Assessing vaccine-mediated protection in an ultra-low dose Mycobacterium tuberculosis murine model.

Despite widespread immunization with Bacille-Calmette-Guerin (BCG), the only currently licensed tuberculosis (TB) vaccine, TB remains a leading cause of mortality globally. There are many TB vaccine candidates in the developmental pipeline, but the lack of a robust animal model to assess vaccine efficacy has hindered our ability to prioritize candidates for human clinical trials. Here we use a murine ultra-low dose (ULD) Mycobacterium tuberculosis (Mtb) challenge model to assess protection conferred by BCG vaccination. We show that BCGconfers a reduction in lung bacterial burdens that is more durable than that observed afterconventional dose challenge, curbs Mtb dissemination to the contralateral lung, and, in a smallpercentage of mice, prevents detectable infection. These findings are consistent with the ability of human BCG vaccination to mediate protection, particularly against disseminated disease, in specific human populations and clinical settings. Overall, our findings demonstrate that the ultra-low dose Mtb infection model can measure distinct parameters of immune protection that cannot be assessed in conventional dose murine infection models and could provide an improved platform for TB vaccine testing.

Thiopentone and methohexital, but not pentobarbitone, reduce early focal cerebral ischemic injury in rats.

PURPOSE: Although barbiturates are considered to be cerebral protectants, little is known regarding the relative efficacy of different barbiturates to reduce ischemic brain injury. In a model of middle cerebral artery occlusion (MCAo), we compared the relative effects of 1.0 and 0.4 burst-suppression doses of thiopentone, methohexital, and pentobarbitone on cerebral infarct. METHODS: During isoflurane anesthesia, MCAo was achieved via a temporal craniotomy. Thirty minutes before MCAo the rats were randomized to receive one of the following which was maintained throughout the study. Halothane (n=20)-1.2 MAC halothane, thiopentone (n=20), methohexital (n=20), or pentobarbitone (n=20). The first ten animals in each barbiturate group received the respective barbiturate in a dose sufficient to maintain burst-suppression of the electroencephalogram (3-5 bursts x min(-1)). The subsequent ten animals in each barbiturate group received 40% of the burst-suppression dose. After 180 min of MCAo and 120 min of reperfusion, cerebral injury was assessed. RESULTS: For the burst-suppression animals, injury volume (mm3, mean +/- SD) was less in the thiopentone group (88 +/- 14) than the halothane (133 +/- 17), methohexital (126 +/- 19), or pentobarbitone (130 +/- 17) groups (P <0.05). For 0.4 burst-suppression animals, injury volume was less for the methohexital group (70 +/- 22) than the halothane (124 +/- 24), thiopentone (118 +/- 15), or pentobarbitone (121 +/- 20) groups (P <0.05). CONCLUSIONS: These data are inconsistent with the longstanding assumption that electrophysiologically comparable doses of the various classes of barbiturates have equivalent protective efficacy. They in turn suggest that mechanisms other than, or at least in addition to, metabolic suppression may contribute to the protective effect of barbiturates.

Subarachnoid molecular hemoglobin after subarachnoid hemorrhage in rats: effect on the area of hypoperfusion.

A previous study indicated that diaspirin-crosslinked hemoglobin (DCLHb) decreases cerebral ischemia after subarachnoid hemorrhage. However, the study was limited in that DCLHb was given to animals with an intact vasculature. As extravasated hemoglobin has been implicated in the pathogenesis of cerebral vasospasm, DCLHb in the subarachnoid space might in theory have a detrimental effect on cerebral perfusion after subarachnoid hemorrhage. In the current study, autologous blood was administered into the cistema magna of isoflurane-anesthetized rats. After 30 minutes, the animals received one of the following in the cistema magna (n=8 for each group): The control group received mock cerebral spinal fluid, the "blood" group received autologous blood, the "DCLHb" group received DCLHb, and the "Alb" group received human serum albumin. After 20 minutes, areas of reduced cerebral blood flow (CBF, 0-20 and 21-40 ml/100 g/min) were assessed in five coronal brain sections with 14C-iodoantipyrine. The data were evaluated by analysis of variance. The areas of 0-20 ml/100 g/min CBF were greater in all five brain sections in the Blood group than in the other three groups; were greater in four brain sections in the DCLHb group than in the Control group; and were greater in three brain sections in the Alb group than in the Control group (p < 0.05). The areas of 21-40 ml/100 g/min CBF were greater in three sections in the Blood group than in the other three groups; and were greater in two brain sections in the DCLHb group than in the Alb group (p < 0.05). These data support a hypothesis that subarachnoid blood induces cerebral hypoperfusion, and that although molecular hemoglobin decreases CBF, the potential adverse effects are less than those produced by blood.

Humoral and cellular aspects of immunologlobulin allotype suppression in the rabbit. III. Production of anti-allotypic antibody by suppressed animals.

Rabbits heterozygous at the 'b' locus (b4b6 or b5b6) were suppressed for b6 production. These suppressed rabbits were immunized to produce anti-allotypic antibody against: (a) determinatns not possessed in their genotype; (b) the suppressed b6 determinants.