RESUMO
We previously reported that a single immunization with an adenovirus serotype 26 (Ad26) vector-based vaccine expressing an optimized SARS-CoV-2 spike (Ad26.COV2.S) protected rhesus macaques against SARS-CoV-2 challenge. In this study, we evaluated the immunogenicity and protective efficacy of reduced doses of Ad26.COV2.S. 30 rhesus macaques were immunized once with 1x1011, 5x1010, 1.125x1010, or 2x109 vp Ad26.COV2.S or sham and were challenged with SARS-CoV-2 by the intranasal and intratracheal routes. Vaccine doses as low as 2x109 vp provided robust protection in bronchoalveolar lavage, whereas doses of 1.125x1010 vp were required for protection in nasal swabs. Activated memory B cells as well as binding and neutralizing antibody titers following vaccination correlated with protective efficacy. At suboptimal vaccine doses, viral breakthrough was observed but did not show evidence of virologic, immunologic, histopathologic, or clinical enhancement of disease compared with sham controls. These data demonstrate that a single immunization with a relatively low dose of Ad26.COV2.S effectively protected against SARS-CoV-2 challenge in rhesus macaques. Moreover, our findings show that a higher vaccine dose may be required for protection in the upper respiratory tract compared with the lower respiratory tract.
RESUMO
DNA microarrays are powerful tools for quantifying gene expression patterns. However, obtaining reliable estimates of gene expression from raw measurements on microarrays presents several problems due to background contributions, nonspecific probe response, possible variation in probe sensitivities, and possible nonlinear responses of the probes to transcript concentration. In an effort to address the nonspecific response of probes, Affymetrix GeneChip arrays use two probes for each measurement. One of these probes, the mismatch (MM) probe, is intended to reflect the nonspecific response of the corresponding perfect match (PM) probe. However, the reliability of this approach has not been established by published experiments. Indeed, some research has shown that at high transcript concentrations, the nonspecific component of the PM signal is a negligible part of the MM signal. Five variations of a method to model and estimate levels of gene expression on Affymetrix chips, without the use of MM cells, are presented. To test the validity of the algorithms, six different concentrations of human liver cRNA were prepared. Each of these solutions was then hybridized on five Affymetrix hg95A arrays using five different scanners. The expression estimates obtained using each of the five algorithms bore a strong linear relationship to the cRNA concentrations, particularly at low cRNA concentrations. The five variations were applied to a Latin square data set and the results compared with those obtained using Affymetrix MAS 5.0 and using robust multichip analysis. R2 values obtained using the new techniques were comparable, while fold changes were superior.
