Comparison of host resistance to primary and secondary Listeria monocytogenes infections in mice by intranasal and intravenous routes

There have been no studies on the susceptibility and host immune responses to an intranasal infection with Listeria monocytogenes. In this study, we compared the susceptibilities and cytokine responses between intranasal and intravenous infections with L. monocytogenes in mice. Moreover, we compared efficiency of acquisition of host resistance to L. monocytogenes infection between intranasally and intravenously immunized mice because an intranasal immunization of vaccines is reportedly available for induction of adaptive immunity against various infectious pathogens. The susceptibility to an intranasal infection with L. monocytogenes was markedly lower than that to the intravenous infection. The bacterial growth in the lungs, spleens, and livers was substantially similar between intranasally and intravenously infected mice. Titers of endogenous gamma interferon (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) in the spleens, livers, and lungs were parallel to bacterial numbers in each organ of mice during intranasal infection and intravenous infection. IFN-gamma-deficient mice and TNF-alpha-deficient mice were highly susceptible to intranasal infection as well as intravenous infection. Susceptibilities to intranasal and intravenous L. monocytogenes infection were the same in these cytokine-deficient mice. These results suggest that both IFN-gamma and TNF-alpha play critical roles in host resistance to intranasal L. monocytogenes infection as well as the intravenous infection. Acquisition of host resistance to intravenous and intranasal L. monocytogenes infection was induced in intranasally immunized mice as well as intravenously immunized mice, suggesting that intranasal immunization is effective for prevention of a systemic infection with L. monocytogenes.     

Host resistance to primary and secondary Campylobacter jejuni infections in C57Bl/6 mice

Campylobacter jejuni has been known as a main causative agent of human enterocolitis for more than 30 years. This has prompted the research on defence mechanisms of the host involved. Although the humoral immune response to C. jejuni has been addressed in many studies, relatively little is known about the role of T lymphocytes in campylobacteriosis. The current study was based on in vivo T-cell subsets depletion to evaluate the role of CD4+ and CD8+ T lymphocytes in disseminated C. jejuni infection in C57BL/6 mice. Depletion of either CD8+ or CD4+ cells did not change the overall infection kinetics of primary campylobacteriosis. To assess the role of T cells in acquired immunity that develops during primary infection in C57BL/6 mice, in vivo depletions were performed during reinfection. Depletion of CD4+ cells did not have any effect on secondary infection kinetics, whereas depletion of CD8+ cells resulted in secondary liver infection that failed to resolve during the observed period. This study showed that both CD8+ and CD4+ T cells contribute to protection of C57BL/6 mice against C. jejuni. However, the predominant role resides in the CD8+ cell subpopulation. The exact mechanisms by which CD8+ cells operate during the course of campylobacteriosis will be the subject of our further research.     

Interactions between endogenous gamma interferon and tumor necrosis factor in host resistance against primary and secondary Listeria monocytogenes infections.

Intravenous injection of rat anti-mouse gamma interferon (IFN-gamma) monoclonal antibody as well as rabbit anti-mouse tumor necrosis factor (TNF) antibody into mice which had received a sublethal infection with Listeria monocytogenes cells resulted in acceleration of listeriosis. Endogenous IFN-gamma seemed to be produced early in infection, because suppression of antilisterial resistance was significant when a single injection of anti-IFN-gamma monoclonal antibody was given on day 0 or day 1 of infection. Production of TNF but not of IFN-gamma in the bloodstream early in infection was inhibited by administration of anti-IFN-gamma monoclonal antibody. The suppressive effect of anti-IFN-gamma and anti-TNF antibodies on antilisterial resistance was not augmented by simultaneous administration of these antibodies. On the other hand, in the secondary infection, simultaneous administration of anti-IFN-gamma and anti-TNF antibodies, but not of either of these antibodies alone, into L. monocytogenes-immune mice resulted in high mortality and explosive multiplication of bacterial cells in the spleens and livers. These results suggest that endogenously produced IFN-gamma and TNF are both essential to the host defense against L. monocytogenes infection and that these cytokines might act by different modes between the primary infection and the secondary infection.     

Airway hyper-reactivity and blood, lung and airway eosinophilia in rats treated with Sephadex particles

The intravenous injection of Sephadex particles (G200) into rats produced a specific increase in numbers of blood eosinophils peaking 7 days later. A second injection, given on day 14 when the numbers of blood eosinophils had fallen to control levels, produced a dose-dependent increase in numbers, greater than the first, and peaking 5 days later. At this time there was a dose-dependent increase in numbers of eosinophils, but not of other leucocytes, in broncho-alveolar lavage fluids and lung tissue, together with an increase in sensitivity of the rats to the respiratory effect produced by the intravenous injection of 5-hydroxytryptamine.     

Differences in brain and liver blood flow during and after acute blood loss in rats with different resistance to circulatory hypoxia

Variations of blood flow and vascular resistance in the common carotid arteries and of blood flow in the hepatic artery and portal vein are examined during and after acute massive blood loss in rats with low and high resistance to circulatory hypoxia. In rats with low resistance, arterial pressure and the rates of cerebral and hepatic blood macro- and microflow, which have decreased during blood loss, continued to fall during the posthemorrhagic period. After cessation of bleeding, a transient arterial pressure rise to 70 mm Hg is observed in rats with high resistance, while the blood flow via carotid arteries increases to 65% of its initial value, being maintained at this level throughout the period of changes in carotid vascular resistance; intrinsic hepatic arterial blood flow increases to 115% of baseline value, while the portal vein blood flow and hepatic microflow increase to 75%. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 123, No. 3, pp. 253–257, March, 1997     

Role of interleukin-6 in T-cell activation during primary and secondary infection with Listeria monocytogenes.

Injection of recombinant interleukin-6 (IL-6) into mice enhances recovery from infection with Listeria monocytogenes. In this study, the role of IL-6 during primary and secondary Listeria infection was further tested. Neutralization of IL-6 by polyclonal antibody exacerbated primary infection and significantly delayed gamma interferon production by cultured spleen cells. In contrast, administration of anti-IL-6 antibody at the time of secondary infection did not affect the recovery of mice from infection or gamma interferon production, showing that activated T cells are not dependent on IL-6.     

Temporal dynamics of the cellular,humoral and cytokine responses in chickens during primary and secondary infection with Salmonella enterica serovar Typhimurium

Salmonella enterica serovar Typhimurium (S. Typhimurium) infections cause systemic disease in the young chick, whereas in the older chicken the infection is mainly restricted to the intestine. Chickens infected orally with S. Typhimurium (F98) at 6 weeks of age and re-infected 10 weeks later were monitored for antibody production, T-cell proliferation and production of selected cytokines (interferon-γ, interleukin-1β and transforming growth factor-β₄). A strong coordinated antigen-specific humoral and cellular immune response was temporally linked to resolution of the primary infection. Enhanced levels of mRNA encoding the cytokines, interleukin-1β, transforming growth factor-β₄ and interferon-γ were also evident during early phases of primary infection. Secondary infection was restricted to the intestine and of shorter duration than primary infection. Splenic immune responses were not further enhanced by secondary infection; indeed, antigen-specific proliferation was significantly reduced at 1 day after secondary infection, which may be interpreted as the trafficking of reactive T cells from the spleen to the gut.     

Neonatally thymectomized Lewis rats infected with Mycobacterium leprae: response to primary infection, secondary challenge, and large inocula.

Several experiments were carried out to measure the ability of neonatally thymectomized Lewis rats (NTLR) to limit multiplication of Mycobacterium leprae. NTLR inoculated in one hind footpad with 10(7) viable M. leprae and challenged in the other hind footpad with 5 x 10(3) organisms simultaneously or 120 or 180 days later permitted multiplication in both sites. By contrast, immunologically intact rats similarly inoculated did not permit multiplication from either inoculum. NTLR and immunologically normal BALB/c mice were equally susceptible to infection with M. leprae, in that multiplication occurred regularly in the footpads of both species when inoculated with a bacterial suspension diluted to provide five organisms per footpad. Finally, multiplication occurred when five viable M. leprae diluted with 10(7) heat-killed organisms were inoculated into the footpads of NTLR. Although there was some evidence that NTLR are not completely immunosuppressed, NTLR appear to be capable of detecting much smaller proportions of viable M. leprae than can be detected by immunologically normal mice.     

Analysis of specific IgM responses in secondary dengue virus infections: levels and positive rates in comparison with primary infections.

BACKGROUND: Dengue viruses are a serious cause of illness in tropical and subtropical areas of the world. Laboratory diagnosis is essential for confirmation of dengue virus infections. Detection of specific IgM by IgM-capture enzymed-linked immunoassay (ELISA) has been widely used as a main serological diagnostic technique. OBJECTIVES: The levels of specific IgM in secondary dengue virus infections were compared with those in primary infections. STUDY DESIGN: A total of 1780 samples collected from 924 confirmed dengue cases were tested for anti-dengue IgM by IgM-capture ELISA. RESULTS AND CONCLUSIONS: Specific IgM was detected in all the cases with primary dengue virus infection on disease day 9 or later. However, specific IgM cannot be detected in 28% (204/716) of the cases in secondary infections. The average titers of IgM were higher in primary infections than in secondary infections. The results confirmed that IgM detection is a reliable serological diagnostic test in primary dengue virus infections. Although IgM detection is also a useful test, other serological diagnostic tests or tests for dengue virus detection are necessary for confirmation of all the secondary dengue virus infections.     

ExperimentalAncylostoma tubaeforme infection of cats: Changes in blood values and worm burden in relation to single infections of varying size

Worm-free cats about 12 weeks old were infected with 100, 500, 1,000, and 2,000 third-stage larvae (L₃) ofAncylostoma tubaeforme. The changes in packed cell volume (PCV) and haemoglobin content were monitored, and the worm populations developing in each infection recorded. Cats receiving infection doses of 1,000 L₃ and above showed morbidity symptoms by the third week and a rapid decline especially in the PCV value. The low dose rates (500 L₃ and below) produced an apparently symptomless condition without pronounced changes in the blood values. Adult hookworm populations were linearly related to the logarithm of the dose of infective larvae administered, but there was a lower female to male ratio (FMR) at high dose levels. No significant size differences were observed in the adult hookworm populations.     

Evaluation of primary and secondary responses to a T-cell-dependent antigen,keyhole limpet hemocyanin,in rats

To develop a rat T-cell-dependent antibody response (TDAR) model evaluating both primary and secondary antibody responses, keyhole limpet hemocyanin (KLH) was used to immunize rats twice during a 14-day course of study, a pattern closely linked to that of a short-term general toxicity study. Female rats of four representative strains (e.g., Sprague-Dawley, Wistar, Fischer, and Lewis) were immunized twice with intravenous administrations of KLH (300 µg/rat) on Days 5 and 9 during a 14-day treatment regimen with cyclophosphamide (CPA) at 1, 3, or 6 mg/kg/day. The primary and secondary immunizations of KLH markedly elevated serum anti-KLH IgM and IgG levels in all strains on Days 9 and 15. Remarkable higher levels of anti-KLH IgG (≈ 1000 µg/ml) were noted in all strains, which were more than 4-times compared with those of anti-KLH IgM levels at Day 9, indicating that predominant IgG reactions were induced by the dual immunizations. A large inter-individual variability in KLH-specific IgM and IgG production was observed in all strains. However, levels of the KLH-specific antibodies were considered sufficient for the evaluation, even in Sprague-Dawley and Wistar rats reported as strains with a wide range of variability since immunosuppression of CPA on responses in both anti-KLH IgM and IgG were observed in all strains to the same extent. In addition, the sensitivity of the KLH-ELISA assay system detecting the immunosuppressive effects of CPA was comparable to other assay systems with PFC assay or ELISA using SRBC. The results here demonstrated that these experimental designs could provide valuable information about the influence on both the primary and secondary humoral immune responses in rats when exposed to potential immunomodulatory drugs. Furthermore, the design of the presented TDAR study would support comprehensive evaluation together with the outcome of the conventional general toxicity study.     

Experimental dermatophytosis in mice: correlation between light and electron microscopic changes in primary, secondary and chronic infections

The histopathological and electron microscopic features of experimental dermatophytosis due to Trichophyton quinckeanum in Balb/c mice have been studied in animals with primary, secondary and chronic infections. Infected animals all showed pathological changes with adherence of microconidia to keratinocytes within 4 h of infection. Other features were the early infiltration of neutrophils, the formation of a mycelial mass (scutulum) in the epidermis, and epidermal oedema. Increased thickness of the epidermis was measured within 3 days of infection, although this was mainly due to oedema. The main differences seen in secondary infections were the paucity of fungal elements, even after 24 h, a sustained increase in epidermal thickness, and the dense dermal infiltrate of mononuclear cells. Chronically infected animals showed similar changes to those at the peak of a primary infection, but in addition there were large numbers of mast cells in the dermis. Cells carrying Ia markers were identified in the epidermis (Langerhans cells) and the dermis (macrophages) in all infections and their distribution did not appear to change. Although recovery from infection has been correlated previously with T lymphocyte mediated responses an increase in the number of cell layers of the epidermis and a dense infiltrate of neutrophils at the zone of infection were both seen within 2 days of infection. It is suggested that neutrophil killing of fungi and increased epidermal proliferation, not dependent on T cell activation, may also be implicated in host defence against dermatophytes.     

Organ-specific characteristics of blood supply in the liver, kidney, and brain in acute blood loss in rats with various resistance to circulatory hypoxia

A marked fall in arterial blood pressure, organ blood flow rates and tissue perfusion in the liver, kidneys and brain was registered by ultrasound and laser Doppler flowmetry in rats with low (LR) and high resistance (HR) to circulatory hypoxia (average life spans less than 1.5 h and more than 3 h were 42 and 58%, respectively) at the end of acute massive hemorrhage. In the posthemorrhagic period organ hemodynamics and microcirculation showed a tendency to further decrease in LR rats. In HR rats blood flow in hepatic, renal and common carotid arteries were restored for a while up to 115-120%, 85-90% and 60-65%, respectively, following bleeding arrest. At this new posthemorrhagic level the brain flow was actively maintained in the compensatory phase of the posthemorrhagic period due to autoregulatory changes in the carotid resistance. Such a peculiar reaction of the brain blood vessels in HR rats is considered as an adaptive response protecting the brain during massive hemorrhage under severe tissue hypoxia against autoreperfusion and reoxygenation-induced damage.     

Experimental dermatophytosis in mice: correlation between light and electron microscopic changes in primary,secondary and chronic infections.

The histopathological and electron microscopic features of experimental dermatophytosis due to Trichophyton quinckeanum in Balb/c mice have been studied in animals with primary, secondary and chronic infections. Infected animals all showed pathological changes with adherence of microconidia to keratinocytes within 4 h of infection. Other features were the early infiltration of neutrophils, the formation of a mycelial mass (scutulum) in the epidermis, and epidermal oedema. Increased thickness of the epidermis was measured within 3 days of infection, although this was mainly due to oedema. The main differences seen in secondary infections were the paucity of fungal elements, even after 24 h, a sustained increase in epidermal thickness, and the dense dermal infiltrate of mononuclear cells. Chronically infected animals showed similar changes to those at the peak of a primary infection, but in addition there were large numbers of mast cells in the dermis. Cells carrying Ia markers were identified in the epidermis (Langerhans cells) and the dermis (macrophages) in all infections and their distribution did not appear to change. Although recovery from infection has been correlated previously with T lymphocyte mediated responses an increase in the number of cell layers of the epidermis and a dense infiltrate of neutrophils at the zone of infection were both seen within 2 days of infection. It is suggested that neutrophil killing of fungi and increased epidermal proliferation, not dependent on T cell activation, may also be implicated in host defence against dermatophytes.     

Adaptation to stress improves resistance to gastric damage during acute stress in Wistar rats and decreases resistance in August rats: role of serotonin

In August rats more resistant to acute stress-induced gastric damage than Wistar rats, preadaptation to nondamaging stress exposure did not prevent damage and even potentiated these damages. By contrast, in Wistar rats such adaptation decreased gastric damage caused by acute stress. Higher initial resistance of August rats to stress damage was associated with higher serotonin level and lower norepinephrine/serotonin ratio in the gastric mucosa than in Wistar rats. The negative effect of adaptation in August rats was associated with decreased serotonin level and increased norepinephrine/serotonin ratio in the stomach during stress. In Wistar rats exposed to stress the protective effect of adaptation was associated with an increase of serotonin content and a decrease of the norepinephrine/serotonin ratio in the stomach. Hence, the degree of resistance to stress-induced gastric damage can be due to genetically determined serotonin level and norepinephrine/serotonin ratio in the stomach.     

Invasive pneumococcal infections in Denmark from 1995 to 1999: epidemiology, serotypes, and resistance

Danish nationwide surveillance data on invasive pneumococcal disease from the 5-year period from 1995 to 1999, including 5,452 isolates, are presented and described. Annual overall incidence rates, serotype distribution, and antimicrobial susceptibility patterns of the isolates were monitored. Major changes in the total annual incidence rate from 27/100,000 in 1996 to 17/100,000 in 1999 and a significant change in the proportion of invasive isolates belonging to types 1 and 12F were observed. The serotype coverage rate by the 23-valent polysaccharide vaccine among the elderly was 92.9%, and the serotype coverage rate by the 7-, 9-, and 11-valent pneumococcal conjugate vaccines among children less than 2 years old were 71.7, 75.2, and 81.4%, respectively. Invasive isolates with reduced susceptibility to penicillin or erythromycin increased from 1995 to 1999, with a high proportion of the penicillin-nonsusceptible invasive isolates originating from people 60 years old or older (57.0%). These observations underline the importance of adequate surveillance systems of invasive pneumococcal disease to introduce and maintain national vaccine strategies and adequate antibiotic policy.     

Relationships between IgG, IgM, IgE and resistance to reinfection during the early phase of infection with Clonorchis sinensis in rats

An enzyme linked immunosorbent assay (ELISA) was used to study the correlation between the levels of IgG, IgM and IgE immunoglobulin isotypes and resistance to reinfection in rats during the first month of infection with Clonorchis sinensis. Rats were infected with Clonorchis sinensis (primary infection), and then treated with praziquantel on the 1st, 3rd, 7th, 14th and 28th day post infection (p.i.). To measure resistance, rats were re-infected with C. sinensis (secondary infection), 2 weeks after the treatment and worms were recovered 4 weeks later. During the primary infection, significantly increased levels of IgG isotype were observed on days 14 and 28 p.i. (P < 0.001) and IgM levels were significantly increased on 3rd and 28th day (P < 0.001). During the secondary infection, significantly increased levels of IgG isotype were found from 3rd to 28th day and IgE isotype on 7th and 14th day (P < 0.01) while significant levels of IgM were found on the 3rd and 28th day (P < 0.05). Furthermore, significant differences of worm numbers between infected and control group was found on the 14th and 28th day (P < 0.001). An inverse correlation betwee the IgG levels and the resistance to re-infection was also observed (r = -0.948, P = 0.004), indicating that the resistance to reinfection is highly associated with the levels of IgG during the early phase of infection, and then with the IgM and IgE.     

CXCR4 antagonist AMD3100 redistributes leukocytes from primary immune organs to secondary immune organs,lung, and blood in mice

AMD3100 (plerixafor), is a specific CXCR4 antagonist approved by the FDA for mobilizing hematopoietic stem cells from bone marrow to blood for transplantation in cancer. AMD3100 also mobilizes most mature leukocyte subsets to blood; however, their source and trafficking potential have not been fully delineated. Here, we show that a single injection of AMD3100 10 mg/kg into C57Bl/6 mice rapidly mobilizes (peak ～ 2.5 h) the same leukocyte subsets to blood as in humans. Using this model, we found that AMD3100 mobilization of neutrophils, lymphocytes, and monocytes to blood is not reduced by splenectomy or by blockade of lymphocyte egress from lymph node with FTY720, but is coupled to (i) reduced content of each of these cell types in the bone marrow; (ii) reduced T‐cell numbers in thymuses; (iii) increased lymphocytes in lymph nodes; and (iv) increased neutrophil and monocyte content in the lung. Direct intrathymic labeling showed that AMD3100 selectively mobilizes naïve thymic CD4⁺ and CD8⁺ T cells to blood. Finally, AMD3100‐induced neutrophil mobilization to blood did not reduce neutrophil trafficking to thioglycollate‐inflamed peritoneum. Thus, AMD3100 redistributes lymphocytes, monocytes, and neutrophils from primary immune organs to secondary immune organs, peripheral tissues, and blood, without compromising neutrophil trafficking to inflamed sites.