Susceptibility and signs associated with mouse adenovirus type 1 infection of adult outbred Swiss mice.

Adult Swiss outbred mice from two sources had a nearly 6,000-fold difference in susceptibility to mouse adenovirus type 1-induced disease. This difference was not attributable to differential organ tropism. Signs associated with mouse adenovirus type 1 infection that have not been previously reported are described at the clinical, gross pathological, and histological levels.     

Fatal disseminated mouse adenovirus type 1 infection in mice lacking B cells or Bruton's tyrosine kinase

Mouse adenovirus type 1 (MAV-1) infection of B-cell-deficient and Bruton's tyrosine kinase (Btk)-deficient mice resulted in fatal disseminated disease resembling human adenovirus infections in immunocompromised patients. Mice lacking B cells or Btk were highly susceptible to acute MAV-1 infection, in contrast to controls and mice lacking T cells. To our knowledge, this is the first demonstration that mice with an X-linked immunodeficiency phenotype (Btk deficient) are susceptible to virus-induced disease. Mice lacking B cells or Btk on a C57BL/6 background succumbed with encephalomyelitis, hepatitis, and lymphoid necrosis. Mice lacking B cells on a BALB/c background succumbed with enteritis and hepatitis. Survival of acute MAV-1 infection correlated with early T-cell-independent neutralizing antibody and T-cell-independent antiviral immunoglobulin M. Treatment of MAV-1-infected Btk(-/-) mice 4 to 9 days postinfection with antiserum harvested 6 to 9 days postinfection from MAV-1-infected Btk(+/+) mice was therapeutic. Our findings implicate a critical role for B-cell function in preventing disseminated MAV-1 infection, particularly production of early T-cell-independent antiviral immunoglobulin M.     

Endogenous IFN-gamma production is induced and required for protective immunity against pulmonary chlamydial infection in neonatal mice

Chlamydia trachomatis infection in neonates, not adults, has been associated with the development of chronic respiratory sequelae. Adult chlamydial infections induce Th1-type responses that subsequently clear the infection, whereas the neonatal immune milieu in general has been reported to be biased toward Th2-type responses. We examined the protective immune responses against intranasal Chlamydia muridarum challenge in 1-day-old C57BL/6 and BALB/c mice. Infected C57BL/6 pups displayed earlier chlamydial clearance (day 14) compared with BALB/c pups (day 21). However, challenged C57BL/6 pups exhibited prolonged deficits in body weight gain (days 12-30) compared with BALB/c pups (days 9-12), which correlated with continual pulmonary cellular infiltration. Both strains exhibited a robust Th1-type response, including elevated titers of serum antichlamydial IgG2a and IgG2b, not IgG1, and elevated levels of splenic C. muridarum-specific IFN-gamma, not IL-4, production. Additionally, elevated IFN-gamma, not IL-4 expression, was observed locally in the infected lungs of both mouse strains. The immune responses in C57BL/6 pups were significantly greater compared with BALB/c pups after chlamydial challenge. Importantly, infected mice deficient in IFN-gamma or IFN-gamma receptor demonstrated enhanced chlamydial dissemination, and 100% of animals died by 2 wk postchallenge. Collectively, these results indicate that neonatal pulmonary chlamydial infection induces a robust Th1-type response, with elevated pulmonary IFN-gamma production, and that endogenous IFN-gamma is important in protection against this infection. The enhanced IFN-gamma induction in the immature neonatal lung also may be relevant to the development of respiratory sequelae in adult life.     

Cell-mediated immunity to mouse adenovirus infection. Macrophage migration inhibition test.

Cell-mediated immunity (CMI) to mouse adenovirus (M-Ad) infection was studied by macrophage migration inhibition test (MMI) as one of in vitro correlates of CMI. Both direct and indirect tests showed clearly that migration of packed peritoneal exudate cells (PEC) (immune mouse or nonimmune guinea pig) was remarkably inhibited; MIF was produced by interactions between immune PEC and infected cell extracts and between immune spleen cells and infected cells or their extracts. The antigen(s) responsible for the above MMI was demonstrated in 6- to 12-hour infected ME cells, and FUdR-treated infected ME cells. Since under these conditions there is S antigen(s) synthesis but not capsid antigen synthesis, the antigen(s) concerned must be an S antigen(s). T cells sensitized to infected cells were shown to be required to induce MMI. The MMI is specific for M-Ad, since no cross MMI was observed between M-Ad and SV40 systems. Time course study of the development of CMI to M-Ad by MMI tests showed that CMI became detectable 4 days post-infection (pi), reached its peak level about 10 days pi, and faded away rapidly in about 10 days thereafter.     

A DNA-priming protein-boosting regimen significantly improves type 1 immune response but not protective immunity to Trypanosoma cruzi infection in a highly susceptible mouse strain

BALB/c or C57Bl/6 mice immunized with plasmids containing Trypanosoma cruzi genes developed specific immune responses and protective immunity against lethal parasitic infection. In contrast, in the highly susceptible mouse strain A/Sn, DNA vaccination reduced the peak parasitemia but promoted limited mouse survival after challenge. In the present study, we tested whether the immunogenicity and protective efficacy of vaccination could be improved by combining DNA and recombinant protein immunization regimens. A/Sn mice immunized with plasmid p154/13 which harbours the gene encoding Trypanosoma cruzi trans-sialidase developed a predominant type 1 immune response. In contrast, immunization with the recombinant Trypanosoma cruzi trans-sialidase protein adsorbed to alum generated a typical type 2 immune response. Simultaneous administration of both p154/13 and recombinant Trypanosoma cruzi trans-sialidase protein also led to a predominant type 2 immune response. Sequential immunization consisting of two priming doses of p154/13 followed by booster injections with recombinant Trypanosoma cruzi trans-sialidase protein significantly improved specific type 1 immune response, as revealed by a drastic reduction of the serum IgG1/IgG2a ratio and by an increase in the in vitro interferon-gamma secretion by CD4 T cells. Our observations confirm and extend previous data showing that a DNA-priming protein-boosting regimen might be a general strategy to enhance type 1 immune response to DNA vaccines. Upon challenge with Trypanosoma cruzi, no improvement in protective immunity was observed in mice immunized with the DNA-priming protein-boosting regimen when compared to animals that received DNA only. Therefore, our results suggest that in this experimental model there is no correlation between the magnitude of type 1 immune response and protective immunity against Trypanosoma cruzi infection.     

Complement receptor type 3 plays an important role in development of protective immunity to primary and secondary Corynebacterium pseudotuberculosis infection in mice

The present study was performed to investigate the role of CR3, the type 3 complement receptor, in host defense against primary and secondary Corynebacterium (C.) pseudotuberculosis infection in mice. Treatment of mice with 5C6, an anti-CR3 monoclonal antibody (mAb), resulted in unrestricted multiplication of bacteria in the organs and dramatically increased mortalities of the infected mice. Histological examinations showed the inflammation, degeneration and necrosis of organs and revealed that the infection-enhancing effect of 5C6 mAb was associated with the failure of mice to focus mononuclear phagocytes at sites of bacterial multiplication. These results suggest that CR3 plays an important role in host defense against primary as well as secondary C. pseudotuberculosis infection in mice.     

Identification of quantitative trait loci for susceptibility to mouse adenovirus type 1

Adult SJL/J mice are highly susceptible to mouse adenovirus type 1 (MAV-1) infections, whereas other inbred strains, including BALB/cJ, are resistant (K. R. Spindler, L. Fang, M. L. Moore, C. C. Brown, G. N. Hirsch, and A. K. Kajon, J. Virol. 75:12039-12046, 2001). Using congenic mouse strains, we showed that the H-2(s) haplotype of SJL/J mice is not associated with susceptibility to MAV-1. Susceptibility of MAV-1-infected (BALB/cJ x SJL/J)F(1) mice was intermediate between that of SJL/J mice and that of BALB/cJ mice, indicating that susceptibility is a genetically controlled quantitative trait. We mapped genetic loci involved in mouse susceptibility to MAV-1 by analysis of 192 backcross progeny in a genome scan with 65 simple sequence length polymorphic markers. A major quantitative trait locus (QTL) was detected on chromosome 15 (Chr 15) with a highly significant logarithm of odds score of 21. The locus on Chr 15 alone accounts for 40% of the total trait variance between susceptible and resistant strains. QTL modeling of the data indicated that there are a number of other QTLs with small effects that together with the major QTL on Chr 15 account for 54% of the trait variance. Identification of the major QTL is the first step in characterizing host genes involved in susceptibility to MAV-1.     

Polymorphisms in Ly6 genes in Msq1 encoding susceptibility to mouse adenovirus type 1

Strain-specific differences in susceptibility to mouse adenovirus type 1 (MAV-1) are linked to the quantitative trait locus Msq1 on mouse chromosome 15. This region contains 14 Ly6 or Ly6-related genes, many of which are known to be expressed on the surface of immune cells, suggesting a possible role in host defense. We analyzed these genes for polymorphisms between MAV-1-susceptible and MAV-1-resistant inbred mouse strains. Sequencing of cDNAs identified 12 coding-region polymorphisms in 2010109I03Rik, Ly6e, Ly6a, Ly6c1, and Ly6c2, six of which were nonsynonymous and five of which were previously unlisted in dbSNP Build 132. We also clarified sequence discrepancies in GenBank for the coding regions of I830127L07Rik and Ly6g. Additionally, Southern blotting revealed size polymorphisms within the DNA regions of Ly6e, Ly6a, and Ly6g. Collectively, these genetic variations have implications for the structure, function, and/or expression of Ly6 and Ly6-related genes that may contribute to the observed strain-specific differences in susceptibility to MAV-1.     

Induction of protective immunity to Trichostrongylus colubriformis in neonatal merino lambs.

The premise that any bias of immune reactivity in neonatal lambs towards T-helper (TH)2 responses could benefit the induction of protection against gastrointestinal nematodes was investigated. In two trials, lambs were either trickle-immunised with 2000 infective larvae of Trichostrongylus colubriformis (TcL3), 3 times weekly from the day of birth for 6 weeks or inoculated with a recombinant T. colubriformis 17 kDa antigen in incomplete Freund's adjuvant (IFA). In trial 1, trickle immunised and control neonates challenged at 7 weeks of age had similar worm counts 10 days after challenge, but from 25 days, significant reductions (P<0.01) in mean faecal egg count and worm count in excess of 75% were displayed by the immunised lambs. The results of a second, similar trial, gave 85-91% reductions in parasitism in trickle immunised neonates (P<0.001) and around 50% protection in neonates vaccinated with recombinant 17 kDa antigen. Parasitism in immunised neonates in Trial 2 was significantly reduced (P<0.001) compared to that in 4-month-old animals. Antibody responses in trickle-immunised (protected) and challenge control (infected) neonates were almost exclusively of the IgG1 isotype compared to vaccinated animals which exhibited increased levels of anti-17kD IgG2. Trichostrongylus colubriformis infection, but not specific vaccination, induced interleukin-5 production by mesenteric lymph node cells. The results offer the tantalising prospect of generating protective immunity to gastrointestinal parasites prior to weaning in sheep; this was most effectively generated by viable parasites in this investigation.     

Susceptibility of inbred mice to Paragonimus miyazakii infection

Differences in the susceptibility among inbred strains of mice to Paragonimus miyazakii infection were examined. Recovery of worms varied among the strains used. More were recovered from BALB/c mice than from any of the other strains; whereas, the fewest were recovered from C57BL/6 and C57BL/10. No worm formed a cyst in the lung or matured in any of the strains.     

Mechanisms of vaccine-induced protective immunity against Coxiella burnetii infection in BALB/c mice

To elucidate the mechanisms of vaccine-induced protective immunity against Coxiella burnetii infection, we compared the protective efficacy and immunogenicity between formalin-inactivated phase I vaccine (PI-V) and phase II vaccine (PII-V) in BALB/c mice. PI-V generated significant protection while PII-V did not confer measurable protection. Analysis of cytokine and subclass Ab responses indicated that both PI-V and PII-V were able to induce a Th1-dominant immune response but did not identify the component of host response that distinguished their ability to induce protective immunity. Interestingly, immunoblot analysis identified a difference between PI-V and PII-V vaccinates in antigenic recognition by specific Ab isotypes. The observation that PI-LPS elicited significant protection but PII-LPS did not confer measurable protection suggests PI-LPS may play a key role in PI-V-induced protection. Adoptive transfer of either immune sera or splenocytes mediated significant protection in naive BALB/c mice, supporting the notion that both humoral and cellular immunity are important for development of protective immunity. However, the evidence that immune sera and B cells were unable to control infection while T cells conferred significant protection in SCID mice supports the hypothesis that T cell-mediated immunity is critical for host defense against C. burnetii infection. This report presents novel evidence to highlight the importance of PI-LPS and Abs in protective immunity and has important implications for the design of new generation vaccines against Q fever.     

A study on the protective effects of CpG oligodeoxynucleotide-induced mucosal immunity against lung injury in a mouse acute respiratory distress syndrome model

This study aims to determine the feasibility of using oligodeoxynucleotides with unmethylated cytosine-guanine dinucleotide sequences (CpG ODN) as an immunity protection strategy for a mouse model of acute respiratory distress syndrome (ARDS). This is a prospective laboratory animal investigation. Twenty-week-old BALB/c mice in Animal research laboratory were randomized into groups. An ARDS model was induced in mice using lipopolysaccharides (LPSs). CpG ODN was intranasally and transrectally immunized before or after the 3rd and 7th days of establishing the ARDS model. Mice were euthanized on Day 7 after the second immunization. Then, retroorbital bleeding was carried out and the chest was rapidly opened to collect the trachea and tissues from both lungs for testing. CpG ODN significantly improved the pathologic impairment in mice lung, especially after the intranasal administration of 50 μg. This resulted in the least severe lung tissue injury. Furthermore, interleukin-6 (IL-6) and IL-8 concentrations were lower, which was second to mice treated with the rectal administration of 20 µg CpG ODN. In contrast, the nasal and rectal administration of CpG ODN in BALB/c mice before LPS immunization did not appear to exhibit any significant protective effects. The intranasal administration of CpG ODN may be a potential treatment approach to ARDS. More studies are needed to further determine the protective mechanism of CpG ODN.     

T cells cause acute immunopathology and are required for long-term survival in mouse adenovirus type 1-induced encephalomyelitis

Infection of adult C57BL/6 (B6) mice with mouse adenovirus type 1 (MAV-1) results in dose-dependent encephalomyelitis. Utilizing immunodeficient mice, we analyzed the roles of T cells, T-cell subsets, and T-cell-related functions in MAV-1-induced encephalomyelitis. T cells, major histocompatibility complex (MHC) class I, and perforin contributed to acute disease signs at 8 days postinfection (p.i.). Acute MAV-1-induced encephalomyelitis was absent in mice lacking T cells and in mice lacking perforin. Mice lacking alpha/beta T cells had higher levels of infectious MAV-1 at 8 days, 21 days, and 12 weeks p.i., and these mice succumbed to MAV-1-induced encephalomyelitis at 9 to 16 weeks p.i. Thus, alpha/beta T cells were required for clearance of MAV-1. MAV-1 was cleared in mice lacking perforin, MHC class I or II, CD4+ T cells, or CD8+ T cells. Our results are consistent with a model in which either CD8+ or CD4+ T cells are sufficient for clearance of MAV-1. Furthermore, perforin contributed to MAV-1 disease but not viral clearance. We have established two critical roles for T cells in MAV-1-induced encephalomyelitis. T cells caused acute immunopathology and were required for long-term host survival of MAV-1 infection.