Intramammary immunization with ultraviolet-killed Escherichia coli shows partial protection against late gestation intramammary challenge with a homologous strain

Induction of attenuated Nocardia seriolae and their use as live vaccine trials against fish nocardiosis

Nocardia seriolae, a Gram-positive facultative intercellular pathogen, has been identified as the causative agent of fish nocardiosis, causing substantial mortality and morbidity of a wide range of fish species. Looking into that fact, the effective vaccine against this pathogen is urgently needed to control the significant losses in aquaculture practices. In order to induct attenuated strains for developing the potential live vaccines, the mutagenic N. seriolae strain S-250 and U-20 were obtained from wild-type strain ZJ0503 through continuous passaging and ultraviolet (UV) irradiation, respectively. Additionally, the biological characteristic, virulence, stability, mediating immune response and supplying protective efficacy to hybrid snakehead of the S-250 and U-20 strains were determined in the present study. The results showed that U-20 strain displayed dramatic changes in morphological characteristic and significant decreased in the virulence to hybrid snakehead, while that of S-250 strain had no obvious different in comparison to ZJ0503 strain. When hybrid snakehead were intraperitoneally injected with ZJ0503, S-250 and U-20 strains at their respective sub-clinical dosage, the non-specific immunity parameters (serum LYZ, POD, ACP, AKP and SOD activities), specific antibody (IgM) titers production and immune-related genes (CC1, CC2, IL-1β, IL-8, TNFα, IFNγ, MHCIα, MHCIIα, CD4, CD8α, TCRα and TCRβ) expression were up-regulated, indicating that they were able to trigger humoral and cell-mediated immune responses. Furthermore, the protective efficacy in hybrid snakehead after vaccination with ZJ0503, S-250 and U-20 strains, in terms of relative percentage survival (RPS), were 28.85%, 56.89% and 89.65% respectively. Taken together, two attenuated N. seriolae strains S-250 and U-20 were obtained successfully and they could elicit strong immune response and supply protective efficacy to hybrid snakehead against N. seriolae, which suggested that these two attenuated strains were the potential candidates for live vaccine development to control fish nocardiosis in aquaculture.

Escherichia coli Mastitis in Dairy Cattle: Etiology, Diagnosis, and Treatment Challenges

Bovine mastitis is an inflammation of the udder tissue parenchyma that causes pathological changes in the glandular tissue and abnormalities in milk leading to significant economic losses to the dairy industry across the world. Mammary pathogenic Escherichia (E.) coli (MPEC) is one of the main etiologic agents of acute clinical mastitis in dairy cattle. MPEC strains have virulence attributes to resist the host innate defenses and thrive in the mammary gland environment. The association between specific virulence factors of MPEC with the severity of mastitis in cattle is not fully understood. Furthermore, the indiscriminate use of antibiotics to treat mastitis has resulted in antimicrobial resistance to all major antibiotic classes in MPEC. A thorough understanding of MPEC’s pathogenesis and antimicrobial susceptibility pattern is required to develop better interventions to reduce mastitis incidence and prevalence in cattle and the environment. This review compiles important information on mastitis caused by MPEC (e.g., types of mastitis, host immune response, diagnosis, treatment, and control of the disease) as well as the current knowledge on MPEC virulence factors, antimicrobial resistance, and the dilemma of MPEC as a new pathotype. The information provided in this review is critical to identifying gaps in knowledge that will guide future studies to better design diagnostic, prevent, and develop therapeutic interventions for this significant dairy disease.

Colonization and local host response following intramammary Staphylococcus chromogenes challenge in dry cows

Although extensive research has been performed on bovine non-aureus staphylococci (NAS), several aspects such as bacteria-host interaction remain largely unstudied. Moreover, only a few mastitis pathogen challenge studies in cows have been conducted in the dry period, an important period that allows intramammary infection (IMI) to cure and new IMI to occur. We challenged 16 quarters of 4 Holstein Friesian cows at dry off with 100; 100 000 or 10 000 000 CFU of the udder-adapted S. chromogenes IM strain. Four quarters from one cow served as negative controls. Internally sealed quarters remained untouched, whereas non-sealed quarters were sampled 3 times during the dry period. After parturition, colostrum and daily milk samples were taken during the first week of lactation of all quarters. In total, 8 quarters appeared to be colonized, since S. chromogenes IM was recovered at least once during the experiment, as substantiated using Multilocus Sequence Typing. S. chromogenes IM shedding was highest in dry quarters inoculated with 10 000 000 CFU. Colonized quarters had the highest quarter somatic cell count (qSCC) in early lactation. Inoculated quarters (both colonized and non-colonized) had lower IL-6 and IL-10 concentrations in the dry period, whilst IFN-γ levels tended to be higher in colonized quarters compared to non-inoculated quarters. Also, IgG2 levels were higher in inoculated compared to non-inoculated quarters and the IgG2/IgG1 ratio was on average above 1. To conclude, we showed that dry quarters can be colonized with S. chromogenes IM, resulting in a shift towards a Th1 response in late gestation and early lactation characterised by an increased IgG2 concentration. However, further research is needed to confirm our findings.

Intramammary Immunisation Provides Short Term Protection Against Mannheimia haemolytica Mastitis in Sheep

Mastitis affects both dairy and meat/wool sheep industries with losses due to reductions in milk quality and quantity, increased treatment costs and restricted lamb growth. Effective vaccines would be important tools for mastitis control. However, the development of vaccines against mastitis has proved challenging due to the failure to target protective immunity to the mammary gland. In order to target responses to the mammary gland, this study tested whether local administration directly into the gland through the teat canal or in the udder skin confers protection against an intramammary infection. In this study, we tested a vaccine that confers protection against respiratory disease caused by Mannheimia haemolytica to determine if it also protects against intramammary infection by the same organism. No evidence of protection was observed in animals that received a subcutaneous immunisation in the udder skin, however, intramammary immunisation provided almost complete protection against an experimental challenge administered 7 days post immunisation but not if the challenge was delivered 14 days post immunisation. To investigate further the nature of this variation in response, the somatic cell count and concentration of cytokines Interleukin-1β, Interleukin-10 and Interleukin-17A was determined in milk over the course of each study. Intramammary immunisation induced an inflammatory response within the mammary gland, characterised by increases in SCC and in the production of cytokines IL-1β, IL-10, and IL-17A. This response was similar to that observed in un-vaccinated control animals post challenge. The SCC and cytokine levels had returned to levels comparable with un-vaccinated controls prior to challenge at both 7 and 14 days post immunisation. The transient nature of the protective effect is consistent with the priming of an innate antibacterial response within the mammary gland which provides protection against challenge at 7 days but is diminished by 14 days post-vaccination. Further studies are planned to determine the nature of the innate immune mechanisms associated with the protective effect described here to determine whether it may be exploited to improve ruminant udder health.

Th17-related mammary immunity, but not a high systemic Th1 immune response is associated with protection against E. coli mastitis

Vaccination against bovine mastitis lags behind despite high demand from the dairy industry and margin for efficacy improvement. We previously compared two immunization protocols against E. coli using either only the intramuscular route or a combination of intramuscular and mammary ductal routes, also known as 'prime and pull' strategy. A homologous mammary challenge during the memory phase showed that immunization favorably modified the mastitis course, notably in locally immunized cows in comparison to intramuscular and control adjuvant-only groups. Here, we performed whole-blood profiling through RNA-seq transcriptome and plasma cytokine 15-plex analyses at time points of the E. coli mastitis that showed significant clinical and laboratory differences among the groups. Diminished production of inflammatory cytokines and increased IFNγ were detected in the blood of immunized cows, where a T lymphocyte activation profile was evidenced at 12-h post infection. Acute phase neutropenia was less severe in these cows, and pathways related to neutrophil diapedesis and monocyte activation were also present. Furthermore, three intramammary-immunized cows showing faster healing and shorter mastitis duration had gene profiles that differed from their counterparts, but without any clue for the mastitis susceptibility difference. Inasmuch, when gene expression of CD4 T cells was assessed in mammary tissue, enrichment of IL-17-associated pathways was identified in the quarters of intramammary-immunized cows not only after challenge but also in the control quarters that were not infected. These findings indicate that local immunization mobilizes protective mechanisms that rely on the settlement of type 3 immunity-related CD4 T cells prior to infection.

Causes, types, etiological agents, prevalence, diagnosis, treatment, prevention, effects on human health and future aspects of bovine mastitis

Mastitis is among the most common and challenging diseases of dairy animals. It is an inflammation of udder tissues due to physical damage, chemical irritation, or infection caused by certain pathogens. Bovine mastitis has been known for ages, but its complex etiology and multi-factorial nature make it difficult to control. Mastitis may have a negative impact on human health by inducing antibiotic-resistant pathogens that may spread, which is threatening. Researchers are continuously struggling to devise suitable methods for mastitis control. Management strategies are mainly focused on disease prevention by farm management which includes proper hygiene, trained staff to monitor minor changes in the udder or milk, and better diagnostic and treatment methods. New technologies which have the potential to unravel this complicated disease include improved diagnostic tools, based on advanced genomics or proteomics, prevention, based on vaccines and immune modulators, and metabolic products of probiotics such as bacteriocins and gene therapy.

Pathogen-specific responses in the bovine udder. Models and immunoprophylactic concepts

Bovine mastitis is a disease of major economic effects on the dairy industry worldwide. Experimental in vivo infection models have been widely proven as an effective tool for the investigation of pathogen-specific host immune responses. Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) are two common mastitis pathogens with an opposite clinical outcome of the disease. E. coli and S. aureus have proven to be valid surrogates to model clinical and subclinical mastitis respectively. Contemporary transcriptome profiling studies demonstrated that the transcriptomic response in the teat reflects the course of pathogen-specific mastitis, being ultimately determined by the immune response of the mammary epithelial cells. After an experimental in vivo challenge, E. coli induces a vigorous early transcriptional response in udder tissue being quantitatively and - notably - qualitatively distinct from the much weaker response against an S. aureus infection. E. coli mastitis models proved that the local response in the infected udder quarters is accompanied by a response in non-infected neighbouring udder quarters modulating systemically their immune responsiveness. Immunomodulation of the udder was investigated in animal models. Pathophysiological consequences were studied after intramammary administration of cytokines, chemokines, growth factors, steroidal anti-inflammatory drugs, or priming of tissue resident cells with pathogen-derived molecules. The latter approaches resulted only in a temporal protection of the udder, reducing transiently the risk of infection but sustained lowering of the severity of an eventually occurring mastitis. They offer an alternative to vaccination trials, which over decades also did not yield protection against new infections.

An update on environmental mastitis: Challenging perceptions

Environmental mastitis is the most common and costly form of mastitis in modern dairy herds where contagious transmission of intramammary pathogens is controlled through implementation of standard mastitis prevention programmes. Environmental mastitis can be caused by a wide range of bacterial species, and binary classification of species as contagious or environmental is misleading, particularly for Staphylococcus aureus, Streptococcus uberis and other streptococcal species, including Streptococcus agalactiae. Bovine faeces, the indoor environment and used pasture are major sources of mastitis pathogens, including Escherichia coli and S. uberis. A faeco-oral transmission cycle may perpetuate and amplify the presence of such pathogens, including Klebsiella pneumoniae and S. agalactiae. Because of societal pressure to reduce reliance on antimicrobials as tools for mastitis control, management of environmental mastitis will increasingly need to be based on prevention. This requires a reduction in environmental exposure through bedding, pasture and pre-milking management and enhancement of the host response to bacterial challenge. Efficacious vaccines are available to reduce the impact of coliform mastitis, but vaccine development for gram-positive mastitis has not progressed beyond the "promising" stage for decades. Improved diagnostic tools to identify causative agents and transmission patterns may contribute to targeted use of antimicrobials and intervention measures. The most important tool for improved uptake of known mastitis prevention measures is communication. Development of better technical or biological tools for management of environmental mastitis must be accompanied by development of appropriate incentives and communication strategies for farmers and veterinarians, who may be confronted with government-mandated antimicrobial use targets if voluntary reduction is not implemented.

Local immunization impacts the response of dairy cows to Escherichia coli mastitis

Current vaccines to Escherichia coli mastitis have shown some albeit limited efficacy. Their mode of action has not been documented, and immune responses protecting the mammary gland against E. coli are not completely understood. To improve our knowledge of mammary gland immune protection, cows immunized either intramuscularly or intramammarily with the E. coli P4 were submitted to a homologous mastitis challenge. A third group of mock-immunized cows serve as challenge controls. Local immunization modified favorably the course of infection, by improving bacterial clearance while limiting inflammation. Systemic clinical signs and reduction in milk secretion were also contained. This occurred with a modification of the cytokine profile, such as an increase in IFN-γ and a reduction in TNF-α concentrations in milk. Concentrations of IL-17A and IL-22 increased in milk at the onset of the inflammatory response and remained high up to the elimination of bacteria, but concentrations did not differ between groups. Accelerated bacteriological cure was not linked to an increase in the initial efficiency of phagocytosis in milk. Results support the idea that antibodies did not play a major role in the improvement, and that cell-mediated immunity is the key to understanding E. coli vaccine-induced protection of the mammary gland.