Serologic Cross-Reactions between Nucleocapsid Proteins of Human Respiratory Syncytial Virus and Human Metapneumovirus

Abstract

Human respiratory syncytial virus (hRSV) and human metapneumovirus (hMPV) share virologic and epidemiologic features and cause clinically similar respiratory illness predominantly in young children. In a previous study of acute febrile respiratory illness in Bangladesh, we tested paired serum specimens from 852 children presenting fever and cough for diagnostic increases in titers of antibody to hRSV and hMPV by enzyme immunoassay (EIA). Unexpectedly, of 93 serum pairs that showed a >4-fold increase in titers of antibody to hRSV, 24 (25.8%) showed a concurrent increase in titers of antibody to hMPV; of 91 pairs showing an increase to hMPV, 13 (14.3%) showed a concurrent increase to hRSV. We speculated that common antigens shared by these viruses explain this finding. Since the nucleocapsid (N) proteins of these viruses show the greatest sequence homology, we tested hyperimmune antisera prepared for each virus against baculovirus-expressed recombinant N (recN) proteins for potential cross-reactivity. The antisera were reciprocally reactive with both proteins. To localize common antigenic regions, we first expressed the carboxy domain of the hMPV N protein that was the most highly conserved region within the hRSV N protein. Although reciprocally reactive with antisera by Western blotting, this truncated protein did not react with hMPV IgG-positive human sera by EIA. Using 5 synthetic peptides that spanned the amino-terminal portion of the hMPV N protein, we identified a single peptide that was cross-reactive with human sera positive for either virus. Antiserum prepared for this peptide was reactive with recN proteins of both viruses, indicating that a common immunoreactive site exists in this region.H uman respiratory syncytial virus (hRSV) and human metapneumovirus (hMPV) are negative single-stranded, enveloped RNA viruses that are coclassified within the Pneumovirinae subfamily of the Paramyxoviridae. hRSV is the leading cause of severe lower respiratory tract infections in infants and young children and has been associated with community-acquired pneumonia in adults, with the highest mortality rates found among the hospitalized elderly and immunocompromised (1, 2, 3). hMPV was identified first in 2001 by van den Hoogen et al. (4) and subsequently has been shown to have clinical and epidemiological features similar to but distinct from those of hRSV (5, 6). Most hMPV infections occur within the first few years of life, usually later than those for hRSV, and cause 5 to 10% of respiratory infections in children requiring hospitalization, second only to hRSV (7). Both viruses are ubiquitous globally, and recent studies have documented a high prevalence of infection among children in less developed countries (8, 9). Clinical outcomes similar to those for hRSV have been described for hMPV infections in the frail elderly (10).The RNA genomes of hRSV and hMPV are complexed with nucleocapsid (N) protein that together serve as the templates for genome replication and transcription (11). The N protein is the most abundant...

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“…In contrast to the pattern for PIV, the seasonal peaks of RSV and HMPV activity in the United States overlap, increasing opportunities for true coinfections. However, as we and others have shown, these viruses share antigenic sites on their nucleocapsid (32) and fusion (33, 34) proteins, and though less common, heterotypic antibody responses following infections with these vi-ruses have been demonstrated in children presenting with acute febrile respiratory illnesses (32). As with PIV, serologic coresponses to RSV and HMPV should be interpreted with caution.…”

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In silico analysis of amino acid variation in human respiratory syncytial virus: insights into immunodiagnostics

“…Consequently, polyclonal antibodies against this protein or monoclonal antibodies against these regions are not appropriate for HRSV diagnosis. In fact, cross-reactivity between the N proteins of these viral species has already been described for polyclonal antibodies and for monoclonal antibodies against these two mentioned regions ( Zhang et al 2015 ). Alternatively, monoclonal antibodies against the region between aa s 30-160 could specifically identify HRSV since this region is conserved only among HRSV sequences.…”