Prevalence of HIV drug resistance at antiretroviral treatment failure across regions of Russia

BACKGROUND

This study aimed to investigate mutations associated with, the causes of, and the conditions that contribute to HIV drug resistance (DR). This research provides crucial insights into the mechanisms through which HIV evades antiretroviral drugs and suggests strategies to counter this phenomenon. Our objective was to assess the prevalence and structure of DR in HIV-1 across various regions in Russia and identify the primary factors influencing the development of HIV DR.

METHODS

The study used nucleotide sequences from the HIV-1 pol gene obtained from 1369 patients with a history of therapy and virological failure between 2005 and 2019 to analyze the frequency and structure of DR and the factors associated with it.

RESULTS

The analysed HIV-1 genotypes included viruses resistant to nucleoside reverse transcriptase inhibitors (NRTIs; 11.8%), non-nucleoside reverse transcriptase inhibitors (NNRTIs; 6.4%), and NRTIs + NNRTIs (31.7%). The mutations M184V/I and G190A/S/E were the most prevalent, accounting for 54.5% and 26.6%, respectively. The dominance of multiple DR persisted throughout the entire observation period. The likelihood of encountering drug-resistant variants was increased among men, patients in the late stage of infection, and those with a viral load <30 000 RNA copies/mL. Injection drug use was not associated with DR.

CONCLUSION

This study has yielded new insights into HIV DR in Russia, offering valuable information to identify clinical or programmatic events warranting closer attention and support.

Recombinant Forms of HIV-1 in the Last Decade of the Epidemic in the Russian Federation

Currently, HIV-1 displays a substantial level of genetic diversity on a global scale, partly attributed to its recombinant variants. This study seeks to identify and analyze HIV-1 recombinants in Russia during the last decade of the epidemic. A comprehensive examination was conducted, encompassing 3178 partial pol sequences. Subtyping was achieved through various programs including COMET, the Stanford Database, REGA, jpHMM, RIP, and RDP4 for recombination analysis. The study also involved phylogenetic analysis to trace the origins of the identified recombinants. Primary resistance (PrimDR) prevalence and Drug Resistance Mutations (DRMs) were assessed. The study uncovered an overall proportion of recombinants at 8.7%, with a statistically significant increase in their frequency observed over time (p < 0.001). The Northwestern (18.5%) and Siberian (15.0%) Federal Districts exhibited a high prevalence of recombinants, while the Volga (1.9%) and Ural (2.8%) Federal Districts had a lower prevalence. Among HIV-1 recombinants, a PrimDR prevalence of 11.4% was identified. Notably, significant differences in DRMs were observed, with a higher prevalence of M184V in sub-subtype A6 (p = 0.018) and K103N in CRF63_02A6 (p = 0.002). These findings underscore the increasing HIV-1 genetic diversity and highlight a substantial prevalence of PrimDR among its recombinant forms, emphasizing the necessity for ongoing systematic monitoring.

Features of Tat Protein in HIV-1 Sub-Subtype A6 Variants Circulating in the Moscow Region, Russia

Tat, the trans-activator of transcription, is a multifunctional HIV-1 protein that can induce chronic inflammation and the development of somatic diseases in HIV-infected patients. Natural polymorphisms in Tat can impact the propagation of the inflammatory signal. Currently, Tat is considered an object for creating new therapeutic agents. Therefore, the identification of Tat protein features in various HIV-1 variants is a relevant task. The purpose of the study was to characterize the genetic variations of Tat-A6 in virus variants circulating in the Moscow Region. The authors analyzed 252 clinical samples from people living with HIV (PLWH) with different stages of HIV infection. Nested PCR for two fragments (tat1, tat2) with subsequent sequencing, subtyping, and statistical analysis was conducted. The authors received 252 sequences for tat1 and 189 for tat2. HIV-1 sub-subtype A6 was identified in 250 samples. The received results indicated the features of Tat1-A6 in variants of viruses circulating in the Moscow Region. In PLWH with different stages of HIV infection, C31S in Tat1-A6 was detected with different occurrence rates. It was demonstrated that Tat2-A6, instead of a functional significant 78RGD80 motif, had a 78QRD80 motif. Herewith, G79R in Tat2-A6 was defined as characteristic amino acid substitution for sub-subtype A6. Tat2-A6 in variants of viruses circulating in the Moscow Region demonstrated high conservatism.

Identifying HIV-1 Transmission Clusters in Uzbekistan through Analysis of Molecular Surveillance Data

The CRF02_AG and sub-subtype A6 are currently the predominant HIV-1 variants in the Republic of Uzbekistan, but little is known about their time-spatial clustering patterns in high-risk populations. We have applied molecular evolution methods and network analyses to better understand the transmission patterns of these subtypes by analyzing 316 pol sequences obtained during the surveillance study of HIV drug resistance. Network analysis showed that about one third of the HIV infected persons were organized into clusters, including large clusters with more than 35 members. These clusters were composed mostly of injecting drug users and/or heterosexuals, with women having mainly high centrality within networks identified in both subtypes. Phylogenetic analyses of the 'Uzbek' sequences, including those publicly available, show that Russia and Ukraine played a role as the main sources of the current subtype A6 epidemic in the Republic. At the same time, Uzbekistan has been a local center of the CRF02_AG epidemic spread in the former USSR since the early 2000s. Both of these HIV-1 variants continue to spread in Uzbekistan, highlighting the importance of identifying transmission networks and transmission clusters to prevent further HIV spread, and the need for HIV prevention and education campaigns in high-risk groups.

Pre‐existing singleton E138A mutations in the reverse transcriptase gene do not affect the efficacy of first‐line antiretroviral therapy regimens using rilpivirine in human immunodeficiency virus‐infected patients

General consensus suggests that even singleton E138A mutations in HIV reverse transcriptase at baseline are associated with resistance to rilpivirine (RPV). We detected 11 pre‐existing E138A carriers treated with RPV in the pan European EuResist database. However, all 11 patients presented with full virological efficacy for first‐line RPV‐based ART regimens.

Prevalence of Antiretroviral Drug Resistance Mutations Among Pretreatment and Antiretroviral Therapy-Failure HIV Patients in Uzbekistan

To evaluate the national prevalence of antiretroviral therapy (ART)-resistant HIV-1 viruses among both ART-initiators (pretreatment drug resistance, PDR) and ART-failure HIV patients in Uzbekistan. A nation-wide, cross-sectional active HIV-1 PDR surveillance was conducted in Uzbekistan from 2015 to 2016. In total, 713 blood plasma samples from adults were collected, including samples from ART-naive patients initiating ART and ART-failure HIV patients. HIV-1 genome polregion viral sequences were obtained from 309 patients, of those 106 on ART and 203 on ART-initiators. Analysis of HIV-1 subtypes and drug resistance mutations (DRMs) to HIV protease and reverse transcriptase inhibitors was performed. Among all the viruses studied, HIV-1 CRF 02_AG recombinant was the most common-57% (176/309). The second major group was represented by A1-40.5% (125/309). Two viruses were found to be recombinants formed by subtypes A1 and CRF02_AG sequences. ART-naive cohort I (PDR) included six samples that contained at least one surveillance drug resistance mutation (SDRM) (2.96%), with the most common being K103N mutation (4/6). In ART-experienced patients, cohort II, 77.4% (82/106) of viruses contained at least one mutation against PIs, NRTIs, or NNRTIs, with the most common mutations of M184V/I (49.1%; 52/106), K65R (18.9%; 20/106), K103N (23.6%; 25/106), and G190S (22.6%; 24/106). The significant difference in frequency of mutations was found between two dominant subtypes, A1 and CRF02_AG. The molecular epidemiological profile of HIV infection in Uzbekistan has changed toward a predominance of CRF02_AG viruses. In the first national-scale study of the PDR prevalence, it was found to be relatively low (2.96%). The DR mutations in failure patients correspond to the main therapy regimens (NRTI/NNRTI) adopted in the country. The observations provide new evidence for differences in ART efficacy and resistance profiles for different subtypes.

Prevalence and spatiotemporal dynamics of HIV-1 Circulating Recombinant Form 03_AB (CRF03_AB) in the Former Soviet Union countries

Background

HIV-1 circulating recombinant forms (CRFs) infections has been increasing in Former Soviet Union (FSU) countries in the recent decade. One is the CRF03_AB, which circulated in the region since late 1990s and probably became widespread in northwestern FSU countries. However, there is not much information provided about the dissemination of this recombinant. Here, we examine the prevalence, evolutionary dynamics and dispersion pattern of HIV-1 CRF03_AB recombinant.

Methods

We analyzed 32 independent studies and 151 HIV-1 CRF03_AB pol sequences isolated from different FSU countries over a period of 22 years. Pooled prevalence was estimated using a random effects model. Bayesian coalescent-based method was used to estimate the evolutionary, phylogeographic and demographic parameters.

Results

Our meta-analysis showed that the pooled prevalence of CRF03_AB infection in northwestern FSU region was 5.9% [95%CI: 4.1–7.8]. Lithuania (11.6%), Russia (5.9%) and Belarus (2.9%) were the most affected by CRF03_AB. We found that early region wide spread of HIV-1 CRF03_AB originated from one viral clade that arose in the city of Kaliningrad in 1992 [95%HPD: 1990–1995]. Fourteen migration route of this variant were found. The city of Kaliningrad is involved in most of these, confirming its leading role in CRF03_AB spread within FSU. Demographic reconstruction point to this is that CRF03_AB clade seems to have experienced an exponential growth until the mid-2000s and a decrease in recent years.

Conclusion

These data provide new insights into the molecular epidemiology of CRF03_AB as well as contributing to the fundamental understanding of HIV epidemic in FSU.

Molecular Surveillance of HIV-1 Infection in Krasnoyarsk Region, Russia: Epidemiology, Phylodynamics and Phylogeography

BACKGROUND

The information about the dynamics of the viral population and migration events that affect the epidemic in different parts of the Russia is insufficient. Possibly, the huge size of the country and limited transport accessibility to certain territories may determine unique traits of the HIV-1 evolutionary history in different regions.

OBJECTIVE

The aim of this study was to explore the genetic diversity of HIV-1 in the Krasnoyarsk region and reconstruct spatial-temporal dynamics of the infection in the region.

METHODS

The demographic and virologic data from 281 HIV-infected individuals in Krasnoyarsk region collected during 2011-2016 were analyzed. The time to the most recent common ancestor, evolutionary rates, population growth, and ancestral geographic movements was estimated using Bayesian coalescent-based methods.

RESULTS

The study revealed moderate diversity of the HIV-1 subtypes found in the region, which included A6 (92.3%), CRF063_02A (4.3%), B (1.1%), and unique recombinants (2.5%). Phylogenetic reconstruction revealed that the A6 subtype was introduced into Krasnoyarsk region by one viral lineage, which arose around 1996.9 (1994.5-1999.5). The phylogeography analysis pointed to Krasnoyarsk city as the geographical center of the epidemic, which further spread to central neighboring districts of the region. At least two epidemic growth phases of subtype A6 were identified which included exponential growth in early-2000s followed by the decline in the mid/late 2010s.

CONCLUSION

This study demonstrates a change in the genetic diversity of HIV-1 in the Krasnoyarsk region. At the beginning of the epidemic, subtype A6 prevailed, subtypes B and CRF063_02A appeared in the region later.

Human Immunodeficiency Virus-1 Diversity in the Moscow Region, Russia: Phylodynamics of the Most Common Subtypes

This study analyzes the HIV-1 subtype diversity and its phylodynamics in Moscow region, which is the most densely populated area of Russia characterized by high rates of internal and external migration. The demographic and viral data from 896 HIV-infected individuals collected during 2011–2016 were analyzed. The study revealed broad diversity in the HIV-1 subtypes found in Moscow, which included A6 (85.1%), B (7.6%), CRF02_AG (1.2%) and URF_A6/B recombinants (4.2%). Other HIV-1 subtypes were detected as single cases. While A6 was most prevalent (>86.0%) among heterosexuals, injecting drug users and cases of mother-to-child transmission of HIV, subtype B (76.3%) was more common in men who have sex with men. Phylogenetic reconstruction revealed that the A6 sequences were introduced into the epidemic cluster that arose approximately around 1998. Within the subtype B, six major epidemic clusters were identified, each of which contained strains associated with only one or two dominant transmission routes. The date of origin of these clusters varied between 1980 and 1993, indicating that the HIV-1 B epidemic began much earlier than the HIV-1 A6 epidemic. Reconstruction of the demographic history of subtypes A6 and B identified at least two epidemic growth phases, which included an initial phase of exponential growth followed by a decline in the mid/late 2010s. Thus, our results indicate an increase in HIV-1 genetic diversity in Moscow region. They also help in understanding the HIV-1 temporal dynamics as well as the genetic relationships between its circulating strains.

HIV Type 1 Integrase Natural Polymorphisms in Viral Variants Circulating in FSU Countries

BACKGROUND

Natural variability of integrase (IN) across HIV-1 variants may influence the emergence of resistant viruses. The most apparent explanation of this fact is the IN polymorphism and the associated differences in codon usage, which in turn, influence the probability and the terms of DRMs acquisition. Possible mechanisms by which polymorphisms affect DRMs emergence remain disputed and should still be clarified because these substitutions may be associated with a reduced activity of some INSTIs and may impact on ART regimen choice depending of HIV-1 subtype.

OBJECTIVE

The aim of this work was to assess the prevalence of naturally occurring polymorphisms within the HIV-1 integrase gene, which might influence the susceptibility to INSTIs, among the patients from Russia and former USSR countries, according to HIV-1 subtypes.

METHOD

A study involved 506 HIV-1 IN sequences of INSTI-naive patients from Russia, Ukraine, Armenia, Kyrgyzstan, Kazakhstan, Uzbekistan, Belarus, and Georgia. Among them, 194 sequences were newly obtained in this study and 312 were downloaded from Los-Alamos database. The proviral DNA was sequenced using an in-house PCR protocol designed on the basis of a well-conserved integrase region in order to detect all HIV-1 variants.

RESULTS

The phylogenetic analyses based on IN population sequencing found subtype A6 being the most prevalent (259) (51.2%) in the collection studied, followed by subtype G (36) (7.1%), AGrecombinants (148) (29.3%), subtype B (50) (9.9%), and CRF03_AB (5) (1.0%). The major INSTI resistance-associated mutations (DRMs) were found only in two A6 samples. The prevalence of minor/ accessory substitutions depended on HIV-1 variants, while the most notable findings were L74I in subtype A6 (93.1%) and E157Q in subtype B (44.0%). Most of minor DRMs and polymorphic substitutions were concentrated in the central catalytic domain of the IN molecule. Both the DDE triad and HHCC zinc binding motifs were fully conserved.

CONCLUSION

The results of the study suggest a very low risk of initiating INSTI-based therapy in patients with pre-existing polymorphic mutations in Russia and FSU countries. The therapy response in dominating HIV-1 genetic variants might be further studied in the future for a better understanding of their effect on INSTI susceptibility. The INSTI TDR is absent for the moment, but the risk may increase with expanded use of INSTIs, indicating the need for ongoing surveillance.

Genetic Variants of HIV Type 1 in Men Who Have Sex with Men in Russia

The men who have sex with men (MSM) population infected with HIV is poorly studied in Russia because of stigma and discrimination. In the first years of the HIV epidemic, the only HIV genetic variant that circulated among MSM was subtype B, usually acquired abroad. Meanwhile, the massive epidemic of HIV in Russia was caused by a highly homogenic subtype A variant, A_FSU (A6), and spread mainly among drug users. In this study, 155 HIV pol sequences from MSM collected during the 2006-2016 period were analyzed. Phylogenetic analysis found that 19.4% of the viral sequences from MSM clustered with HIV genetic variants A6 and B_FSU, which were previously identified only among drug users and their heterosexual partners. These data show that the MSM population in Russia is gradually becoming less isolated from the general epidemic process. Urgent measures should be taken to prevent the spread of HIV among the MSM population.

HIV Type 1 Subtype A1 Dominates in Armenia

OBJECTIVE

There is scarce information about the molecular epidemiology of HIV-infection in Armenia (former USSR). The objective of this work was to estimate the distribution of HIV-1 subtypes in this country and get any information about HIV drug resistance in naÏve patients.

DESIGN

A joint study involving 78 patients was carried out in Yerevan, Armenia and Moscow, Russia in 2009-2013. The cohort studies included mostly IDUs (28.2%) and heterosexuals (69.2%).

RESULTS

The phylogenetic analyses based on population sequencing of partial pol gene found subtype A1 being the most prevalent (92.3%), followed by subtype B (3.9%). The HIV-1 tropism inferred from env V3-loop sequences was determined in 27 samples, among them R5-tropic viruses were found in 13 (48.1%) patients and X4- variants--in 14 (51.9%) patients. The prevalence of drug resistance in naïve patients was low (1.5%) with the only one mutation K219Q found.

CONCLUSION

The composition and distribution of HIV-1 genetic variants in Armenia are evidently influenced by the Russian and other FSU countries epidemic, due to the significant volume of Armenian migrant/re-emigrant flows. Continued surveillance of HIV-1 circulating subtypes and drug resistance in Armenia is important for the proper management of HIV infection in this country.

HIV-1 genetic variants in the Russian Far East

A molecular analysis of HIV-1 subtypes and recombinants circulating in cities in the Russian Far East was performed. The study included samples from 201 outpatients from Vladivostok, Khabarovsk, and Blagoveshchensk. In most parts of Russia, patients are infected with HIV-1 subtype A, known as the IDU-A variant. Subtype B, including the IDU-B variant, is rare in Russia but widespread in the Ukraine, and the CRF02_AG is prevalent in Central Asian countries and Siberia, Russia. One of the challenges of this study in the Far East was to determine whether the molecular landscape of HIV infection in this region is influenced by the bordering countries, including China and Japan, where a distinct set of HIV subtypes is circulating, such as B', C, and CRF01_AE. The distribution of HIV-1 genetic variants in the cities studied was as follows: subtype A (IDU-A), 55.7%; subtype B, 25.3% (IDU-B variant-24.3%); subtype C, 10.0%; CRF02_AG, 1.5%; and CRF63_02A1, 7.5%. A phylogenetic analysis confirmed the relationship of subtype A viruses with the IDU-A variant predominating in Ukraine, Russia and other former Soviet Union (FSU) countries, of subtype B viruses with IDU-B in the Ukraine and of CRF02_AG variants with variants in Uzbekistan, Russia, and other former USSR countries. Subtype C sequences were not uniform, and most clustered between each other and HIV-1 sequences originating from Africa; there was only one sample possibly related to Chinese variants. Thus, despite close cultural and commercial relationships among Russia, China, and Japan, the distribution of HIV-1 subtypes in the Russian Far East is still primarily influenced by contacts with the countries of the former USSR.

Short communication: molecular epidemiology of HIV type 1 infection in Kazakhstan: CRF02_AG prevalence is increasing in the southeastern provinces

To analyze HIV-1 genetic variants in Kazakhstan, HIV-1 sequences were obtained from 205 antiretroviral-treated (ART) and naive patients in 2009-2013. Samples were collected in the most populous cities and provinces of Kazakhstan. On the basis of phylogenetic analyses of partial pol sequences, subtype A variant intravenous drug user (IDU)-A (which is dominant in the former Soviet Union) was found in 60.0% of the individuals, followed by CRF02_AG (34.6%); the rest of the samples were subtype B, CRF03_AB, CRF63_02A1, and CRF07_BC. The proportion of CRF02_AG has increased significantly since 2001-2003, when it was less than 5%. The majority of the CRF02_AG cases were found in Almaty, the former capital and the most populous city in Kazakhstan. The IDU-A variant dominated in the industrial regions of northern and central Kazakhstan and some other regions. Both dominant HIV-1 genetic variants were almost equally represented in the two main transmission groups: IDUs and heterosexuals. The analysis of drug-resistant mutations found a low prevalence of drug resistance in 165 therapy-naive individuals (3.0%). Thus, in the beginning of the second decade of the 2000s, the HIV epidemic in Kazakhstan is driven by two main genetic variants: IDU-A and CRF02_AG.

Immunogenicity of candidate DNA vaccine based on subtype A of human immunodeficiency virus type 1 predominant in Russia

Human immunodeficiency virus (HIV)-1 subtype A strains circulating among the majority of HIVinfected individuals in the former Soviet Union (FSU) countries demonstrate low genetic diversity. The consensus sequence of the FSU region-specific isolate has been used for the candidate DNA vaccine development. We constructed recombinant plasmids with four viral genes: env (gp140), gag, pol (reverse transcriptase), and nef. We immunized BALB/c mice intramuscularly using equimolar mixture of four recombinant plasmids, and observed significant cytotoxic T lymphocyte response and specific CD8(+) cell production against cells presenting HIV-1 peptides. Overall, the Th1 pathway of immune response clearly dominated. Immunological properties of this candidate DNA vaccine against HIV-1 suggest the possibility of its further study in clinical trials.

An HIV type 1 subtype A strain of low genetic diversity continues to spread among injecting drug users in Russia: study of the new local outbreaks in Moscow and Irkutsk

An explosive epidemic of human immunodeficiency virus type 1 (HIV-1) has been documented among injecting drug users (IDUs) in the former Soviet Union republics. In 1999, the two largest local IDU outbreaks of HIV-1 infection in the Russian Federation were registered in the Moscow and Irkutsk regions, where 13,004 HIV-1 cases were identified (44% of the total number of HIV-1 infections in Russia in 1999). To study the prevailing genetic variants and to estimate the genetic diversity of HIV-1 in these outbreaks, 60 samples from Moscow (n = 36) and from Irkutsk (n = 24) were analyzed using the gag/env heteroduplex mobility assay, and the env gp120 V3 encoding regions obtained from 23 individuals were sequenced. Both virus populations were highly homogeneous (the means of pairwise nucleotide distance were 1.75 +/- 0.83 and 2.35 +/- 1.59 for Irkutsk and Moscow, respectively), and similar to the subtype A viruses obtained earlier from IDUs in the former Soviet Union. The subtype A HIV-1 variant thus dominates in the largest HIV-1 outbreaks among IDUs in the Russian Federation.

A sudden epidemic of HIV type 1 among injecting drug users in the former Soviet Union: identification of subtype A, subtype B, and novel gagA/envB recombinants

The former Soviet Union republics have experienced an explosive human immunodeficiency virus type 1 (HIV-1) epidemic among injecting drug users (IDUs), consisting mainly of subtype A viruses originated from a point source (Bobkov et al.: AIDS Res Hum Retroviruses 1997;13:1195-1201). To determine whether new HIV-1 subtypes have entered the IDU population, 46 samples derived from IDUs in Russia (n = 39) and the Ukraine (n = 7) were genotyped by heteroduplex mobility assay (HMA). It was shown that 83% of IDU HIV-1 strains found in both countries belong to genetic subtype A. However, env subtype B was also found in 17% of cases. The sequence data showed a marked intrasubtype homogeneity of HIV-1 (the average means of interpatient genetic distance were 1.1 and 1.7% [in the gag gene] or 1.8 and 2.3% [in the env gene] for subtype A and subtype B, respectively), confirming the hypothesis of a point source of virus for each subtype variant. Moreover, recombinant gagA/envB variants originating from those two strains were also found in two samples collected in the Kaliningrad region of Russia. In conclusion, our results suggest that two strains of HIV-1 belonging to different genetic subtypes, A and B, as well as gagA/envB recombinants between genomes of these strains, are now circulating simultaneously among IDUs in the former Soviet Union.

An HIV type 1 epidemic among injecting drug users in the former Soviet Union caused by a homogeneous subtype A strain

Epidemiological data have demonstrated rapid growth of HIV-1 infections among injecting drug users (IDUs) in the Ukraine and Russia, during 1996. Here we describe the results of genetic analysis of isolates derived from 12 HIV-1-infected IDUs in different sites of Russia and the Ukraine. The blood samples were taken within a 1- to 2-month period after the first HIV-1-positive test. The results of the heteroduplex mobility assay as well as gag/env phylogenetic analysis reveal that all sequences belong to gag/env genetic subtype A. Moreover, interpatient genetic distances between the nucleotide sequences encompassing the C2-V3, the V4-V5, and p17-encoding regions within this group were low (the average means were 0.9, 1.3, and 0.4%, respectively). These data show a marked homogeneity of HIV-1, probably spreading during primary infection. It is possible that the current epidemic of subtype A HIV-1 among IDUs in the former Soviet Union is caused by a point source exposure.

Genetic heterogeneity of HIV type 1 in Russia: identification of H variants and relationship with epidemiological data

HIV-genetic subtypes were analyzed in 130 subjects from the Russian Federation, by the HMA technique. Six subtypes were identified in heterosexuals, including A, B, C, D, G, and H; however, homosexual men were infected predominantly with the B subtype (33 of 35). The subtype A isolates were found in population of intravenous drug users. HMA successfully identifies 128/130 DNA samples; the phylogenetic analysis of the V1/V5 gp120 encoding region derived from another two samples demonstrated that these isolate belong to subtype H.