COVID-19 outbreak at a reception centre for asylum seekers in Espoo, Finland.

Background shared accommodation may increase the risk of SARS-CoV-2 transmission. In April 2020, an increasing number of asylum seekers at a reception centre in Espoo, Finland presented with COVID-19 despite earlier implementation of preventive measures. We decided to screen the entire population of the centre for SARS-CoV-2. Methods we offered nasopharyngeal swab collection and SARS-CoV-2 real-time polymerase chain reaction (RT-PCR) analysis to the centre's clients. Symptoms were recorded at the time of diagnostic sample collection using electronic forms and followed up for two weeks through phone interviews and a review of medical records. Findings 260 clients were screened. Of them, 96 (37%) were found positive for SARS-CoV-2 and isolated. The high attack rate prompted the local public health authority to set the other clients in quarantine for 14 days to prevent further spread. Of the positive cases, 61 (64%) reported having had symptoms at the time of the screening or one week prior. Of the 35 initially asymptomatic individuals, 12 developed symptoms during follow-up, while 23 (or 18% of all screened SARS-CoV-2 positive clients) remained asymptomatic. No widespread transmission of COVID-19 was detected after the quarantine was lifted. Interpretation in this large COVID-19 outbreak, voluntary mass screening provided valuable information about its extent and helped guide the public health response. Comprehensive quarantine and isolation measures were likely instrumental in containing the outbreak. Funding Finnish Institution for Health and Welfare, Finnish Immigration Agency, City of Espoo.

Clearance of Chlamydia pneumoniae infection in H-2 class I human leucocyte antigen-A2.1 monochain transgenic mice.

CD8+ T cells have been suggested to play an important role in protective immunity against pulmonary Chlamydia pneumoniae infection in mice. Moreover, several classical major histocompatibility complex class I - restricted cytotoxic CD8+ T lymphocytes (CTL) specific for C. pneumoniae- derived peptides have been identified. Here, we studied the outcome of C. pneumoniae infection in human leucocyte antigen (HLA)-A2.1 transgenic mice (HHD mice) that are only able to express a classical human class I molecule (HLA-A2.1). C. pneumoniae infection was self-restricted in HHD mice which were able to develop specific immune responses and a protective immunity against a subsequent rechallenge in a manner comparable to wildtype mice. Furthermore, accumulation of functional and C. pneumoniae-specific T cells to the site of infection was detected after challenge. Antigen processing and HLA-A2.1-dependent presentation was studied by immunizing the HHD mice with chlamydial outer protein N (CopN). Isolation of a peptide-specific CTL line from the CopN-immunized mice suggests that the HLA-A2.1 molecule can support the development of CTL response against a chlamydial protein in mice. These findings suggest that the transgenic mouse model can be used for further characterization of the HLA-A2.1-restricted CD8+ T-cell response during C. pneumoniae infection and for identification of CD8 epitopes from chlamydial antigens.