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Highlights • Serum IgG antibody responses developed in 95% of mildly symptomatic individuals by day 14 and all subjects had seroconverted by day 30. • Serum IgM and IgA antibody responses were lower and less frequent than corresponding IgG responses, and peaked and declined earlier 100% of mild symptomatic individuals developed an IgG antibody response by day 30. • Fewer than 45% of asymptomatic infected individuals had seroconverted by day 30 post-PCR diagnosis. • Impact on modeling of herd immunity., Objectives Studies on serologic responses following COVID-19 have been published primarily in individuals who are moderately or severely symptomatic, but there are few data from individuals who are mildly symptomatic or asymptomatic. Methods We measured IgG, IgM, and IgA to the receptor-binding domain of SARS-CoV-2 by ELISA in mildly symptomatic (n = 108) and asymptomatic (n = 63) on days 1, 7, 14, and 30 following RT-PCR confirmation in Bangladesh, and compared with pre-pandemic samples, including healthy controls (n = 73) and individuals infected with other viruses (n = 79). Results Mildly symptomatic individuals developed IgM and IgA responses by day 14 in 72% and 83% of individuals, respectively, while 95% of individuals developed IgG response, and rose to 100% by day 30. In contrast, individuals infected with SARS-CoV-2 but who remained asymptomatic developed antibody responses significantly less frequently, with only 20% positive for IgA and 22% positive for IgM by day 14, and 45% positive for IgG by day 30 after infection. Conclusions These results confirm immune responses are generated following COVID-19 who develop a mildly symptomatic illness. However, those with the asymptomatic infection do not respond or have lower antibody levels. These results will impact modeling needed for determining herd immunity generated by natural infection or vaccination.

Plants are inherently able to save themselves from any unfavorable conditions. However, they fail to exert ample response when encountered with pathogens like Macrophomina phaseolina which infects more than 500 crops. Wild plant species empowered by superlative mechanisms can conquest deadly pathogens, an example of which is C. trilocularis, a jute plant, resistant to this necrotrophic fungal pathogen. This study tried to ascertain the underlying resistance mechanism regarding the systemic acquired resistance (SAR) and cell wall fortification. Identification and characterization of genes involved in the systemic acquired resistant pathway implicated an activity of these genes with a basal expression in resistant species but irregular in the sensitive one (C. olitorius). Real-time expression analysis of genes involved in the synthesis of cell wall components like cellulose, hemicellulose, and lignin along with chemical and microscopic examinations signified preeminent lignification in C. trilocularis. However, this vital plant cell wall component was found to decrease in C. olitorius. The present investigation provided a deep insight into the defense strategy employed by the two species of jute at the molecular level. This study is expected to help in improving the fungal resistance of susceptible but farmer popular jute species. The same should be applicable to other vulnerable crops as well. Understanding how the pathogen is recognized, and an effective defensive response mounted, could ultimately lead to the development of novel strategies for providing durable plant resistance.