Seroprevalence of four endemic human coronaviruses antibodies among Filipino children and their cross-reactivity and neutralization capacity against SARS-CoV-2

Four endemic human coronaviruses (HCoV), HCoV-229E, HCoV-NL63, HCoVHKU1, and HCoV-OC43, are closely related to SARS-CoV-2. These coronaviruses are known to infect humans living in temperate areas, including children under 5 years old; however, the seroprevalence of anti-HCoV antibodies among children in tropical areas, including the Philippines, remains unclear. This study aimed to assess the prevalence of antibodies against endemic HCoVs among Philippine children and to determine the cross-reactivity and neutralization of these antibodies against SARS-CoV-2. A total of 315 serum samples collected from 2015 to 2018 in Biliran island, Philippines, were tested for the presence of antibodies against four HCoVs and SARS-CoV-2 using recombinant spike proteins. Cross-reactivity to and neutralization of SARS-CoV-2 were also investigated. The seroprevalence of the four HCoVs was 63.8% for HCoV-229E, 71.4% for HCoV-NL63, 76.5% for HCoV-HKU1, and 83.5% for HCoV-OC43. Age group analysis indicated that seropositivity to all HCoVs reached 80% by 2–3 years of age. While 69/315 (21.9%) of the samples showed crossreactivity to SARS-CoV-2, almost no neutralization against SARSCoV-2 was detected. The high anti-HCoVs antibody levels at an early age suggest that there is earlier and higher prevalence of HCoV infections in the Philippines. Cross-reactive samples against SARS-CoV-2 indicated low neutralization capability.