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Abstract Background In Lao PDR, the epidemiology of varicella infection is uncertain, since it is not a notifiable disease and VZV outbreaks are rarely reported as fever/rash (F/R) diseases. Methods We estimated the seroprevalence of VZV (IgG ELISA) in different age cohorts (9 months to 46 years; N = 3139) and investigated VZV and 6 other viruses in patients during F/R outbreaks and in an ad hoc sentinel site in the context of the national reporting system (IgM ELISA, PCR). Results At least 80% of the sampled population had evidence of VZV infection before the age of 15. The largest increase in seroprevalence occurred between the age groups 1 to 5 and 6 to 7 year-olds. A VZV outbreak (clade 2) also occurred in this age group mostly during the first year of primary school (median age 6 years, interquartile range 4.0–7.5). During a dengue outbreak, 6% had varicella. At our F/R sentinel site, 14% of children with viral etiology were laboratory diagnosed as varicella and among others, a sizeable number of measles (N = 12) and rubella cases (N = 25) was detected compared to those reported for the whole country (N = 56 and 45), highlighting nationwide a large challenge of underreporting or misdiagnosis of these notifiable diseases because of lack of diagnostic laboratory capacity. Conclusion We recommend strengthening the clinical and laboratory diagnosis of VZV, measles and rubella, the surveillance and reporting of notifiable F/R diseases by retraining of healthcare workers and by setting up sentinel sites and enhancing laboratory capacity.

The molecular diagnosis of acute Borreliosis is complicated and better strategies to improve the diagnostic processes are warranted. High Throughput Sequencing (HTS) of human B cell repertoires after e.g., Dengue virus infection or influenza vaccination revealed antigen-associated “CDR3 signatures” which may have the potential to support diagnosis in infectious diseases. The human B cell immune response to Borrelia burgdorferi sensu lato—the causative agent of Borreliosis—has mainly been studied at the antibody level, while less attention has been given to the cellular part of the humoral immune response. There are indications that Borrelia actively influence the B cell immune response and that it is therefore not directly comparable to responses induced by other infections. The main goal of this study was to identify B cell features that could be used to support diagnosis of Borreliosis. Therefore, we characterized the B cell immune response in these patients by combining multicolor flow cytometry, single Borrelia-reactive B cell receptor (BCR) sequencing, and B cell repertoire deep sequencing. Our phenotyping experiments showed, that there is no significant difference between B cell subpopulations of acute Borreliosis patients and controls. BCR sequences from individual epitope-reactive B cells had little in common between each other. HTS showed, however, a higher complementarity determining region 3 (CDR3) amino acid (aa) sequence overlap between samples from different timepoints in patients as compared to controls. This indicates, that HTS is sensitive enough to detect ongoing B cell immune responses in these patients. Although each individual's repertoire was dominated by rather unique clones, clustering of bulk BCR repertoire sequences revealed a higher overlap of IgG BCR repertoire sequences between acute patients than controls. Even if we have identified a few Borrelia-associated CDR3aa sequences, they seem to be rather unique for each patient and therefore not suitable as biomarkers.

The identification and tracking of antigen-specific immunoglobulin (Ig) sequences within total Ig repertoires is central to high-throughput sequencing (HTS) studies of infections or vaccinations. In this context, public Ig sequences shared by different individuals exposed to the same antigen could be valuable markers for tracing back infections, measuring vaccine immunogenicity, and perhaps ultimately allow the reconstruction of the immunological history of an individual. Here, we immunized groups of transgenic rats expressing human Ig against tetanus toxoid (TT), Modified Vaccinia virus Ankara (MVA), measles virus hemagglutinin and fusion proteins expressed on MVA, and the environmental carcinogen benzo[a]pyrene, coupled to TT. We showed that these antigens impose a selective pressure causing the Ig heavy chain (IgH) repertoires of the rats to converge toward the expression of antibodies with highly similar IgH CDR3 amino acid sequences. We present a computational approach, similar to differential gene expression analysis, that selects for clusters of CDR3s with 80% similarity, significantly overrepresented within the different groups of immunized rats. These IgH clusters represent antigen-induced IgH signatures exhibiting stereotypic amino acid patterns including previously described TT- and measles-specific IgH sequences. Our data suggest that with the presented methodology, transgenic Ig rats can be utilized as a model to identify antigen-induced, human IgH signatures to a variety of different antigens.