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At least 685 records · Page 38Linked to original sources

PubMed1975

Effect of neuraminidase on potency of inactivated influenza virus vaccines in mice.

The protective effect of neuraminidase was studied in a mouse protection test using isolated neuraminidase of A2/Aichi/68(H3N2) virus and the complete recombinant virus A/eq(Heq-1)-HK(N2) as antigens. Immunized mice were protected against A2/Aichi(H3N2) challenge virus; however, the protection rate was low in comparison to animals immunized with comparable amounts of the complete A2/68(H3N2) virus9 Furthermore there was no cross-protection against A2/Asia/57(H2N2) challenge virus. The protective effect of neuraminidase was not impaired by Tween-ether treatment of the A/eq(Heq-1)-HK(N2) recombinant virus.

Animals↗

PubMed1997

Evaluation of protection by two endotoxin-neutralizing IgM monoclonal antibodies in different peritonitis models.

Two anti-core glycolipid (CGL) IgM monoclonal antibodies (mAbs 8-2 and 26-20), previously shown to display cross-reactivity with heterologous lipopolysaccharide (LPS) in vitro and to provide cross-protectivity against endotoxin challenge in vivo, were evaluated for their potential to protect mice against death from peritonitis caused by heterologous bacterial challenge. Without concurrent antibiotic treatment neither antibody was protective. Compared with a control mAb, prophylactic treatment with mAb 8-2 significantly increased the survival of gentamicin-treated mice challenged with the rough strain Salmonella minnesota Re595. Both mAb 8-2 and a control mAb, in combination with a suboptimal dose of ceftazidime, increased survival following challenge with the clinical isolate Escherichia coli O7:K1. In a model of mucin-enhanced peritonitis, neither mAb was protective against challenge with inocula of E. coli O7:K1, ranging from 10(2) to 10(4) bacteria. We conclude that protection of mice by anti-CGL mAb 8-2 against heterologous challenge is vitally dependent on concurrent treatment with antibiotics and that protection may not be attributable to the anti-CGL specificity of these antibodies.

Animals↗

PubMed2000

Highly reduced protection against Streptococcus pneumoniae after deletion of a single heavy chain gene in mouse.

Phosphocholine (PC) is the immunodominant epitope found on the surface of Streptococcus pneumoniae (SPn). T15-idiotype Abs, whose heavy (H) chain variable region is encoded by the V1 gene, are dominant in the anti-PC response in adult mice and protect mice from lethal pneumococcal infection. The ability of anti-PC Abs using H chains other than the V1 H chain to protect against pneumococcal infection remains controversial. We generated V1(-/-) knockout mice to determine whether protective anti-PC Abs could be produced in the absence of the V1 gene. No anti-PC Abs were produced in V1(-/-) mice immunized with avirulent SPn; however, PC-BSA binding Abs were induced after immunization with PC-keyhole limpet hemocyanin but at significantly lower levels than those in wild-type mice. These Abs provided poor protection against virulent SPn; thus, <25% of V1(-/-) mice survived challenge with 10(4) bacteria as compared with 100% survival of V1(+/+) mice. The anti-PC Abs in V1(-/-) mice were heteroclitic, binding to nitrophenyl-PC better than to PC. None of nine hybridomas produced from V1(-/-) mice provided passive protection. However, the V1(-/-) mice produced normal amounts of Ab to SPn proteins that can partially protect mice against SPn. These data indicate that the V1 gene is critical for the production of anti-PC Abs providing optimum protection against infection with SPn, and the V1(-/-) mice could be useful in unmasking epitopes other than the immunodominant PC epitope on SPn capable of providing cross protection.

Animals↗

PubMed1975

Growth and immunogenicity of photochromogenic strains of mycobacteria in the footpads of normal mice.

Specific pathogen-free CD-1 mice were infected subcutaneously in the footpad with mycobacterium kansasii, three strains of M. marinum, and two strains of M. simiae-habana, and the growth of the organisms in the footpad, the draining popliteal lymph node, and the lung and spleen was followed quantitatively for up to 60 days. The ability of a footpad inoculum of M. marinum to spread to the lungs and spleen correlated with the ability of the organism to survive and multiple at 37 C in vitro cultures. The amount of footpad swelling which developed in the M. kansasii- and M. marinum-infected mice varied depending upon the strain of organism and the size of the original footpad inoculum. Injection of dead M. marinum into the footpad also induced an extensive amount of swelling which varied with the strain used, as well as being dose dependent. M. marinum- and BCG-vaccinated mice were protected against a later footpad challenge with M. marinum or the highly mouse virulent M. tuberculosis strain ERDMAN. The significance of this finding is discussed in relation to cross-protection studies using a variety of mycobacteria in the footpad infection model.

Animals↗

PubMed1987

Protection between different serotypes of bovine rotavirus in gnotobiotic calves: specificity of serum antibody and coproantibody responses.

In a previous study, different U.S. isolates of bovine rotavirus were studied for their serotypes and cross-protective properties (G. N. Woode, N. E. Kelso, T. F. Simpson, S. K. Gaul, L. E. Evans, and L. Babiuk, J. Clin. Microbiol. 18:358-364, 1983). Three viruses belonging to two different serotype groups were used as vaccines in gnotobiotic calves, which were subsequently challenged with B641 or B223, representing the two bovine serotypes. In the present work, the experiments were repeated with more calves and the specificity of their antibody responses was measured and compared with the results of the protection studies. Protection between different serotypes occurred under both homologous and heterologous conditions but was not directly serotype dependent. B223 virus showed both homologous and heterologous protection against B223 and B641 challenge viruses. This was a one-way reaction, as B641 did not induce protection against B223. Neonatal calf diarrhea virus vaccine produced neither homologous (against B641) nor heterologous (against B223) protection. The plaque reduction neutralization titers of serum antibody and coproantibody did not predict a state of protection against the challenge virus. Calves vaccinated with neonatal calf diarrhea virus or B641 developed neutralizing antibodies to their respective heterologous challenge viruses but were not protected. After challenge, the boosted coproantibody plaque reduction neutralization response to the original vaccine virus was greater than that to the challenge virus.

Animals↗

PubMed2006

Protection of rabbits against cutaneous papillomavirus infection using recombinant tobacco mosaic virus containing L2 capsid epitopes.

Cottontail rabbit papillomavirus (CRPV) and rabbit oral papillomavirus (ROPV) represent distantly related, cutaneous and mucosal tissue tropic papillomaviruses respectively that can infect the same host. These two viruses were used to test the effectiveness of an L2 peptide-based vaccine (aa 94-122) that was delivered on the surface of recombinant tobacco mosaic virus (rTMV) particles. Groups of NZW rabbits received combinations of CRPVL2, ROPVL2 and CRPV+ROPVL2 rTMV vaccines, and were then challenged with infectious CRPV and ROPV. The rabbits developed antibodies that reacted to whole L2 protein and these sera were able to neutralize CRPV pseudovirions at half-maximal titers that were between 50 and 500. Rabbits receiving the CRPV L2 vaccine alone or in combination with ROPV L2 vaccines were completely protected against CRPV infections. Those rabbits vaccinated with the ROPV L2 vaccines showed a weak response in some rabbits against CRPV infection. These studies demonstrate that L2-based vaccines provide strong protection against experimental papillomavirus infection that is most likely based upon the induction of virus-neutralizing antibody. Notably, we observed some limited cross-protection induced by the L2 sequences tested in these vaccines. Finally, the study demonstrated that rTMV were excellent agents for the induction of strong protection in a pre-clinical disease model of papillomavirus infection.

Animals↗

PubMed1968

The cholinergic properties of some amino-acid esters and amides.

1. Several amino-acid esters and amides have been prepared and their toxicological and pharmacological properties have been investigated. Some of the quaternary esters and amides were lethal to mice at doses below 1 mg/kg; this lethality was usually associated with high nicotinic activity. None of the compounds showed high muscarinic activity.2. The cause of death was asphyxia due to paralysis of the respiratory muscles, but at higher doses there was also failure of the medullary respiratory centre.3. Administration of sub-lethal doses of nicotine to mice was shown to protect the animals from subsequent lethal doses of nicotine. The amino-acid esters did not share this property, nor was there any cross-protection between nicotine and these esters.4. The possible nature of the nicotinic receptor is discussed with reference to these compounds and other known nicotinic agents. A tentative suggestion is made that nicotinic activity can result from a two-point interaction between the drug and the receptor.

Amides↗

PubMed1997

Characterization of PACAP receptors and signaling pathways in rabbit gastric muscle cells.

Pituitary adenylate cyclase-activating peptide (PACAP) receptors and their signaling pathways were characterized in dispersed rabbit gastric muscle cells. 125I-PACAP-27 and 125I-vasoactive intestinal peptide (VIP) binding to muscle cells were inhibited equally by PACAP and VIP (mean inhibitory concentration 0.8 to 1.3 nM) and desensitized to the same extent (70-80%) by exposure to either peptide. PACAP, like VIP, increased cytosolic free Ca2+ and the formation of L-[3H]citrulline, NO-3/NO-2, guanosine 3',5'-cyclic monophosphate (cGMP), and adenosine 3'5'-cyclic monophosphate (cAMP) and induced relaxation (mean effective concentration 1.8 +/- 0.1 nM) that was partly inhibited by NG-nitro-L-arginine (L-NNA), VIP-(10-28), and PACAP 6-38. L-[3H]citrulline and cGMP formation were blocked by nifedipine, L-NNA, and pertussis toxin (PTx), implying activation of a G protein-coupled, Ca(2+)-calmodulin-dependent nitric oxide (NO) synthase. PACAP-induced relaxation was inhibited to the same extent (46-49%) by nifedipine, L-NNA, PTx, and the protein kinase G inhibitor KT-5823; the inhibition reflected the component of relaxation mediated by the NO-cGMP pathway. The residual relaxation was abolished by the protein kinase A inhibitor H-89. The pattern of inhibition of all responses was identical to that observed with VIP. Desensitization with VIP or PACAP abolished cAMP formation but had no effect on L-[3H]citrulline and cGMP formation induced by either peptide. Receptor protection with VIP or PACAP preserved fully all responses (L-[3H]citrulline, cGMP, and cAMP formation and relaxation) to either peptide. The complete cross-competition, cross-desensitization, cross-antagonism, and cross-protection of receptors by either VIP or PACAP are consistent with interaction of both peptides with the same receptors; the receptors consist of two classes, each coupled to a distinct signaling pathway.

Adenylate Cyclase Toxin↗

PubMed1973

Immunity in experimental cholera: effect of parenteral immunization with vaccines and toxoid.

The protection conferred by parenteral cholera vaccines and cholera toxoid was determined in the rabbit ileal loop model of experimental cholera. Vibrio cholerae strains belonging to two different serotypes were employed, for immunization and challenge, to differentiate antibacterial and antitoxic immunity patterns. It was found that vaccines were protective but cholera toxoid was not, although serum antitoxin levels were high after administration of the latter. Antibacterial immunity was strictly serotype-specific, with evidence of cross-protection only between Ogawa and Inaba subtypes of serotype 1. Bivalent serotype 1 vaccines conferred protection against homologous challenge strains but immunity to Inaba infection was of shorter duration than immunity to Ogawa infection.

Animals↗

PubMed1986

Intracerebral infection of mice with ovine strains of Chlamydia psittaci: an animal screening test for the assay of vaccines.

Intracerebral inoculation of mice with the A22 strain of ovine C. psittaci gave a reproducible non-lethal infection; multiplication of the inoculum could be quantitated by titration of mouse brain extracts in tissue culture. Mice which had recovered from infection, or which had been inoculated subcutaneously with living organisms of A22 strain, showed solid resistance to intracerebral challenge infection. However, subcutaneous inoculation of formalin-inactivated chlamydia showed little protective effect unless given in very high dosage. Inactivated vaccines of the heterologous ZC113 strain gave better, but still incomplete, protection against A22 challenge infection than did the homologous inactivated vaccine. The implication of these findings is discussed. The mouse intracerebral protection test appears to be a suitable laboratory procedure for assessing the potency of vaccines against enzootic ewe abortion and for comparing the immunological cross-protection between the various strains of C. psittaci currently found in the natural disease in sheep.

Animals↗

PubMed2000

Basic features of the stress response in three species of bifidobacteria: B. longum, B. adolescentis, and B. breve.

The presence of the dnaK heat shock gene could be demonstrated for B. longum NCC481, B. longum NCC490, B. longum NCC585, B. adolescentis NCC251, and B. breve NCC298. Induction of dnaK on the transcriptional level was shown for NCC251 and NCC481 by increasing temperatures. NCC251 showed an additional chaperone-induction after salt or bile-salt treatment. In both strains preconditioning with bile-salts protected against otherwise lethal concentrations thereof. NCC251 when subjected to a heat stress was able to survive an otherwise lethal temperature (55 degrees C). Cross-protection was demonstrated for NCC251 since salt pretreatment resulted in increased tolerance after freeze-thawing cycles or lethal heat stress.

Bifidobacterium↗

PubMed1999

Pseudomonas aeruginosa UV-A-induced lethal effect: influence of salts, nutritional stress and pyocyanine.

The presence of NaCl in plating media shows an important protection against the Pseudomonas aeruginosa UV-A-induced lethal effect, contrasting with the known sensitizing action of salts on UV-A-irradiated Escherichia coli cells. MgSO4 exhibits a similar protection, but lower concentrations than for NaCl are needed to achieve the same effect. NaCl protection from lethal effects involves an osmotic mechanism, while MgSO4 could act by a different process. On the other hand, when cells grown in a complete medium are then incubated for 20 min in a synthetic medium and irradiated with UV-A, a very marked protection is obtained. This protection is dependent on protein synthesis, since treatment with tetracycline, during the nutritional stress, blocks its induction. These results offer a new example of cross-protection among different stressing agents. In our experimental conditions, natural phenazines of P. aeruginosa are not present in the cells, ruling out the possibility that these pigments act as photosensitizers. Conversely, pyocyanine (the major phenazine produced by this microorganism) prevents the UV-A killing effect in a concentration-dependent way when present in the irradiation media. Finally, UV-A irradiation induces, as in E. coli, the accumulation of guanosine tetraphosphate and guanosine pentaphosphate, although the physiological meaning of this finding has yet to be determined.

Culture Media↗

PubMed1988

T-cell-mediated immunity in persistent Mycobacterium intracellulare infections in mice.

Growth of mouse-virulent Mycobacterium intracellulare D673 and TMC 1405 in the lung was affected by T-cell depletion in susceptible C57BL/6 mice. Significant differences also occurred between the growth patterns seen in congenitally athymic (nu/nu) mice and their nu/+ littermates. Treatment of the mice with an immunosuppressive regimen of cyclosporin A (75 mg/kg of body weight per day subcutaneously) provided further evidence of the importance of T cells in controlling growth of M. intracellulare in the normal host. Adoptive transfer experiments indicated the presence of a T-cell-mediated specific protective immunity against a subsequent M. intracellulare challenge when transfer was carried out 3 weeks after immunization of the donor host. At this time, cross-protective immunity was also observed against a virulent M. tuberculosis challenge. There was no difference in the rate of growth by M. intracellulare as challenge in Mycobacterium bovis BCG-activated or normal peritoneal macrophages from C57BL/6 mice tested in vitro during a 7-day period. However, M. tuberculosis growth rates were decreased substantially in the BCG-activated macrophages. These studies suggest that mice infected with M. intracellulare do not eliminate the infection, because this organism can resist the bactericidal activity of the T-cell-activated macrophage better than M. tuberculosis can.

Animals↗

PubMed1986

Characterization of cyclically transmitted Trypanosoma (T.) brucei isolates from man.

Four different trypanosome isolates from human patients isolated in 1979 during the epidemic of sleeping sickness in Busoga, south-east Uganda, were characterized by the following methods: isoenzyme analyses of bloodstream forms by isoelectric focusing; in vitro tests of human serum resistance of bloodstream as well as metacyclic forms; tsetse fly transmission through Glossina morsitans centralis and Glossina morsitans morsitans to compare the above characteristics of parasite populations before and after the cyclical passage; the indirect immunofluorescent antibody test (IFAT) to analyse the antigenic relationship between metacyclic populations of the four different stocks. The results of the isoenzyme analyses and the in vitro tests of human serum resistance separated one stock (TH K 86) from the 3 other isolates which behaved similarly. The tsetse fly transmission did not influence the characteristics except that a temporary switch to human serum sensitivity occurred in the metacyclic population of isolate TH K 86. The indirect immunofluorescent antibody test (IFAT) revealed a close antigen relationship between the four metacyclic populations. Mice immunized against metacyclic forms of two isolates exhibited solid cross-protection against the infection with one different isolate.

Animals↗

PubMed1988

Isolation and characterization of bovine Theileria parasites in Zimbabwe.

Theilerial parasites of cattle were isolated by a variety of methods from the Harare area of Zimbabwe. Parasite stocks were established in lymphoid cell cultures and as cryopreserved sporozoite stabilates in the laboratory. Fourteen stocks in culture were characterized by testing them with monoclonal antibodies (MAb) raised against T. parva parva and T. parva lawrencei antigen. Two of these stocks had profiles similar to T. taurotragi isolates from East Africa, the other stocks had profiles similar to T. parva parva, however, many of them failed to bind MAb No. 7, and this may be a distinctive feature for T. parva bovis. Three T. p. bovis stocks were titrated by injecting different doses of the respective stabilates into pairs of cattle. Reactions ranged from severe to inapparent according to the stocks and dose used, but no fatal reactions were recorded, even at the highest dose rate. On recovery, all cattle were given homologous and then heterologous challenge. The results of the latter challenge showed that the Boleni stock gave good cross-protection against challenge with two other Zimbabwean stocks. This stock may therefore be a candidate for immunizing cattle, under field conditions, to protect them against T. p. bovis in Zimbabwe. Non-pathogenic strains of T. p. bovis may be difficult to distinguish from T. taurotragi unless cross-challenge experiments can be conducted and/or MAb profiles have been made. An improved serological test is needed to differentiate antibodies to these parasites in the sera of recovered cattle.

Animals↗

PubMed2004

A prospective study of Plasmodium falciparum multiplicity of infection and morbidity in Tanzanian children.

Several studies suggest that in individuals with substantial previous exposure to malaria, co-infection with multiple clones of Plasmodium falciparum can protect against subsequent clinical malaria attacks. Other studies, mainly of individuals with little previous exposure, found the converse relationship. To test whether acquisition of such cross-protection tracks the acquisition of clinical immunity in general, 610 Tanzanian children aged 0-6 years were enrolled in a nine-month prospective study of the risk of morbidity in relation to parasitological status and merozoite surface protein 2 genotypes on enrolment. Prevalence of parasitaemia and multiplicity of infection increased with age. In the first year of life, the incidence of clinical malaria was almost three times higher in children with parasites at baseline than in those without. In older children, baseline P. falciparum infections appeared to protect against both parasitaemic and non-parasitaemic fever episodes. In children aged less than three years, baseline multiple infection tended to be associated with higher prospective risk of clinical malaria than single infection while in children aged more than three years the converse was found, but these effects were not statistically significant. These results provide further evidence that relationships between asymptomatic malaria infections and clinical malaria change with cumulative exposure.

Age Distribution↗

PubMed1993

Efficacy of an Australian Babesia bovis vaccine strain in Malawi.

Three calves vaccinated with the Australian Ka strain of Babesia bovis were fully protected against experimental infection with an isolate from a farm on which four of 210 vaccinated cattle had died from B bovis infection. A degree of cross protection against the isolate was demonstrated in one calf which had been infected previously with Babesia bigemina.

Animals↗

PubMed1999

Immunization with recombinant transferrin binding protein B enhances clearance of nontypeable Haemophilus influenzae from the rat lung.

Nontypeable Haemophilus influenzae (NTHI) is an opportunistic pathogen, and heterogeneity in the surface-exposed immunodominant domains of NTHI proteins is thought to be associated with the failure of an infection to stimulate an immune response that is cross-protective against heterologous NTHI strains. The aim of this study was to assess the vaccine potential of a surface-exposed component of the NTHI human transferrin receptor, TbpB, and to determine if the antibody response elicited was cross-reactive with heterologous strains of NTHI. The efficacy of immunization with a recombinant form of TbpB (rTbpB) was determined by assessing the pulmonary clearance of viable bacteria 4 h after a live challenge with NTHI. There was a significant reduction in the number of viable bacteria in both the bronchoalveolar lavage fluid (34% for the 20-microgram dose and 58% for the 40-microgram dose) and lung homogenates (26% for the 20-microgram dose and 60% for the 40-microgram dose) of rats immunized with rTbpB compared to the control animals. While rTbpB-specific antibodies from immunized rats were nonspecific in the recognition of TbpB from six heterologous NTHI strains on Western blots, these antibodies differed in their ability to block transferrin binding to heterologous strains and to cross-react in bactericidal assays. If bactericidal antibodies are key indicators of the efficacy of the immune response in eliminating NTHI, this data suggests that while immunization with rTbpB stimulates protective responses against the homologous isolate, variability in the recognition of TbpB from heterologous isolates may limit the potential of rTbpB as an NTHI vaccine component.

Amino Acid Sequence↗