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Introduction: Respiratory Syncytial Virus (RSV) is a significant cause of respiratory illnesses worldwide, particularly in infants and elderly individuals. Despite the burden RSV imposes, effective preventive measures are limited. The research application of adeno-associated virus (AAV) in vaccine platforms has been expanding, and its potential in prevention and treatment has garnered much attention., Methods: In this study, we explored the potential application of a recombinant adeno-associated virus 5 (rAAV5) vector-based RSV vaccine, focusing on the expression of the pre-fusion (Pre-F) protein structure. Through intramuscular immunization in mice. The immunogenicity of the vaccine was evaluated in Balb/c mice immunized intramuscularly and intranasal, respectively., Results: The rAAV5-RSV-Fm vaccine demonstrated positive humoral and induced antibody titers against RSV strains A and B for up to 120 days post-immunization. Notably, intranasal administration also elicited protective antibodies. Characterization studies confirmed the ability of the vac-cine to express the Pre-F protein and its superior immunogenicity compared to that of full-length F protein., Conclusion: These findings underscore the potential application of rAAV5 vector platforms in RSV vaccine development and further investigation into their protective efficacy is warranted., Competing Interests: Authors ZX, CL, JG, GZ, HL, XC were employed by Guangdong Keguanda Pharmaceutical Technology Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Ma, Xu, Li, Zhou, Hu, Guo, Ke, Chen, Zhang, Lau, Pan, Chen, Li and Liu.)

Objectives: The aim was to understand persistence of the virus in body fluids the and immune response of an infected host to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), an agent of coronavirus disease 2019 (COVID-19)., Methods: We determined the kinetics of viral load in several body fluids through real time reverse transcription polymerase chain reaction, serum antibodies of IgA, IgG and IgM by enzyme-linked immunosorbent assay and neutralizing antibodies by microneutralization assay in 35 COVID-19 cases from two hospitals in Guangdong, China., Results: We found higher viral loads and prolonged shedding of virus RNA in severe cases of COVID-19 in nasopharyngeal (1.3 × 10 6 vs 6.4 × 10 4 , p < 0.05; 7∼8 weeks) and throat (6.9 × 10 6 vs 2.9 × 10 5 , p < 0.05; 4∼5 weeks), but similar in sputum samples (5.5 × 10 6 vs 0.9 × 10 6 , p < 0.05; 4∼5 weeks). Viraemia was rarely detected (2.8%, n = 1/35). We detected early seroconversion of IgA and IgG at the first week after illness onset (day 5, 5.7%, n = 2/35). Neutralizing antibodies were produced in the second week, and observed in all 35 included cases after the third week illness onset. The levels of neutralizing antibodies correlated with IgG (r s  = 0.85, p < 0.05; kappa = 0.85) and IgA (r s  = 0.64, p < 0.05; kappa = 0.61) in severe, but not mild cases (IgG, r s  = 0.42, kappa = 0.33; IgA, r s  = 0.32, kappa = 0.22). No correlation with IgM in either severe (r s  = 0.17, kappa = 0.06) or mild cases (r s  = 0.27, kappa = 0.15) was found., Discussion: We revealed a prolonged shedding of virus RNA in the upper respiratory tract, and evaluated the consistency of production of IgG, IgA, IgM and neutralizing antibodies in COVID-19 cases., (Copyright © 2020. Published by Elsevier Ltd.)

Herein, we report that a recombinant fusion protein, containing a 457 amino acid SARS-CoV-2 receptor binding domain (RBD, residues 319-541) and a mouse IgG1 Fc domain, could induce highly potent neutralizing antibodies and stimulate humoral and cellular immunity in mice. The antibodies also effectively suppressed SARS-CoV-2 RBD binding to soluble ACE2, indicating that RBD-mFc may be further developed as a safe and effective SARS-CoV-2 vaccine.

The first imported case of Middle East respiratory syndrome (MERS) in China recently occurred, allowing for the characterization of antibody titers in a series of the patient's sera using the following methods based on recombinant viral structural antigens: inactivated MERS coronavirus (MERS-CoV) enzyme-linked immunosorbent assay (ELISA), recombinant MERS-CoV spike (S, or fragments of S) ELISA, nucleoprotein (NP) ELISA and MERS S pseudovirus particle-based neutralization test (ppNT). A longitudinal profile of the infection showed that seroconversion detected by ELISAs based on the recombinant extracellular domain, S, S1 and receptor-binding domain (RBD) antigens occurred as early as neutralizing antibodies were detected by the ppNT and earlier than antibodies were detected by the inactivated MERS-CoV and N-terminal domain (NTD) ELISAs. Antibodies detected by the NP ELISA occurred last. Strong correlations were found between the S1, RBD and NP ELISAs and the inactivated MERS-CoV ELISA. The S and RBD ELISAs were highly correlated with the commercial S1 ELISA. The S ELISA strongly correlated with the ppNT, although the MERS-CoV, S1, NTD and RBD ELISAs were also significantly correlated with the ppNT (P<0.001).

Guangdong Province is recognized for dense populations of humans, pigs, poultry and pets. In order to evaluate the threat of viral infection faced by those working with animals, a cross-sectional, sero-epidemiological study was conducted in Guangdong between December 2013 and January 2014. Individuals working with swine, at poultry farms, or live poultry markets (LPM), and veterinarians, and controls not exposed to animals were enrolled in this study and 11 (4 human, 3 swine, 3 avian, and 1 canine) influenza A viruses were used in hemagglutination inhibition (HI) assays (7 strains) and the cross-reactivity test (9 strains) in which 5 strains were used in both tests. Univariate analysis was performed to identify which variables were significantly associated with seropositivity. Odds ratios (OR) revealed that swine workers had a significantly higher risk of elevated antibodies against A/swine/Guangdong/L6/2009(H1N1), a classical swine virus, and A/swine/Guangdong/SS1/2012(H1N1), a Eurasian avian-like swine virus than non-exposed controls. Poultry farm workers were at a higher risk of infection with avian influenza H7N9 and H9N2. LPM workers were at a higher risk of infection with 3 subtypes of avian influenza, H5N1, H7N9, and H9N2. Interestingly, the OR also indicated that LPM workers were at risk of H1N1 swine influenza virus infection, perhaps due to the presence of pigs in the LPM. While partial confounding by cross-reactive antibodies against human viruses or vaccines cannot be ruled out, our data suggests that animal exposed people as are more likely to have antibodies against animal influenza viruses., (Copyright © 2015 Elsevier B.V. All rights reserved.)

To assess the potential transmission for zoonotic influenza, sero-antibodies against two kinds of influenza viruses--classical swine H1N1 and human H1N1pdm09 virus were detected in persons whose profession involved contact with swine in Guangdong province, China. Compared to the non-exposed control group, a significantly higher proportion of subjects with occupational contact to pigs exhibited positive seroreaction against the classical H1N1 SIV. Participants aged 26-50 years were at high risk of classic swine H1N1 infections. Seropositive rate to 2009 pandemic H1N1 virus among swine workers was similar with controls. The major impact of age was apparent for younger populations. Our present study has documented evidence for swine influenza virus infection among persons with occupational swine exposures. The differences of seroreactivity for the two tested influenza subtypes emphasize the necessity of regular surveillance both in pigs and human.

Background: Considered an epicenter of pandemic influenza virus generation, southern China has recently seen an increasing number of human H7N9 infections. However, it is not the only threat. On 30 November 2013, a human H10N8 infection case was first described in China. The origin and genetic diversity of this novel virus is similar to that of H7N9 virus. As H10N8 avian influenza virus (AIV) was first identified from a duck in Guangdong Province during 2012 and there is also evidence of H10N8 infected dogs in this region, we sought to examine archived sera from animal workers to see if there was evidence of subclinical human infections before the first human H10N8 cases., Methods: We studied archived serum samples (cross-sectional study, convenience sample) collected between May and September 2013 from 710 animal workers and 107 non-animal exposed volunteers living in five cities of Guangdong Province. Study participants' sera were tested by horse red blood cells (RBCs) hemagglutination inhibition (HI) and microneutralization (MN) assays according to World Health Organization guidelines. The A/Jiangxi-Donghu/346-1/2013(H10N8) virus was used. Sera which have an HI assay ≥1:20 were further tested with the MN assay. Questionnaire data were examined for risk factor associations with positive serological assays. Risk factor analyses failed to identify specific factors associated with probable H10N8 infections., Results: Among the 827 sera, only 21 animal workers had an HI titer ≥1:20 (18 had an HI titer of 1:20 and 3 had an HI titer of 1:40). None of these 21 subjects reported experiencing any influenza symptoms during the three months before enrollment. Among the three subjects with HI titers of 1:40, two had MN antibody titers of 1:40, and one had a MN antibody titer of 1:80 (probable H10N8 infections)., Conclusions: Study data suggest that animal workers may have been infected with the H10N8 virus before the first recognized H10N8 human infection cases. It seems prudent to continue surveillance for H10N8 viruses among animal workers.

Background: The aim of this study was to assess the prevalence of the novel avian influenza A virus (H7N9) in three high risk groups. The groups were divided into those exposed through infected individuals, those exposed through poultry and those individuals exposed through the external environment, in the early stage of the epidemic in Guangdong Province, which is located in the southern region of China., Methods: Serologic studies were conducted among samples collected from individuals who had close contact with the first H7N9 infected patient reported in Guangdong Province, those who were most likely exposed to the first group of H7N9 infected poultry, and those who might have been exposed to H7N9 in the environmental settings, namely hemagglutinin inhibition (HI) and microneutralizaiton(MN) assays using three viruses as antigens., Results: The alignment results of the viral sequences indicated the similarity of the HA gene sequence among viruses from exposure to infected poultry, infected humans and contaminated environments were highly conserved. Seven samples of individuals exposed to contaminated environments were positive in the HI assay and one sample among them was positive in the MN assay using poultry H7N9 virus as the antigen. One sample was positive against human H7N9 virus and 3 samples were positive against environmental H7N9 among those that were in contact with infected patients in HI assay. None of these were positive in MN assay. All HI titers of the 240 samples from those individuals in contact with infected poultry were less than 40 aganist the antigens from three viruses., Conclusions: The results suggest that when the H7N9 virus was in the early stages of circulation in Guangdong Province, the antigenic sites of the HA proteins of the H7N9 strain isolated from different hosts were highly conserved. The risk of new infection is low in individuals who have contact with the infected patients, poultry or a contaminated environment in the early stages of the circulation of the H7N9 virus.

Human bocavirus (HBoV) is a nonenveloped, single-stranded DNA virus, classified recently into the genus Bocavirus in the family Parvoviridae. A recombinant baculovirus expression system was used to express the major capsid protein VP2 of HBoV1, HBoV2, HBoV3 and HBoV4 in insect cells. A large amount of the 61-kDa VP2 capsid protein (p61) of HBoVs was generated and efficiently released into the supernatant. The capsid protein was self-assembled into 22-nm-dia. virus-like particles (VLPs) with a buoyant density of 1.30g/cm(3). The morphology of HBoVs-LPs was similar to that of the native HBoV particles, and immunogenic studies demonstrated the cross-reactivity among HBoV1, HBoV2, HBoV3 and HBoV4. When VP1 and VP2 protein of HBoV1 were co-expressed in insect cells, both proteins were detected in the same fraction after CsCl gradient centrifugation, suggesting that the VP1 protein is a minor structural protein of HBoVs. We developed an ELISA using purified VLPs as the antigen and used it to detect antibodies against HBoV1, HBoV2, HBoV3 and HBoV4. A high prevalence of antibodies against HBoVs was found in a general population of healthy Japanese, indicating that HBoVs have spread throughout Japan., (Copyright © 2014 Elsevier B.V. All rights reserved.)

In parts of southern China, some large-scale swine farms are adjacent to lakes and ponds that are home to many types of birds. Some swine farms will also raise poultry for consumption and sale. Swine farms in rural China may be the source of the AIV outbreak. A seroepidemiological study was conducted among swine farm residents to understand the prevalence of antibodies against avian influenza virus (AIV) H9N2 in southern China. A total of 2,006 swine farm residents were sampled. Serum samples were tested for the presence of antibodies against H9N2 AIV by hemagglutination inhibition (HI) and microneutralization assays. A total of 37 serum samples from swine farm residents were HI positive for A/chicken/Guangdong/V/2008(H9N2), and 24 serum samples (all of which were also HI positive) were microneutralization assays positive for A/chicken/Guangdong/V/2008(H9N2). Due to the special pig farming model in southern China, the residents are in close contact with different kinds of birds. Thus, controlling bird-to-human transmission of AIV in swine farms with poultry may be an important means of preventing widespread AIV infection in humans., (© 2014 Wiley Periodicals, Inc.)

Infection of human with avian-like A (H1N1) swine influenza virus (SIV) occasionally occurs in China, suggesting a potential risk of cross-species transmission of the swine influenza H1N1 virus from pigs to humans, particularly to those having direct contact with pigs. A seroepidemiological study was conducted to assess the prevalence of antibodies against the avian-like A (H1N1) SIV among swine farm residents and pigs in southern China to evaluate the risk of infection to swine farm workers. Hemagglutination inhibition (HI) assays revealed that 11.17% (61/546) of the sera samples from swine farm residents in southern China were positive for antibodies against the avian-like A (H1N1) SIV. The difference in numbers of antibody-positive samples obtained from swine farm residents and a control group of healthy city residents was statistically significant (P = 0.031). In addition, 219 of the 1,180 serum samples from pigs were positive for the antibodies against an avian-like A (H1N1) SIV, A/swine/Guangdong/SS1/2013(H1N1), as assessed by HI. The data suggest that occupational exposure of swine farm residents and veterinarians in southern China to pigs may increase their risk of acquiring avian-like A (H1N1) SIV infection. According to a special pig farming model in southern China, the staff and residents are in close contact with infected pigs and may be among the first to become infected.

Background: Human Enterovirus 71 and Coxsackie A16 have caused many outbreaks in the last decade in mainland China, resulting in thousands of fatal cases. Seroepidemiology which provides important information to document population immunity is rare in China., Methodology/principal Findings: A cross sectional study of Enterovirus 71 (EV71) and Coxsackie A16 (CA16) seroprevalence was carried out in Guangdong, China, pre- and post- the 2010 hand, foot and mouth disease (HFMD) epidemic period. The levels of EV71 and CA16 specific antibodies were evaluated by a microneutralization test and the geometric mean titer (GMT) was calculated and compared. Our results indicated frequent infection by EV71 and CA16 in Guangdong before the 2010 epidemic. Only EV71 neutralizing antibody but not CA16 seroprevalence was significantly increased after the 2010 HFMD epidemic. Children less than 3 years old especially those aged 2 years showed the lowest positive rates for EV71 and CA16 NA before epidemic and the most significantly increased EV71 seroprevalence after epidemic. CA16 GMT values declined after the 2010 epidemic., Conclusions: These results indicate EV71 was the major pathogen of HFMD in Guangdong during the 2010 epidemic. The infection occurs largely in children less than 3 years, who should have first priority to receive an EV71 vaccine.

Background: Since 1997, the H5 avian influenza viruses (AIVs) circulating in China have become an international concern. Clade 2.3.2 of H5N1 AIVs is genetically distinct from the viruses isolated before 2007 and antigenically different from the vaccine strains widely used in China. Swine farms in rural China are thought to play an important role in AIVs ecology., Objectives: A seroepidemiological study was undertaken among swine farm residents and pigs to understand the prevalence of antibodies against H5N1 AIVs in southern China., Study Design: During the period March 24, 2008 to December 25, 2012,serum samples were collected from 1606 swine farm residents on 40 swine farms in southern China. A total of 1980 pigs' serum samples were collected in the same swine farms where swine workers' serum samples were collected from March 2009 to March 2013. For a control group, 104 serum samples were collected from healthy city residents in Nanchang. All the serum samples were collected to perform hemagglutination inhibition (HI) and (neutralization) NT assays to investigate the prevalence of H5N1 AIV infections in southern China., Results: Sixteen human samples were positive by HI assay and 10 of these were also positive by NT assay against H5N1. No serum samples from human control and pigs were HI positive for H5N1 AIV., Discussion: Our results demonstrate minimal transmission H5N1 AIV from birds to pigs in the swine farms studied and the risk of poultry-to-human and poultry-to-pig transmission for at least clades 2.3.2 seemed very low. This study provides the first data regarding antibodies against H5N1 AIV in humans and pigs on swine farms in China. The findings of this study can serve as a baseline for additional serologic studies to assess transmission of H5N1 viruses between avian species, pigs and swine workers., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Pigs are susceptible to both human and avian influenza viruses (AIV). Moreover, they are suspected of being the intermediate hosts or mixing vessels of pandemic influenza viruses. Researchers suspect that the influenza viruses are able to undergo reassortment or to adapt to various mammalian hosts while they incubate in pigs. For the present report, we conducted a serological surveillance of pigs in southern China from 2008 to 2012 to establish the prevalence of antibodies against H5N1 and H9N2 AIV. A total of one hundred pig farms from the Guangdong, Zhejiang, Fujian, and Yunnan Provinces were sampled, yielding a total of 3960 serum specimens. The haemagglutination inhibition (HI) tests revealed no evidence of H5 infection when the Clade 2.3.2 virus was used as the antigen, but a 4.6% positive rate of H9 infection was observed when using the Beijing/1/94-like virus as the antigen. The positive sera for H9 infection were further verified with neutralization tests, which confirmed a 3.7% rate of positive sera of H9 infection. In summary, the results imply that the swine populations in southern China had not been affected greatly by the H5N1 avian influenza virus. Nevertheless, these swine H9N2 influenza viruses might pose a threat to human health, and so researchers should continue to carry out swine influenza virus surveillance in China., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Background: Cases of human infections with H5N1 avian influenza viruses have been reported all over the world with the reason of direct contact with sick or diseased poultry, which suggests the direct contact with poultry may be one of the major risk factors for human infection., Objectives: In this study, we estimated the seroprevalence of antibodies against avian influenza A (H5N1) virus in veterinarians with exposure to avians., Study Design: From May 21, 2011 through April 22, 2012, 406 veterinarians exposure to poultry in Guangdong province were interviewed a questionnaire. A serum specimen was collected from participants to test for H5N1 antibodies by HI and NT assay., Results: None of the 406 sera from occupationally exposed veterinarians was positive according to the HI test and the NT test with the H5N1 AIV., Conclusion: Our seroepidemiologic survey suggests that the risk of avian-to-human transmission of the H5N1 AIV is very low based on the samples that we tested. However, prevention regarding the risk of H5N1 AIV transmission is essential and should be recommended as public health measures., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Background: Severe acute respiratory syndrome (SARS) is a newly discovered disease caused by a novel coronavirus. The present study studied the longitudinal profile of antibodies against SARS-coronavirus (SARS-CoV) in SARS patients and evaluated the clinical significance of these antibodies., Methods: Two methods, ELISA and indirect immunofluorescent assay, were used for the detection of the anti-SARS-CoV IgG and IgM in 335 serial sera from 98 SARS patients. In 18 patients, serum antibody profiles were investigated and antibody neutralization tests were performed from 7 to 720 days after the onset of symptoms., Results: The ratios of positive IgG/IgM by ELISA were 0/0, 45.4/39.4, 88.6/71.4, 96/88, 100/48.6, 100/30.9, 100/17.1, 100/0 per cent, respectively, on 1-7, 8-14, 15-21, 22-28, 29-60, 61-90, 91-180 and 181-720 days after the onset of symptoms. Antibodies were not detected within the first 7 days of illness, but IgG titre increased dramatically on day 15, reaching a peak on day 60, and remained high until day 180 from when it declined gradually until day 720. IgM was detected on day 15 and rapidly reached a peak, then declined gradually until it was undetectable on day 180. Neutralizing viral antibodies were demonstrated in the convalescence sera from SARS patients., Conclusion: The persistence of detectable IgG antibodies and neutralizing viral antibodies for up to 720 days suggest that SARS patients may be protected from recurrent SARS-CoV infection for up to 2 years.