Rhesus macaques self-curing from a schistosome infection can display complete immunity to challenge.

The rhesus macaque provides a unique model of acquired immunity against schistosomes, which afflict >200 million people worldwide. By monitoring bloodstream levels of parasite-gut-derived antigen, we show that from week 10 onwards an established infection with Schistosoma mansoni is cleared in an exponential manner, eliciting resistance to reinfection. Secondary challenge at week 42 demonstrates that protection is strong in all animals and complete in some. Antibody profiles suggest that antigens mediating protection are the released products of developing schistosomula. In culture they are killed by addition of rhesus plasma, collected from week 8 post-infection onwards, and even more efficiently with post-challenge plasma. Furthermore, cultured schistosomula lose chromatin activating marks at the transcription start site of genes related to worm development and show decreased expression of genes related to lysosomes and lytic vacuoles involved with autophagy. Overall, our results indicate that enhanced antibody responses against the challenge migrating larvae mediate the naturally acquired protective immunity and will inform the route to an effective vaccine.

Early exposure to environmental enrichment protects male rats against neuropathic pain development after nerve injury.

Because environmental elements modify chronic pain development and endogenous mechanisms of pain control are still a great therapeutic source, we investigated the effects of an early exposure to environmental enrichment (EE) in a translational model of neuropathic pain. Young male rats born and bred in an enriched environment, which did not count on running wheel, underwent chronic constriction injury (CCI) of sciatic nerve. EE abolished neuropathic pain behavior 14 days after CCI. Opioid receptors' antagonism reversed EE-analgesic effect. ß-endorphin and met-enkephalin serum levels were increased only in EE-CCI group. Blockade of glucocorticoid receptors did not alter EE-analgesic effect, although corticosterone circulating levels were increased in EE animals. In the spinal cord, EE controlled CCI-induced serotonin increase. In DRG, EE blunted the expression of ATF-3 after CCI. Surprisingly, EE-CCI group showed a remarkable preservation of sciatic nerve fibers compared to NE-CCI group. This work demonstrated global effects induced by an EE protocol that explain, in part, the protective role of EE upon chronic noxious stimulation, reinforcing the importance of endogenous mechanisms in the prevention of chronic pain development.

Distinct environmental enrichment protocols reduce anxiety but differentially modulate pain sensitivity in rats.

Environmental enrichment (EE) can alter anxiety as well as perception of nociceptive stimuli, suggesting a relationship between well-being and analgesia. Considering that, we aimed to evaluate the influence of different EE types on anxiety and peripheral pain sensitivity of male Wistar rats. Animals were submitted to two different types of EE: On the first one, animals were housed in standard size cages after weaning and received three different objects, one type per week, on a regular basis (simple EE - sEE). On the second one, animals were born in an already enriched environment and, after five weeks, were housed in larger cages and received five different objects, three of each type per week, on a regular basis (improved EE - iEE). Control group remained in standard cages and did not receive objects. Within 7 weeks of life, anxiety and thermal sensibility were evaluated using elevated plus maze and tail flick tests, respectively. Mechanical hyperalgesia was analyzed in the presence of acute and chronic noxious stimuli by paw pressure test. Both EE protocols tested were effective in diminish anxiety but they did not alter thermal sensibility. On the other hand, sEE protocol did not alter acute and chronic induced mechanical hypersensitivity, whereas iEE completely abolished such pain behavior, even without exercise wheel as part of the enrichment. Our results show that specific parameters (anxiety and pain sensitivity) can be differentially modulated depending on EE protocol used, making possible the implementation of welfare to experimental animals in pain research.

Comparative study of platelet aggregation and secretion induced by Bothrops jararaca snake venom and thrombin.

Victims of Bothrops jararaca snakebites manifest bleedings, blood incoagulability, platelet dysfunction, and thrombocytopenia, and the latter has been directly implicated in the genesis of hemorrhagic diathesis. We addressed herein the direct effects of B. jararaca venom (BjV) on ex vivo platelet aggregation and granule secretion in washed human and mouse platelets. BjV directly aggregated platelets, but the extent of platelet aggregation was lower in human than mouse platelets. On the other hand, BjV (24.4 µg/mL) and thrombin (0.1 U/mL) induced a similar extent of ATP and platelet factor 4 (PF4) secretion in both species. BjV-induced platelet aggregation was independent of the platelet dense body content, as in pearl mouse (Ap3b1-/-) platelets, whose dense bodies are deficient in adenine nucleotides and serotonin, the extent of platelet aggregation was superior to that induced in BALB/c or C57BL/6 mice. BjV-induced ß-hexosaminidase secretion in human platelets was less intense than that evoked by thrombin, and the contrary was observed in mouse platelets. Irreversible inactivation of platelet cyclooxygenase 1 by acetylsalicylic acid did not reduce BjV-induced platelet aggregation. BjV exerted no cytotoxic activity in human and mouse platelets, as evaluated by lactate dehydrogenase loss. Eptifibatide, which inhibits the binding of fibrinogen to platelet glycoprotein complex GPIIb-IIIa, differently blocked BjV-induced platelet aggregation in mice and humans. BjV-induced platelet aggregation did not depend on snake venom serine proteinases nor metalloproteinases in mice, whilst serine proteinases were rather important for platelet aggregation in humans. Our results show that BjV induces direct activation, aggregation, and secretion in human and mouse platelets, but it exerts diverse responses in them, which should be considered in comparative studies to understand pathophysiological events during Bothrops envenomation.

The gingival vein as a minimally traumatic site for multiple blood sampling in guinea pigs and hamsters.

Laboratory animals are still necessary in scientific investigation and vaccine testing, but while novel methodological approaches are not available for their replacement, the search for new, humane, easy, and painless methods is necessary to diminish their stress and pain. When multiple blood samples are to be collected from hamsters and guinea pigs, the number of available venipuncture sites-which are greatly diminished in these species in comparison with other rodents due to the absence of a long tail-, harasses animal caregivers and researchers. Thus, this study aimed to evaluate if gingival vein puncture could be used as an additional route to obtain multiple blood samples from anesthetized hamsters and guinea pigs in such a way that animal behavior, well-being or hematological parameters would not be altered. Thus, twelve anesthetized Syrian golden hamsters and English guinea pigs were randomly allocated in two groups: a control group, whose blood samples were not collected, and an experimental group in which blood samples (200 microliters) were collected by gingival vein puncture at weekly intervals over six weeks. Clinical assessment, body weight gain and complete blood cell count were evaluated weekly, and control and experimental animals were euthanized at week seven, when the mentolabial region was processed to histological analyses. Multiple blood sampling from the gingival vein evoked no clinical manifestations or alteration in the behavioral repertoire, nor a statistically significant difference in weight gain in both species. Guinea pigs showed no alteration in red blood cell, leukocyte or platelet parameters over time. Hamsters developed a characteristic pattern of age-related physiological changes, which were considered normal. Histological analyses showed no difference in morphological structures in the interdental gingiva, confirming that multiple blood sampling is barely traumatic. Thus, these results evidence that blood collection from multiple gingival vein puncture is minimally invasive and traumatic to hamsters and guinea pigs, and that it can be accomplished during at least six weeks.

Produtividade de ratos Wistar em diferentes sistemas de acasalamento / Productivity of Wistar rats in different mating systems

O objetivo foi avaliar a produtividade e uniformidade da produção de ratos Wistar (Rattus norvegicus) em três sistemas de acasalamento: monogâmico permanente, com um casal mantido permanentemente em cada gaiola; poligâmico permanente, com duas matrizes e um macho, mantidos permanentemente em cada gaiola; e poligâmico temporário, em que o macho foi mantido na gaiola com duas matrizes até a certificação de cada cópula e, em seguida, foi retirado, retornando após o desmame das ninhadas. Para isso, 69 fêmeas de 90 dias de idade (matrizes) foram aleatoriamente distribuídas nos três grupos. As avaliações compreenderam cinco ciclos reprodutivos por matriz. Foram obtidas ninhadas mais pesadas a desmama no sistema poligâmico temporário. Além disso, não houve mortalidade de matrizes neste sistema, o que é um indicador importante de bem estar animal. No sistema monogâmico permanente, o intervalo de tempo necessário para produzir um filhote desmamado por matriz foi menor que nos sistemas poligâmicos. Deve-se considerar, no entanto, que este sistema requer o dobro do número de gaiolas e de machos reprodutores que os poligâmicos. Portanto, o sistema poligâmico temporário pode ser recomendado nas colônias de expansão e produção de ratos Wistar, com a ressalva de que necessita de mão de obra qualificada para identificação de cópula nas matrizes e manejo de rotação dos machos.

The objective was to evaluate the productivity and production uniformity of Wistar female rats (Rattus norvegicus) submitted to three mating systems: permanent monogamous, with a couple permanently maintained in each cage, permanent polygamous, with two females and one male permanently maintained in each cage, and temporary polygamous in which a male was maintained in a cage with two females until each mating was verified and was removed afterwards, returning after both litters were weaned. For that, 69 90-days-old females were randomly assigned to three groups. The evaluations comprised five reproduction cycles per dam. Litters that were heavier at weaning were obtained in the temporary polygamous systems. In addition, dam mortality was null in this system, which is an important animal welfare indicator. In the permanent monogamous system, the interval of time required to produce one weaned pup per dam was shorter than in the polygamous systems. One should consider, however that this system requires twice as many cages and sires than the polygamous systems. Therefore, the temporary polygamous mating system may be recommended for the expansion and production Wistar rats colonies, provided that qualified personnel is available to identify copulation in breeding females and to perform male rotation.