups. Moreover, the sperm fertilization potential was investigated by in vitro fertilization (IVF). For this purpose, the preimplantation embryo development at 2-cell, 4-cell, morula, and blastocyst stages was investigated and compared. Observations revealed that diabetes significantly diminished sperm count, motility, viability, chromatin condensation, and DNA integrity percentages versus a control group. On the other hand, 1.20 mg kg^-1 and 1.80 mg kg^-1 of liraglutide did not improve sperm motility and viability, while ameliorated sperm count and chromatin condensation and DNA integrity in diabetic animals. The diabetic animals represented diminished preimplantation embryo development, which was not altered in liraglutide-received groups. In conclusion, at least in administrated doses, liraglutide could not improve the sperm viability and motility and, via this mechanism, could not induce an appropriate/beneficial effect on IVF outcome.

Risk Assessment for Use of a Porcine Circovirus-Contaminated Reagent in a Barrier Maintained Rodent Colony

A proposal for the use of porcine pancreatic elastase (PPE) to develop a mouse model of pulmonary emphysema raised concerns about introducing contaminating porcine viruses into our barrier facility. Porcine Circovirus (PCV) is a known contaminant of vaccines and cell cultures that have been exposed to porcine-derived reagents. Endemic infection of PCV3 in laboratory mice has been reported, and some evidence supports natural PCV infection in wild mice. PPE samples from 2 different vendors tested positive for DNA from both PCV2 and 3. To allow model development with these reagents to proceed, we developed a protocol that would meet scientific objectives, minimize exposure of mice, and provide information on the potential for the virus to spread. Five d after BALB/c mice received intralaryngeal administration of PPE, lungs were harvested and analyzed for evidence of disease. Tissues from other major organs were submitted to test for disseminated PCV2 and 3 DNA. Similarly, tissues (including lungs) from direct contact nude sentinel mice were analyzed for the presence of the virus. To evaluate the possibility of endemic PCV2/3 infection, we also surveyed non-porcine reagent exposed mice on other studies. PCV2 and 3 was not detected in any of the tissues submitted. Although this study provided no evidence of infection and transmission of PCV2/3 from the contaminated PPE sample over the 5 d study, further work is needed to understand the risks and impact of introducing PCV contaminated cells or reagents into barrier maintained rodent colonies.

Incorporation of a truncated form of flagellin (TFlg) into porcine circovirus type 2 virus-like particles enhances immune responses in mice

Background

Porcine circovirus type 2 (PCV2) is an economically important pathogen in the swine industry worldwide. Vaccination remains the principal tool to control PCV2-associated diseases (PCVADs). Current vaccines do not eliminate viral shedding in the environment. To enhance the efficacy of PCV2 vaccines, recombinant virus-like particles (VLPs) of PCV2 were generated by fusing a truncated form of flagellin FliC (TFlg: 85-111aa) with the PCV2 capsid protein (Cap).

Results

The recombinant proteins were expressed in Escherichia coli and detected using Western blotting. The abilities of the recombinant proteins to assemble into VLPs were observed under transmission electron microscopy (TEM). The protective immune responses of recombinant VLPs were further evaluated by immunization of mice. The results showed that insertion of TFlg into C terminal of the Cap protein did not affect the formation of VLPs and boosted both humoral and cellular immune responses in mice. After a challenge with PCV2, in the Cap-TFlg vaccinated group, viremia was milder and viral loads were lower as compared with those in the Cap vaccinated group.

Conclusion

These results suggest that recombinant VLPs of PCV2 containing a TFlg adjuvant can be used as a promising PCV2 vaccine candidate.

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.

Interleukin-10 Promotes Porcine Circovirus Type 2 Persistent Infection in Mice and Aggravates the Tissue Lesions by Suppression of T Cell Infiltration

Interleukin (IL)-10, as a key anti-inflammatory cytokine, increases during porcine circovirus type 2 (PCV2) infection, but the role of IL-10 in the process remains to be defined. In the present study, using an IL-10 deficient mice model, we found that IL-10 deficiency prevented the reduction of splenic lymphocytes (CD45⁺ cells) induced by PCV2 and promoted CD4⁺ and CD8⁺ T cell infiltration in lungs through inducting more T cell chemokines (CCL3, CXCL9, and CXCL10). Simultaneously, PCV2 infection induced a significant increase of pro-inflammatory cytokines and PCV2-specific antibodies in IL-10 deficient mice than in wild-type mice, resulting in a lower viral load in lung and a milder lung lesion in IL-10 deficient mice relative to wild-type mice. Moreover, the amounts of pulmonary CD4⁺ and CD8⁺ T cells were all inversely correlated with the lung lesions, as well as the viral load of PCV2. These results demonstrate that PCV2 infection employs IL-10 to block the transfer of T cells to the lungs of mice, and IL-10 attenuates the production of pro-inflammatory cytokines and PCV2-specific antibodies. The lack of T cell infiltration, pro-inflammatory cytokines, and PCV2-specific antibodies promote PCV2 replication, leading to a more severe lung lesion in mice.

Mouse models of porcine circovirus 2 infection

PCV2 is considered the main pathogen of porcine circovirus diseases and porcine circovirus-associated diseases (PCVD/PCVAD). However, the exact mechanism underlying PCVD/PCVAD is currently unknown. Mouse models of PCV2 are valuable experimental tools that can shed light on the pathogenesis of infection and will enable the evaluation of antiviral agents and vaccine candidates. In this review, we discuss the current state of knowledge of mouse models used in PCV2 research that has been performed to date, highlighting their strengths and limitations, as well as prospects for future PCV2 studies.