Stanley A. Plotkin’s research while affiliated with University of Pennsylvania and other places

The pursuit of a vaccine against the human cytomegalovirus (HCMV) has been ongoing for more than 50 years. HCMV is the leading infectious cause of birth defects, including damage to the brain, and is a common cause of complications in organ transplantation. The complex biology of HCMV has made vaccine development difficult, but a recent meeting sponsored by the National Institute of Allergy and Infectious Diseases in September of 2023 brought together experts from academia, industry, and federal agencies to discuss progress in the field. The meeting reviewed the status of candidate HCMV vaccines under study and the challenges in clinical trial design in demonstrating efficacy against congenital CMV infection or the reduction of HCMV disease following solid organ transplantation or hematopoietic stem cell transplantation. Discussion in the meeting revealed that, with the numerous candidate vaccines that are under study, it is clear that a safe and effective HCMV vaccine is within reach. Meeting attendees achieved a consensus opinion that even a partially effective vaccine would have a major effect on the global health consequences of HCMV infection.

Lyme disease is caused by Borrelia species that are transmitted by Ixodes ticks prevalent in parts of the United States and Europe. A Lyme vaccine containing the OspA antigens from the single Borrelia species most prevalent in the United States was marketed in the 1990s, but was withdrawn because of unproven concerns about safety, which led to insufficient sales. Since then, the incidence of Lyme disease has increased in the United States owing to the geographical spread of infected ticks. Lyme disease due to multiple different species of Borrelia also is widely prevalent in many European countries. New Lyme vaccines, using OspA antigens from multiple species of American and European Borrelia, are in advanced clinical development, and one such vaccine is in phase 3 trials. When licensed, new vaccines are likely to have an impact in preventing Lyme disease, although the need for periodic boosters remains to be defined.

Mumps virus (MuV) is a highly contagious paramyxovirus that is endemic in most regions of the world and continues to cause outbreaks even in highly immunized populations. Outbreaks of mumps in countries with high measles, mumps, and rubella vaccination coverage have been attributed to waning immunity and antigenic differences between the Jeryl Lynn vaccine strain (genotype A) and circulating wild-type viruses. To obtain a subunit vaccine, we used structure-based design to engineer the mumps fusion (F) glycoprotein stabilized in its prefusion conformation (Pre-F) as well as a chimeric immunogen comprising Pre-F linked to mumps hemagglutinin neuraminidase (HN); in mice, both Pre-F antigen and the chimeric antigen elicited potent cross-reactive plaque reducing neutralizing titers to genotypes A, G, and H mumps. A crystal structure of mumps Pre-F at 2.16 Å resolution validated the stabilization strategy, while a post-fusion form of F was engineered as a comparator. Monoclonal antibodies to mumps Pre-F and HN were isolated from immunized mice; 7 of 14 Pre-F-specific antibodies and 9 of 15 HN-specific antibodies were capable of neutralizing genotype G MuV with a range of potencies. Additionally, 7 of 14 Pre-F-specific antibodies neutralized genotype A mumps. Structural and binding analyses of Pre-F-specific antibodies revealed binding to four discrete neutralizing antigenic sites and binding analyses of HN-specific antibodies revealed binding to five discrete neutralizing antigenic sites. Overall, the PreF and the chimeric Pre-F/HN immunogens are promising candidates to boost MMR-elicited immunity to mumps or as a next-generation vaccine.

Congenital cytomegalovirus (cCMV) is the most common infectious cause of disability in children. The major theme of this National Institute of Allergy and Infectious Diseases (NIAID) workshop, “CMV Vaccine Development—How Close Are We?”, was to report progress on the development of a pre-conception vaccine that could confer protective immunity for women of child-bearing age. Such a vaccine could result in a reduced cCMV disease burden, although other populations, including solid organ transplant and hematopoietic stem cell transplant patients, could benefit as well. To frame the compelling need for a cCMV vaccine, a keynote lecture by Dr. Megan Pesch, immediate past-president of the National CMV Foundation and a leading cCMV researcher from the University of Michigan, was given. This manuscript provides a summary of Dr. Pesch’s presentation from this workshop, which was written as the introductory conference report for the meeting.

Congenital cytomegalovirus (cCMV) is the most common infectious cause of disability in children, including sensorineural hearing loss. There is interest in developing a pre-conception vaccine that could confer protective immunity on a woman of child-bearing age, hence resulting in a reduced cCMV disease burden. Other populations, including solid organ transplant (SOT) and hematopoietic stem cell transplant (HSCT) patients, could also benefit from CMV vaccination. To review and discuss vaccines that are in clinical development, a workshop, sponsored by the National Institutes of Health (NIH) and the National Institute of Allergy and Infectious Diseases (NIAID), was empaneled. At this workshop, correlates of protective immunity against CMV, epidemiologic features of CMV transmission, and vaccine platforms in development were reviewed. Representatives from academia, pharma, and the NIH engaged in discussion on the current state-of-the-art in CMV vaccinology. A summary of the presentations from this is provided in this report.