The state of specific immunity of population of the Republic of Tajikistan to measles, rubella, poliomyelitis viruses

Relevance. To achieve the goals of measles and rubella elimination and poliomyelitis eradication programs, immunization coverage of at least 95% of the target population is required. Objective data on the state of specific herd immunity are provided only by the results of serosurveys. In the Republic of Tajikistan, such monitoring is not carried out regularly. Therefore, the purpose of the study was to assess the actual state of the specific herd immunity to measles, rubella, and poliomyelitis viruses. Materials and methods. The blood sera of 563 children and adults collected in 7 cities and 13 districts of Tajikistan in 2020 were investigated. The level of antibodies (ABs) to measles and rubella viruses was determined using enzyme immunoassay. Test systems VectoKor-IgG (VECTOR-BEST, Russia) and Ecolab, Russia were used to determine ABs to measles and rubella virus, respectively. Neutralizing antibodies (nABs) to the 3 types of poliovirus (PV) were determined in 359 sera using a neutralization reaction with Sabin strains of types 1, 2, 3. Results. The conducted serosurvey showed the level of the specific herd immunity to rubella to be 87.9% in total population, including 86.2% in children, 93.1% in adolescents, and 93.5% and adults, that is sufficient to prevent transmission of the rubella virus. The proportion of individuals seropositive to measles was 54.5%, which is not enough to prevent sustained secondary transmission of infection and the resumption of circulation of the endemic strain of measles virus. The children under 15 years of age should be considered a population at risk of the infection, since children accounted for 38% among seronegative individuals. In general, less than 95% of the examined patients had nABs to PV: 94.4% to PV1, 86.1% to PV2, 83.6% to PV3; 3.3% did not have antibodies to all three types of PV. The level of herd immunity varied in the examined groups depending on the vaccination schedule and the composition of the poliovirus vaccines used: nABs to PV2 had 59.6% of children born during the period when vaccines containing PV2 were not used, and 85.7% of children born after the introduction of trivalent IPV. Deficiency in immunity to PV2 was the cause of a polio outbreak in 2021 caused by circulating vaccine-derived PV type 2. Conclusion. A high level of humoral immunity to the rubella virus was determined. Shortcomings of routine immunization against measles and polio associated with insufficient coverage and lack of IPV have been identified. Conducting regular serological monitoring in the Republic of Tajikistan is advisable to obtain objective information about the level of herd immunity, identify vulnerable groups of the population, and plan additional immunization activities

A recombinase polymerase amplification assay for rapid detection of Crimean-Congo Haemorrhagic fever Virus infection

<div><p>Background</p><p>Crimean-Congo Haemorrhagic fever Virus (CCHFV) is a rapidly emerging vector-borne pathogen and the cause of a virulent haemorrhagic fever affecting large parts of Europe, Africa, the Middle East and Asia.</p><p>Methodology/principle findings</p><p>An isothermal recombinase polymerase amplification (RPA) assay was successfully developed for molecular detection of CCHFV. The assay showed rapid (under 10 minutes) detection of viral extracts/synthetic virus RNA of all 7 S-segment clades of CCHFV, with high target specificity. The assay was shown to tolerate the presence of inhibitors in crude preparations of mock field samples, indicating that this assay may be suitable for use in the field with minimal sample preparation. The CCHFV RPA was successfully used to screen and detect CCHFV positives from a panel of clinical samples from Tajikistan.</p><p>Conclusions/significance</p><p>The assay is a rapid, isothermal, simple-to-perform molecular diagnostic, which can be performed on a light, portable real-time detection device. It is ideally placed therefore for use as a field-diagnostic or in-low resource laboratories, for monitoring of CCHF outbreaks at the point-of-need, such as in remote rural regions in affected countries.</p></div

Negative viral panel testing.

<p>Table showing the results of a CCHF RPA with a negative viral panel, consisting of a selection of strains from the <i>Alphavirus</i>, <i>Mammarenavirus</i>, <i>Marburgvirus</i>, <i>Flavivirus</i>, <i>Orthohantavirus</i>, <i>Henipavirus</i> and <i>Orthonairovirus</i> genera. Results represent 3 separate experiments, each performed with 3 replicates.</p

Limit of detection.

<p>Limit of detection of the CCHF RPA assay with a serial (1 in 10) dilution of synthetic RNA template of Europe I strain AY277672. The data is represented graphically as <b>(a)</b> Delta Rn against time (minutes), in the form of a table of time to positive (TTP value) vs target copy number and as TTP vs target copy number, with a regression line indicating data correlation <b>(b)</b>. The data is also shown as a probit analysis performed using the statistical software Matlab for more accurate detection limit approximation <b>(c)</b>, with application of a curve-fitting programme (a shape-preserving piecewise cubic interpolation). Note that the probit analysis uses a lower threshold (Delta Rn 18000) to enable the calculation. The values shown for all LOD data are the mean of 8 independent experiments, each of which was performed with three replicates.</p

Assay design.

<p><b>(a) Primer, probe and synthetic template DNA sequences.</b> Table showing primer and probe sequences and information on the synthetic DNA templates which were used as transcription templates to create the RNA assay controls. Please see supplementary data for the full DNA sequences of the synthetic DNA templates. <b>(b) Alignment of CCHF strains at the assay design region.</b> Alignment of a selection of strains of CCHFV representing all 7 S-segment clades of CCHFV (Africa 1, Africa 2, Africa 3, Asia 1, Asia 2, Europe 1 and Europe 2), with inclusion of the RPA forward primer (CCHF RPA Fw), the reverse primer (CCHF RPA Rev) and the probe (CCHF RPA probe 1).</p

Cross-clade detection of CCHF.

<p>Table showing detection of CCHF viral extracts and synthetic CCHF RNA templates by CCHF RPA assay, in the form of TTP (minutes) and number of replicates detected. The synthetic RNA templates were used at 5X10⁵ copies/reaction and viral extracts were confirmed positive by CCHF RT-PCR. The RT-PCR TTP (minutes) are included in the table. Note that the RPA values shown are the mean of 3 independent experiments, performed with 2–3 replicates.</p

Effect of inhibitors in crude sample preparations.

<p><b>(a) Effect of crude sample dilution on detection in the RPA assay.</b> RPA performed with 5X10⁶ copies/ reaction of synthetic RNA template of Europe I strain AY277672 and a serial (1 in 10) dilution of crude preparations of human male serum, urine and tick pool homogenate. <b>(b) Effect of crude material on assay sensitivity–limit of detection.</b> RPA performed with a serial (1 in 10) dilution of synthetic RNA template of Europe I strain AY277672 and 1 in 10 diluted crude preparations of serum and urine, or 1 in 100 diluted crude preparations of tick pool homogenate. The RPA results are shown as TTP (minutes) and represent the mean of 3–4 independent experiments, each of which was performed with three replicates. RT-PCR data is also included for comparison, with the values shown representing the mean TTP (mins) of 2–3 separate experiments, each of which was performed with 2 replicates.</p

Testing of field samples from Tajikistan CCHF outbreaks between 2013 and 2015.

<p>CCHF RPA testing of a collection of field samples from the 2013–2015 CCHF outbreaks in Tajikistan. Sample types include extracted human sera and extracted tick pool homogenate. The RPA results are shown as TTP (minutes) and number of replicates detected. RT-PCR results are shown as TTP (minutes).</p

Characterization of the Emerging HIV Type 1 and HCV Epidemics among Injecting Drug Users in Dushanbe, Tajikistan

This study aimed to determine HIV, HCV, and syphilis prevalence and correlates, and to characterize the molecular epidemiology of HIV-1 among injecting drug users (IDUs) in Dushanbe, Tajikistan. A cross-sectional study assessing risk factors for HIV and HCV through an interview administered survey was conducted. A total of 491 active adult IDUs were recruited from May to November 2004 in Dushanbe, Tajikistan. HIV-1 antibody status was determined with rapid testing and confirmed with ELISA. HCV antibody testing was conducted using a BIOELISA HCV kit. HIV-1 subtyping was done on a subset with full-length sequencing. Correlates of HIV and HCV infection were assessed using logistic regression. Overall prevalence of HIV was 12.1%, HCV was 61.3%, and syphilis was 15.7%. In a multivariate logistic regression model controlling for gender and ethnicity, daily injection of narcotics [odds ratio (OR) OR 3.22] and Tajik nationality (OR 7.06) were significantly associated with HIV status. Tajik nationality (OR 1.91), history of arrest (OR 2.37), living/working outside Tajikistan in the past 10 years (OR 2.43), and daily injection of narcotics (OR 3.26) were significantly associated with HCV infection whereas being female (OR 0.53) and always using a sterile needle (OR 0.47) were inversely associated with HCV infection. Among 20 HIV-1-positive IDU with specimens available for typing, 10 were subtype A, 9 were CRF02_AG, and one was an A-CRF02_AG recombinant. Epidemics of HIV-1, HCV, and drug use are underway in Dushanbe. The molecular epidemiology is distinctive, with West African variants accounting for roughly 50% of prevalent infections. Targeted prevention programs offering both needle exchange programs and opiate substitution therapies are urgently called for to prevent the further spread of HIV and HCV in Tajikistan