No rarefaction of cerebral arterioles in hypertensive rats.

A reduction in the density of small arterioles (rarefaction) has been reported in several vascular beds of the spontaneously hypertensive rat (SHR). There have been conflicting reports on the existence of rarefaction in the pial vasculature of SHR. In this study, we determined whether there was rarefaction of pial arterioles in several models of hypertension. We studied SHR; two-kidney, one-clip Goldblatt hypertensive rats; deoxycorticosterone-salt hypertensive rats; and Dahl salt-sensitive rats fed high salt diet. The two groups of normotensive controls were Wistar--Kyoto rats and Dahl salt-sensitive rats fed low salt diet. The duration of hypertension was about 2 months. Density of first-, second-, third-, and fourth-order arterioles was determined by counting the number of vessels from enlarge photographs. We also measured the lengths of segments of the arterioles. We did not observe any evidence of rarefaction of arterioles in the pial vasculature in any of the hypertensive groups of rats. We conclude that (i) rarefaction of arterioles does not occur in the pial microvasculature after approximately 2 months of hypertension and (ii) rarefaction of pial arterioles does not account for abnormalities in the cerebral circulation of hypertensive rats such as protection of the blood-brain barrier or changes in autoregulation of cerebral blood flow.

Acute neuropathology in soman poisoned rats.

Groups of rats received single subcutaneous injections of the highly toxic organophosphate compound, soman, in doses of 106, 133 or 165 micrograms/kg and were observed during the acute phase of intoxication. Survivors were killed at intervals up to fourteen days after exposure, and brain sections were examined by light microscopy. A consistent pattern of neuronal degeneration and necrosis was observed in brains of animals which had experienced convulsions during the intoxication. The lesions had an appearance and distribution similar to that reported for both hypoxic injury and status epilepticus. No lesions were observed in animals which did not experience convulsions. The results indicate that soman, and possibly other similar organophosphate compounds, may produce significant irreversible damage to the central nervous system.

Glucan-induced enhancement of host resistance to selected infectious diseases.

We conducted studies with mice, rats, and monkeys which demonstrated the ability of glucan to induce either nonspecific or specific enhancement of host resistance to infectious diseases. Intravenous pretreatment of mice with glucan significantly enhanced the survival of mice challenged with either Venezuelan equine encephalomyelitis (VEE) virus or Rift Valley fever virus. Pretreatment was beneficial when initiated 3 days before challenge with VEE virus and 7 days before challenge with Rift Valley fever virus. Treatment of mice after VEE challenge did not increase their survival compared with controls. Glucan pretreatment of rats provided increased resistance to both intraperitoneal and low-dose aerosol challenges with virulent Francisella tularensis when the glucan was given intravenously, but not when it was administered intranasally. In contrast, intranasal glucan pretreatment enhanced the survival of mice when they were challenged by aerosol with Pseudomonas pseudomallei, whereas intravenous glucan pretreatment did not increase survival. mice given glucan combined with a marginally immunogenic dose of VEE vaccine were more resistant to homologous virus challenge than were mice given either Freund complete adjuvant plus vaccine or vaccine alone. Similarly, both primary and secondary VEE antibody titers in cynomolgus monkeys given glucan with VEE vaccine were significantly greater than titers in vaccine controls.

Evaluation of a formalin-inactivated Rift Valley fever vaccine in sheep.

A formalin-inactivated Rift Valley fever (RVF) vaccine prepared in cell culture for human use was immunogenic in sheep. Vaccine was administered as a single dose of diluted (1:5) or undiluted vaccine with or without an adjuvant. Serum-neutralizing antibodies induced by RVF vaccine persisted for at least 7 months. Seven of 11 vaccinated sheep with prechallenge plaque-reduction neutralization (PRN80) antibody titers of less than or equal to 10 were protected against challenge exposure with 10(6) plaque-forming units of Zagazig 501 strain of RVF virus. Challenge exposure induced abortion in 2 of 2 pregnant sheep. Five sheep with PRN80 titers greater than or equal 1:20 were protected from detectable viremia after challenge exposure. Additionally, 5 of 6 lambs (3 months old) were protected (by maternal antibodies) against challenge exposure. Challenge control sheep developed clinical disease and detectable viremia after exposure. Virus was isolated from saliva of 1 challenge control sheep and virus was transmitted by contact exposure to 1 of 4 seronegative contact-control sheep. Immunization of sheep with formalin-inactivated RVF vaccine induced a priming effect against RVF viral antigens. Challenge exposure with RVF virus resulted in significantly higher neutralizing titers in vaccinated sheep than in nonvaccinated sheep.

Mechanisms of protective immunogenicity of microbial vaccines: effects of cyclophosphamide pretreatment in Venezuelan encephalitis, Q fever and tularaemia.

Administration of high-dose (250 mg/kg) cyclophosphamide (CY) to guinea-pigs and mice 3 days prior to immunization with inactivated vaccine derived from Venezuelan encephalitis virus (VE), Coxiella burnetii and Francisella tularensis resulted in accentuated and prolonged delayed-type hypersensitivity (DTH) and in vitro cellular immunity (CMI) to specific antigen. Humoral antibody were either absent or significantly lower in CY-pretreated animals compared to immunized non-pretreated controls. CY pretreatments precluded protection in the VE virus model, suggesting that resistance is related to antibody. In the Q fever model, the protective immunogenicity of vaccine was preserved or increased by CY pretreatment suggesting that cell-mediated immunity is the important factor. In the tularaemia bacterial system, there was a complex effect of CY pretreatment on the low-grade protection afforded by killed vaccine against virulent infection. These findings suggest that the inability of killed vaccines to induce high-grade resistance against tularaemia and Q fever may be due in part to a suppressive B cell response which is eliminated by CY. These studies have given useful information on the relative significance of components of the specific immune response and may lead to an increased understanding of the mechanisms of action of vaccines and adjuvants.

Adjuvant activity of a novel metabolizable lipid emulsion with inactivated viral vaccines.

Studies were conducted in mice, hamsters, sheep, and two species of nonhuman primates which demonstrate the adjuvant activity of a new metabolizable lipid emulsion with marginally immunogenic doses of Formalin-inactivated viral vaccines. The lipid base consists of highly refined peanut oil emulsified in aqueous vaccines with glycerol and lecithin. Hamsters and mice inoculated with lipid emulsion plus western or Venezuelan equine encephalitis vaccine were significantly more resistant than vaccinated controls to lethal homologous virus challenge. Sheep given one dose of lipid emulsion plus Rift Valley fever vaccine developed significantly higher antibody titers than control sheep receiving only vaccine. Cynomolgous monkeys inoculated with lipid emulsion plus Rift Valley fever vaccine developed 16-fold greater peak primary and 20-fold greater secondary antibody titers than those of vaccine controls. Similar lipid emulsion-Rift Valley fever studies in rhesus monkeys resulted in 37- and 300-fold increases in primary and secondary titers, respectively, compared with monkeys given vaccine alone. Neither the sequence of combining antigen with lipid nor the exact ratio of aqueous phase to lipid phase affected the survival of Venezuelan equine encephalitis-vaccinated mice challenged with homologous lethal virus. This lipid formulation has several advantages over other water-in-oil adjuvants for potential use in humans. The components are metabolizable or normal host constituents, it is easily emulsified with aqueous vaccines by gentle agitation, and it is relatively nonreactogenic in recipients.

Adjuvant effects of low doses of a nuclease-resistant derivative of polyinosinic acid . polycytidylic acid on antibody responses of monkeys to inactivated Venezuelan equine encephalomyelitis virus vaccine.

Polyriboinosinic.polyribocytidylic acid [poly(I).poly(C)] stabilized with poly-l-lysine and carboxymethylcellulose [poly(ICLC)] has been previously shown to be a compound with marked adjuvant activity when given in high doses with inactivated Venezuelan equine encephalomyelitis (VEE) virus vaccine. This study investigated the effects of much lower doses of poly(ICLC) on the magnitude and kinetics of the primary and secondary humoral antibody responses of rhesus monkeys to inactivated VEE virus vaccine. Monkeys given a single injection of vaccine developed very low neutralizing antibody titers, whereas those given adjuvant plus vaccine had 30- to 100-fold-higher titers which remained elevated for longer than 6 months. Low doses of poly(ICLC) given with VEE virus vaccine resulted in a profound but transient increase in priming of secondary antibody responses to the antigen. In contrast, the administration of poly-l-lysine and carboxymethylcellulose alone without the poly(I).poly(C) component of the complex had no adjuvant effect on antibody responses of monkeys to VEE virus vaccine. The temporal development of antibody by class (immunoglobulin M-immunoglobulin G) in monkeys given two injections of adjuvant-vaccine was not different from that with vaccine alone. Serial hematological and clinical chemistry determinations on monkeys given single or multiple doses of poly(ICLC) with vaccine were not different from values in monkeys given vaccine alone.

Femoral venipuncture for repeated blood sampling in miniature swine.

Repetitive blood sampling of miniature swine was accomplished by percutaneous puncture of the femoral vein. Swine were restrained manually in dorsal recumbency. The skin was penetrated in the inguinal area approximately 2.5 cm laterally to the most posterior mammary gland with a 21-gauge, 3 cm (1.5 inch) needle. Ten milliliters of blood were withdrawn of frequent intervals for 4 months without apparent harm to the animals.

Intestinal Tyzzer's disease and spirochetosis in a guinea pig.

Tyzzer's disease (bacillus pilirformis infection) was diagnosed in young guinea pig killed because of diarrhea and poor condition. There was necrosis and inflammation of the colon, cecum and ileum. Typical B. piliformis were in intestinal epithelial cells. Spirochetes were in large numbers in intestinal crypts and were often adjacent to the intracellular B. piliformis. Extracellular B. piliformis occasionally were surrounded by spirochetes.