Scrub typhus is an acute undifferentiated febrile infectious disease transmitted by a chigger (genus Leptotrombidium) bite carrying Orientia (O.) tsutsugamushi, affecting millions of people annually while more than one billion people are susceptible. Endemic areas are expanding to Africa, Europe, Middle East, and South America which is concerning, as despite best efforts, there is no vaccine to combat the bacteria. There are now three species of Orientia and over 20 strains of O. tsutsugamushi. The past attempts to develop a vaccine have been ineffective as they confer homologous strain-specific immunity. Various immunogenic proteins of O. tsutsugamushi have been identified that interact with the extracellular matrix (fibronectin) or vMLL5 receptor and modify the cytoskeleton of non-phagocytic host cells, which aids in host cell adhesion and invasion. These highly conserved proteins involve type specific antigen 56 (TSA56), 47 kDa, OmpA, and autotransporter proteins (ScaA, ScaB and ScaC). TSA56 is the most immunogenic and contains four types of hypervariable regions. Out of all autotransporter proteins, ScaA provides the homologous strains specific immunity and when coupled with TSA56 it shows better protective immunity against heterologous strains. The review provides detailed insight into the potential immunogenic proteins of Orientia which can be utilized to develop the vaccine. Furthermore, studies focused on highly antigenic proteins will provide more insight into their roles in developing therapeutics and easy-to-handle rapid diagnostic kits.
Objective: To assess antiretroviral therapy (ART) adherence rates and associated factors among people living with HIV in Vietnam.
Methods: A cross-sectional study was conducted at the Hospital for Tropical Diseases, Ho Chi Minh City from June to August 2022. Data were collected from 347 people living with HIV using structured questionnaires assessing sociodemographics, substance use, drug side effects, treatment beliefs, treatment satisfaction, and depression. ART adherence was evaluated using a multi-method tool, including selfreport, pill count, the Provider Interview Tool, and the Visual Analog Scale. Participants were classified as having high adherence only if they met all four criteria across these methods. Multivariable logistic regression was used to identify factors influencing adherence, with significance set at P<0.05.
Results High ART adherence was observed in 69.5% of the participants. Adherence was significantly lower among tobacco users (OR 0.49, 95% Cl 0.30-0.83, P=0.007), those with higher depression scores (per 1-point increase) (OR 0.89, 95% Cl 0.84-0.95, P<0.001), frequent substance users (OR 0.50, 95% Cl 0.30-0.83, P=0.007), and those experiencing more severe drug side effects (per level increase) (OR 0.64, 95% Cl 0.45-0.92, P=0.016). Participants able to afford treatment had nearly three times higher odds of adherence than those unable to pay (OR 2.85, 95% Cl 1.48-5.47, P=0.002).
Conclusions:ART adherence among people living with HIV in Vietnam remains suboptimal. Interventions should target substance use, drug side effects, financial barriers, and depression screening to improve adherence.
Objective: To confirm the presence of Culex (Cx.) (Lophoceraomyia) cinctellus in Sri Lanka using morphological and molecular evidence.
Methods From October 2019 to April 2020, mosquito surveillance was conducted fort-nightly in the Banduragoda Public Health Inspector area. Larvae were collected using standard siphoning methods, while adults were sampled using Cattle Baited Trap, Gravid Traps, Light Traps, Bird-Baited Traps, Dog Baited Traps, and diurnal human landing collections. Specimens were transported to the Entomology Laboratory at the Medical Research Institute for identification. Morphological identification was performed using standard taxonomic keys. Molecular confirmation was achieved through DNA sequencing of mosquito head and thoracic regions, followed by sequence analysis using NCBI BLAST and Geneious software (version 7.1.3).
Results: Adults of Cx. cinctellus were identified in Bird-Baited Traps and human bait collections. Unique morphological characteristics, including well-developed pulvilli, wing vein 1A ending before the apex of cross vein mcu, basal transverse pale bands on abdominal terga, and two labial basal setae on the proboscis, confirmed species identity. Morphometric measurements included mean thoracic length (0.58±0.02) mm, thoracic width (0.63±0.02) mm, abdominal length (2.15±0.03) mm, abdominal width (0.61±0.01) mm, and wing length (2.91±0.02) mm. Molecular analysis corroborated the morphological identification, affirming the species as Cx. cinctellus. COI sequences of the collected specimen (452 bp) were confirmed as Cx. cinctellus for sequence identity by BLAST and BOLD analysis. These sequences were subsequently deposited in GenBank under the accession number OR225623.1.
Conclusions: This study documents the first occurrence of Cx. cinctellus in Sri Lanka, highlighting the need to enhance entomological surveillance to monitor its dispersal and population dynamics.
Objective: To characterize the group-29 allergens from Dermatophagoides (D.) pteronyssinus and investigate their ability to cross-react with other group-29 allergens from D. pteronyssinus as well as those from D. farinae and Tyrophagus putrescentiae.
Methods Der p 29, Der f 29, and Tyr p 29 cDNA sequences were amplified from total RNA isolated from D. pteronyssinus, D. farinae and Tyrophagus putrescentiae, respectively. Then they were cloned into the pET28a vector, expressed in Rosetta2(DE3)plysS, and purified using anion exchange chromatography. The IgE-binding rates of rDer p 29 were assessed by IgE Western blotting. The four epitopes of rDer p 29 were predicted, synthesized, and detected by IgE-ELISA. The cross-reactivity among the recombinant proteins rDer p 29, rDer f 29, and rTyr p 29 was investigated using dot blot and IgE-ELISA inhibition experiments. The allergens’ physiochemical properties, amino acid sequences, and tertiary structures were also compared.
Results: Der p 29 was successfully expressed in Rosetta2(DE3)plysS as a single, 393-bp open reading frame. Western blotting showed that the purified rDer p 29 protein exhibited an high IgE-binding rate when tested on patient sera. The following four Der p 29 epitopes were predicted and synthesized: 37-45 (EP1), 57-69 (EP2), 75-80 (EP3), and 104-117 (EP4). IgE-ELISA tests on 20 D. pteronyssinus- positive sera yielded IgE-binding rates of 85% (rDer p 29), 80% (EP1), 55% (EP2), 40% (EP3), and 55% (EP4), respectively. The dot blot experiments further confirmed cross-reactivity among the three group-29 proteins. When used as an inhibitor, rDer p 29 demonstrated an average cross-reactive inhibition rate of 49.7% against rDer f 29 and 54.4% against rTyr p 29. When rTyr p 29 was used as an inhibitor, it showed an average cross-reactive inhibition rate of 56.3% against rDer f 29.
Conclusions: A recombinant protein, rDer p 29 with strong allergenicity was produced. Moreover, it was found that rDer p 29 cross-reacted with rDer f 29 and rTyr p 29, due to their highly homologous sequences and structures. These findings highlight the importance of considering cross-reactivity when diagnosing and treating allergic diseases.
Rationale: Melioidosis is a serious opportunistic infection caused by Burkholderia (B.) pseudomallei, primarily affecting immunocompromised individuals, particularly in endemic regions. Timely diagnosis and appropriate treatment are crucial to prevent fatal outcomes.
Patient concerns: Case 1 was a 34-year-old male kidney transplant recipient who presented with a 15-day history of intermittent fever, accompanied by liver and spleen abscesses. Case 2 was a 37-year- old female kidney transplant recipient who presented with acute febrile illness and developed leucopenia. Blood cultures for both patients grew B. pseudomallei.
Diagnosis: Both patients were diagnosed with melioidosis caused by B. pseudomallei, with the diagnosis confirmed through pus culture from the liver abscess in Case 1 and blood culture in Case 2.
Interventions: Both patients were treated with an intensive regimen of meropenem (renal-adjusted doses), followed by a 3-month course of oral cotrimoxazole for eradication therapy.
Outcomes: Case 1 experienced resolution of liver and spleen abscesses after 3 months of treatment and continued to recover well. In Case 2, blood cultures became sterile after 4 weeks, with no further complications observed.
Lessons: Melioidosis should be suspected in immunocompromised patients, especially kidney transplant recipients, who present with unexplained fever and sepsis-like symptoms. Early diagnosis through aspiration of abscesses and prompt treatment are critical for preventing relapses and improving patient outcomes.