Myopathy and spontaneous Pasteurella pneumotropica-induced abscess formation in an HIV-1 transgenic mouse model

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.

Time to include the gut microbiota in the hygienic standardisation of laboratory rodents

The gut microbiota (GM) composition and its impact on animal experiments has become currently dramatically relevant in our days: (1) recent progress in metagenomic technologies, (2) the availability of large scale quantitative analyses to characterize even subtle phenotypes, (3) the limited diversity of laboratory rodent GM due to strict barriers at laboratory animal vendors, and (4) the availability of up to 300.000 different transgenic mouse strains from different sources displaying a huge variety in their GM composition. In this review the GM is described as a variable in animal experiments which need to be reduced for scientific as well as ethical reasons, and strategies how to implement this in routine diagnostic procedures are proposed. We conclude that we have both enough information available to state that the GM has an essential impact on animal models, as well as the methods available to start dealing with these impacts.

Impairment of the splenic immune system in P2X2/P2X3 knockout mice

The isolated spleens from male and female mice lacking P2X(2) and P2X(3) receptors (P2X(2)/P2X(3) knockout (KO) mice) and those from wild-type (WT) mice were investigated by flow cytometry, immunohistochemistry and functionally by organ-bath pharmacology. The spleens from the P2X(2)/P2X(3) KO mice weighed significantly more than the corresponding WT mice. Flow cytometry was used to isolate the mononuclear cells, which were then phenotyped. T-lymphocytes, B-lymphocytes and macrophages were identified and counted. It was found that the increase in size of the spleens from the KO animals corresponded to an increase in the numbers of mononuclear cells present and that all three cell types (T-lymphocytes, B-lymphocytes and macrophages) increased in much the same proportion as those from the WT animals. Immunohistochemical localisation of P2Y(1), P2Y(2) and P2X(1) receptors revealed their presence on the spleen capsule and trabeculae. P2X(1) receptors were also present on blood vessels. There was no difference in the expression of these receptors between the WT and P2X(2)/P2X(3) KO spleens. Functional studies revealed the presence of multiple P2 receptors inducing the contraction of the spleen capsule, from both WT and KO mice. There was no difference in the contractions induced by adenosine 5'-triphosphate (ATP), alpha,beta-methylene ATP, 2-methylthio ADP or uridine triphosphate from WT and KO mice. It is concluded that mice lacking both P2X(2) and P2X(3) receptors have enlarged spleens and that this is correlated with an increase in the number of immune cells, perhaps as a consequence of a compromised immune system and chronic infection.

Mice transgenic for monocyte-tropic HIV type 1 produce infectious virus and display plasma viremia: a new in vivo system for studying the postintegration phase of HIV replication

To generate an in vivo system for investigating the postintegration phase of HIV-1 replication, mouse lines transgenic for a full-length infectious proviral clone of a monocyte-tropic HIV-1 isolate, HIV-1JR-CSF, were constructed. Leukocytes from two independent JR-CSF transgenic mouse lines produced HIV-1 that infected human PBMCs. Plasma viremia was detected in these mice at levels (mean, >60,000 HIV RNA copies/ml) comparable to those reported for HIV-1-infected individuals. The levels of HIV RNA in these mice increased several-fold after either treatment with the superantigen Staphylococcus enterotoxin B or infection with Mycobacterium tuberculosis. Thus, a provirus encoding a monocyte-tropic HIV-1 strain under the control of its LTR expressed as a transgene in mice can proceed through the postintegration replication phase and produce infectious virus. In addition, the presence of plasma viremia that can be monitored by measuring plasma HIV-1 RNA levels permits these mice to be used to study the impact of different interventions on modulating in vivo HIV-1 production. Therefore, these mice provide a novel manipulable system to investigate the in vivo regulation of HIV-1 production by factors that activate the immune system. Furthermore, this murine system should be useful in delineating the role of human-specific factors in modulating HIV-1 replication and investigating the in vivo therapeutic efficacy of agents that target the postintegration stages of HIV-1 replication.