SARS-CoV-2 Omicron virus causes attenuated disease in mice and hamsters.

The recent emergence of B.1.1.529, the Omicron variant1,2, has raised concerns of escape from protection by vaccines and therapeutic antibodies. A key test for potential countermeasures against B.1.1.529 is their activity in preclinical rodent models of respiratory tract disease. Here, using the collaborative network of the SARS-CoV-2 Assessment of Viral Evolution (SAVE) programme of the National Institute of Allergy and Infectious Diseases (NIAID), we evaluated the ability of several B.1.1.529 isolates to cause infection and disease in immunocompetent and human ACE2 (hACE2)-expressing mice and hamsters. Despite modelling data indicating that B.1.1.529 spike can bind more avidly to mouse ACE2 (refs. 3,4), we observed less infection by B.1.1.529 in 129, C57BL/6, BALB/c and K18-hACE2 transgenic mice than by previous SARS-CoV-2 variants, with limited weight loss and lower viral burden in the upper and lower respiratory tracts. In wild-type and hACE2 transgenic hamsters, lung infection, clinical disease and pathology with B.1.1.529 were also milder than with historical isolates or other SARS-CoV-2 variants of concern. Overall, experiments from the SAVE/NIAID network with several B.1.1.529 isolates demonstrate attenuated lung disease in rodents, which parallels preliminary human clinical data.

A cohort study measuring SARS-CoV-2 seroconversion and serial viral testing in university students.

BACKGROUND: To improve understanding of the antibody response to SARS-CoV-2 infection, we examined seroprevalence, incidence of infection, and seroconversion among a cohort of young adults living on university campuses during the fall of 2020. METHODS: At the beginning (semester start) and end (semester end) of an 11-week period, serum collected from 107 students was tested using the qualitative Abbott Architect SARS-CoV-2 IgG and AdviseDx SARS-CoV-2 IgG II assays. Results were matched to interim weekly surveillance viral testing and symptom data. RESULTS: With the SARS-CoV-2 IgG assay, 15 (14.0%) students were seropositive at semester start; 29 (27.1%) students were seropositive at semester end; 10 (9.3%) were seropositive at both times. With the AdviseDx SARS-CoV-2 IgG II assay, 17 (16.3%) students were seropositive at semester start, 37 (35.6%) were seropositive at semester end, and 16 (15.3%) were seropositive at both times. Overall, 23 students (21.5%) had positive viral tests during the semester. Infection was identified by serial testing in a large majority of individuals who seroconverted using both assays. Those seropositive at semester end more frequently reported symptomatic infections (56.5%) than asymptomatic infections (30.4%). CONCLUSION: Differences between antibody targets were observed, with more declines in antibody index values below the threshold of positivity with the anti-nucleocapsid assay compared to the anti-spike assay. Serology testing, combined with serial viral testing, can detect seroconversions, and help understand the potential correlates of protection provided by antibodies to SARS-CoV-2.

Interventions to Disrupt Coronavirus Disease Transmission at a University, Wisconsin, USA, August-October 2020.

University settings have demonstrated potential for coronavirus disease (COVID-19) outbreaks; they combine congregate living, substantial social activity, and a young population predisposed to mild illness. Using genomic and epidemiologic data, we describe a COVID-19 outbreak at the University of Wisconsin-Madison, Madison, Wisconsin, USA. During August-October 2020, a total of 3,485 students, including 856/6,162 students living in dormitories, tested positive. Case counts began rising during move-in week, August 25-31, 2020, then rose rapidly during September 1-11, 2020. The university initiated multiple prevention efforts, including quarantining 2 dormitories; a subsequent decline in cases was observed. Genomic surveillance of cases from Dane County, in which the university is located, did not find evidence of transmission from a large cluster of cases in the 2 quarantined dorms during the outbreak. Coordinated implementation of prevention measures can reduce COVID-19 spread in university settings and may limit spillover to the surrounding community.

Assessing the dilution effect of specimen pooling on the sensitivity of SARS-CoV-2 PCR tests.

The SARS-CoV-2 pandemic has led to an unprecedented demand for diagnostic tests. Many studies have modeled the efficiency gains of specimen pooling, but few have systematically evaluated the dilution effect of pooling on the sensitivity of tests. Using the frequency distribution of cycle threshold (Ct ) values of our first 838 SARS-CoV-2 positive specimens, we modeled 100 specimens on the same frequency distribution. Given this distribution, we then tested dilutions of 1:5, 1:10, and 1:50 to find the percentage of specimens positive at each Ct value with each pool size. Using the frequency distribution and the percentage of specimens positive at each Ct value, we estimate that pools of 5 lead to 93% sensitivity, pools of 10 lead to 91% sensitivity, and pools of 50 lead to 81% sensitivity. Pools of 5 and 10 lead to some specimens with Ct values of ≥32 becoming negative, while pools of 50 lead to some specimens with Ct values of ≥28 becoming negative. These sensitivity estimates can inform laboratories seeking to implement pooling approaches as they seek to balance test efficiency with sensitivity.

Clinical Impact of a Multiplex Gastrointestinal Polymerase Chain Reaction Panel in Patients With Acute Gastroenteritis.

Background: Molecular syndromic diagnostic panels can enhance pathogen identification in the approximately 2-4 billion episodes of acute gastroenteritis that occur annually worldwide. However, the clinical utility of these panels has not been established. Methods: We conducted a prospective, multi-center study to investigate the impact of the BioFire FilmArray Gastrointestinal polymerase chain reaction panel on clinical diagnosis and decision-making, and compared the clinical acuity of patients with positive results obtained exclusively with the FilmArray with those detected by conventional stool culture. A total of 1887 consecutive fecal specimens were tested in parallel by FilmArray and stool culture. Laboratory and medical records were reviewed to determine rates of detection, turnaround times, clinical features, and the nature and timing of clinical decisions. Results: FilmArray detected pathogens in 35.3% of specimens, compared to 6.0% for culture. Median time from collection to result was 18 hours for FilmArray and 47 hours for culture. Median time from collection to initiation of antimicrobial therapy was 22 hours for FilmArray and 72 hours for culture. Patients diagnosed by FilmArray were more likely to receive targeted rather than empirical therapy, compared to those diagnosed by culture (P = .0148). Positive Shiga-like toxin-producing E. coli results were reported 47 hours faster with FilmArray and facilitated discontinuation of empirical antimicrobials. Patients diagnosed exclusively by FilmArray had clinical characteristics similar to those identified by culture. Conclusions: FilmArray markedly improved clinical sensitivity in patients with acute diarrhea, identified cases with clinical acuity comparable to those identified by culture, and enabled clinicians to make more timely and targeted therapeutic decisions.

Laboratory Focus on Improving the Culture of Biosafety: Statewide Risk Assessment of Clinical Laboratories That Process Specimens for Microbiologic Analysis.

The Wisconsin State Laboratory of Hygiene challenged Wisconsin laboratories to examine their biosafety practices and improve their culture of biosafety. One hundred three clinical and public health laboratories completed a questionnaire-based, microbiology-focused biosafety risk assessment. Greater than 96% of the respondents performed activities related to specimen processing, direct microscopic examination, and rapid nonmolecular testing, while approximately 60% performed culture interpretation. Although they are important to the assessment of risk, data specific to patient occupation, symptoms, and travel history were often unavailable to the laboratory and, therefore, less contributory to a microbiology-focused biosafety risk assessment than information on the specimen source and test requisition. Over 88% of the respondents complied with more than three-quarters of the mitigation control measures listed in the survey. Facility assessment revealed that subsets of laboratories that claim biosafety level 1, 2, or 3 status did not possess all of the biosafety elements considered minimally standard for their respective classifications. Many laboratories reported being able to quickly correct the minor deficiencies identified. Task assessment identified deficiencies that trended higher within the general (not microbiology-specific) laboratory for core activities, such as packaging and shipping, direct microscopic examination, and culture modalities solely involving screens for organism growth. For traditional microbiology departments, opportunities for improvement in the cultivation and management of highly infectious agents, such as acid-fast bacilli and systemic fungi, were revealed. These results derived from a survey of a large cohort of small- and large-scale laboratories suggest the necessity for continued microbiology-based understanding of biosafety practices, vigilance toward biosafety, and enforcement of biosafety practices throughout the laboratory setting.

Copy Number Heterogeneity of JC Virus Standards.

Quantitative PCR is a diagnostic mainstay of clinical virology, and accurate quantitation of viral load among labs requires the use of international standards. However, the use of multiple passages of viral isolates to obtain sufficient material for international standards may result in genomic changes that complicate their use as quantitative standards. We performed next-generation sequencing to obtain single-nucleotide resolution and relative copy number of JC virus (JCV) clinical standards. Strikingly, the WHO international standard and the Exact v1/v2 prototype standards for JCV showed 8-fold and 4-fold variation in genomic coverage between different loci in the viral genome, respectively, due to large deletions in the large T antigen region. Intriguingly, several of the JCV standards sequenced in this study with large T antigen deletions were cultured in cell lines immortalized using simian virus 40 (SV40) T antigen, suggesting the possibility of transcomplementation in cell culture. Using a cutoff 5% allele fraction for junctional reads, 7 different rearrangements were present in the JC virus sequences present in the WHO standard across multiple library preparations and sequencing runs. Neither the copy number differences nor the rearrangements were observed in a clinical sample with a high copy number of JCV or a plasmid control. These results were also confirmed by the quantitative real-time PCR (qPCR), droplet digital PCR (ddPCR), and Sanger sequencing of multiple rearrangements. In summary, targeting different regions of the same international standard can result in up to an 8-fold difference in quantitation. We recommend the use of next-generation sequencing to validate standards in clinical virology.

Quantification of BK Virus Standards by Quantitative Real-Time PCR and Droplet Digital PCR Is Confounded by Multiple Virus Populations in the WHO BKV International Standard.

BACKGROUND: The WHO recently released a BK virus (BKV) international standard. This study evaluated the WHO international standard and commercially available BKV standards by quantitative real-time PCR (qPCR) and droplet digital PCR (ddPCR). METHODS: WHO, Exact Diagnostics, Acrometrix, and Zeptometrix BKV standards were tested by qPCR and ddPCR. Two preparations of NIST BKV clones were also tested. Nucleic acid was extracted with the Roche MP96 and MPLC, followed by quantification in duplicate. To resolve discrepancies, we sequenced the WHO and NIST materials. RESULTS: Manufacturers' expected copies/mL were close to WHO IU/mL: linear regression of qPCR data revealed 1.12 Exact copies/IU, 0.76 Acrometrix copies/IU, and 0.70 Zeptometrix copies/IU. For ddPCR, similar concentrations were measured when either the VP1 region or the T region was targeted, and concentrations were almost 2-fold higher when both regions were targeted simultaneously. ddPCR results for the VP1 and T regions were similar for all commercial standards, but targeting the T region of the WHO standard led to a 4-fold lower result than the VP1 region. Next-generation sequencing revealed no primer or probe mismatches. However, large differences in coverage across the WHO standard and junctional reads were observed, indicating subpopulations of the WHO standard with deletions in the T region. CONCLUSIONS: BKV standards showed concordance among providers, but the WHO standard contains subpopulations of viruses with various deletions in the T region. PCR results will vary depending on which region of the WHO standard is targeted.

Cutaneous phaeohyphomycosis in a hematopoietic stem cell transplant patient caused by Alternaria rosae: First case report.

Alternaria species have been reported as a rare cause of fungal infection in organ and stem cell transplant recipients, but to date, no reports have been published of infection in humans caused by Alternaria rosae. Here, we report cutaneous A. rosae infection in a 66-year-old farmer with a history of primary myelofibrosis who had undergone allogeneic unrelated donor hematopoietic stem cell transplantation. Forty-nine days post transplant, he presented with a nodule on the thumb with no findings suggestive of disseminated infection. Pathology, culture, and molecular speciation showed the nodule was caused by cutaneous A. rosae. He had been on voriconazole as antifungal prophylaxis, but was found to have a subtherapeutic voriconazole level. He was switched to posaconazole based on published in vitro data showing its superior efficacy in Alternaria treatment. Susceptibility testing showed that the A. rosae isolate was indeed susceptible to posaconazole. His cutaneous lesion remained stable, but he died from respiratory failure secondary to lobar pneumonia. At lung autopsy, A. rosae was not identified in the lungs. We believe this to be the first published report, to our knowledge, of A. rosae infection in humans.

Clinical Performance Validation of 4 Point-of-Care Cervical Cancer Screening Tests in HIV-Infected Women in Zambia.

OBJECTIVES: We sought to determine the clinical performance of visual inspection with acetic acid (VIA), digital cervicography (DC), Xpert human papillomavirus (HPV), and OncoE6 for cervical cancer screening in an HIV-infected population. MATERIALS AND METHODS: HIV-infected women 18 years or older were included in this cross-sectional validation study conducted in Lusaka, Zambia. The screening tests were compared against a histological gold standard. We calculated sensitivity, specificity, positive and negative predictive values, positive and negative likelihood ratios, and odds ratios using cervical intraepithelial neoplasia grade 2 or worse (CIN 2+) and grade 3 or worse (CIN 3+) thresholds. RESULTS: Between January and June 2015, a total of 200 women were enrolled. Fifteen percent were screen positive by VIA, 20% by DC, 47% by Xpert HPV, and 6% by OncoE6. Using a CIN 2+ threshold, the sensitivity and specificity of VIA were 48% (95% CI = 30%-67%) and 92% (95% CI = 86%-95%), respectively. Similarly, the sensitivity and specificity of DC were 59% (95% CI = 41%-76%) and 88% (95% CI = 82%-93%), respectively. The sensitivity and specificity of Xpert HPV were 88% (95% CI = 71%-97%) and 60% (95% CI = 52%-68%), respectively. Finally, the sensitivity and specificity of OncoE6 were 31% (95% CI = 16%-50%) and 99% (95% CI = 97%-100%), respectively. CONCLUSIONS: VIA and DC displayed moderate sensitivity and high specificity. Xpert HPV performed equivalently to currently approved HPV DNA tests, with high sensitivity and moderate specificity. OncoE6 displayed excellent specificity but low sensitivity. These results confirm an important role for VIA, DC, and Xpert HPV in screen-and-treat cervical cancer prevention in low- and middle-income countries, such as Zambia.

The burden of cervical pre-cancer and cancer in HIV positive women in Zambia: a modeling study.

BACKGROUND: HIV infection is associated with a higher incidence of precancerous cervical lesions and their progression to invasive cervical cancer (ICC). Zambia is a global epicenter of HIV and ICC, yet the overall burden of cervical pre-cancer [cervical intraepithelial neoplasia 3 (CIN3)] and ICC among its HIV positive adult female population is unknown. The objective of this study was to determine the burden of cervical disease among HIV positive women in Zambia by estimating the number with CIN3 and ICC. METHODS: We conducted a cross-sectional study among 309 HIV positive women attending screening in Lusaka (Zambia's most populated province) to measure the cervical disease burden by visual inspection with acetic acid enhanced by digital cervicography (DC), cytology, and histology. We then used estimates of the prevalence of CIN3 and ICC from the cross-sectional study and Spectrum model-based estimates for HIV infection among Zambian women to estimate the burden of CIN3 and ICC among HIV positive women nationally. RESULTS: Over half (52 %) of the study participants screened positive by DC, while 45 % had cytologic evidence of high grade squamous intraepithelial lesions (SIL) or worse. Histopathologic evaluation revealed that 20 % of women had evidence of CIN2 or worse, 11 % had CIN3 or worse, and 2 % had ICC. Using the Spectrum model, we therefore estimate that 34,051 HIV positive women in Zambia have CIN3 and 7,297 have ICC. CONCLUSIONS: The DC, cytology, and histology results revealed a large cervical disease burden in this previously unscreened HIV positive population. This very large burden indicates that continued scale-up of cervical cancer screening and treatment is urgently needed.

Identification of human papillomaviruses from formalin-fixed, paraffin-embedded pre-cancer and invasive cervical cancer specimens in Zambia: a cross-sectional study.

BACKGROUND: The most common human papillomavirus (HPV) genotypes isolated from cervical cancer in select African countries are HPV-16, HPV-18, HPV-35, and HPV-45, but the most common genotypes in Zambia are unknown. The overall objective of this study was to assess the potential impact of current HPV vaccines in preventing cervical cancer in Zambia, by determining the combined prevalence of HPV-16 and/or HPV-18 in invasive cervical cancer (ICC) and high-grade pre-cancer [cervical intraepithelial neoplasia 2 or 3 (CIN2/3)] cases. FINDINGS: We compared DNA extraction techniques to determine which assay performs well in the Zambian context, where unbuffered formalin is used to fix specimens. We then tested specimens with the Abbott RealTime High-Risk HPV test to estimate the prevalence of HPV-16/18 in formalin-fixed, paraffin-embedded ICC and CIN2/3 specimens. DNA extraction using heat (without xylene) was more successful than xylene-based extraction. Over 80% of specimens tested using heat extraction and the Abbott RealTime HPV test were positive for HPV. HPV-16 and/or HPV-18 were identified in 65/93 (69.9%) ICC specimens positive for HPV and in 38/65 (58.5%) CIN2/3 specimens positive for HPV. CONCLUSIONS: To our knowledge this is the first report to identify HPV genotypes in cervical cancers in Zambia. A combined HPV-16/18 prevalence of 69.9% in ICC specimens suggests that current vaccines will be highly protective against cervical cancer in Zambia.

Identification of viral and bacterial pathogens from hospitalized children with severe acute respiratory illness in Lusaka, Zambia, 2011-2012: a cross-sectional study.

BACKGROUND: Morbidity and mortality from respiratory infections are higher in resource-limited countries than developed countries, but limited studies have been conducted in resource-limited settings to examine pathogens from patients with acute respiratory infections. Influenza surveillance has been conducted in Zambia since 2008; however, only 4.3% of patients enrolled in 2011-2012 were positive for influenza. Therefore, we examined non-influenza respiratory pathogens in children with severe acute respiratory illness (SARI) in Zambia, to estimate the scope of disease burden and determine commonly-identified respiratory pathogens. METHODS: Two reverse transcriptase polymerase chain reaction (rRT-PCR) methods (single and multiplex) were used to analyze nasopharyngeal and throat swabs collected from SARI cases under five years of age from January 2011 through December 2012. All specimens were negative for influenza by rRT-PCR. The panel of singleplex reactions targeted seven viruses, while the multiplex assay targeted thirty-three bacteria, fungi, and viruses. RESULTS: A set of 297 specimens were tested by singleplex rRT-PCR, and a different set of 199 were tested by multiplex rRT-PCR. Using the singleplex assay, 184/297 (61.9%) specimens were positive for one or more viruses. The most prevalent viruses were human rhinovirus (57/297; 19.2%), human adenovirus (50/297; 16.8%), and respiratory syncytial virus (RSV) (45/297; 15.2%). Using multiplex PCR, at least one virus was detected from 167/199 (83.9%) specimens, and at least one bacteria was detected from 197/199 (99.0%) specimens. Cytomegalovirus (415/199; 208.5%) and RSV (67/199; 33.7%) were the most commonly detected viruses, while Streptococcus pneumonie (109/199; 54.8%) and Moraxella catarrhalis (92/199; 46.2%) were the most commonly detected bacteria. CONCLUSIONS: Single infections and co-infections of many viruses and bacteria were identified in children with SARI. These results provide an estimate of the prevalence of infection and show which respiratory pathogens are commonly identified in patients. Further studies should investigate causal associations between individual pathogens and SARI.

The Effect of Cryotherapy on Human Papillomavirus Clearance Among HIV-Positive Women in Lusaka, Zambia.

OBJECTIVE: We sought to investigate the progression of human papillomaviruses (HPV) infection in HIV-positive women after cryotherapy. METHODS: We examined changes in detection of high-risk HPV (hrHPV) cervical infections among HIV-infected women over a 12-week period after cryotherapy using stored specimens from a cohort study conducted between June 2009 and March 2011 in Lusaka, Zambia. Samples from visits at baseline and weeks 4, 8, and 12 were tested using the Roche Linear Array assay. RESULTS: A total of 89 women were included in the analysis. The median age was 32 years (interquartile range [IQR], 28-36 years). The median CD4+ cell count was 350 cells/µL (IQR, 214-470 cells/µL), and 66% of women were receiving antiretroviral therapy. At baseline, the prevalence of hrHPV was 91% (95% confidence interval [CI], 83%-95%). HPV45 was the most common HPV type, present in (30%) women, followed by HPV16 (27%), HPV18 (27%), HPV51 (20%), and HPV58 (22%). Among women with valid results both at baseline and 12 weeks, 25% (17/67) cleared their initial hrHPV infection within 12 weeks of treatment, although 65% (11/17) had new hrHPV types detected. CONCLUSIONS: Cryotherapy led to clearance of 25% of hrHPV infections within 12 weeks of treatment. However, hrHPV infection remained persistent in most women, and new hrHPV types were detected often, explaining the high rate of persistence and recurrence of cervical disease in this population. Continued efforts to scale up HPV vaccination and cervical screening should remain a priority in high HIV burden settings such as Zambia.

Effectiveness of monovalent 2009 pandemic influenza A virus subtype H1N1 and 2010-2011 trivalent inactivated influenza vaccines in Wisconsin during the 2010-2011 influenza season.

BACKGROUND: The 2009 influenza A virus subtype H1N1 (A[H1N1]pdm09) did not exhibit antigenic drift during the 2010-2011 influenza season, providing an opportunity to investigate the duration of protection after vaccination. We estimated the independent effects of 2010-2011 seasonal trivalent inactivated influenza vaccine (TIV) and A(H1N1)pdm09 vaccine for preventing medically attended influenza A virus infection during the 2010-2011 season. METHODS: Individuals were tested for influenza A virus by real-time reverse transcription polymerase chain reaction (rRT-PCR) after a clinical encounter for acute respiratory illness. Case-control analyses compared participants with rRT-PCR-confirmed influenza A virus infection and test-negative controls. Vaccine effectiveness was estimated separately for monovalent pandemic vaccine and TIV and was calculated as 100 × [1 - adjusted odds ratio], where the odds ratio was adjusted for potential confounders. RESULTS: The effectiveness of TIV against influenza A virus infection was 63% (95% confidence interval [CI], 37%-78%). The effectiveness of TIV against A(H1N1)pdm09 infection was 77% (95% CI, 44%-90%). Monovalent vaccine administered between October 2009 and April 2010 was not protective during the 2010-2011 season, with an effectiveness of -1% (95% CI, -146% to 59%) against A(H1N1)pdm09 infection. CONCLUSIONS: Monovalent vaccine provided no sustained protection against A(H1N1)pdm09 infection during the 2010-2011 season. This waning effectiveness supports the need for annual revaccination, even in the absence of antigenic drift in A(H1N1)pdm09.

Efficacy of vaccination and previous infection against the Omicron BA.1 variant in Syrian hamsters.

The emergence of the SARS-CoV-2 Omicron (B.1.1.529) variant with a surprising number of spike mutations raises concerns about reduced sensitivity of this virus to antibody neutralization and subsequent vaccine breakthrough infections. Here, we infect Moderna mRNA-vaccinated or previously infected hamsters with the Omicron BA.1 variant. While the Moderna mRNA vaccine reduces viral loads in the respiratory tissues upon challenge with an early S-614G isolate, the vaccine efficacy is not as pronounced after infection with the Omicron variant. Previous infection with the early SARS-CoV-2 isolate prevents replication after rechallenge with either virus in the lungs of previously infected hamsters, but the Omicron variant replicates efficiently in nasal turbinate tissue. These results experimentally demonstrate in an animal model that the antigenic changes in the Omicron variant are responsible for vaccine breakthrough and re-infection.

Glycan analysis and influenza A virus infection of primary swine respiratory epithelial cells: the importance of NeuAc{alpha}2-6 glycans.

To better understand influenza virus infection of pigs, we examined primary swine respiratory epithelial cells (SRECs, the primary target cells of influenza viruses in vivo), as a model system. Glycomic profiling of SRECs by mass spectrometry revealed a diverse range of glycans terminating in sialic acid or GalαGal. In terms of sialylation, α2-6 linkage was more abundant than α2-3, and NeuAc was more abundant than NeuGc. Virus binding and infection experiments were conducted to determine functionally important glycans for influenza virus infection, with a focus on recently emerged swine viruses. Infection of SRECs with swine and human viruses resulted in different infectivity levels. Glycan microarray analysis with a high infectivity "triple reassortant" virus ((A/Swine/MN/593/99 (H3N2)) that spread widely throughout the North American swine population and a lower infectivity human virus isolated from a single pig (A/Swine/ONT/00130/97 (H3N2)) showed that both viruses bound exclusively to glycans containing NeuAcα2-6, with strong binding to sialylated polylactosamine and sialylated N-glycans. Treatment with mannosamine precursors of sialic acid (to alter NeuAc/NeuGc abundances) and linkage-specific sialidases prior to infection indicated that the influenza viruses tested preferentially utilize NeuAcα2-6-sialylated glycans to infect SRECs. Our data indicate that NeuAcα2-6-terminated polylactosamine and sialylated N-glycans are important determinants for influenza viruses to infect SRECs. As NeuAcα2-6 polylactosamine glycans play major roles in human virus infection, the importance of these receptor components in virus infection of swine cells has implications for transmission of viruses between humans and pigs and for pigs as possible adaptation hosts of novel human influenza viruses.