The HPIV3 subclaster C3 (genetic lineage C3a) became the most detected circulating HPIV3 strain in Croatia. The results indicated that the HN 582 nt and the entire F gene sequences were as good for phylogenetic analysis as the entire HN gene sequence.

Human metapneumovirus (HMPV) is recognized as a global and frequent cause of acute respiratory tract infections among people of all ages. The objectives of this study were molecular epidemiology and evolutionary analysis of HMPV strains which produced moderate and severe acute respiratory tract infections in children in Croatia during four consecutive seasons (2011-2014). A total of 117 HMPV-positive samples collected from hospitalized pediatric patients presenting with acute respiratory tract infections and tested by direct immunofluorescence assay were first analyzed by amplifying a part of the F gene. Sixteen samples were further analyzed based on complete F, G, and SH gene sequences. HMPV genome was identified in 92 of 117 samples (78%) and the circulation of multiple lineages of HMPV was confirmed. In 2011, 2012, and 2014, subgroups A2 and B2 co-circulated, while B1 gained prevalence in 2013 and 2014. The study established the presence of a novel subcluster A2c in Croatia. This subcluster has only recently been detected in East and Southeast Asia. This study provides new insights into epidemiology and genetic diversity of HMPV in this part of Europe.

The dynamics and evolution of the human parainfluenza virus type 2 (HPIV2) in Croatia, and also globally, are largely unknown. Most HPIV2 infections are treated symptomatically outside the hospital setting. Thus, the diagnosis is missing making it difficult to follow the genetic variation and evolution of the HPIV2. This study explores hospitalized HPIV2 cases in Croatia during 4-year period (2011-2014). Most cases in this period were reported in October or November (68.75%) and most of patients were under 2 years of age (81.25%). For molecular analyses, we used the F and HN gene sequences and showed that although both regions are equally suitable for phylogenetic analyses it would be advantageous to use regions longer than 2 kb for HPIV2 analyses of isolates which are spatially and temporally closely related. We show here that the dominant cluster in this area was cluster G3 while only one strain isolated in this period was positioned in the distant cluster G1a. Further monitoring of the HPIV2 will determine whether cluster G3 will remain dominant or it will be overruled by cluster G1a. This will be important for the surveillance of virus circulation in population and significance of the viral infection. J. Med. Virol. 88:1733-1741, 2016. © 2016 Wiley Periodicals, Inc.

During the ongoing COVID-19 epidemic many efforts have gone into the investigation of the SARS-CoV-2–specific antibodies as possible therapeutics. Currently, conclusions cannot be drawn due to the lack of standardization in antibody assessments. Here we describe an approach of establishing antibody characterisation in emergent times which would, if followed, enable comparison of results from different studies. The key component is a reliable and reproducible assay of wild-type SARS-CoV-2 neutralisation based on a banking system of its biological components - a challenge virus, cells and an anti-SARS-CoV-2 antibody in-house standard, calibrated to the First WHO International Standard immediately upon its availability. Consequently, all collected serological data were retrospectively expressed in an internationally comparable way. The neutralising antibodies (NAbs) among convalescents ranged from 4 to 2869 IU mL-1 in a significant positive correlation to the disease severity. Their decline in convalescents was on average 1.4-fold in a one-month period. Heat-inactivation resulted in 2.3-fold decrease of NAb titres in comparison to the native sera, implying significant complement activating properties of SARS-CoV-2 specific antibodies. The monitoring of NAb titres in the sera of immunocompromised COVID-19 patients that lacked their own antibodies evidenced the successful transfusion of antibodies by the COVID-19 convalescent plasma units with NAb titres of 35 IU mL-1 or higher.