Bacterial endotoxin and infection cause behavioural hypothermia in infant mice

• 1.1. When placed in a temperature gradient, 3–10 day old mice injected with living Escherichia coli or with E. coli endotoxin, select 2–3°C lower temperatures than their litter-mate controls injected with saline.
• 2.2. At the lower selected temperature (32°C) young mouse pups resist bacterial infection for longer and tolerate higher doses of endotoxin than at the temperature selected by the controls (35°C).
• 3.3. It is possible that a controlled hypothermic state, here called cryexia, is in small mammals an alternative strategy to fever for coping with infections.

     

SARS-CoV-2 infection: The role of cytokines in COVID-19 disease

COVID-19 disease, caused by infection with SARS-CoV-2, is related to a series of physiopathological mechanisms that mobilize a wide variety of biomolecules, mainly immunological in nature. In the most severe cases, the prognosis can be markedly worsened by the hyperproduction of mainly proinflammatory cytokines, such as IL-1, IL-6, IL-12, IFN-γ, and TNF-α, preferentially targeting lung tissue. This study reviews published data on alterations in the expression of different cytokines in patients with COVID-19 who require admission to an intensive care unit. Data on the implication of cytokines in this disease and their effect on outcomes will support the design of more effective approaches to the management of COVID-19.     

Bacterial canker of stone-fruits: Infection experiments with Pseudomonas mors-prunorum and P. syringae

The effect was compared of inoculating Pseudomonas mors-prunorum and P. syringae at high inoculum concentration through wounds in plum stems and cherry branches, and through cherry-leaf scars. In the wound inoculations a North American cherry strain of P. syringae was considerably more virulent than any of three indigenous cherry strains of P. mors-prunorum, but two pear strains of P. syringae were less virulent. P. mors-prunorum showed a much greater capacity to invade through leaf scars, particularly towards the end of the leaf-fall period, when all three P. syringae strains were largely ineffective. Evidence is discussed which suggests that the greater infectivity of the P. mors-prunorum strains through leaf scars was related to their capacity to colonize the host tissues from small inocula. The P. syringae strains died out in cherry cankers earlier than P. mors-prunorum strains and they were less stable during host passage. The results of the experiments indicate that virulence in these organisms is a complex phenomenon and determined by several factors.     

The cause of parasitic infection in natural populations of Daphnia (Crustacea: Cladocera): the role of host genetics.

Disease patterns in nature may be determined by genetic variation for resistance or by factors, genetic or environmental, which influence the host-parasite encounter rate. Elucidating the cause of natural infection patterns has been a major pursuit of parasitologists, but it also matters for evolutionary biologists because host resistance genes must influence the expression of disease if parasite-mediated selection is to occur. We used a model system in order to disentangle the strict genetic component from other causes of infection in the wild. Using the crustacean Daphnia magna and its sterilizing bacterial parasite Pasteuria ramosa, we tested whether genetic variation for resistance, as determined under controlled conditions, accounted for the distribution of infections within natural populations. Specifically, we compared whether the clonally produced great-granddaughters of those individuals that were infected in field samples (but were subsequently 'cured' with antibiotics) were more susceptible than were the great-granddaughters of those individuals that were healthy in field samples. High doses of parasite spores led to increased infection in all four study populations, indicating the importance of encounter rate. Host genetics appeared to be irrelevant to natural infection patterns in one population. However, in three other populations hosts that were healthy in the field had greater genetic-based resistance than hosts that were infected in the field, unambiguously showing the effect of host genetic factors on the expression of disease in the wild.     

Bacterial kidney disease: the potential role of soluble protein antigen(s)

Soluble protein antigens, isolated from the supernatants of Renibacterium salmoninarum cultures, have been found to suppress the in vitro antibody reponses of coho salmon, Oncorhynchus kisutch , lymphocytes and to be associated with decreasing haematocrit values in vivo.     

The role of chemokines in Schistosoma mansoni infection: insights from human disease and murine models

Chemokines are a superfamily of low-molecular-weight cytokines that were initially described for their chemoattractant activity. It is now clear chemokines have several other activities that modulate immune processes. More than 50 chemokines ligands and at least 19 receptors have been described to date. Depending on the number of N-terminal cysteine residues, chemokines are grouped in the subfamilies CXC, CC, C or CX3C. A growing body of evidence suggests a role for chemokines in the pathogenesis of several inflammatory diseases. Our studies involving mice and humans infected with Schistosoma mansoni suggest an important role of the chemokine CCL3 and its receptors (CCR1 and CCR5) in the pathogenesis of severe schistosomiasis. We suggest that the differential activation of CCR1 or CCR5 during the course of schistosomiasis may dictate the outcome of the disease.     

The flock-to-flock force of infection for scrapie in Britain

A postal survey of British sheep farmers provided information on the proportion of farms that experienced their first case of scrapie in each year between 1962 and 1998. We found no evidence of a large increase in the proportion of scrapie-affected farms prior to, during or following the epidemic of BSE in British cattle. After correcting for between-farm heterogeneity in the probability of acquiring scrapie, we estimated the yearly between-flock force of infection since 1962. The current force of infection is estimated at approximately 0.0045 per farm per year and combined with a simple model of scrapie spread provides an estimate of the average duration of a scrapie outbreak on an individual farm. Considering all farms, the average outbreak lasts for five years, but if only those farms that have cases in animals born on the farm are considered, it lasts 15 years. We use these parameter estimates to compare the proportion of farms with scrapie in time periods of different lengths. In the survey, 2.7% of farms had a case in 1998. The 5.3% of farms reporting having a case between 1993 and 1997 is consistent with the hypothesis that the scrapie force of infection remained constant over this period.     

The role of vitamin D in pulmonary disease: COPD,asthma, infection,and cancer

The role of vitamin D (VitD) in calcium and bone homeostasis is well described. In the last years, it has been recognized that in addition to this classical function, VitD modulates a variety of processes and regulatory systems including host defense, inflammation, immunity, and repair. VitD deficiency appears to be frequent in industrialized countries. Especially patients with lung diseases have often low VitD serum levels. Epidemiological data indicate that low levels of serum VitD is associated with impaired pulmonary function, increased incidence of inflammatory, infectious or neoplastic diseases. Several lung diseases, all inflammatory in nature, may be related to activities of VitD including asthma, COPD and cancer. The exact mechanisms underlying these data are unknown, however, VitD appears to impact on the function of inflammatory and structural cells, including dendritic cells, lymphocytes, monocytes, and epithelial cells. This review summarizes the knowledge on the classical and newly discovered functions of VitD, the molecular and cellular mechanism of action and the available data on the relationship between lung disease and VitD status.     

The mentor pollen phenomenon in poplars: a new concept

Summary The mentor effect has been investigated in poplars. Attempts to overcome interspecific incompatibility are analysed by pollen germination and pollen tube behaviour in situ, both for compatible and incompatible crosses. We have demonstrated that following the mixed pollination, the two pollen sets interact at different levels of the progamic phase. A hypothetical model is proposed which describes mentor effect as the result of interactions of antagonist and cynergic forces applying on compatible pollen and tubes. These forces promote pollen tube growth both on the female partner surface and within the tissues.     

Pasteurisation and the control of milkborne infection in Britain.

Infections carried in milk, particularly salmonellosis and campylobacter enteritis, have continued to feature in Great Britain in recent years. Less commonly reported infections included an outbreak in 1984 in England due to Streptococcus zooepidemicus, in which 12 people, eight of whom died, were admitted to hospital. The implementation of legislation in 1983 requiring heat treatment of cows'' milk for sale to the public reduced the incidence of milkborne infection in Scotland compared with previous years and compared with England and Wales, where, without legislative control, outbreaks continue to occur. Until compulsory pasteurisation is introduced throughout Britain and dairy farming communities can be persuaded to drink only heat treated milk outbreaks of milkborne infection will continue.     

Bacterial osmoadaptation: the role of osmolytes in bacterial stress and virulence

Two general strategies exist for the growth and survival of prokaryotes in environments of elevated osmolarity. The 'salt in cytoplasm' approach, which requires extensive structural modifications, is restricted mainly to members of the Halobacteriaceae. All other species have convergently evolved to cope with environments of elevated osmolarity by the accumulation of a restricted range of low molecular mass molecules, termed compatible solutes owing to their compatibility with cellular processes at high internal concentrations. Herein we review the molecular mechanisms governing the accumulation of these compounds, both in Gram-positive and Gram-negative bacteria, focusing specifically on the regulation of their transport/synthesis systems and the ability of these systems to sense and respond to changes in the osmolarity of the extracellular environment. Finally, we examine the current knowledge on the role of these osmostress responsive systems in contributing to the virulence potential of a number of pathogenic bacteria.     

The role of proinflammatory cytokines in wasting disease during lymphocytic choriomeningitis virus infection

Infection with pathogens often leads to loss of body weight, but the cause of weight loss during infection is poorly understood. We used the infection of mice with lymphocytic choriomeningitis virus (LCMV) as a model to study how pathogens induce weight loss. If LCMV is introduced into the CNS of CTL-deficient mice, the immune response against the virus leads to a severe weight loss called wasting disease. We planned to determine what components of this antiviral immune response mediate wasting disease. By adoptive transfer, we show that CD4 T cells activated by LCMV infection are sufficient to cause wasting disease. We examined the role of cytokines in LCMV-induced wasting disease using mice lacking specific cytokines or cytokine receptors. Results of adoptive transfer experiments suggest that TNF-alpha is not involved in LCMV-induced wasting disease and show that IFN-gamma contributes to the disease. Consistent with a role for IFN-gamma in wasting, we find that IFN-gamma is necessary for LCMV-specific CD4 T cell responses in the CNS, most likely because it is required to induce MHC class II expression. Our data also indicate that IL-1 is required for LCMV-induced wasting and that IL-6 contributes to the wasting disease. Additionally, our results identify alpha-melanocyte-stimulating hormone as a potential mediator of the disease. Overall, this work defines the critical role of virus-primed CD4 T cells and of proinflammatory cytokines in the pathogenesis of wasting disease induced by LCMV infection.