Vaccine Strain Research Articles

Construction of the First Russian Recombinant Live Attenuated Vaccine Strain and Evaluation of Its Protection Efficacy Against Two African Swine Fever Virus Heterologous Strains of Serotype 8

Background/Objectives: The spread of African swine fever virus (ASFV) has led to major economic losses to pork worldwide. In Russia, there are no developed or registered vaccines against ASFV genotype II, which is associated with numerous ASFV outbreaks in populations of domestic pigs and wild boars in the country. Methods: We introduced deletions of the six MGF360 and MGF505 genes of the ASFV virulent Stavropol_01/08 strain, isolated in Russia in 2008. Results: We show here that this deletion did lead to full attenuation of the ASFV virulent Stavropol_01/08 strain. Animals intramuscularly inoculated with 104 HAD50 of ΔMGF360/505_Stav developed a strong immune response and short period of viremia (at 3–7 days post-inoculation). Recombinant ΔMGF360/505_Stav strain provides complete protection of pigs against the ASFV parental Stavropol_01/08 strain (103 HAD50). Therefore, in our experiment, we did not detect the genome of both the virulent and the recombinant strains in the blood and organs post-challenge with the Stavropol_01/08. In contrast, we found only partial protection (40%) of the ΔMGF360/505_Stav-immunized pigs against challenge with the ASFV heterologous Rhodesia strain. Additionally, the surviving animals had a prolonged fever, and their condition was depressed for most of the experiment. Conclusions: Thus, the ASFV recombinant ΔMGF360/505_Stav strain is the first live attenuated vaccine (LAV) in Russia that induces complete protection in pigs challenged with the highly virulent, epidemiologically relevant strains genotype II and serotype 8. However, this ASF LAV is not able to provide a high level of protection against other variants of serotype 8.

Immune Characterisation of Human Local Pneumotropic Isolates of Streptococcus pneumoniae Serotype 1 and 6 as Local Vaccine Strains

Immune Characterisation of Human Local Pneumotropic Isolates of Streptococcus pneumoniae Serotype 1 and 6 as Local Vaccine Strains

Humoral correlate of vaccine-mediated protection from tuberculosis identified in humans and non-human primates.

Development of an effective tuberculosis (TB) vaccine has been challenged by incomplete understanding of specific factors that provide protection against Mycobacterium tuberculosis (Mtb) and the lack of a known correlate of protection (CoP). Using a combination of samples from a vaccine showing efficacy (DarDar [ NCT00052195 ]) and Bacille Calmette-Guerin (BCG)- immunized humans and nonhuman primates (NHP), we identify a humoral CoP that translates across species and vaccine regimens. Antibodies specific to the DarDar vaccine strain ( M. obuense ) sonicate (MOS) correlate with protection from the efficacy endpoint of definite TB. In humans, antibodies to MOS also scale with vaccine dose, are elicited by BCG vaccination, are observed during TB disease, and demonstrate cross-reactivity with Mtb; in NHP, MOS-specific antibodies scale with dose and serve as a CoP mediated by BCG vaccination. Collectively, this study reports a novel humoral CoP and specific antigenic targets that may be relevant to achieving vaccine-mediated protection from TB.

Molecular Pathotyping and Phylogeny of Recent Subgenotype XIV.2 Newcastle Disease Viruses from Chickens and Pigeons in Nigeria

Abstract Genomic studies of Newcastle disease virus (NDV) affecting chickens and pigeons in Nigeria are limited. This study characterized NDVs from chickens and pigeons within households and live bird markets in Bauchi State, Nigeria. A total of 80 pooled oropharyngeal and cloacal swab samples were collected from November 2021 to February 2022 and tested using one-step RT-PCR. Interestingly, 73 (91.25%) of the samples were found to be positive, and 40 sequences of the partial NDV F gene were obtained. The fusion protein cleavage site amino acid motifs 112R-R-Q/R-K-R-F117 and 112G-R-Q-G-R-L117 were observed for the virulent (95.0%) and lentogenic (5.0%) pathotypes, respectively. The virulent NDV strains clustered with subgenotype XIV.2 NDV strains from Nigeria and neighboring Benin, whereas the lentogenic pathotypes belonged to the genotype II cluster along with NDV vaccine strains. This study highlighted the serious threat of virulent NDV, warranting surveillance and improved biosecurity to control local and transboundary spread of NDV.

Multiplexed Detection, Partitioning, and Persistence of Wild-Type and Vaccine Strains of Measles, Mumps, and Rubella Viruses in Wastewater.

Wastewater surveillance of vaccine-preventable diseases may provide early warning of outbreaks and identify areas to target for immunization. To advance wastewater monitoring of measles, mumps, and rubella viruses, we developed and validated a multiplexed RT-ddPCR assay for the detection of their RNA. Because the measles-mumps-rubella (MMR) vaccine is an attenuated live virus vaccine, we also developed an assay that distinguishes between wild-type and vaccine strains of measles in wastewater and validated it using a wastewater sample collected from a facility with an active measles outbreak. We also evaluated the partitioning behavior of the viruses between the liquid and solid fractions of influent wastewater. We found that assaying the liquid fraction of the wastewater resulted in more sensitive detection of the viruses despite the fact that the viral RNA was enriched in the solid fraction due to the low solids content of the influent wastewater. Finally, we investigated the stability of measles, mumps, and rubella RNA in wastewater samples spiked with viruses over 28 days at two different concentrations and two temperatures (4 °C and room temperature) and through freeze-thaw and observed limited viral decay. Our study supports the feasibility of wastewater monitoring for measles, mumps, and rubella viruses for population-level surveillance.

Risk of Transmission of Vaccine-Strain Rotavirus in a Neonatal Intensive Care Unit That Routinely Vaccinates.

Many neonatal intensive care units (NICUs) do not give rotavirus vaccines to inpatients due to a theoretical risk of horizontal transmission of vaccine strains. We aimed to determine incidence and clinical significance of vaccine-strain transmission to unvaccinated infants in a NICU that routinely administers pentavalent rotavirus vaccine (RV5). This prospective cohort study included all patients admitted to a 100-bed NICU for 1year. Stool specimens were collected weekly; real-time quantitative reverse-transcription polymerase chain reaction was used to detect any RV5 strain. Incidence of transmission to unvaccinated infants was calculated assuming each unvaccinated patient's stool contributed 1 patient-day at risk for transmission. Investigations and geospatial analyses were conducted for suspected transmission events. Of 1238 infants admitted, 560 (45%) were premature and 322 (26%) had gastrointestinal pathology. During observation, 226 RV5 doses were administered. Overall, 3448 stool samples were tested, including 2252 from 686 unvaccinated patients. Most (681, 99.3%) unvaccinated patients never tested positive for RV5 strain. Five (<1%) tested RV5 strain positive. The estimated rate of transmission to unvaccinated infants was 5/2252 stools or 2.2/1000 patient-days at risk (95% CI: 0.7-5.2). No gastroenteritis symptoms were identified in transmission cases within 7 days of collection of RV5-positive stool. Of 126 patients for whom the RV5 series was initiated before the discharge date, 55% would have become age-ineligible to start the series if vaccination was allowed only at discharge. Transmission of RV5 strain was infrequent and without clinical consequences. Benefits of allowing vaccine-induced protection against rotavirus disease in infants through in-NICU RV5 vaccination appear to have outweighed risks from vaccine-strain transmission.

Molecular and ultrastructural characteristics of virulent and attenuated vaccine strains of goose parvovirus LIV-22.

The disease caused by goose parvovirus (GPV) affects young goslings and ducks and leads to substantial losses for farmers due to high mortality rates, reaching 70-100% in naive flocks. Here, we present the results of a study focusing on the historical virulent GPV LIV-22 strain, which was isolated in the USSR in 1972. An attenuated GPV LIV-22 vaccine strain that was generated by continuous passaging in goose embryonic fibroblasts was also studied. Phylogenetic analysis placed both GPV LIV-22 strains in the classical GPV group, close to the vaccine and low-pathogenic strains. However, several individual changes in the GPV LIV-22 VP1 gene highlight the uniqueness of the evolution and adaptation mechanism of GPV LIV-22 strains. Transmission electron microscopy (TEM) revealed severe ultrastructural changes in goose hepatocytes and enterocytes as early as 24-48 h postinfection, confirming abrupt GPV pathogenesis. This description of some of the essential characteristics of the GPV LIV-22 virulent and vaccine strain will be useful for studying GPV evolution and molecular pathogenesis.

Assessment of the immunity gap of two vaccination programs against Gumboro disease in Luong Phuong chicken

Maternal-derived antibody (MDA) is the priority protection against environmental Infectious Bursal Disease Virus (IBDV) in the first weeks. The passive immunity decreases, but the active immunity is not enough to protect chicks, so shortening the high-risk period is crucial to IBD control. The objective of this study was to evaluate the immunity gap between 2 vaccination programs against infectious bursal disease (IBD) in Luong Phuong chickens. A total of 34,600 chicks were administered by subcutaneous injection of IBD vaccine at 0.1 mL/dose at the hatchery. At 12 days old, 18,000 chicks were vaccinated with the M.B strain vaccine and 16,600 chicks were vaccinated with the 228E strain vaccine by drinking water. The IBD and Newcastle disease (ND) antibody evaluations were based on the Enzyme-linked immunosorbent assay (ELISA) technique. Parameters were recorded until slaughter including body weight, average daily gain, feed conversion rate, and mortality. The IBD MDA at 1 day old was medium and uniform (3809 and 45.3%), which could protect against IBD virus from 1 to 2 weeks old. At 28 days old, the IBD antibody titer of the MB vaccine was higher than that of the 228E vaccine, various proportions of samples in the M.B group exceeding 1,000 titers (40% vs. 0%), and it was a statistically significant difference (1,133 vs. 161) (P &lt; 0.01). Besides, the M.B vaccine created a faster and stronger immune response than the 228E vaccine, shortening the immune gap and protecting chicks earlier. The humoral immune response to the ND vaccine was good, with no difference between 2 groups, which proved that the M.B virus did not cause immunosuppression. The production parameters of chickens between the 2 groups were the same. In summary, the M.B vaccine made a short immune gap and did not cause immunodeficiency in chickens.

Influenza A virus continues to circulate among children in Linyi, northern China, after the relaxation of COVID-19 control measures

Following the relaxation of control measures for COVID-19 in China in December 2022, there was a resurgence of influenza A among children in Linyi. This research aims to analyze the epidemiology and genetic characteristics of influenza A viruses circulating among children in Linyi from April 2022 to March 2024. Throat swab specimens were collected from children with influenza-like illness (ILI), and the types of influenza were identified. The hemagglutinin (HA) genes of influenza A viruses were amplified using reverse transcription-polymerase chain reaction (RT-PCR) and then sequenced. Subsequently, the gene characteristics and phylogenetics of these sequences were analyzed. A total of 6258 cases of influenza A were tested from 54,926 children with ILI over two years, showing three epidemic waves: one in summer 2022 and two in spring and winter 2023. The epidemic waves in summer 2022 and winter 2023 were caused by influenza A(H3N2) viruses. In spring 2023, influenza A(H1N1)pdm09 viruses accounted for 77.1% and A(H3N2) viruses accounted for 22.9%, respectively. The influenza A(H1N1)pdm09 viruses belonged to clade 6B.1A.5a.2a, while the influenza A(H3N2) viruses evolved from clade 3C.2a1b.2a.1a to 3C.2a1b.2a.2a.3a.1. Compared with the vaccine strain of the Northern Hemisphere of the current year, multiple amino acid substitutions and glycosylation sites changes were observed in the HA protein that most likely resulted in antigenic drift. The influenza A viruses have been circulating and evolving persistently in Linyi from 2022 to 2024. Continuous surveillance is essential for comprehending the dynamics of influenza in the post-COVID-19 era.

Detection and molecular epidemiology of canine parvovirus and identification of highly pathogenic CPV-2c isolates from Shandong, China.

Canine parvovirus (CPV) is an important pathogen of dogs and wild carnivores. It is a single-stranded DNA virus with a high mutation frequency and antigenic drift. To research the prevalence and genetic variation of CPV in Shandong, 62 samples from diseased dogs were collected and examined by using PCR for parvovirus. Our results showed that the positivity was 62.9% (n = 39), VP2 gene were sequenced and compared with reference strains. For the parvovirus subtype prevalence, 7 strains were CPV-2a (17.9%) and 32 strains were CPV-2c (82.1%). The results of phylogenetic analysis of VP2 gene of the CPVs showed all 39 isolates formed a major clade and were distantly related to the commercial vaccine strains. By comparing amino acid (aa) sequences, this study discovered new mutations not previously reported which may be related to host range and antigenicity. Moreover, one CPV-2c strain (QN-55) was isolated and cultured on F81 cells, and characterized by whole-genome sequencing. The TCID50 of this strain was 10-3.2/0.1 mL and animal tests have shown that the strain is fatal to infected dogs.

Live attenuated goatpox vaccination in pregnant Murcia-Granada goats: dosage implications and outcomes

BackgroundInfectious diseases, particularly the Goatpox virus (GTPV) from the Poxviridae family, significantly impact livestock health and agricultural economies, especially in developing regions. Recent GTPV outbreaks in previously eradicated areas underscore the need for effective control measures, with vaccination being the most reliable strategy. This study investigates the effects of administering standard and double doses of live attenuated goatpox vaccine in pregnant Murcia-Granada goats, a non-native breed in Iran, to determine optimal vaccination protocols.ResultsIn 2018, 400 healthy and pregnant Murcia Granada goats imported from Spain were divided into groups of 200 and vaccinated with either a standard dose (0.5 ml) or a double dose (single 0.9 ml injection) of live attenuated goatpox vaccine. Post-vaccination, the goats were monitored daily for clinical signs of infection, with samples collected for PCR analysis to detect the presence of GTPV strains. In group A, which received the standard vaccine dose, no abortions or vaccine-related side effects were observed, and body temperatures remained normal. In group B, administered a double dose, 37% of the goats experienced abortions, displaying signs of GTPV infection, such as skin lesions (pox lesions) and increased body temperatures. Molecular analysis confirmed the vaccine strain of GTPV as the infection source, ruling out external contamination. Statistical analysis showed no significant differences in abortion rates concerning gestational age or t he age of the pregnant goats.ConclusionThe study highlights the importance of adhering to standard vaccine dosages in pregnant Murcia Granada goats to prevent adverse outcomes like abortions. This study emphasizes the necessity to review and revise vaccination protocols tailored to specific breeds and varying maintenance conditions, including pregnancy and outbreak scenarios. These findings stress the necessity for cautious and tailored vaccination strategies to ensure the safety and efficacy of vaccines in different goat breeds.

Meteorological factors, population immunity, and COVID-19 incidence: A global multi-city analysis.

While COVID-19 continues to challenge the world, meteorological variables are thought to impact COVID-19 transmission. Previous studies showed evidence of negative associations between high temperature and absolute humidity on COVID-19 transmission. Our research aims to fill the knowledge gap on the modifying effect of vaccination rates and strains on the weather-COVID-19 association. Our study included COVID-19 data from 439 cities in 22 countries spanning 3 February 2020 - 31 August 2022 and meteorological variables (temperature, relative humidity, absolute humidity, solar radiation, and precipitation). We used a two-stage time-series design to assess the association between meteorological factors and COVID-19 incidence. For the exposure modeling, we used distributed lag nonlinear models with a lag of up to 14 days. Finally, we pooled the estimates using a random effect meta-analytic model and tested vaccination rates and dominant strains as possible effect modifiers. Our results showed an association between temperature and absolute humidity on COVID-19 transmission. At 5 °C, the relative risk of COVID-19 incidence is 1.22-fold higher compared to a reference level at 17 °C. Correlated with temperature, we observed an inverse association for absolute humidity. We observed a tendency of increased risk on days without precipitation, but no association for relative humidity and solar radiation. No interaction between vaccination rates or strains on the weather-COVID-19 association was observed. This study strengthens previous evidence of a relationship of temperature and absolute humidity with COVID-19 incidence. Furthermore, no evidence was found that vaccinations and strains significantly modify the relationship between environmental factors and COVID-19 transmission.

Functional impact of a deletion in Mycobacterium bovis BCG Moreau celA1 gene

Several mycobacterial species are known to cause human diseases, such as tuberculosis and leprosy. In addition to these pathogenic species, there are also saprophytic representatives, which occasionally cause opportunistic infections. It is well established that numerous mycobacteria produce biofilms containing cellulose, and their genomes frequently harbor genes involved in cellulose degradation, such as celA1. Notably, the BCG Moreau vaccine strain carries a specific deletion of two-base pairs, resulting in a predicted protein with fewer than 100 amino acids in the catalytic portion at the C-terminal end. We investigated the functional consequences of this polymorphism and observed that recombinant enzyme from the Moreau strain lack catalytic activity. Furthermore, compared to the Pasteur strain, Moreau is unable to utilize carboxymethylcellulose (CMC) as the sole carbon source. These findings suggest an absence of cellulolytic activity in this strain, which may influence the bacterium virulence.

A simple Magnetic-aided microfluidic screening approach for rabies virus via rolling circle amplification

Rabies, being a fatal neurologic disease, is one of the neglected tropical diseases. Timely post-exposure prophylaxis is the key to healthcare, demanding an early diagnosis towards the much-envisaged ‘One Health’ measures. Despite being a disease with almost 100 % mortality cases, no significant progress has been made towards its early and accurate diagnosis. Herein, we report a simple microfluidic device based on magnetic trapping, without any complex design, in order to specifically screen rabies virus from biofluids. For this, we exploit Rolling Circle Amplification (RCA), a highly recommended isothermal nucleic acid amplification test (NAAT), with rapid and robust point-of-care diagnosis capabilities. This specific molecular assay was used for sensitive detection down to 2.69 fM and 14.5 fM for N- and L-gene targets, respectively. COMSOL simulations have accelerated experimental optimization time, resulting in effective capture and detection of magnetically-coupled amplicons. Fluorescently-tagged RCA products mixed with magnetic microparticles (M−RCPs) showed a clearly distinguishable signal between rabies vaccine strain and blood samples of healthy dogs. This simple technique presents a scalable proof-of-concept prototype for a highly specific ‘yes-or-no’ detection method for rabies virus, using a minimal sample volume and extendable for sensitive-cum-specific screening of other pathogens using tunable molecular probes.

Molecular characterization of circulating infectious bursal disease viruses in chickens from different Egyptian governorates during 2023

Infectious bursal disease virus (IBDV) induces severe immunosuppression in chickens, leading to significant economic losses in the global poultry industry. This study investigated 52 chicken flocks, including commercial broilers, layers, and baladi, from various Egyptian governorates in 2023. These flocks exhibited symptoms of depression, along with kidney and bursa lesions, indicative of IBDV infection. Pooled Bursal homogenates were tested using RT-PCR with VP2-specific primers, revealing that 20 flocks tested positive for IBDV. Six representative samples were selected from 20 positive flocks for isolation in embryonated chicken eggs. The embryonic lesions observed included haemorrhage, skull swelling, and liver necrosis with a pale-yellow appearance, in addition to congestion and thickening in the chorioallantoic membrane (CAM). Partial amplification of the VP2 gene from the harvested embryo suspensions of the six IBDV isolates was performed for sequencing. Phylogenetic analysis of the sequences revealed that five IBDV isolates (VV4, VV5, VV6, VV10, and VV16) belonged to the very virulent strain group A3 cluster, whereas one isolate (VV2) clustered with Chinese Variant strains in the A2d group. Sequence analysis of the hypervariable region (HVR) of VP2 compared to that of Egypt-USC-IBD-1-2019 and vvIBDV/Beh21/Egypt/18 highly virulent IBDV strains revealed several amino acid mutations. The VP2 HVR of all isolates maintained the serine-rich heptapeptide sequence SWSASGS, which is adjacent to the major hydrophilic peak B and serves as a virulence marker. Histopathological examination revealed that bursae from chickens infected with vvIBDV exhibited marked interlobular oedema and lymphoid depletion. In contrast, bursae from chickens infected with Variant IBDV showed massive lymphoid depletion, with hyperplasia of the bursal capsule. These findings highlight the circulation of both virulent and Variant IBDV strains in Egyptian chicken flocks, complicating disease control. Consequently, there is a need to update vaccination programs and vaccine strains for IBDV in Egypt.

Wild Brazilian Yellow Fever Virus infection in Syrian hamsters (Mesocricetus auratus): Clinical and histopathological analyses

The Yellow Fever virus (YFV) wild-type strains studied until now have little or no ability to evade the Syrian hamster interferon antiviral response. Thus, evaluating the susceptibility of this model to new YFV isolates is paramount to aid in the understanding of their viscerotropic phenotype. To this end, Syrian hamsters were inoculated intraperitoneally with two Brazilian wild-type YFV isolates originated from dying or dead howler monkeys obtained during outbreaks in the states of Rio Grande do Sul in 2008 (PR4408) and Rio de Janeiro in 2019 (RJ155). The results were compared with a YFV experimental vaccine strain (17DDexp). The main findings observed for animals infected with the PR4408 strain were progressive weight loss and persistent viremia (at least up to day seven post-infection), associated with viral RNA detection in the liver, and hepatic, splenic, and pancreatic histological alterations consistent with YF. The infection was eliminated seven days post-infection in animals inoculated with the RJ155 strain. No changes were observed for animals infected with 17DDexp virus. The findings indicate that both Brazilian isolates are able to infect Syrian hamsters, resulting in histopathological changes compatible with the YF pathology observed in humans. Furthermore, the PR4408 strain exhibited increased virulence in this mammalian model, despite causing a non-fatal infection.

The genome sequence of a non-capsular natural Bacillus anthracis strain of A.Br.001/002 canSNP group isolated from permafrost in Yakutia, Russia.

We present the results of the whole-genome sequencing of a Bacillus anthracis strain isolated from a permafrost sample collected in Yakutia, Russia. This strain was named YakM12. Phylogenetic analysis showed that YakM12 belongs to the canSNP group A.Br.001/002 and is genetically close to the Sterne vaccine strain.

Genetic, phylogenetic, and serological analysis of a Getah virus strain isolated from Culex tritaeniorhynchus mosquitoes in Nagasaki, Japan in 2022.

Getah virus (GETV), belonging to the genus Alphavirus within the family Togaviridae, is a mosquito-borne virus that causes fever, rash, and edema in horses and fatalities and pregnancy disorders in pigs. It has caused occasional outbreaks in horse populations in Japan, China, and India, and endemic areas are gradually expanding, particularly in Asia and Oceania. In this study, we isolated a new GETV strain from Culex tritaeniorhynchus mosquitoes collected from Nagasaki Prefecture, Japan in 2022. Phylogenetic analysis revealed that this new strain, 22IH8, is more closely related to previous Chinese strains than to the strains prevalent in Japan in the 2010s. Furthermore, some amino acid substitutions in the viral proteins of strain 22IH8 were found to be common with those in previous Chinese strains. These results suggest that 22IH8 strain may have recently invaded the Japanese archipelago from mainland Asia. The antiserum against the current vaccine strain, MI-110, showed high neutralization activity against the 22IH8 strain indicating the efficiency of the current vaccine for horses in Japan.

Evaluation of the Effect of the Mycoplasma hyopneumoniae Live Vaccine (Strain 168) in Ningxiang Pigs

[Background/Objectives] Mycoplasma hyopneumoniae (M. hyopneumoniae) is widespread in the global swine industry, leading to significant economic losses, and is particularly severe in native Chinese pig breeds. The Ningxiang pig, a well-known native breed in China, is susceptible to M. hyopneumoniae, exhibiting high morbidity and mortality rates. This study was designed to evaluate the clinical effectiveness of the M. hyopneumoniae live vaccine (strain 168). [Methods] The vaccine was delivered to 7-day-old piglets in the farrowing room through intrapulmonary administration, and its efficacy was compared with that of the M. hyopneumoniae inactivated vaccine (strain J). Four experimental groups were designed: Group 1 (inactivated vaccine + inactivated vaccine), Group 2 (live vaccine + inactivated vaccine), Group 3 (live vaccine), and Group 4 (control), which was not vaccinated. The production performance of each group was measured, and the lung lesion scores and pneumonia lesion reduction rates were evaluated at slaughter. Nasal swabs and serum samples were collected on days 0, 14, 28, 56, 84, 112, and 140 to assess SIgA, IgG antibody levels, and the M. hyopneumoniae pathogen. [Results] The results showed that Group 3 had the best production performance and clinical outcomes, with the lowest average lung lesion score, of 4.43 ± 2.44, which was significantly different from the other groups (*** p &lt; 0.001). [Conclusions] This study provided scientific evidence to support vaccination strategies for preventing and controlling the M. hyopneumoniae in native pig populations.

A new record of avian reovirus genogroup clusters isolated and molecularly characterized in chickens in Egypt

BackgroundThe global poultry industry has been experiencing increasing condemnation at slaughterhouses since 2011, due to the emergence of avian reovirus (ARV) variant strains. Recently seven ARV genogroup clusters were identified based on the σC sequence of the S1 segment that was used as a genetic marker to characterize and classify ARV.ResultsAmong ninety-seven suspected broilers, breeders, and commercial grandparent’s homogenates, ARV was PCR confirmed in thirty-five (36%). Samples were collected from different governorates in Egypt, including Giza–Ismailia–Sharqia–Menoufia, and Behira, between 2020 and 2023. A viral isolation trial was performed on weak positive samples, successfully isolating sixteen samples on the LMH cell line forming the characteristic giant cells of ARV infection. Partial sequencing and phylogenetic analysis of the σC gene of ten ARV PCR positive samples revealed the circulation of ARV genogroup clusters 1, 2, 4, and 5, eight samples being distinguished from commercially available vaccine strains with a low percentage of nucleotides and amino acid identities.ConclusionsThis research demonstrated that the ARV isolates were distinct compared to commercially available vaccine strains based on partial σC sequence. Detection, isolation, and classification of ARV as genogroups 1, 2, 4, and 5 are recorded. A vigilant surveillance to evaluate the ARV situation in Egypt is urgent. We recommend re-evaluating the ARV commercial vaccines by challenging them with circulating Egyptian field isolates, as well as their cross-protection. In addition, the development of autologous vaccines from both classical and variant strains to provide optimal protection.