Cross-protection between the metacestodes of Mesocestoides corti and Taenia crassiceps in mice.
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Our laboratory strain of Schistosoma japonicum has been isolated for 51 years, but is comparable to the indigenous Chinese parasite in terms of its infectivity to both the intermediate and definitive hosts. Vaccination with our strain protects mice against challenge with wild isolates of S. japonicum from China. Thus any defined antigen vaccine developed using our laboratory strain would be expected to protect against S. japonicum in the field in China.
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Tick-borne encephalitis virus isolates from widely separated geographic regions of the USSR, six isolates from Hungary and one from France were compared with the European and Far Eastern prototype viruses. Peptide mapping by limited proteolysis yielded similar patterns for five selected isolates from the USSR. All isolates from Hungary and France exhibited the same reactivity pattern with a panel of 16 protein E-specific monoclonal antibodies, whereas 10 out of 12 isolates from the Soviet Union showed minor differences at certain epitopes. However, no correlation between geographic origin of the isolates and their antigenic structure was observed. No statistically significant difference in the degree of protection was detected when mice were immunized with the European prototype vaccine and challenged with three selected Asian isolates and one from the European part of the USSR.
In order to assess the level of protection against a lethal influenza virus infection provided by a primary infection with a virus strain of another subtype, C57BL/6 mice were infected with the sublethal influenza virus X-31 (H3N2) and subsequently challenged with the lethal strain A/PR/8/34 (H1N1). The outcome of the challenge infection was compared with that in mice that did not experience an infection with influenza virus X-31 prior to the challenge infection. The X-31 experienced mice cleared the infection with influenza virus A/PR/8/34 in an accelerated fashion, displayed less clinical signs and a reduction of lesions in the lungs resulting in improved survival rates of these mice compared to the naive mice. The improved outcome of the challenge infection with influenza virus A/PR/8/34 in the X-31 experienced mice correlated with priming for anamnestic virus-specific CD8(+) cytotoxic T lymphocyte (CTL) responses as was demonstrated by the detection of CTL specific for the H-2D(b) restricted NP(366-374) epitope that was shared by the influenza viruses X-31 and A/PR/8/34. Thus previous exposure to influenza A viruses affords partial protection against infection in the absence of virus-neutralizing antibodies specific for the hemagglutinin and the neuraminidase. The implications of these observations are discussed in the light of the current pandemic threat and development of vaccines that aim at the induction of virus-specific CTL.
Feline calicivirus (FCV) is characterised by a high degree of antigenic variation potentially compromising vaccine efficacy. Inclusion of several FCV strains or antigens in current vaccines could be a means to improve protection against antigenically distinct isolates. This study evaluated the synergy between two FCV strains (FCVG1 and FCV431) by comparing immunity induced by either strain with that provided by a combination of the two strains against an heterologous challenge with antigenically distant FCV strains (FCV393 and FCV220). Thirty-two SPF kittens were randomly allocated to four groups of eight cats in each group. Groups B, C and D cats were vaccinated once subcutaneously with strains FCVG1, FCV431, and FCVG1 + FCV431, respectively. Each kitten received a total dose of 10(3.4) CCID50 of FCV. Control group A was not immunised. On day 31, four cats from each group were challenged oronasally with FCV220 and four cats with FCV393. Following challenge, the cats were monitored for clinical signs, viral shedding and antibody responses. FCV220 and FCV393 induced severe clinical signs in control cats typical of FCV infection. Immunisation with both strains mixed together induced higher neutralizing antibody titres against FCV220 and FCV393 strains on average. Protection was observed in all groups, however combination of the two strains resulted in a better clinical protection and reduction of virus shedding after heterologous challenge. A moderate correlation was observed between neutralizing antibody titres at the time of challenge and protection against clinical signs. These results indicated that vaccines combining antigens from different FCV strains may induce a broader heterologous protection.
Taking into account the close antigenic relationship between bovine herpesvirus 1 (BoHV-1) and caprine herpesvirus 1 (CpHV-1), a live attenuated glycoprotein E (gE) negative BoHV-1 vaccine was assessed in goats with the aim to protect against CpHV-1 infection. Vaccine safety was evaluated by intranasal inoculation of two groups of goats with either a gE-negative BoHV-1 vaccine or a virulent BoHV-1. The length of viral excretion and the peak viral titre were reduced with the gE-negative vaccine. To assess the efficacy, two goats were inoculated intranasally twice 2 weeks apart with a gE-negative BoHV-1 vaccine. Four weeks later, immunised and control goats were challenged with CpHV-1. A 2 log(10) reduction in the peak viral titre was observed and the challenge virus excretion lasted 2 days more in immunised than in control goats. These data indicate the safety and the partial efficacy of a live attenuated gE-negative BoHV-1 vaccine intranasally administrated in goats.
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A study was done to determine survival and growth characteristics of acid-adapted, acid-shocked, and control cells of Escherichia coli O157:H7 inoculated into tryptic soy broth (TSB) acidified with organic acids and three commercial brands of apple cider and orange juice. The three types of cells behaved similarly in TSB acidified with acetic acid; however, in TSB (pH 3.9) acidified with lactic acid, acid-adapted cells were more tolerant than acid-shocked cells which, in turn, were more tolerant than control cells. The ability of the three types of cells to grow after inoculation into acidified TSB, then plated on tryptic soy agar containing sodium chloride was determined. Tolerance of acid-adapted cells and, less markedly, acid-shocked cells to sodium chloride was diminished, compared to control cells. The pathogen showed extraordinary tolerance to the low pH of apple cider and orange juice held at 5 or 25 degrees C for up to 42 days. Growth occurred in one brand of apple cider (pH 3.98) incubated at 25 degrees C. Regardless of test parameters, there was no indication that cell types differed in tolerance to the acidic environment in apple cider or orange juice. Survival of control, acid-adapted, and acid-shocked cells heated in apple cider and orange juice was studied. Within each apple cider or orange juice, D(52 degrees C)-values of acid-adapted cells were considerably higher than those of acid-shocked or control cells, which indicates that heat tolerance can be substantially enhanced by acid adaptation compared to acid shock.
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Human respiratory syncytial virus (hRSV) transmission dynamics are inherently cyclical, and the observed genetic diversity (between groups A and B) also appears to have a repeating pattern. A key unknown is the extent to which genetic variants interact immunologically, and thus impact on epidemiology. We developed a novel mathematical model for hRSV transmission including seasonal forcing of incidence and temporary intra- and inter-group partial immunity. Simultaneous model fits to data from two locations (England & Wales, UK, and Turku, Finland) successfully reproduced the contrasting infection dynamics and group A/B dominance patterns. Parameter estimates are consistent with direct estimates. Differences in the magnitude and seasonal variation in contact rate between the two populations alone could account for the variation in dynamics between these populations. The A/B group dominance patterns are explained by reductions in susceptibility to and infectiousness of secondary homologous and heterologous infections. The consequences of the observed dynamic complexity are discussed.
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