We applied an immunoscreening technique, in vivo-induced antigen technology (IVIAT), to identify immunogenic bacterial proteins expressed during human infection with Salmonella enterica serovar Typhi, the cause of typhoid fever. We were able to assign a functional classification to 25 of 35 proteins identified by IVIAT. Of these 25, the majority represent proteins with known or potential roles in the pathogenesis of S. enterica. These include proteins implicated in fimbrial structure and biogenesis, antimicrobial resistance, heavy metal transport, bacterial adhesion, and extracytoplasmic substrate trafficking as well as secreted hydrolases. The 10 remaining antigens represent proteins with unknown functions. Of the 35 identified antigens, four had no immunoreactivity when probed with control sera from individuals never exposed to serovar Typhi organisms; these four included PagC, TcfB, and two antigens of unknown function encoded by STY0860 and STY3683. PagC is a virulence factor known to be upregulated in vivo in S. enterica serovar Typhimurium infection of mice. TcfB is the major structural subunit of a fimbrial operon found in serovar Typhi with no homolog in serovar Typhimurium organisms. By examining differential immunoreactivities in acute-versus convalescent-phase human serum samples, we found specific anti-PagC and anti-TcfB immunoglobulin G responses in patients with serovar Typhi bacteremia. Serovar Typhi antigens identified by IVIAT warrant further evaluation for their contributions to pathogenesis, and they may have diagnostic, therapeutic, or preventive uses.In humans, infection with Salmonella enterica serovar Typhi causes a spectrum of illness that includes diarrhea, a selflimited febrile illness, and most significantly, typhoid fever, a systemic infection characterized by persistent fever, lymphadenopathy, hepatosplenomegaly, encephalopathy, and intestinal hemorrhage and perforation (16). Worldwide, approximately 20 million cases of typhoid fever resulting in 200,000 deaths occur annually (2). The increasing incidence of disease caused by multidrug-resistant serovar Typhi organisms underscores the importance of developing novel approaches to the diagnosis, treatment, and prevention of typhoid fever (22).Although many S. enterica serovars infect a broad range of animal hosts and cause gastroenteritis in humans, serovar Typhi is among the few serovars for which natural infection appears to be limited to human hosts. In humans, serovar Typhi organisms penetrate the gastrointestinal epithelial barrier and infect phagocytes within the lamina propria. However, unlike organisms from other broad-host-range serovars, serovar Typhi organisms are adapted for prolonged intracellular survival in human macrophages, allowing the bacteria to spread to reticuloendothelial organs, including the liver, spleen, and bone marrow (16).Because serovar Typhi organisms are human specific, there is no optimal animal model of serovar Typhi infection, and presumed factors that contribute to the pathogenesis and immunology of...

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.

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To identify the circulating serotype(s) of dengue viruses in Bangladesh, a retrospective molecular identification was performed on stored serum samples of dengue surveillance during the period of 2013-2016. Real time RT-PCR was performed on serum samples collected from the patients with less than 5 days fever for detection of dengue virus nucleic acid. The samples, positive for dengue PCR were further analyzed for serotypes by real time RT-PCR. The overall prevalence of dengue virus infection was varied among 13-42% in study years with a single peak flanked by April to September. Among the four dengue serotypes DEN1 and DEN2 were in the circulation in three metropolitan cities with sequential emergence of DEN1 where DEN2 was persisted constantly during the study period. Persistence of all four serotypes in the neighboring country makes Bangladesh vulnerable for devastating secondary infection by introduction of new serotype(s) other than currently circulating viruses in the country. Thus continuous virological surveillance is crucial for early warning of emergence of new serotype in the circulation and public health preparedness.

As the COVID-19 pandemic erupted, the WHO recommended the use of nasopharyngeal or throat swabs for the detection of SARS-CoV-2 etiology of COVID-19. The collection of NPS causes discomfort because of its invasive collection procedure.