A metatranscriptomic evaluation of viruses in field-collected bed bugs.

Cimex lectularius, known as the common bed bug, is a widespread hematophagous human ectoparasite and urban pest that is not known to be a vector of any human infectious disease agents. However, few studies in the era of molecular biology have profiled the microorganisms harbored by field populations of bed bugs. The objective of this study was to examine the viruses present in a large sampling of common bed bugs and related bat bugs (Cimex pipistrelle). RNA sequencing was undertaken on an international sampling of > 500 field-collected bugs, and multiple workflows were used to assemble contigs and query these against reference nucleotide databases to identify viral genomes. Shuangao bed bug virus 2, an uncharacterized rhabdovirus previously discovered in Cimex hemipterus from China, was found in several bed bug pools from the USA and Europe, as well as in C. pipistrelle, suggesting that this virus is common among bed bug populations. In addition, Shuangao bed bug virus 1 was detected in a bed bug pool from China, and sequences matching Enterobacteria phage P7 were found in all bed bug pools, indicating the ubiquitous presence of phage-derived elements in the genome of the bed bug or its enterobacterial symbiont. However, viral diversity was low in bed bugs in our study, as no other viral genomes were detected with significant coverage. These results provide evidence against frequent virus infection in bed bugs. Nonetheless, our investigation had several important limitations, and additional studies should be conducted to better understand the prevalence and composition of viruses in bed bugs. Most notably, our study largely focused on insects from urban areas in industrialized nations, thus likely missing infrequent virus infections and those that could occur in rural or tropical environments or developing nations.

Succinyl-CoA synthetase (SUCLA2) deficiency in two siblings with impaired activity of other mitochondrial oxidative enzymes in skeletal muscle without mitochondrial DNA depletion.

Mutations in SUCLA2 result in succinyl-CoA ligase (ATP-forming) or succinyl-CoA synthetase (ADP-forming) (A-SCS) deficiency, a mitochondrial tricarboxylic acid cycle disorder. The phenotype associated with this gene defect is largely encephalomyopathy. We describe two siblings compound heterozygous for SUCLA2 mutations, c.985A>G (p.M329V) and c.920C>T (p.A307V), with parents confirmed as carriers of each mutation. We developed a new LC-MS/MS based enzyme assay to demonstrate the decreased SCS activity in the siblings with this unique genotype. Both siblings shared bilateral progressive hearing loss, encephalopathy, global developmental delay, generalized myopathy, and dystonia with choreoathetosis. Prior to diagnosis and because of lactic acidosis and low activity of muscle pyruvate dehydrogenase complex (PDC), sibling 1 (S1) was placed on dichloroacetate, while sibling 2 (S2) was on a ketogenic diet. S1 developed severe cyclic vomiting refractory to therapy, while S2 developed Leigh syndrome, severe GI dysmotility, intermittent anemia, hypogammaglobulinemia and eventually succumbed to his disorder. The mitochondrial DNA contents in skeletal muscle (SM) were normal in both siblings. Pyruvate dehydrogenase complex, ketoglutarate dehydrogenase complex, and several mitochondrial electron transport chain (ETC) activities were low or at the low end of the reference range in frozen SM from S1 and/or S2. In contrast, activities of PDC, other mitochondrial enzymes of pyruvate metabolism, ETC and, integrated oxidative phosphorylation, in skin fibroblasts were not significantly impaired. Although we show that propionyl-CoA inhibits PDC, it does not appear to account for decreased PDC activity in SM. A better understanding of the mechanisms of phenotypic variability and the etiology for tissue-specific secondary deficiencies of mitochondrial enzymes of oxidative metabolism, and independently mitochondrial DNA depletion (common in other cases of A-SCS deficiency), is needed given the implications for control of lactic acidosis and possible clinical management.