Empirical criteria for identification of hydrogen bonds were analyzed to produce a set of geometrically consistent criteria. For a data set of 30 structures, application of a set of purely geometrical criteria, along with exclusion of abnormal backbone conformations, also excluded a common interaction of Ser/Thr side chains with Asp/Glu side chains ([ST]/[DE] pairs). These interactions were termed `bifurcated hydrogen bonds/', which implies delocalization of a positively charged hydrogen of hydroxyl between the two acceptor atoms of the carboxylic group. These `bifurcated/' interactions are among the most common packing patterns for [ST]/[DE] pairs of side chains. Therefore, the identification of hydrogen bonds cannot be based on geometrical criteria only and requires introduction of some physico-chemical criteria.

Rubella viruses (RV) have been found in an association with granulomas in children with primary immune deficiencies (PID). Here, we report the recovery and characterization of infectious immunodeficiency-related vaccine-derived rubella viruses (iVDRV) from diagnostic skin biopsies of four patients. Sequence evolution within PID hosts was studied by comparison of the complete genomic sequences of the iVDRVs with the genome of the vaccine virus RA27/3. The degree of divergence of each iVDRV correlated with the duration of persistence indicating continuous intrahost evolution. The evolution rates for synonymous and nonsynonymous substitutions were estimated to be 5.7 x 10⁻³ subs/site/year and 8.9 x 10⁻⁴ subs/site/year, respectively. Mutational spectra and signatures indicated a major role for APOBEC cytidine deaminases and a secondary role for ADAR adenosine deaminases in generating diversity of iVDRVs. The distributions of mutations across the genes and 3D hotspots for amino acid substitutions in the E1 glycoprotein identified regions that may be under positive selective pressure. Quasispecies diversity was higher in granulomas than in recovered infectious iVDRVs. Growth properties of iVDRVs were assessed in WI-38 fibroblast cultures. None of the iVDRV isolates showed complete reversion to wild type phenotype but the replicative and persistence characteristics of iVDRVs were different from those of the RA27/3 vaccine strain, making predictions of iVDRV transmissibility and teratogenicity difficult. However, detection of iVDRV RNA in nasopharyngeal specimen and poor neutralization of some iVDRV strains by sera from vaccinated persons suggests possible public health risks associated with iVDRV carriers. Detection of IgM antibody to RV in sera of two out of three patients may be a marker of virus persistence, potentially useful for identifying patients with iVDRV before development of lesions. Studies of the evolutionary dynamics of iVDRV during persistence will contribute to development of infection control strategies and antiviral therapies. Primary immunodeficiency diseases (PID) are caused by genetic defects and lead to serious problems including chronic granulomas (abnormal collections (nodules) of inflammatory cells), sometimes lasting for decades and sometimes leading to severe ulcers. Initial reports (2014–2016), including our report of a blinded study using ultrasensitive virus detection in biopsies, proved the association between granuloma of the skin in PID patients and rubella virus. The viruses in these reports and the current report were derived from a widely used vaccine strain of the rubella virus. Work reported here shows that these vaccine-derived viruses are biologically different from the vaccine virus and that their genomes have changed. Genomic changes could be analyzed largely because the exact sequence of starting vaccine virus genome was known. These genomic differences are likely generated via mechanisms similar to those occurring during normal circulation of wild type rubella. We present data that newly recognized mechanisms for generation of sequence diversity in viruses (because of cellular deaminases) likely occurs in the generation of these vaccine-derived rubella viruses. Thousands of PID patients in the United States are likely shedding these vaccine-derived rubella viruses. Our work presented here characterizing viruses in diagnostic specimens highlights at least two areas where insufficient work has been done: 1) research on the properties of rubella virus (limited understanding of the antibody binding sites on the virus); 2) controlled research studies to assess the public health impact of viruses in populations with high immunity.

Analysis of criteria for the solvability/regularity of problems and of the correctness of algorithms is applied here to the problem of prediction of the values of numerical variables. It is shown that partial regularity is a necessary and sufficient condition for the solvability of the corresponding system of the classification problems. Cross-validation experiments conducted on several datasets from the field of biomedicine (non-invasive diagnostics of magnesium concentration in blood plasma), bioinformatics (prediction of the protein secondary structure), and solid-state physics (prediction of the properties of high-temperature superconductors) have demonstrated the effectiveness of the developed methods for generating “synthetic” informative numerical features and for increasing the accuracy of prediction of the numerical target variables.

The HIV‐1 proteinase (PR) has proved to be a good target for antiretroviral therapy of AIDS, and various PR inhibitors are now in clinical use. However, there is a rapid selection of viral variants bearing mutations in the proteinase that are resistant to clinical inhibitors. Drug resistance also involves mutations of the nucleocapsid/p1 and p1/p6 cleavage sites of Gag, both in vitro and in vivo. Cleavages at these sites have been shown to be rate limiting steps for polyprotein processing and viral maturation. Furthermore, these sites show significant sequence polymorphism, which also may have an impact on virion infectivity. We have studied the hydrolysis of oligopeptides representing these cleavage sites with representative mutations found as natural variations or that arise as resistant mutations. Wild‐type and five drug resistant PRs with mutations within or outside the substrate binding site were tested. While the natural variations showed either increased or decreased susceptibility of peptides toward the proteinases, the resistant mutations always had a beneficial effect on catalytic efficiency. Comparison of the specificity changes obtained for the various substrates suggested that the maximization of the van der Waals contacts between substrate and PR is the major determinant of specificity: the same effect is crucial for inhibitor potency. The natural nucleocapsid/p1 and p1/p6 sites do not appear to be optimized for rapid hydrolysis. Hence, mutation of these rate limiting cleavage sites can partly compensate for the reduced catalytic activity of drug resistant mutant HIV‐1 proteinases.

Meta-analysis of clinical trials of osteoarthritis treatment effectiveness with Chondroguard