Recent studies have focused on the importance of better diagnosis for RSV in adults as well as improved understanding of which viral strains are circulating at any given time. Both have the potential of improving and increasing uptake of vaccines, according to the researchers.

Emory University School of Medicine researchers led the study on RSV, which is a leading cause of acute respiratory illness (ARI) in older adults. “Optimizing diagnosis could improve understanding of RSV burden,” the authors pointed out.

For the study published in the Journal of Infectious Diseases, the investigative team enrolled 1,558 adults aged 50 years and older who were hospitalized with ARI and adults of any age hospitalized with congestive heart failure or chronic obstructive pulmonary disease exacerbations at two hospitals during two respiratory seasons (2018–2020).

Nasopharyngeal (NP) and oropharyngeal (OP) swabs, acute and convalescent sera, and expectorated sputum (n = 153) were collected from participants. RSV antibodies were determined by two immunoassays, and the researchers performed BioFire testing on respiratory specimens.

The results found that 92 (5.9%) tested positive for RSV by any diagnostic method. Combined NP/OP PCR yielded 58 positives, while separate NP and OP testing identified 11 additional positives (18.9% increase). “Compared to Study NP/OP PCR alone, the addition of paired serology increased RSV detection by 42.9% (28 vs 40) among those with both specimen types, while the addition of SOC [standard-of-care] swab RT-PCR [real-time polymerase chain reaction] results increased RSV detection by 25.9% (47 vs 59),” the authors wrote.

The researchers concluded that the addition of paired serology testing, SOC swab results, and separate testing of NP and OP swabs improved RSV diagnostic yield in hospitalized adults.

In another study published in the Journal of Virology, researchers from Washington University School of Medicine in Saint Louis and colleagues advised that RSV is classified into two strains, A and B, each with several subgroups or genotypes.

“One issue with the definition of these subgroups is the lack of a unified method of identification or genotyping. We propose that genotyping strategies based on the genes coding for replication-associated proteins could provide critical information on the replication capacity of the distinct subgroups, while clearly distinguishing genotypes,” the authors explained.

Analyzing the virus replication-associated genes N, P, M2, and L from de novo assembled RSV A sequences obtained from 31 newly sequenced samples from hospitalized patients in Philadelphia and 78 additional publicly available sequences from different geographic locations within the United States, the study team performed an in-depth analysis. This included an annotation of variants in the replication-associated proteins identified the polymerase protein L as a robust target for genotyping RSV subgroups.

“Importantly, our analysis revealed non-synonymous variations in L that were consistently accompanied by conserved changes in its co-factor P or the M2-2 protein, suggesting associations and interactions between specific domains of these proteins. Similar associations were seen among sequences of the related human metapneumovirus,” the authors wrote, adding, “These results highlight L as an alternative to other RSV genotyping targets and demonstrate the value of in-depth analyses and annotations of RSV sequences as it can serve as a foundation for subsequent in vitro and clinical studies on the efficiency of the polymerase and fitness of different virus isolates.”

That is important, the researchers pointed out, because there is a need to understand the properties of the circulating RSV strains each season.

“Our results also suggest a genotyping strategy that can prove to be particularly important in understanding the genotype-phenotype correlation in the era of RSV vaccination, where selective pressure on the virus to evolve is anticipated,” the study authors added. “More importantly, the categorization of pneumoviruses based on these patterns may be of prognostic value.”

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