Advances in antiviral therapy

Recent developments have increased the options for treatment of viral infections. Vidarabine, an agent originally released for herpes simplex encephalitis, has more recently been shown to be of benefit in neonatal herpes simplex infection and in varicella-zoster infections in immunocompromised hosts. The introduction of acyclovir represents a major advance in antiviral therapy because of its low host toxicity and marked selectivity for herpes simplex and varicella-zoster viruses. Extensive controlled clinical trials demonstrate efficacy in the treatment of infections caused by these viruses in the immunocompromised host and in genital herpes simplex infections in normal hosts. The use of recombinant DNA technology has increased the purity, variety, and availability of interferons for clinical trial. Earlier experience with natural buffy coat-derived alpha interferon showed efficacy in the treatment of varicella-zoster infections in the immunocompromised host, as well as prophylaxis of herpes virus infections in high-risk populations. These results have to be confirmed using the newer interferon preparations. Under development are a variety of new drugs with broadened viral spectrum and improved pharmacokinetic properties. These include nucleoside analogues and novel interferons with modified amino acid sequences. One or more of these agents, used singly or in combination, may prove useful in the more difficult therapeutic problems, such as cytomegalovirus and hepatitis B infections.

Slow release of insulin from a biodegradable matrix implanted in diabetic rats

This report describes the development of a long-acting insulin accomplished by the slow release of hormone from an implantable, biodegradable matrix. Rats made diabetic with streptozotocin received a single subcutaneous implant of insulin-albumin microbeads that released biologically active insulin for periods up to 3 wk. The mean fasting blood glucose level for treated animals was 88 mg/dl as compared with 392 mg/dl for untreated diabetic controls. With a mean starting body weight of 187 g, treated animals gained weight reaching a mean weight of 228 g; in contrast, untreated animals lost weight to a mean of 175 g. When insulin-albumin microbeads were periodically implanted and removed, lower blood glucose levels were only associated with the presence of the implants. The microbead implants biodegraded in 4-8 wk, thus obviating the need for surgical removal. These results suggest that a long-acting insulin may be produced by the entrapment of insulin within a biodegradable matrix.

Rapid detection and quantitation of human cytomegalovirus in urine through DNA hybridization

We detected cytomegalovirus DNA in clinical urine specimens after immobilization on nitrocellulose filters and hybridization with a radioactively labeled, cloned fragment of cytomegalovirus DNA. We accomplished the specific detection and quantitation of viral DNA within 24 hours with 39 urine specimens from nine patients with cytomegalovirus viruria, mostly at a tissue-culture infective titer of 10(3) per milliliter or higher. None of 57 urine specimens from 21 patients that were culture-negative for cytomegalovirus gave false-positive results. Analysis of specimens from patients with cytomegalovirus viruria showed a correlation of the infective titer with the intensity of DNA hybridization (r = 0.77). Hybridization of sequential urine specimens from a patient undergoing treatment with interferon for cytomegalovirus retinitis revealed quantitative variations in hybridizable viral DNA over a period that correlated with clinical findings. This assay can be useful in the selection of patients for antiviral therapy and for the assessment of its efficacy.

A new approach to antibiotic therapy in colon surgery based on bioassay tissue concentrations

The authors investigated the kinetics, in serum and tissues, of clindamycin, metronidazole, cefoxitin and moxalactam given during colon surgery in the dog. Colon, rectus muscle and subcutaneous fat samples were taken at times of maximal contamination during the initial operation and at a second operation, 9 days after the first, when septic complications were most likely to occur in the healing tissues. Bioassay was used to measure the amount of active antibiotics in serum and tissues. Clindamycin achieved therapeutic levels in all tissues except those of the fresh wound, thus making it a better therapeutic than prophylactic agent. Metronidazole achieved therapeutic levels in both fresh and healing tissues. Cefoxitin and moxalactam did not achieve adequate levels in either fresh or healing tissues.

Insulin-albumin microbeads: an implantable, biodegradable system

A feasibility study on developing an implantable, biodegradable insulin delivery system was carried out. Insulin-albumin microbeads (50-1,000 microns diameter) were implanted in diabetic rats. After a single subcutaneous implant of the glutaraldehyde crosslinked microbeads, elevated blood-insulin levels were detected in the diabetic animals for longer than two months. While the blood-insulin levels of the treated animals were sustained between 10 and 67 microU/ml during the initial two month post-implantation period, complete in-vivo biodegradation of the microbeads took longer than five months. The diabetic animals, with the insulin-albumin microbead implants, gained weight. In contrast, untreated diabetic controls lost weight. Fibrous capsules were found to have surrounded the microbeads when the implants were recovered at one and two months post-implantation. The results suggest that the fibrous capsules played a role in retarding insulin release from the albumin microbead system. Cross-linked serum albumin microbeads have the clinical potential of providing long-term in-vivo drug release. This system has the additional advantage of being biodegradable and also provides more options for the method and site of implantation.

Controlled clinical trial of intravenous acyclovir in heart-transplant patients with mucocutaneous herpes simplex infections

Viral cultures of mucocutaneous herpes simplex lesions became negative in 5 heart-transplant patients given a 7-day course of intravenous acyclovir. Relief of pain and healing of lesions paralleled the virological response. Similar clinical and virological responses were not seen in the 5 placebo-treated patients in this double-blind placebo-controlled trial. No adverse reactions attributable to acyclovir were noted. Shedding of herpes simplex viruses recurred in 3 patients after acyclovir therapy.

Communicating hydrocephalus as a cause of aqueductal stenosis

Eleven cases of presumed aqueductal stenosis with onset of symptoms after the first decade were reviewed. Ten patients had complete occlusion and one a high-grade stenosis. In 10, the dilated lateral ventricles caused a marked inferior displacement of the third ventricle. Postshunting diagnostic studies on six of these patients revealed ascent of the third ventricle, and in three of these the aqueduct was shown to be patent. It appears that in some cases of advanced communicating hydrocephalus the descending third ventricle kinks or pinches shut the aqueduct, adding an obstructive component which accelerates the clinical picture. The mechanism and clinical features of this process are discussed.

Isolation of a new simian foamy virus from a spider monkey brain culture

A syncytium-forming (foamy) virus was isolated from a spider monkey brain cell culture. Cytopathic effect was observed both in the brain culture and in human embryonic kidney cells. Neutralizing antibody was present in the sera of the spider monkey from whom the isolation was made. The virus was inhibited by 5-bromo-2-deoxyuridine (20 mug/ml), contained a ribonucleic acid-dependent deoxyribonucleic acid polymerase, and had an infectivity peak at 1.15 g/cm(3) in a sucrose density gradient. The virus passed through a 220-nm but not a 100-nm membrane filter, was chloroform sensitive, and was inactivated at 56 C in 30 min. Hemagglutinating and hemadsorption activity was not noted with a variety of erythrocytes. The virion was spherical, formed in the cytoplasm, and was 105 to 115 nm in diameter. Ring-shaped nucleoids, 45 to 50 nm in diameter, were associated with tubular profiles. The virus was not neutralized by sera prepared against known viruses, including simian foamy virus types 1 through 7, Mason-Pfizer monkey virus, and bovine syncytial and measles viruses. Sera from a rabbit hyperimmunized with the isolate and sera from 19 spider monkeys had neutralizing antibody to the isolate; however, these sera did not cross-react with simian foamy virus types 1 through 7. Neutralizing antibody to the isolate was not detected in sera from 16 humans, 9 rhesus monkeys, and 10 chimpanzees.