Magnetic Resonance Imaging-Guided Frameless Stereotactic Injections of the Bilateral Cerebellar Dentate Nuclei in Nonhuman Primates: Technical Note.

BACKGROUND AND OBJECTIVES: Nonhuman primates (NHPs) are important preclinical models for evaluating therapeutics because of their anatomophysiological similarities to humans, and can be especially useful for testing new delivery targets. With the growing promise of cell and gene therapies for the treatment of neurological diseases, it is important to ensure the accurate and safe delivery of these agents to target structures in the brain. However, a standard guideline or method has not been developed for stereotactic targeting in NHPs. In this article, we describe the safe use of a magnetic resonance imaging-guided frameless stereotactic system to target bilateral cerebellar dentate nuclei for accurate, real-time delivery of viral vector in NHPs. METHODS: Seventeen rhesus macaques (Macaca mulatta) underwent stereotactic surgery under real-time MRI guidance using the ClearPoint® system. Bilateral cerebellar dentate nuclei were targeted through a single parietal entry point with a transtentorial approach. Fifty microliters of contrast-impregnated infusate was delivered to each dentate nucleus, and adjustments were made as necessary according to real-time MRI monitoring of delivery. Perioperative clinical outcomes and postoperative volumes of distribution were recorded. RESULTS: All macaques underwent bilateral surgery successfully. Superficial pin site infection occurred in 4/17 (23.5%) subjects, which resolved with antibiotics. Two episodes of transient neurological deficit (anisocoria and unilateral weakness) were recorded, which did not require additional postoperative treatment and resolved over time. Volume of distribution of infusate achieved satisfactory coverage of target dentate nuclei, and only 1 incidence (2.9%) of cerebrospinal fluid penetration was recorded. Mean volume of distribution was 161.22 ± 39.61 mm3 (left, 173.65 ± 48.29; right, 148.80 ± 23.98). CONCLUSION: MRI-guided frameless stereotactic injection of bilateral cerebellar dentate nuclei in NHPs is safe and feasible. The use of this technique enables real-time modification of the surgical plan to achieve adequate target coverage and can be readily translated to clinical use.

Protection against herpes simplex virus type 2 infection in a neonatal murine model using a trivalent nucleoside-modified mRNA in lipid nanoparticle vaccine.

Neonatal herpes is a dreaded complication of genital herpes infection in pregnancy. We recently compared two vaccine platforms for preventing genital herpes in female mice and guinea pigs and determined that HSV-2 glycoproteins C, D and E expressed using nucleoside-modified mRNA in lipid nanoparticles provided better protection than the same antigens produced as baculovirus proteins and administered with CpG and alum. Here we evaluated mRNA and protein immunization for protection against neonatal herpes. Female mice were immunized prior to mating and newborns were infected intranasally with HSV-2. IgG binding and neutralizing antibody levels in mothers and newborns were comparable using the mRNA or protein vaccines. Both vaccines protected first and second litter newborns against disseminated infection based on virus titers in multiple organs. We conclude that both vaccines are efficacious at preventing neonatal herpes, which leaves the mRNA vaccine as our preferred candidate based on better protection against genital herpes.

Vaccines to prevent genital herpes.

Genital herpes increases the risk of acquiring and transmitting Human Immunodeficiency Virus (HIV), is a source of anxiety for many about transmitting infection to intimate partners, and is life-threatening to newborns. A vaccine that prevents genital herpes infection is a high public health priority. An ideal vaccine will prevent both genital lesions and asymptomatic subclinical infection to reduce the risk of inadvertent transmission to partners, will be effective against genital herpes caused by herpes simplex virus types 1 and 2 (HSV-1, HSV-2), and will protect against neonatal herpes. Three phase 3 human trials were performed over the past 20 years that used HSV-2 glycoproteins essential for virus entry as immunogens. None achieved its primary endpoint, although each was partially successful in either delaying onset of infection or protecting a subset of female subjects that were HSV-1 and HSV-2 uninfected against HSV-1 genital infection. The success of future vaccine candidates may depend on improving the predictive value of animal models by requiring vaccines to achieve near-perfect protection in these models and by using the models to better define immune correlates of protection. Many vaccine candidates are under development, including DNA, modified mRNA, protein subunit, killed virus, and attenuated live virus vaccines. Lessons learned from prior vaccine studies and select candidate vaccines are discussed, including a trivalent nucleoside-modified mRNA vaccine that our laboratory is pursuing. We are optimistic that an effective vaccine for prevention of genital herpes will emerge in this decade.

Effects of Standard and Sustained-release Buprenorphine on the Minimum Alveolar Concentration of Isoflurane in C57BL/6 Mice.

Both standard and sustained-release injectable formulations of buprenorphine (Bup and BupSR, respectively) are used as preemptive analgesics, potentially affecting gas anesthetic requirements. This study tested the effects of Bup and BupSR on isoflurane requirements and confirmed that buprenorphine could reduce isoflurane requirements during a laparotomy in mice. We hypothesized that both Bup and BupSR would significantly decrease the required minimum alveolar concentration (MAC) of isoflurane. C57BL/6 mice received either isotonic crystalloid fluid (control), Bup (0.1 mg/kg), or BupSR (1.2 mg/kg) subcutaneously 10 min prior to the induction of anesthesia. Each anesthetized mouse was tested at 2 isoflurane concentrations. A 300-g noxious stimulus was applied at each isoflurane concentration, alternating between hindfeet. In addition, a subset of mice underwent terminal laparotomy or 60 min of anesthesia after injection with Bup, BupSR, or saline to ensure an appropriate surgical plane of anesthesia. Mice were maintained at the lowest isoflurane concentration that resulted in 100% of mice at a surgical plane from the aforementioned MAC experiments (control, 2.0%; Bup and BupSR, 1.7%). Analysis showed that both Bup and BupSR significantly decreased isoflurane requirements by 25.5% and 14.4%, respectively. The isoflurane MAC for the control injection was 1.80% ± 0.09%; whereas Bup and BupSR decreased MAC to 1.34% ± 0.08% and 1.54% ± 0.09%, respectively. Sex was not a significantly different between the injection groups during MAC determination. All of the mice that underwent surgery achieved a surgical plane of anesthesia on the prescribed regimen and recovered normally after discontinuation of isoflurane. Lastly, heart and respiratory rates did not differ between mice that underwent surgery and those that were anesthetized only. Bup and BupSR are MAC-sparing in male and female C57BL/6 mice and can be used for effective multimodal anesthesia.

Suspected Anaphylactic Reaction to Ketamine in 3 Yucatan Swine (Sus scrofa).

This case series describes the clinical courses of 3 juvenile Yucatan miniature swine (Sus scrofa) that experienced a suspected anaphylactic reaction to ketamine hydrochloride during premedication for protocol-related surgery. All 3 swine rapidly developed diffuse erythema shortly after injection with ketamine-containing drug combinations. Clinical signs ranged from tachycardia and erythema alone to tachycardia and erythema followed by respiratory and cardiac arrest. Ketamine was considered the most likely cause of these reactions because it was the only agent in the premedication sedation combination that was used in all 3 swine. Subsequent intradermal skin testing confirmed this suspicion. With supportive care measures and standard medical interventions for anaphylaxis, all 3 animals recovered well and went on to be successful experimental subjects when an alternative anesthetic regimen that did not contain ketamine was used. To our knowledge, this report is the first description of a suspected adverse ketamine reaction of this type in swine despite the widespread use of the drug in this species. Ketamine anaphylaxis is rare in people, but the few cases described presented with symptoms similar to the clinical signs seen in the pigs in this report. In addition to highlighting a potential adverse drug reaction to ketamine in swine, this case series demonstrates the value of emergency preparedness for even the most routine of procedures.

Efficacy of a Single, Percutaneous, Across Midline, Octrode® Lead Using a "Midline Anchoring" Technique in the Treatment of Chronic Low Back and/or Lower Extremity Pain: A Retrospective Study.

Introduction. Spinal cord stimulation is a widely used treatment modality for chronic pain, especially failed back surgery syndrome. However, migration of the lead or leads, coverage of axial pain, and the selection of an optimal system configuration continue to be subjects for serious debate. Materials and Methods. A retrospective study of the use of the method of "midline anchoring" of a single Octrode® lead, in 54 patients with low back and/or lower extremity pain, was done to assess the efficacy of this technique. Results. During the study period of 9.3 months, only a 4% revision rate was reported. Reduction in pain of more than 50% and individual patient satisfaction scores were very high (85% and 87%, respectively). Successful bilateral pain coverage was obtained with a single Octrode® lead. The lower extremities and buttocks area were captured in 89% of the patients. Axial pain coverage was achieved in the majority of the patients, with 71% reporting adequate coverage of the upper lumbar spine. A "guarded cathode" array was used in the vast majority of the cases, with a relatively low position of the lead. Conclusions. "Midline anchoring" of the spinal cord stimulation lead is an effective implantation technique, allowing the use of a single, percutaneous, Octrode® lead, while preventing lead migration and allowing capture of axial and lower extremity pain, unilateral as well as bilateral. This study revives the idea of a single lead as a possible optimal configuration.