Challenge Dose Research Articles

Demonstration of durable hepatitis B immune memory in children vaccinated with a DTaP5-IPV-HepB-Hib infant-toddler series 7 to 8 years previously

ABSTRACT Vaccination against hepatitis B (HepB) provides long-term protection against infection. This is despite a reduction in HepB surface antibody (anti-HBs) concentrations over time to levels below the well-accepted correlate of protection of ≥10 mIU/mL. Continued evidence of immune memory and protection despite declined anti-HBs concentrations can be demonstrated by HepB virus surface antigen challenge studies. Long-term immune memory and protection against HepB infection has not been demonstrated previously for the pediatric hexavalent vaccine DTaP5-IPV-HepB-Hib. This phase 3, multicenter, single-group, open-label challenge study (NCT04490499; EudraCT: 2020–000126–26) evaluated immune memory against HepB infection in children who had received DTaP5-IPV-HepB-Hib at 2, 4, and 11–12 months of age, or at 2, 3, 4, and 12 months of age. At age 8–9 years, they were each challenged with 5 μg of monovalent HepB vaccine. Anti-HBs levels were measured on pre-challenge day 1 and post-challenge day 30. At baseline, 45.4% (93 of 205) had anti-HBs levels ≥10 mIU/mL. On post-challenge day 30, 99.5% (201 of 202) had anti-HBs levels ≥10 mIU/mL, regardless of initial vaccination schedule. Post-challenge, geometric mean concentrations increased 71-fold over baseline and 96.0% of children had a ≥4-fold rise in anti-HBs concentrations with similar results across both dosing schedules. The challenge dose was well tolerated. The robust anti-HBs responses after a single 5-μg dose of HepB vaccine confirm the persistence of a HepB immune memory and demonstrate that DTaP5-IPV-HepB-Hib provides long-term protection against HepB.

Protective efficacy of new-generation anticoccidial vaccine candidates against Eimeria infection in chickens: A meta-analysis of challenge trials

Limitations of live oocyst anticoccidial vaccines in poultry have led to a search for the new generation of anticoccidial vaccines. Several sources may influence the protective efficacy of the new generation of anticoccidial vaccine candidates. Therefore, the objective of this study was to explore the sources influencing the protective efficacy (in terms of the lesion score and the oocyst output) of the new-generation anticoccidial vaccine candidates from the challenge trials in chickens, using meta-analysis techniques. The overall effect size was also estimated to get the overview of the protective efficacy. The study outcomes were the standardized mean difference (SMD) of the lesion score and the difference in mean (DM) of the oocyst output. Descriptive statistics of the oocyst decrease ratio (%) and anticoccidial index (ACI) were also presented. Relevant citations were retrieved from PubMed, Scopus, and Web of Science. Of 1524 retrieved citations, 63 were included for meta-analysis (60 for the lesion score and 44 for the oocyst output). Overall, the new generation of anticoccidial vaccine candidates partially protected chickens from coccidiosis because they significantly reduced the lesion score (SMD = −3.69, [95% CI: −4.08 to −3.29], P < 0.001) with high heterogeneity (I2 = 96.85%) and the oocyst output (DM = −1.48, [95% CI: −1.75 to −1.21], P < 0.001) with high heterogeneity (I2 = 99.69%). The median oocyst decrease ratio was 66.15% (a range from 4.27% to 95.93%, n = 125 subgroups). The median ACI was 164.71 (a range from 50.05 to 196.40, n = 115 subgroups). Vaccine platform and route of administration were identified as sources of heterogeneity for the lesion score and the oocyst output. However, severe publication bias threatened validity of the lesion score outcome. After accounting for other sources of variation, the anticoccidial vaccine candidates were shown to be less effective in reducing the oocyst output when the challenge dose, the length between the day of last immunization and the day of the challenge, or the length between the day of the challenge and the day of sampling, increased. In conclusion, although the new generation of anticoccidial vaccine candidates clearly showed a partial protection of chickens from coccidiosis in experimental trials, the protective efficacy was influenced by several sources, such as the vaccine platform and route of administration. Sources of high heterogeneity such as protein antigens are worth exploring when additionally relevant data are available. Therefore, additional experimental trials in chickens are required to better understand the protective efficacy of the new-generation anticoccidial vaccine candidates.

Absence of active systemic anaphylaxis in guinea pigs upon intramuscular injection of inactivated SARS-CoV-2 vaccine (Vero cells)

Background: The safety of novel vaccines against COVID-19 is currently a major focus of preclinical research. As a part of the safety evaluation testing package, 24 healthy guinea pigs were used to determine whether repeated administration of inactivated SARS-CoV-2 vaccine could induce active systemic anaphylaxis (ASA), and to evaluate its degree of severity. Method: According to sex and body weight, the animals were randomly divided into three experimental groups (eight animals per group). The negative control group received 0.9% sodium chloride (priming dose: 0.5 mL/animal; challenge dose: 1 mL/animal); the positive control group received 10% ovalbumin (priming dose: 0.5 mL/animal; challenge dose: 1 mL/animal); and the inactivated SARS-CoV-2 vaccine group received inactivated SARS-CoV-2 vaccines (priming dose: 100 U in 0.5 mL/animal; challenge dose: 200 U in 1 mL/animal). Priming dose administration was conducted by multi-point injection into the muscles of the hind limbs, three times, once every other day. On days 14 and 21 after the final priming injection, a challenge test was conducted. Half of the animals in each group were injected intravenously with twice the dose and volume of the tested substance used for immunization. During the experimental course, the injection site, general clinical symptoms, body weight, and systemic allergic reaction symptoms were monitored. Result: After intramuscular injection of inactivated SARS-CoV-2 vaccine, there were no abnormal reactions at the injection site, clinical symptoms, or deaths. There was no difference in body weight between the groups, and there were no allergic reactions. Conclusion: Thus, inactivated SARS-CoV-2 vaccine injected intramuscularly in guinea pigs did not produce ASA and had a good safety profile, which can provide actual data on vaccine risks and important reference data for clinical research on this vaccine.

Recombinant PBP2a/autolysin conjugate as PLGA-based nanovaccine induced humoral responses with opsonophagocytosis activity, and protection versus methicillin-resistant Staphylococcus aureus infection.

Objective(s):Methicillin-resistant Staphylococcus aureus (MRSA) reasons extreme infections, can resist various conventional antimicrobial agents, and cause morbidity and mortality worldwide. Vaccination seems to help modulate MRSA infections. Nanovaccine is considered a novel strategy in vaccine technology. The primary purpose of the present study was to develop a conjugate vaccine based on recombinant PBP2a and MRSA autolysin formulated in PLGA as a nanoparticle capable of enhancing protective responses against MRSA in the murine model.Materials and Methods:Recombinant PBP2a and autolysin have been expressed and purified by nickel-nitrilotriacetic acid (Ni-NTA) affinity column and characterized by SDS-PAGE and western blot. PLGA was bound to recombinant proteins by using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDAC) and adipic acid dihydrazide (ADH) as a linker and spacer, respectively. Conjugation of recombinant proteins to PLGA was confirmed by the AFM assay, zeta potential, and size distribution, and its efficacy was evaluated in mice. Total IgG, IgG1, IgG2a, IgG2b, and IgM titers were analyzed to assess immune responses. Lastly, the bioactivity of antibodies was tested by using the opsonophagocytosis assay. Results:Mice immunized with the r-PBP2a-r-autolysin–PLGA nanovaccine led to increased levels of opsonic antibodies and IgG1, IgG2a, IgG2b, and IgM when compared with other experimental groups. Our results confirmed that vaccination with nanovaccine could reduce the mortality rate against the sub-lethal dose of MRSA challenge. Furthermore, the nanovaccine could eliminate MRSA from the kidney of infected mice. Conclusion:This study may provide valuable insights into the protective power of the r-PBP2a-r-autolysin–PLGA conjugate vaccine against MRSA infection.

Attenuation of opioid tolerance by ETA receptor antagonist, BQ123, administered intravenously in mice

Intracerebroventricular injection of endothelin-A receptor antagonist BQ123 potentiates opioid analgesia and reverses analgesic tolerance. This study explores whether these effects can be replicated by injecting BQ123 intravenously. Male Swiss-Webster mice were used. Morphine tolerance was induced using 3- or 7-day dosing. Intravenous BQ123 (8mg/kg) was injected only once on Day 1, 2, 3 or 4 (3-day studies), and on Day 4, 6 or 8 (7-day studies). On Day 4 or 8, respectively, tail-flick and hot-plate latencies were measured following a morphine challenge dose. Intravenous BQ123 increased the potency and duration of morphine antinociceptive responses. In the 3-day study, the antinociceptive response was unaffected by BQ123 given on Days 1 or 2. BQ123 treatment on Day 3 or 4 (Day 4, BQ123 given 15-min before morphine) significantly potentiated antinociceptive response versus vehicle-treated tolerant mice. In 7-day studies, the antinociceptive response was unaffected by BQ123 given on Day 4. BQ123 given on Day 6 or 8 (Day 8, BQ123 given 15-min before morphine) produced a >100% increase in antinociceptive response versus vehicle-treated tolerant mice for at least 48h. Intravenous administration of BQ123 is effective in potentiating morphine analgesia and restoring antinociceptive response in morphine-tolerant mice.

Differential and long-lasting changes in neurotransmission in the amygdala of male Wistar rats during extended amphetamine abstinence

Amphetamine addiction is associated with maladaptive actions that promotes continued use despite negative consequences, and a high risk of relapse even after protracted abstinence. Considering the role of the amygdala in regulating incentive motivation and reward-based behavior, the aim of this study was to assess neuroadaptations in subregions of the amygdala elicited by a brief period of discontinuous amphetamine exposure (2.0 mg/kg/day, 5 days) followed by abstinence (2 weeks, 1 month, 3 months) in male Wistar rats. Electrophysiological field potential recordings demonstrated that repeated amphetamine exposure significantly depressed evoked populations spikes in the basolateral amygdala (BLA). Evoked populations spikes were normalized after three months abstinence, but one challenge dose of amphetamine (0.5 mg/kg) was sufficient to reinstate synaptic depression in animals previously receiving amphetamine. In the central nucleus of the amygdala (CeA), amphetamine produced a long-lasting hyperexcitability that sustained even after three months abstinence. In the CeA, there were no significant differences between treatment groups following bath perfusion of the GABAA receptor antagonist bicuculline, indicating that amphetamine acts by reducing the inhibitory tone. Recordings performed in brain subregions interlinked with the amygdala, including medial prefrontal cortex, orbitofrontal cortex, and nucleus accumbens shell (nAc), revealed no significant neuroadaptations after two weeks abstinence. However, synaptic output was significantly depressed in the nAc after one- and three-month abstinence. In conclusion, the data presented here shows that five days of discontinuous exposure to amphetamine is sufficient to produce long-lasting neuroadaptations, which may contribute to compulsive drug taking and increase the risk for relapse.

Reduced pathogenicity of the SARS-CoV-2 omicron variant in hamsters

BackgroundThe severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron (B.1.1.529) variant has proven to be highly transmissible and has outcompeted the Delta variant in many regions of the world. Early reports have also suggested that Omicron may result in less severe clinical disease in humans. Here, we show that Omicron is less pathogenic than prior SARS-CoV-2 variants in Syrian golden hamsters.MethodsHamsters were inoculated with either SARS-CoV-2 Omicron or other SARS-CoV-2 variants. Animals were followed for weight loss, and upper and lower respiratory tract tissues were assessed for viral loads and histopathology.FindingsInfection of hamsters with the SARS-CoV-2 WA1/2020, Alpha, Beta, or Delta strains led to 4%–10% weight loss by day 4 and 10%–17% weight loss by day 6. In contrast, infection of hamsters with two different Omicron challenge stocks did not result in any detectable weight loss, even at high challenge doses. Omicron infection led to substantial viral replication in both the upper and lower respiratory tracts but demonstrated lower viral loads in lung parenchyma and reduced pulmonary pathology compared with WA1/2020 infection.ConclusionsThese data suggest that the SARS-CoV-2 Omicron variant may result in robust upper respiratory tract infection, but less severe lower respiratory tract clinical disease, compared with prior SARS-CoV-2 variants.FundingFunding for this study was provided by NIH grant CA260476, the Massachusetts Consortium for Pathogen Readiness, the Ragon Institute, and the Musk Foundation.

Intranasal administration of BReC-CoV-2 COVID-19 vaccine protects K18-hACE2 mice against lethal SARS-CoV-2 challenge

SARS-CoV-2 is a viral respiratory pathogen responsible for the current global pandemic and the disease that causes COVID-19. All current WHO approved COVID-19 vaccines are administered through the muscular route. We have developed a prototype two-dose vaccine (BReC-CoV-2) by combining the Receptor Binding Domain (RBD) antigen, via conjugation to Diphtheria toxoid (EcoCRM®). The vaccine is adjuvanted with Bacterial Enzymatic Combinatorial Chemistry (BECC), BECC470. Intranasal (IN) administration of BreC-CoV-2 in K18-hACE2 mice induced a strong systemic and localized immune response in the respiratory tissues which provided protection against the Washington strain of SARS-CoV-2. Protection provided after IN administration of BReC-CoV-2 was associated with decreased viral RNA copies in the lung, robust RBD IgA titers in the lung and nasal wash, and induction of broadly neutralizing antibodies in the serum. We also observed that BReC-CoV-2 vaccination administered using an intramuscular (IM) prime and IN boost protected mice from a lethal challenge dose of the Delta variant of SARS-CoV-2. IN administration of BReC-CoV-2 provided better protection than IM only administration to mice against lethal challenge dose of SARS-CoV-2. These data suggest that the IN route of vaccination induces localized immune responses that can better protect against SARS-CoV-2 than the IM route in the upper respiratory tract.

Co-administration of Zingiber officinale Extract and Sodium Valproate Ameliorates Seizure Severity, Cognitive Deficit, and Neuronal Cell Loss in Pentylenetetrazole-kindled Mice

Preparations of Zingiber officinale are used in Nigerian folk medicine to manage colds, pain, arthritis, nausea, and epilepsy. The ameliorative effects of co-administering aqueous Zingiber officinale extract (GE) and sodium valproate (SDV) on pentylenetetrazole-kindled mice were evaluated regarding cognitive deficits, neuronal cell loss, and seizure severity. GFAP was also quantified. Male mice were pretreated with GE (50 mg/kg), SDV (100 and 200 mg/kg), and GE + SDV before kindling. After kindling, the mice underwent a learning performance test. The animals received a challenge dose of pentylenetetrazole one week after kindling. The brains were excised one day after the challenge test and were processed for GFAP immunohistochemistry and histopathology. GE alone did not affect PTZ-kindled seizures. However, treatment with GE and SDV significantly improved learning performance and protected against neuronal cell loss in pentylenetetrazole-kindled mice. The level of astrocyte activation was reduced in the kindled group pretreated with the extract. The results obtained suggested that co-administration of GE and a low dose of SDV significantly ameliorated learning deficits and protected against neuronal cell loss, astrogliosis, and neuroinflammation, suggesting that GE might be a beneficial co-medication in the management of epilepsy.

Differential molecular response in mice and human thymocytes exposed to a combined-dose radiation regime

In the quest for more effective radiation treatment options that can improve both cell killing and healthy tissue recovery, combined radiation therapies are lately in the spotlight. The molecular response to a combined radiation regime where exposure to an initial low dose (priming dose) of ionizing radiation is administered prior to a subsequent higher radiation dose (challenging dose) after a given latency period have not been thoroughly explored. In this study we report on the differential response to either a combined radiation regime or a single challenging dose both in mouse in vivo and in human ex vivo thymocytes. A differential cell cycle response including an increase in the subG1 fraction on cells exposed to the combined regime was found. Together with this, a differential protein expression profiling in several pathways including cell cycle control (ATM, TP53, p21CDKN1A), damage response (γH2AX) and cell death pathways such as apoptosis (Cleaved Caspase-3, PARP1, PKCδ and H3T45ph) and ferroptosis (xCT/GPX4) was demonstrated. This study also shows the epigenetic regulation following a combined regime that alters the expression of chromatin modifiers such as DNMTs (DNMT1, DNMT2, DNMT3A, DNMT3B, DNMT3L) and glycosylases (MBD4 and TDG). Furthermore, a study of the underlying cellular status six hours after the priming dose alone showed evidence of retained modifications on the molecular and epigenetic pathways suggesting that the priming dose infers a “radiation awareness phenotype” to the thymocytes, a sensitization key to the differential response seen after the second hit with the challenging dose. These data suggest that combined-dose radiation regimes could be more efficient at making cells respond to radiation and it would be interesting to further investigate how can these schemes be of use to potential new radiation therapies.

On the Similarity Between the Reinforcing and the Discriminative Properties of Intracranial Self-Stimulation.

Rats work very hard for intracranial self-stimulation (ICSS) and tradeoff effort or time allocation for intensity and frequency parameters producing a sigmoidal function of the subjective reward magnitude of ICSS. Previous studies using electrical intracranial stimuli (ICS) as a discriminative cue focused on estimating detection thresholds or on the discrimination between intensities. To our knowledge, there is no direct comparison of the reinforcer tradeoff functions with the discriminative functions. Rats were trained to press and hold the lever for ICSS using the maximum reinforcing intensity below motor alterations or avoidance behavior. First, rats were trained to hold the lever for 1 s; after stability, they undergo trials where intensity or frequency was decreased on 0.1 log step. Thereafter, they undergo further training with a hold of 2 and later of 4 s to determine tradeoff with intensity or frequency. The same rats were trained on a discrimination task where the previously used ICSS signaled a lever where a 1 s hold response was followed by a reinforcing ICSS; on randomly alternating trials, a −0.6 log ICS signaled an alternate lever where a similar hold response led to a reinforcer. After mastering discrimination, generalization tests were carried out with varying intensity or frequency. Rats completed training with 2 and later 4 s hold response. After the completion of each task, the rats had different doses of a pimozide challenge while their intensity and hold-down requirement were varied. With regards to the rats’ tradeoff response time allocation as a function of intensity or frequency, sigmoid functions were displaced to the right when long responses were required. Rats that learned the discrimination task attained a discrimination index of 90–98%. Discrimination accuracy decreased slightly with the increase of hold requirement, but generalization gradients were not displaced to the right as a function of the response requirement. Pimozide induced a dose-dependent displacement of the time-allocation gradients, but it did not affect the generalization gradients. It is concluded that rats integrate response requirements as part of the reinforcement tradeoff function, but the response cost is not integrated into the discriminative function of ICSS.

CoVac501, a self-adjuvanting peptide vaccine conjugated with TLR7 agonists, against SARS-CoV-2 induces protective immunity

Safe, effective, and economical vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are needed to achieve adequate herd immunity and end the pandemic. We constructed a novel SARS-CoV-2 vaccine, CoVac501, which is a self-adjuvanting peptide vaccine conjugated with Toll-like receptor 7 (TLR7) agonists. The vaccine contains immunodominant peptides screened from the receptor-binding domain (RBD) and is fully chemically synthesized. It has been formulated in an optimized nanoemulsion formulation and is stable at 40 °C for 1 month. In non-human primates (NHPs), CoVac501 elicited high and persistent titers of protective neutralizing antibodies against multiple RBD mutations, SARS-CoV-2 original strain, and variants (B.1.1.7 and B.1.617.2). Specific peptides booster immunization against the B.1.351 variant has also been shown to be effective in improving protection against B.1.351. Meanwhile, CoVac501 elicited the increase of memory T cells, antigen-specific CD8+ T-cell responses, and Th1-biased CD4+ T-cell immune responses in NHPs. Notably, at an extremely high SARS-CoV-2 challenge dose of 1 × 107 TCID50, CoVac501 provided near-complete protection for the upper and lower respiratory tracts of cynomolgus macaques.

Modified oral food challenge protocol approach in the diagnosis of Food Protein-Induced Enterocolitis Syndrome

BackgroundFood Protein-Induced Enterocolitis Syndrome (FPIES) is a non-IgE mediated food allergy most commonly presenting in infants. The most common food triggers include soy, cow’s milk and grains. Symptoms may include intractable vomiting, diarrhea, lethargy, pallor, abdominal distention, hypotension and/or shock. Oral food challenges (OFCs) given at food protein dose of 0.06–0.6 g/kg in 3 equivalent doses administered over a few hours are recommended in guidelines to confirm a diagnosis.Case presentationThe patient is a 6-month-old girl with a history of severe FPIES symptoms to egg. In our clinic, we perform OFC with 1/100 serving dose on visit 1 and then increase the dose monthly. The patient takes the tolerated dose daily at home between visits. An OFC to baked egg at 1/100 of a serving was performed and was well-tolerated on her initial visit. The patient remained on the same dose upon returning home. Within 1-week, she developed FPIES symptoms including watery diarrhea and severe emesis requiring ondansetron. She required an Emergency Department visit for one of the reactions.ConclusionsOur patient had severe FPIES symptoms with a small amount of egg. We believe that administration of three large food challenge doses on one clinic visit, as guidelines currently suggest, does not allow adequate time for symptoms to appear. Our patient likely would have suffered a severe reaction. Also, this guidelines protocol does not allow for monitoring of more delayed or chronic FPIES. We propose a modified protocol to OFCs with cautious up-dosing to allow for safer OFCs and monitoring of chronic FPIES. We have implemented an OFC approach where only one food challenge dose (starting with 1/100 of final dose) is given at each visit. The up-titration of the dose is completed every 4-weeks with one dose only. When the serving sized dose is reached and tolerated, the food can be maintained in the diet.

A VLP-Based Vaccine Candidate Protects Mice against Japanese Encephalitis Virus Infection.

Japanese encephalitis virus (JEV) is the leading cause of epidemic encephalitis in Asia, and vaccination is the most effective way to prevent JE. Although several licensed vaccines were widely used, there is still a demand for developing safer, cheaper, and more effective JE vaccines. In the current study, a virus-like particle (VLP) vaccine candidate containing the envelope structural protein of JEV expressed by the Pichia pastoris was assembled in vitro. It elicited a robust humoral and cellular immune response in mice model, conferring immunodeficient mice complete protection against lethal doses of JEV challenge. Furthermore, pigs immunized with VLP alone without adjuvant via intramuscular produced high neutralizing antibodies against JEV. Consequently, this study showed a new design of JEV subunit vaccine based on VLP strategy and demonstrated the potential for clinical application.

Domestic pigs experimentally infected with Mycobacterium bovis and Mycobacterium tuberculosis exhibit different disease outcomes

The domestic pig shares many similarities with humans in anatomy, physiology, and immunology. As such it is an attractive animal model to study human tuberculosis (TB). In this study, we examined disease outcome in pigs challenged via two different routes with either the human TB bacillus Mycobacterium tuberculosis Erdman (M. tb) or bovine TB bacillus M. bovis AF2122/97 in head-to-head comparisons. Pigs challenged intravenously with M. bovis exhibited greater morbidity and rapid onset of mortality, higher bacterial burden and tissue necrosis compared to pigs challenged similarly with M. tb. Concordantly, pigs challenged with aerosolized M. bovis exhibited reduced weight gain and more severe pathology than pigs challenged similarly with M. tb. Specifically, M. bovis challenged pigs presented a spectrum of granulomatous lung lesions similar to that in human TB. In contrast, pigs challenged with M. tb presented mostly early-stage granulomas. Irrespective of challenge dose and pathology however, peripheral IFN-γ responses were similar in both M. bovis and M. tb aerosol challenged pigs. Although M. bovis appears to be more virulent than M. tb, both can be used to model different facets of human TB in pigs, depending on whether one seeks to recapitulate active or latent forms of the disease.

Protection Generated by Prior Exposure to Pathogens Depends on both Priming and Challenge Dose.

Free-living hosts encounter pathogens at a wide range of frequencies and concentrations, including low doses that are largely aclinical, creating a varied landscape of exposure history and reinfection likelihood. While several studies show that higher priming doses result in stronger immunological protection against reinfection, it remains unknown how the reinfection challenge dose and priming dose interact to determine the likelihood and severity of reinfection. We manipulated both priming and challenge doses of Mycoplasma gallisepticum, which causes mycoplasmal conjunctivitis, in captive house finches (Haemorhous mexicanus), to assess reinfection probability and severity. We found a significant interaction between priming and challenge doses on reinfection probability, with the likelihood of reinfection by a high but not a low challenge dose decreasing exponentially at higher priming doses. While this interaction was likely driven by lower average infection probabilities for low-dose versus high-dose challenges, even the highest priming dose provided only negligible protection against reinfection from low-dose challenges. Similarly, pathogen loads during reinfection were significantly reduced with increasing priming doses only for birds reinfected at high but not low doses. We hypothesize that these interactions arise to some degree from fundamental differences in host immune responses across doses, with single low doses only weakly triggering host immune responses. Importantly, our results also demonstrate that reinfections can occur from a variety of exposure doses and across diverse degrees of standing immunity in this system. Overall, our study highlights the importance of considering both initial and subsequent exposure doses where repeated exposure to a pathogen is common in nature.

Acute and chronic ethanol administration: A potential model of behavioral sensitization using wheel-running in male CD1 mice

RationaleWe define behavioral sensitization as an augmented response to subsequent dosing after chronic intermittent administration of a drug. However, the biphasic effects of ethanol (EtOH), first stimulatory followed by depressive, make animal models of behavioral sensitization rare. ObjectivesThis study aimed to determine a dose of EtOH that did not depress wheel-running (WR) in CD1 mice and then to develop a model of EtOH-induced behavioral sensitization. MethodsFor the first part of this study, male CD1 mice (n = 24, 6/group) were administered either phosphate buffer saline (PBS), 0.5 g/kg, 1 g/kg, or 2 g/kg EtOH at a volume of 3 ml/kg, intraperitoneally (IP). Mice were divided into equal groups and received the weight-based dose once daily on Days 1, 2, 3, 4, and 5. All mice received a challenge dose of 0.5 g/kg on Day 10. In both parts of the study, mice were habituated to the running wheel for 5 min prior to dosing and wheel running was measured for 10 min after each dose. ResultsThe acute dose-response of EtOH effects on wheel running determined a significant difference between doses in wheel running (p < 0.05), with a post-hoc analysis establishing that 0.5 g/kg EtOH resulted in significantly more WR compared to 2 g/kg EtOH (p < 0.05). The chronic study demonstrated a significant main effect of Day (1 vs. 5 vs. Challenge, p < 0.001) and an interaction between Day and Treatment, with post-hoc analysis determining the effect to be between PBS and EtOH WR on Day 5 (p < 0.05). In addition, Bonferroni post-hoc analysis determined no differences between Days in the PBS condition, but a significant difference in the EtOH condition between Day 1 and Day 5 (p < 0.001) and that difference from Day 1 persisted when comparing to the Challenge Day (p < 0.01). ConclusionAfter chronic, intermittent, low dose administration of EtOH, male mice showed an increase in activity as measured by wheel running. Therefore, we laid the groundwork for a potentially useful rodent model for EtOH-induced behavioral sensitization.

Induction of adaptive response in utero by ionizing radiation: A radiation quality dependent phenomenon

Investigation on possible induction of adaptive response (AR) by high-liner energy transfer (LET) particle radiation for protection against low-LET photon radiation-induced detrimental effects has not yet been performed <i>in utero</i>. This study verified if an AR could be induced by high-LET particle radiation from accelerated heavy ions against low-LET X-ray radiation-induced detrimental effects on fetal mice. Total body irradiation of pregnant C57BL/6J mice were performed by delivering a priming dose ranging from 10 mGy to 320 mGy of particle radiation on gestation day 11 followed one day later by a challenge dose at 3500 mGy from X-ray radiation. The monoenergetic beams of carbon, silicon and iron with the LET values of about 15, 55, and 200 KeV/μm, respectively, were examined. Significant suppression by the priming radiation of the detrimental effects (fetal death, malformation, or low body weight) was used as the endpoints for judgment of a successful AR induction on gestation day 18. Existence of AR was not observed. On the other hand, the priming dose of high-LET particle radiation, in some cases, even increased the detrimental effects induced by the challenge dose from low-LET X-ray radiation. Although existence of AR induced by high-LET radiation in cultured mammalian cells<i> in vitro </i> and in certain tissues of laboratory mice <i>in vivo</i> was demonstrated, the present study did not suggest that low dose of high-LET particle radiation could induce an AR in fetal mice <i>in utero</i> under the setup of our experimental system.

EV71 was Detected by Real-Time Fluorescence Quantitative RT-PCR Combined with Hand-Foot-Mouth Disease Rhesus Monkey Model

In this study, a real-time fluorescence quantitative RT-PCR method was developed for the detection of enterovirus 71 (EV71) and the detection of EV71 viral load during the establishment of hand-foot-mouth disease (HFMD) model in rhesus monkeys. The model of hand-foot-mouth macaque was established by injecting newborn macaques infected with the virus venom, and the dynamic changes of virus content in blood samples from 0 to 14 days after infection were monitored by real-time quantitative RT-PCR. The linear range of the standard curve was between 103 and 108 copies/µL, and the PCR amplification rate was 99.37%. The results showed that the established method could detect a minimum of 102 copies of viral RNA, 100 times higher than the conventional RT-PCR method. It has the characteristics of strong specificity, high sensitivity and good stability. The results of blood sample analysis showed that the three groups of rhesus monkey models were successfully infected with EV71, and the copy number of virus proliferation was correlated with time and challenge dose. The results showed that real-time quantitative PCR could be used for quantitative detection of EV71 viral load.

No protection seen on challenge with live virus after single intranasal immunization with heat inactivated virus in murine model of EHV-1 infection

Equine herpes virus (EHV-1) causes respiratory disease, abortion, neonatal death, paresis, retinopathy, and latent infection and is wide-spread among equine worldwide. Horses show transient immunity after natural or experimental EHV-1 infection and immune responses to EHV-1 begin to decline after a few months after infection. As a result, recovered horses are prone to subsequent EHV-1 infection. Due to transient immune responses, effective and lasting vaccination remains a challenge. As this virus is widespread among equine, development of effective vaccine is a challenge. We used a murine model to study the efficacy of heat inactivated virus in terms of protection in a challenge study. After 34 days following intranasal inoculation with heat inactivated virus, mice were challenged with live virus along with previously placebo control group. Clinical signs, virus titres, and viraemia were studied in both groups. We noticed that mice on challenge showed more clinical signs at peak of infection but no significant difference in virus titres and infectious centre assay was noted. The results of this study suggest that heat inactivated virus does not provide any protection to challenge dose but in fact these group looked clinically worse. These results are discussed along with the possible mechanism involved in more clinical signs seen on challenge after single dose of intranasal immunization by heat inactivate virus in current communication.