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Human Metapneumovirus Infections
Published in Sunit K. Singh, Human Respiratory Viral Infections, 2014
Jennifer Elana Schuster, John V. Williams
Human metapneumovirus (HMPV, MPV) is a member of the Paramyxoviridae family that causes upper and lower respiratory tract disease in humans. In 2001, researchers identified a novel virus from nasopharyngeal aspirates (NPAs) of 28 Dutch children with respiratory tract disease.1 Under electron microscopy, the virus had a paramyxovirus-like appearance with filamentous, pleomorphic, and spherical particles. Projection length was approximately 15 nm with a nucleocapsid diameter of 17 nm. Particles varied in size: spherical particles averaged 209 nm and filamentous particles about 282 × 62 nm.2 Based on these images, virologic data, and genome organization, the new virus was classified in the subfamily of Pneumovirinae, which contains the genera Pneumovirus, type species human respiratory syncytial virus (HRSV), and Metapneumovirus, type species avian metapneumovirus (APV).1
Repeated vaccination and ‘vaccine exhaustion’: relevance to the COVID-19 crisis
Published in Expert Review of Vaccines, 2022
Md Anwarul Azim Majumder, Mohammed S. Razzaque
Additionally, declining protection from repeated vaccination may be related to viral mutations [20]. Vaccination against the hepatitis B virus, which has significantly reduced the hepatic disease burden (e.g. cirrhosis, hepatocellular carcinoma) [21], was developed to act against viral envelope proteins (as anti-HBsAg), thus providing broad-spectrum protection against all hepatitis B virus genotypes (from A to H). However, viral mutations affecting the amino acids in envelope proteins also resulted in a reduced vaccine effectiveness [22,23]. Reduced vaccine efficacy due to pathogen evolution is also documented with animal vaccines. For Marek’s disease, a common and highly contagious viral (Gallid herpesvirus 2) neoplastic disease of poultry, the effectiveness of the earlier generation of vaccine was impaired due to viral evolution [24]. Vaccine resistance was documented against the bacteria Yersinia ruckeri, which is the causative agent of enteric redmouth disease in farmed salmonids [25]; the fish vaccine resistance was attributed to a single mutational event leading to loss of flagellar motility in Yersinia ruckeri [26]. Rhinotracheitis in Turkey and other poultry is caused by Avian metapneumovirus. However, outbreaks of rhinotracheitis among the vaccinated Turkey were reported in various parts of the world [27,28]. Again, vaccine resistance was linked to the pathogen evolution that resulted in variation in the surface glycoprotein of the virus [29]. Microbial recombination events in Streptococcus pneumoniae reduced protection for patients who received the pneumococcal conjugate vaccine [30,31]. A similar vaccine-induced microbial evolution was also observed with Bordetella pertussis, a causative microorganism for whooping cough [32].