Preventing neonatal herpes: Protection after maternal mRNA-lipid nanoparticle vaccination equals or exceeds that from prior maternal genital infection in murine models

Neonates are vulnerable to poor outcomes from herpes simplex virus (HSV), but maternal infection eliciting non-sterilizing immunity prior to delivery provides some protection. We are therefore pursuing birthing parent vaccination with nucleoside-modified mRNA-lipid nanoparticles (mRNA-LNPs) to prevent neonatal herpes. Our trivalent vaccine encodes HSV type 2 (HSV-2) proteins involved in attachment and immune evasion (gC2, gD2, and gE2). We have shown that this vaccine protects against genital HSV and neonatal HSV-2 in mice. Here, we tested how well murine dam vaccination prior to pregnancy protects pups against HSV type 1 (HSV-1) challenge compared to prior maternal intravaginal HSV-1 infection. Dams were immunized intramuscularly with the HSV-2 trivalent mRNA-LNP vaccine or a control immunogen (PolyC RNA-LNP), or were infected intravaginally with HSV-1 (HSV-1 ivag). Pups were challenged intranasally with HSV-1 on the 3rd day of life. Pups born to dams previously immunized or infected survived through 28 days (mRNA 95% vs. HSV-1 ivag 96%, N.S.; vs. PolyC 13%, p<0.0001). Likewise, they were protected from HSV-1 dissemination to the brain, lung, liver, spleen, and kidney by plaque assay (mRNA 2/45 organs affected vs. HSV-1 ivag 6/20, p=0.0083; vs. PolyC 69/80, p<0.0001). Additionally, fewer organs showed necrosis by histopathology of brain, lung, and liver, though not statistically significant, and fewer mRNA and HSV-1 ivag pups had detectable HSV-1 DNA in the trigeminal ganglia by qPCR (mRNA 6/30 vs. HSV-1 ivag 7/26, N.S.; vs. PolyC 17/18, p<0.0001). These studies demonstrate that the mRNA vaccine provides comparable to improved protection against neonatal HSV-1 challenge versus prior maternal HSV-1 intravaginal infection.

AD was supported by NIH NIAID T32 AI118684. HMF, SA, GHC, and DW were supported by NIH NIAID R01 AI139618 and an unrestricted grant from BioNTech SE. KPE was supported by NIH T32 NS007180. The funders had no input or influence on the content of this abstract.

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.

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.

Hydromorphone-induced Neurostimulation in a Yorkshire Swine (Sus scrofa) after Myocardial Infarction Surgery

Opiates play an important role in the control of pain associated with thoracotomy in both people and animals. However, key side effects, including sedation and respiratory depression, could limit the use of opiates in animals that are lethargic due to cardiac disease. In addition, a rare side effect-neuroexcitation resulting in pathologic behavioral changes (seizures, mania, muscle fasciculation)-after the administration of morphine or hydromorphone is well-documented in many species. In pigs, however, these drugs have been shown to stimulate an increase in normal activity. In the case presented, we describe a Yorkshire-cross pig which, after myocardial infarction surgery, went from nonresponsive to alert, responsive, and eating within 30 min of an injection of hydromorphone. This pig was not demonstrating any signs associated with pain at this time, suggesting that the positive response was due to neural stimulation. This case report is the first to describe the use of hydromorphone-a potent, pure μ opiate agonist-for its neurostimulatory effect in pigs with experimentally-induced cardiac disease.