Respiratory Syncytial Virus Subgroups A and B Contribute Equally to the Global RSV Burden, Study Finds

Respiratory syncytial virus (RSV) A and B contribute to the global RSV burden, and both subgroups cause severe disease, with no available evidence suggesting differences in clinical severity between the subgroups, according to a study published in Infectious Diseases and Therapy.

RSV, a common cause of respiratory infections in children and adults, remains a significant public health concern. The virus is divided into 2 major subgroups, A and B, which co-circulate annually. While both subgroups can cause severe respiratory illness, whether one subgroup leads to more severe outcomes has been a topic of scientific scrutiny.

“The aim of this study is to investigate differences between RSV subgroups A and B on the two key surface proteins, F and G, that might explain differences in the immune response and clinical severity following infection,” wrote Charles Nuttens, Pfizer Vaccines, Paris, France, and coauthors. “We will also discuss the potential impact these differences could have on the prevention measures of RSV (mAbs and vaccines).”

A comprehensive review of 46 studies examining the impact of RSV subgroups on clinical severity revealed mixed results. Twenty-nine studies found no significant differences between subgroups A and B, while 14 studies reported that subgroup A infections resulted in more severe outcomes. Conversely, only 2 studies suggested that subgroup B infections led to more severe cases.

The variability in these findings may be attributed to differences in study duration, geographical location, and the emergence of new genotypes. Notably, studies conducted after 2014, following the global predominance of the ON (RSV A subgroup) and BA (RSV B subgroup) genotypes, showed no difference in disease severity between the 2 subgroups.

Immunity against RSV remains a challenge. Most neutralizing antibodies target the conserved prefusion F protein, but some monoclonal antibodies demonstrate reduced efficacy against RSV B strains. T-cell responses also vary between subgroups, with RSV A potentially eliciting more robust cellular immunity. Researchers emphasize the need for a standardized severity index to improve study comparability and yield more conclusive data. Additionally, ongoing surveillance of RSV strains and their genetic variations is crucial for understanding the virus's evolution and its potential impact on clinical outcomes.

As RSV continues to pose a significant health risk, particularly to infants and older adults, this research underscores the importance of developing vaccines and treatments that target both subgroups. The findings also highlight the complexity of RSV infections and the need for continued research to better understand the factors influencing disease severity.

“Prevention strategies should ensure that both subgroups are targeted to avoid one subgroup becoming dominant and/or escaping immunity once immunization programs are deployed,” the authors concluded.

Reference

Nuttens C, Moyersoen J, Curcio D, et al. Differences between RSV A and RSV B subgroups and implications for pharmaceutical preventive measures. Infect Dis Ther. 2024;13(8):1725-1742. doi:10.1007/s40121-024-01012-2