Differential interleukin-10 and gamma interferon mRNA expression in lungs of cilium-associated respiratory bacillus-infected mice

Health Monitoring of Laboratory Rodent Colonies-Talking about (R)evolution

The health monitoring of laboratory rodents is essential for ensuring animal health and standardization in biomedical research. Progress in housing, gnotobiotic derivation, and hygienic monitoring programs led to enormous improvement of the microbiological quality of laboratory animals. While traditional health monitoring and pathogen detection methods still serve as powerful tools for the diagnostics of common animal diseases, molecular methods develop rapidly and not only improve test sensitivities but also allow high throughput analyses of various sample types. Concurrently, to the progress in pathogen detection and elimination, the research community becomes increasingly aware of the striking influence of microbiome compositions in laboratory animals, affecting disease phenotypes and the scientific value of research data. As repeated re-derivation cycles and strict barrier husbandry of laboratory rodents resulted in a limited diversity of the animals' gut microbiome, future monitoring approaches will have to reform-aiming at enhancing the validity of animal experiments. This review will recapitulate common health monitoring concepts and, moreover, outline strategies and measures on coping with microbiome variation in order to increase reproducibility, replicability and generalizability.

Bacterial species to be considered in quality assurance of mice and rats

Bacteria are relevant in rodent quality assurance programmes if (a) the animals are at risk and (b) presence in the animals makes a difference for animal research or welfare, for example because the agent regulates clinical disease progression or impacts its host in other ways. Furthermore, zoonoses are relevant. Some bacterial species internationally recommended for the health monitoring of rats and mice, that is, Citrobacter rodentium, Corynebacterium kutscheri, Salmonella spp. and Streptococcus pneumonia, are no longer found in either laboratory or pet shop rats or mice, while there is still a real risk of impact on animal research and welfare from Filobacterium rodentium, Clostridium piliforme, Mycoplasma spp., Helicobacter spp. and Rodentibacter spp., while Streptobacillus moniliformis may be considered a serious zoonotic agent in spite of a very low risk. Modern molecular techniques have revealed that there may, depending on the research type, be equally good reasons for knowing the colony status of some commensal bacteria that are essential for the induction of specific rodent models, such as Alistipes spp., Akkermansia muciniphila, Bifidobacterium spp., Bacteroides fragilis, Bacteroides vulgatus, Faecalibacterium prausnitzii, Prevotella copri and segmented filamentous bacteria. In future, research groups should therefore consider the presence or absence of a short list of defined bacterial species relevant for their models. This list can be tested by cost-effective sequencing or even a simple multiple polymerase chain reaction approach, which is likely to be cost-neutral compared to more traditional screening methods.

Increased production of proinflammatory cytokines following infection with porcine reproductive and respiratory syndrome virus and Mycoplasma hyopneumoniae

Induction of the proinflammatory cytokines interleukin-1 (IL-1) (alpha and beta), IL-6, IL-8, IL-10, IL-12, and tumor necrosis factor alpha (TNF-alpha) in pulmonary alveolar macrophages (PAMs) was assessed following experimental infection with porcine reproductive and respiratory syndrome virus (PRRSV) and/or Mycoplasma hyopneumoniae by using in vivo and in vitro models. The in vivo model consisted of pigs infected with PRRSV and/or M. hyopneumoniae and necropsied at 10, 28, or 42 days postinfection. Pigs infected with both pathogens had a greater percentage of macroscopic lung lesions, increased clinical disease, and slower viral clearance than pigs infected with either pathogen alone. The pigs infected with both PRRSV and M. hyopneumoniae had significantly increased levels of mRNA for many proinflammatory cytokines in PAMs collected by bronchoalveolar lavage (BAL) at all necropsy dates compared to those in uninfected control pigs. Increased levels of IL-1beta, IL-8, IL-10, and TNF-alpha proteins in BAL fluid, as measured by enzyme-linked immunosorbent assay, confirmed the increased cytokine induction induced by the pathogens. An in vitro model consisted of M. hyopneumoniae-inoculated tracheal ring explants cultured with PRRSV-infected PAMs. PAMs were harvested at 6 or 15 h postinfection with either or both pathogens. The in vitro study detected increased IL-10 and IL-12 mRNA levels in PAMs infected with PRRSV at all time periods. In addition, IL-10 protein levels were significantly elevated in the culture supernatants in the presence of M. hyopneumoniae-inoculated tracheal ring explants. The increased production of proinflammatory cytokines in vivo and in vitro associated with concurrent M. hyopneumoniae and PRRSV infection may play a role in the increased rates of pneumonia associated with PRRSV infection. The increased levels of IL-10 may be a possible mechanism that PRRSV and M. hyopneumoniae use to exacerbate the severity and duration of pneumonia induced by PRRSV and modulate the respiratory immune response.

Role of interleukin-4 (IL-4) and IL-10 in serum immunoglobulin G antibody responses following mucosal or systemic reovirus infection

Mucosal and parenteral immunizations elicit qualitatively distinct immune responses, and there is evidence that mucosal immunization can skew the balance of T helper 1 and T helper 2 responses. However, a clear picture of the effect of the route of infection on the balance of the T helper responses has not yet emerged. Our laboratory previously demonstrated that oral reovirus infection elicits specific serum immunoglobulin G2a (IgG2a), while parenteral reovirus infection elicits the mixed production of specific serum IgG2a and IgG1 in mice of the H-2(d) haplotype. Knowing that IgG2a production is indicative of a T helper 1 response and IgG1 production is indicative of a T helper 2 response, we hypothesized that the route of infection influences the development of T helper 1 and T helper 2 responses. Using quantitative reverse transcription-PCR, we found that mRNA for the T helper 1 cytokines gamma interferon and interleukin-12 (IL-12) were expressed in draining lymphoid tissues following both oral and parenteral infections. However, we observed that mRNA for the T helper 2 cytokine IL-10 was suppressed in the Peyer's patches and mesenteric lymph nodes and IL-4 mRNA was suppressed in the mesenteric lymph nodes compared to noninfected controls, following oral infection. Using recombinant cytokines and cytokine knockout mice, we confirmed that IL-4 plays a major role in mediating the route-of-infection-dependent differences in serum IgG subclass responses. Therefore, the route of infection needs to be taken into consideration when developing vaccines and adjuvant therapies.

Interleukin-10, interleukin-12, and interferon-gamma levels in the respiratory tract following mycoplasma hyopneumoniae and PRRSV infection in pigs

The cytokine profile associated with either a T helper 1 (Th1) or Th2 response in a porcine respiratory disease model was assessed by measuring IL-12, IL-10 and IFN-gamma using RT-PCR and ELISA, respectively. IL-10, IL-12, and IFN-gamma levels in pulmonary alveolar macrophages and bronchial lavage fluid were increased in pigs infected with porcine reproductive and respiratory syndrome virus (PRRSV), Mycoplasma hyopneumoniae, or both pathogens. At 10 days post-infection (DPI), both IL-10 and IL-12 mRNA levels were increased in both groups infected with PRRSV. The IL-12 levels were increased in pigs infected with both pathogens and IFN-gamma protein levels were increased in pigs infected with PRRSV alone and only numerically increased in the dual infection. At 28 DPI, IL-12 mRNA levels and IL-10 protein levels were increased in all infected groups. The mRNA level of IL-12 remained elevated in the group infected with both pathogens at 42 DPI. Production of IFN-gamma did not appear to be closely correlated with elimination of virus from the respiratory tract. However, when the virus existed in the lung, the local IFN-gamma production appeared to increase. Although IL-12 mRNA levels were significantly elevated in the pigs infected with both pathogens, the increased protein levels of IL-12 may compromise the immune system's ability to clear PRRSV from the lung. This could explain the prolonged presence of PRRSV, IFN-gamma production and the increased pneumonia observed in the lungs of dual-infected pigs. The increased levels of cytokines associated with both Th1 and Th2 responses in the respiratory tract of pigs infected with PRRSV and M. hyopneumoniae provides valuable information on the pathogenesis of these diseases.