Development of a malaria T-cell vaccine for blood stage immunity.

We have defined a strategy for the development of a T-cell vaccine for blood stage immunity, taking into consideration the central role of T cells and MHC restriction in malaria immune responses. We have used the AMPHI computer algorithm to identify putative T-cell epitopes from conserved regions of 11 Plasmodium falciparum asexual stage proteins. Ten of the eleven proteins are currently candidates for vaccine development. Using this algorithm we selected 22 putative T-cell epitope peptides and 8 control peptides. These peptides were used to test the T-cell responses of three defined populations of Caucasians who have (1) recovered from P. falciparum malaria, (2) been exposed, but never clinically infected, (3) never been exposed or infected. Preliminary analysis of our data shows population differences in T-cell responses to putative T-cell epitope peptides. Ultimately, these studies will help to identify those T epitopes that can be incorporated into a T-cell vaccine for protective immunity.

Perfluorocarbon compounds: effects on the rheological properties of sickle erythrocytes in vitro.

The effects of oxygenated perfluorotributylamine (Fluosol-43) on the rheological properties of sickle (HbSS) erythrocytes have been determined by means of microviscometry and positive pressure cell filtration. Incubation of deoxygenated sickled erythrocytes (pO2 congruent to 30 mmHg) with oxygenated Fluosol-43 reduced the percentage of sickled erythrocytes from about 63 to 33%. Deoxygenation of 40% suspension of sickle erythrocytes in autologous plasma increased the viscosity by about 160% at shear rate of 1.15 sec-1. Incubation of the deoxygenated sickled erythrocytes with oxygenated Fluosol-43 significantly reduced the viscosity at the low shear rates. Filtration of 0.2% suspension of deoxygenated sickle erythrocytes through capillary-sized Nuclepore filters showed high resistance at low flow rates. Oxygenated Fluosol-43 increased the deformability of HbSS erythrocytes and thereby reduced the resistance at flow rates less than 1 ml/min. These data suggest that perfluorocarbons may be useful in reducing the propensity of hemoglobin S polymerization and sickling and thereby prevent tissue infarction in vaso-occlusive crisis. Therefore, the concept of examining the potential application of perfluorochemicals for alleviating severe vaso-occlusive events may be useful.

Temporal relationships between urinary salt retention and altered systemic hemodynamics in dogs with experimental cirrhosis.

In the present study, we undertook to examine the relationship between urinary sodium retention and systemic hemodynamics in dogs with experimental portal cirrhosis induced by the sporadic feeding of dimethylnitrosamine. Sodium handling was studied by blanace techniques; plasma volume was measured serially with Evan's blue; and CO, blood pressure, CVP, and PVR were monitored through indwelling catheters. Six dogs were studied while standing quietly in a Pavlov sling, in a serial fashion starting 4 weeks after drug administration and continuing for some 3 months thereafter, until all dogs developed cirrhosis and ascites. Urinary sodium retention commenced generally between the ninth to twelfth week following the initation of treatment, but renal perfusion remained normal. Plasma volume expansion was noted within 1 week following the onset of sodium retention. Ascites was generally detected about 2 weeks following the initiation of sodium retention. No alteration in CO or PVR could be detected until ascites was present in significant amount. At that time, CO rose and PVR fell by about 20%. ABP tended to fall during the period of observation, but this was not significant. The initiation of sodium retention in this canine model does not depend on antecedent changes in CO or PVR.

Autoregulation of cerebral blood flow during early experimental renal hypertension in the conscious dog.

Using the radioactive microsphere technique, cerebral blood flow (CBF) was measured in six conscious dogs before intervention and again on the 3rd-5th days after inducing hypertension by the one-kidney Goldblatt (1-KGH) procedure. Sham-operated controls were also studied. The normal temporal variability of CBF, as well as the precision of the microsphere technique in measuring CBF were also determined in other normal dogs. A left atrial catheter was used for the microsphere injections (15 micrometer diam spheres) and an aortic catheter was used for cardiac output and blood pressure measurements. On the 3rd-5th days after 1-KGH, mean aortic pressure increased from a control value of 94 +/- 7 mmHg to 135 +/- 20 mmHg (P less than 0.005). CBF did not change significantly from the control flow of 57.1 +/- 7.9 ml/100 g per min. Calculated cerebral vascular resistance increased by 47 percent (P less than 0.025) above the control value. Hence, the early phase of experimental renal hypertension is associated with adequate autoregulation of cerebral blood flow.