Difficulties associated with the development and licensing of vaccines for protection against bio-warfare and bio-terrorism.

Today there is an increasing need to license vaccines for the protection of individuals against bio-warfare and bio-terrorism. While the need is apparent, the actual road to developing, producing and licensing such vaccines successfully is as yet undefined. Bio-defence vaccine candidates may come from several sources. They may come from vaccines that were previously licensed but are no longer in production, vaccines that are currently in an IND status, vaccines currently licensed in foreign countries, and newer vaccines currently under development. The issues that apply to the development and licensing of these vaccines can be defined by currently accepted standards for manufacture, and the requirement to demonstrate safety and efficacy to a level that gives the scientific and medical community, regulatory agencies, users and the public at large confidence. Requirements for manufacturing and demonstration of safety will be consistent with vaccines being developed for traditional purposes. However, demonstration of efficacy will be more difficult. Because field trials for these vaccines are generally not feasible and the conduct of human challenge studies is generally considered unethical, the demonstration of efficacy will need to be based on existing efficacy data, a thorough understanding of both the disease's pathogenesis and mechanism of protection, the ability to identify surrogate markers for efficacy, and the use of the proposed FDA "animal rule".

Protection against botulinum toxins provided by passive immunization with botulinum human immune globulin: evaluation using an inhalation model.

Pentavalent botulinum toxoid adsorbed (ABCDE) vaccine is intended to protect military personnel from battlefield exposures to botulinum serotypes A-E. To determine the neutralizing antibody levels in serum that are indicative of protection against aerosolized botulinum toxins, a guinea pig model of passive antibody transfer was developed. Botulinum immune globulin (BIG), derived from plasma of vaccinated volunteers, was administered to guinea pigs by intraperitoneal injection to attain neutralizing antibody levels in serum of ca. 0.25 U ml(-1). Control groups were treated with vaccinia immune globulin (VIG), with dosages normalized to antibody content. Neutralizing antibody levels were determined by a mouse bioassay. Twenty-four hours after BIG treatment, animals were challenged with lethal levels (target of 25 x LCt(50)) of botulinum toxins by an inhalation route. Protection was defined as 80% or greater survival for BIG-treated animals. If protective, additional groups were treated with progressively smaller BIG dosages (75% decreases per iteration) and challenged with 25 x LCt(50) until protection was no longer afforded. Greater than 80% survival was observed at target levels of 0.25 U ml(-1) for all five serotypes. Breakthrough mortality (>20%) was observed at test levels of 0.05, 0. 004, 0.015, 0.014 and 0.003 U ml(-1) for serotypes A-E, respectively. These results, along with neutralizing antibody measurements from clinical trials, can be used to predict human efficacy following vaccination with pentavalent botulinum toxoid adsorbed (ABCDE) vaccine.

Effect of palytoxin on endothelium-dependent and -independent relaxation in rat aortic rings.

Endothelium-intact rat aortic rings were incubated with palytoxin (PTX, 10(-11)-10(-9)M, 10 min) in oxygenated (O2 95%, CO2 5%) baths. Phenylephrine (PE)-contracted vascular rings demonstrated decreasing relaxation to acetylcholine (ACh), depending upon PTX incubation in a dose-dependent manner; however, sodium nitroprusside (NaNP) persisted in returning the ring to its pre-PE tension. After incubation with PTX, relaxation to the receptor-independent, endothelium-dependent relaxant A23187 was also attenuated. Thus, endothelium-dependent mechanism(s) normally responsive to both ACh and A23187, stimulators of nitric oxide (NO) release, were disrupted. Following incubation with PTX, endothelium-independent relaxation to NaNP remained intact but relaxation to atriopeptin II (APII) decreased. Electron microscopy demonstrated microvesiculation of endothelial cell cytoplasm and an irregular luminal surface following incubation with PTX. The intact response to NaNP, despite the loss of relaxation to ACh, indicated that soluble guanylate cyclase was not affected by PTX. However, loss of relaxation to AP-II, involving particulate guanylate cyclase of vascular smooth muscle (VSM), was inhibited by PTX pre-incubation. Determination of the site(s) of action of PTX requires further study.

Who should get the kidney machine?

This paper considers the problem that arises when the number of patients who need a resource exceeds the supply. An initial decision-making model is proposed that uses two essential criteria, medical prognosis and the priority of life-threatening situations. The model is then subjected to the criticism that it is grotesque to ignore questions relating to the value of, for example, a productive mother over against an aged recluse, and to treat them as having equal rights to access. It is argued that this criticism need not be an expression of prejudice but may reflect a defendable view in which utilitarian considerations enter into the selection process provided that certain fundamental, or 'deontological' rights are observed for all. In the light of the discussion the model is modified in order to contain both a non-utilitarian feature that stresses the intrinsic importance of all persons, and a utilitarian feature that can allow one, in certain circumstances, to take consequences into account, especially those that follow from the 'irreplaceability' of some people.

The Moot Court in teaching bioethics.

The first part of this paper describes the nature of a Moot Court (or Mock Trial) and how it has been used in recent years as a teaching method for students in medicine and nursing at the Memorial University of Newfoundland. A whole day is spent in the enactment of an imaginary court case in which issues in bioethics are raised. Civil and criminal cases are used in alternate years. A considerable degree of realism is maintained except for the occasions when the presiding judge needs to make comments to the students in order to explain what is going on. The realism is helped by the fact that the roles of judge and of legal counsel are played by members of the judiciary and lawyers from the Newfoundland bar. In the second part of the paper there is a discussion of the principal issue that arose in the 1988 Moot Court, namely informed consent. In the third part the secondary legal and moral issues that arose are described and in the fourth part there is a discussion of the interface between law and morality that is illustrated by the issues that came up in the Moot Court.

Fluid resuscitation after an otherwise fatal hemorrhage: I. Crystalloid solutions.

One half of deaths among trauma victims occur within 1 hour of injury and are due to rapid hemorrhage or CNS trauma. We developed a rapid hemorrhage model in unanesthetized swine to simulate human exsanguination. We compared the ability of four crystalloid solutions to prevent death after an otherwise fatal hemorrhage: normal saline (NS), Ringer's lactate (RL), Plasmalyte-A (PA), and Plasmalyte-R (PR). Five days before hemorrhage swine received an aortic sideport and a central venous treatment catheter. Aortic blood (54 ml/kg) was removed in 15 minutes from 116 swine. The percentages of shed blood replaced were 14% in 5 minutes with NS, 100% in 20 minutes with NS, and 300% in 30 minutes with NS, RL, PA, or PR. We found that all mortalities were determined within 2 hours after hemorrhage and that RL provided the best survival rate of 67% (NS 300% = 50%, PR = 40%, and PA = 30%.) After an analysis of arterial blood gas, lactate, acid-base, heart rate, and aortic pressure measurements, we conclude that RL is the superior crystalloid solution because of its decreased chloride load (compared to NS) and because of the absence of acetate or magnesium (compared to PA and PR).

Fluid resuscitation after an otherwise fatal hemorrhage: II. Colloid solutions.

We developed a fixed-volume porcine hemorrhage model that simulates the rapid exsanguination of combat or civilian trauma victims. In this study we compared the ability of colloid resuscitation solutions to prevent death after an otherwise lethal hemorrhage in 100 swine. The shed blood was replaced in a 1:1 ratio with either autologous whole blood (WB), untyped swine fresh frozen plasma (FFP), typed FFP, 5% human serum albumin (ALB), or normal saline (NS). Survival rate analysis indicated that WB was significantly better than FFP (untyped), ALB, or NS but not better than typed FFP. The 24-hour survival rates were: WB = 90%, typed FFP = 79%, untyped FFP = 56%, ALB = 57%, and NS = 25%. All deaths in the untyped FFP group suddenly occurred during or within 15 minutes after treatment in a recovering animal. Deaths in the ALB group steadily occurred for up to 2 1/2 hours after treatment. Analysis of hemodynamic, arterial blood gas, and acid-base data indicated that WB and FFP provided a better acid-buffering capacity in surviving animals than NS or ALB. We conclude that compatible FFP is a better resuscitation agent than ALB after an otherwise fatal hemorrhage because FFP is a better acid buffer.