Serological exposure to influenza A in cats from an area with wild birds positive for avian influenza

Influenza A is an emerging zoonotic virus with worldwide distribution. To our knowledge, no studies have been conducted to assess influenza A exposure in stray cats in regions with positive cases of wild birds. This study aimed to determine the seroprevalence of anti-influenza A antibodies in feral cats from a region in Spain with cases of positive wild birds. A cross-sectional study of stray cats (n = 183) was conducted between March 2022 and March 2023. The presence of antibodies against the influenza A virus was tested using a commercial enzyme-linked immunosorbent assay kit adapted for this study and confirmed by competitive enzyme-linked immunosorbent assay for the detection of antibodies against the haemagglutinin H5. During sample collection, none of the cats exhibited clinical signs of illness. Four of the 183 animals tested showed anti-influenza A antibodies by ELISA, and the seroprevalence of influenza A was 2.19% (95% confidence interval 0.85%-5.48%). Due to the low number of positive cases detected, it appears that cats did not have an important epidemiological role in influenza A transmission during this period.

Seroprevalence of anti-SARS-CoV-2 antibodies in household domestic ferrets (Mustela putorius furo) in Spain, 2019-2023

SARS-CoV-2 is the causal agent of Coronavirus Disease 2019 (COVID-19) in humans that emerged in late 2019. This virus is able to infect humans and different animal species. Among pets, cats and ferrets are more susceptible to be infected by the SARS-CoV-2. Epidemiological studies are an important tool to provide information under natural conditions of exposure to SARS-CoV-2 virus. In comparison to cats, limited epidemiological studies have been performed in domestic ferrets (Mustela putorius furo) reporting the presence of antibodies in this species. This study analysed the presence of anti-SARS-CoV-2 antibodies in 432 cliend-owned ferrets from different geographical areas of Spain during the different waves of COVID-19 outbreaks from December 2019 to May 2023 (42 months). For this purpose, anti-SARS-CoV-2 antibodies were detected by an enzyme-linked immunosorbent method (ELISA) using the receptor binding domain (RBD) of Spike antigen and confirmed by serum virus neutralization assay. Eighteen of the 432 ferrets included were seroreactive by the in-house ELISA (4.17%, 95% Confidence Interval (CI): 2.65-6.49). In this sense, the wave of COVID-19 with the higher number of seropositive ferrets occurred during the seventh wave when the different Omicron subvariants were the dominant virus variants. Our results suggest that the risk of SARS-CoV-2 transmission in domestic ferrets in natural conditions is low. Further research is need to evaluate the potential risk of transmission of SARS-CoV-2 from human to pets.

Molecular and Serological Studies on Potential SARS-CoV-2 Infection among 43 Lemurs under Human Care-Evidence for Past Infection in at Least One Individual

In the setting of the recent COVID-19 pandemic, transmission of SARS-CoV-2 to animals has been reported in both domestic and wild animals and is a matter of concern. Given the genetic and functional similarities to humans, non-human primates merit particular attention. In the case of lemurs, generally considered endangered, they are believed to be susceptible to SARS-CoV-2 infection. We have conducted a study for evidence of SARS-CoV-2 infection among the 43 lemurs of Mundomar, a zoological park in Benidorm, Spain. They belong to two endangered lemur species, 23 black-and-white ruffed lemurs (Varecia variegata) and 20 ring-tailed lemurs (Lemur catta). Health assessments conducted in 2022 and 2023 included molecular analyses for SARS-CoV-2 RNA of oral and rectal swabs using two different RT-qPCR assays, always with negative results for SARS-CoV-2 in all animals. The assessment also included serological testing for antibodies against the receptor-binding domain (RBD) of the spike protein (S) of SARS-CoV-2, which again yielded negative results in all animals except one black-and-white ruffed lemur, supporting prior infection of that animal with SARS-CoV-2. Our data, while not indicating a high susceptibility of lemurs to SARS-CoV-2 infection, show that they can be infected, adding to the existing information body on potential ways for SARS-CoV-2 virus spreading in zoos, highlighting the need for animal surveillance for the virus.

The dynamics of neutralizing antibodies against SARS-CoV-2 in cats naturally exposed to virus reveals an increase in antibody activity after re-infection

Severe Acute Respiratory Syndrome Coronavirus 2 is the causative agent of Coronavirus Disease 2019 in humans. To date, little is known about the persistence of antibodies against SARS-CoV-2 in animals under natural conditions, in particular susceptible pets such as cat. This study reports the detection and monitoring of the humoral response against SARS-CoV-2 including the detection of immunoglobulins G specific for receptor binding domain of SARS-CoV-2 spike protein by an enzyme-linked immunosorbent assay and neutralizing antibodies by virus neutralization assay. Results showed that these antibodies last longer than 16 months in two naturally apparently healthy infected cats with the absence of clinicopathological findings during the follow-up. Moreover, re-infection is also possible with an important increase in virus neutralization test titers in both animals with no evident systemic signs found during each physical examination and with values of hematologic and biochemical parameters inside the normal reference intervals. Our results confirm a slow but progressive decrease of the kinetics and immunity of neutralizing antibodies in cats after the infection. Furthermore, similar to humans SARS-CoV-2 reinfection can stimulate an increase of the neutralizing antibodies determined by these two serological techniques in domestic cats.

A ventilation early warning system (VEWS) for diaphanous workspaces considering COVID-19 and future pandemics scenarios

The COVID-19 pandemic has generated new needs due to the associated health risks and, more specifically, its rapid infection rate. Prevention measures to avoid contagions in indoor spaces, especially in office and public buildings (e.g., hospitals, public administration, educational centres, etc.), have led to the need for adequate ventilation to dilute the possible concentration of the virus. This article presents our contribution to this new challenge, namely the Ventilation Early Warning System (VEWS) which has aims to adapt the operation of the current Heating, Ventilating and Air Conditioning (HVAC) systems to the ventilation needs of diaphanous workspaces, based on a Smart Campus Digital Twin (SCDT) framework approach, while maintaining sustainability. Different technologies such as the Internet of Things (IoT), Building Information Modelling (BIM) and Artificial Intelligence (AI) algorithms are combined to collect and integrate monitoring data (historical records, real-time information, and location-related patterns) to carry out forecasting simulations in this digital twin. The generated outputs serve to assist facility managers in their building governance, considering the appropriate application of health measures to reduce the risk of coronavirus contagion in combination with sustainability criteria. The article also provides the results of the implementation of the VEWS in a university workspace as a case study. Its application has made it possible to detect and warn of inadequate ventilation situations for the daily flow of people in the different controlled zones.

Surveillance of Immunological Status after Vaccination by two Serological Assays based on SARS-CoV-2 Spike Protein

Purpose

Two serological assays, an Enzyme-Linked Immunosorbent Assay (ELISA) and a Lateral Flow Assay (LFA), have been developed based on the SARS-CoV-2 recombinant Receptor Binding Domain (RBD-ELISA) and the combination of Trimeric Spike (S) and Nucleoprotein (N), S-LFA and N-LFA, respectively, as candidate tools for both indirect measurement of virus circulation and assessment of infection and vaccine-induced immunity.

Methods & Materials

A total of 1272 human serum samples collected from volunteers (SARS-CoV-2 infected, non-infected or vaccinated) were evaluated by the two assays. For the RBD-ELISA, plates were coated with RBD, sera were added at 1/5 dilution and bound antibodies were detected with RBD labelled with Horseradish Peroxidase. For the LFA, two parallel strips were used: one for detection of N-specific antibodies (Hoste A. el al, 2020); and another one for detection of S-specific antibodies, using S both as capture and detector reagent. Twenty microliters of blood or ten microliters of serum were applied to each cassette and results were interpreted after ten minutes.

A seroneutralization assay was used as reference for the detection of neutralizing antibodies with RBD-ELISA and Reference sera (World Health Organization), for determination of the Limit of detection (LoD). MedCalc® 10 software was used for statistical analysis.

Results

The potential diagnostic application with sera from naturally infected and non-infected volunteers showed sensitivity, specificity and agreement (kappa) values of 95.1%, 99.0% and 0.94 respectively for RBD-ELISA; while 97.2%, 99.3% and 0.967 respectively for N-LFA; or 93.2% 98.3 %, 0.923, respectively for S-LFA. Serum samples from vaccinated individuals were analyzed for the specific detection of antibodies to the S protein: for vaccinated but non-infected individuals, sensitivity reached 97.3% after 15 days post-second vaccination dose whereas for previously infected people reached 100% after only 15 days post-first dose. The performance of RBD-ELISA showed good agreement with seroneutralization and excellent agreement with S-LFA (kappa 0.979).

Conclusion

The dual N/S LFA represents a valuable tool to detect SARS-CoV-2 infection due to its complementary information on N and S-specific antibody response. Furthermore, the S-LFA and RBD-ELISA are both proven to be able to determine the extent of antibody response after vaccination.

8 fs laser pulses from a compact gas-filled multi-pass cell

Compression of 42 fs, 0.29 mJ pulses from a Ti:Sapphire amplifier down to 8 fs (approximately 3 optical cycles) is demonstrated by means of spectral broadening in a compact multi-pass cell filled with argon. The efficiency of the nonlinear pulse compression is limited to 45 % mostly by losses in the mirrors of the cell. The experimental results are supported by 3-dimensional numerical simulations of the nonlinear pulse propagation in the cell that allow us to study spatio-spectral properties of the pulses after spectral broadening.

P3747Does pulmonary vein isolation have similar results for treating AF in Chagas disease?

Background

AF is reported in up to 20% of patients with Chagas, a prevalent disease in Latin-America. PV isolation (PVI) in the cornerstone of AF ablation. However, in Chagas cardiopathy (ChC), microvascular and autonomic abnormalities, atrial fibrosis and sinoatrial dysfunction are possible mechanisms of AF. Therefore, the results of PVI may be different in this subgroup.

Objectives

To describe long-term results of AF ablation in pts with Chagas versus non-Chagas disease (ChC x NonCh) and evaluate risk factors for post-ablation recurrence.

Methods

This is a prospective, single-center study that included pts with nonvalvular AF who underwent PVI between 2013 and 2016. All procedures were guided by eletroanatomic mapping and intracardiac echocardiogram. Categorical variables were analyzed using chi-square test and numerical variables with t-student test. Binary logistic regression was performed to identify independent predictors of recurrence of any sustained atrial tachyarrhythmias.

Results

Ablation was performed in 160 pts (54±15 yo, 59% male): 42 pts with ChC (26%, 62±8 yo) and 118 NonChC (74%, 53±15 yo; p<0,001)). There was no difference in AF type (38x34% paroxysmal, 42x43% persistent, and 19x23% long-term persistent, p=NS) and left atrium diameter (38±5 vs 40±8mm, p=NS). In ChC the mean CHADSVASC score was higher (2.4 vs 1.4, p<0,001) and LVEF was lower (52±18% vs 64±8%, p=0.02). After a follow-up of 31±14 mo and 1.1 ablation per group, recurrence of AF/AT was higher in ChC (33% vs 14%, p=0.03) although more pts with Chagas were on AAD (71 vs 31%, p<0,001). During follow-up, occurrence of embolic events and cardiac or all-cause mortality were not different between groups (0% vs 1.7%, p=NS and 2.4 vs 1.7% p=NS; for ChC vs and NonChC, respectively).

At multivariate analysis, long-term persistent AF, hypertension and Chagas disease (HR= 2.21, 3.36 and 3.16, respectively) were independent predictors of recurrence.

Conclusions

Chagas disease is an independent predictor of recurrence after PVI. Further studies should address which strategy is more appropriate to this group of patients.

Development of a novel lateral flow assay for detection of African swine fever in blood

Background

African swine fever (ASF) is a viral infectious disease of domestic and wild suids of all breeds and ages, causing a wide range of hemorrhagic syndromes and frequently characterized by high mortality. The disease is endemic in Sub-Saharan Africa and Sardinia. Since 2007, it has also been present in different countries of Eastern Europe, where control measures have not been effective so far. The continued spread poses a serious threat to the swine industry worldwide. In the absence of vaccine, early detection of infected animals is of paramount importance for control of the outbreak, to prevent the transmission of the virus to healthy animals and subsequent spreading of the disease. Current laboratory diagnosis is mainly based on virological methods (antigen and genome detection) and serodiagnosis.

Results

In the present work, a Lateral Flow Assay (LFA) for antigen detection has been developed and evaluated. The test is based on the use of a MAb against VP72 protein of ASFV, the major viral capsid protein and highly immunogenic. First experiments using VP72 viral and recombinant protein or inactivated culture virus showed promising results with a sensitivity similar to that of a commercially available Antigen-ELISA. Moreover, these strips were tested with blood from experimentally infected pigs and field animals and the results compared with those of PCR and Antigen-ELISA. For the experimentally infected samples, there was an excellent correlation between the LFA and the ELISA, while the PCR always showed to be more sensitive (38 % positive samples by PCR versus 27 % by LFA). The LFA was demonstrated to be positive for animals with circulating virus levels exceeding 10⁴ HAU. With the field samples, once again, the PCR detected more positives than either the Antigen-ELISA or LFA, although here the number of positive samples scored by the LFA exceeded the values obtained with the Antigen-ELISA, showing 60 % positivity vs 48 % for the ELISA. For the two groups of sera, the specificity was close to 100 % indicating that hardly any false positive samples were found.

Conclusions

The newly developed LFA allows rapid and reliable detection of ASFV, at field and laboratory level, providing a new useful tool for control programs and in situations where laboratory support and skilled personnel are limited.

Threshold Evolution as an Analysis of the Different Pulse Frequencies in Rechargeable Systems for Spinal Cord Stimulation

INTRODUCTION

Pulse frequency (Fc) is one of the most important parameters in neurostimulation, with Pulse Amplitude (Pw) and Amplitude (I). Up to certain Fc, increasing the number of pulses will generate action potentials in neighboring neural structures and may facilitate deeper penetration of the electromagnetic fields. In addition, changes in frequency modify the patient's sensation with stimulation.

MATERIALS/METHODS

Fifty patients previously implanted with rechargeable current control spinal cord stimulation. With pulse width fixed at 300 μsec, we stimulated at 26 different Fc values between 40 and 1200 Hz and determine the influence of these changes on different stimulation thresholds: perception threshold (Tp ), therapeutic perception (Tt), and discomfort threshold (Td). Simultaneously, paresthesia coverage of the painful area and patient's sensation and satisfaction related to the quality of stimulation were recorded.

RESULTS

Pulse Fc is inversely proportional to stimulation thresholds and this influence is statistically significant (p < 0.05). As Pulse Fc increased from 40 to 1200 Hz, the mean threshold decreases from 7.25 to 1.38 mA (Tp ), 8.17 to 1.63 (Tt ), and 9.20 to 1.85 (Td). Significant differences for Tp and Tt began at 750 Hz (Tp , Tt ) and at 650 Hz for Td. No significant influence was found regarding paresthesia coverage. As expected, Fc affects significantly patient's sensation and satisfaction.

DISCUSSION

Changes in Fc affect the quality of paresthesias. Within the evaluated parameters higher frequencies are inversely proportional to stimulation thresholds and Tt. It seems that Fc is a vital parameter to achieve therapeutic success.

CONCLUSIONS

Changes in Fc is a useful parameter to modulate the patient's sensory perception. Fc can be successfully used to adjust the quality of the paresthesias and to modify patient's subjective sensation. We showed that as the frequency increases, the patient's satisfaction with the perceived sensation decreases, suggesting that higher Fc may need to be set up at subthreshold amplitude to achieve positive response.

Development of a Microsphere-based Immunoassay for Serological Detection of African Horse Sickness Virus and Comparison with Other Diagnostic Techniques

African horse sickness (AHS) is a viral disease that causes high morbidity and mortality rates in susceptible Equidae and therefore significant economic losses. More rapid, sensitive and specific assays are required by diagnostic laboratories to support effective surveillance programmes. A novel microsphere-based immunoassay (Luminex assay) in which beads are coated with recombinant AHS virus (AHSV) structural protein 7 (VP7) has been developed for serological detection of antibodies against VP7 of any AHSV serotype. The performance of this assay was compared with that of a commercial enzyme-linked immunosorbent assay (ELISA) and commercial lateral flow assay (LFA) on a large panel of serum samples from uninfected horses (n = 92), from a reference library of all AHSV serotypes (n = 9), on samples from horses experimentally infected with AHSV (n = 114), and on samples from West African horses suspected of having AHS (n = 85). The Luminex assay gave the same negative results as ELISA when used to test the samples from uninfected horses. Both assays detected antibodies to all nine AHSV serotypes. In contrast, the Luminex assay detected a higher rate of anti-VP7 positivity in the West African field samples than did ELISA or LFA. The Luminex assay detected anti-VP7 positivity in experimentally infected horses at 7 days post-infection, compared to 13 days for ELISA. This novel immunoassay provides a platform for developing multiplex assays, in which the presence of antibodies against multiple ASHV antigens can be detected simultaneously. This would be useful for serotyping or for differentiating infected from vaccinated animals.

Is the introduction of another variable to the strength-duration curve necessary in neurostimulation?

INTRODUCTION

Neurostimulation is the process and technology derived from the application of electricity with different parameters to activate or inhibit nerve pathways. Pulse width (Pw) is the duration of each electrical impulse and, along with amplitude (I), determines the total energy charge of the stimulation.

OBJECTIVES

The aim of the study was to test Pw values to find the most adequate pulse widths in rechargeable systems to obtain the largest coverage of the painful area, the most comfortable paresthesia, and the greatest patient satisfaction.

MATERIAL AND METHODS

A study of the parameters was performed, varying Pw while maintaining a fixed frequency at 50 Hz. Data on perception threshold (Tp ), discomfort threshold (Td ), and therapeutic threshold (Tt ) were recorded, applying 14 increasing Pw values ranging from 50 µsec to 1000 µsec. Lastly, the behavior of the therapeutic range (TR), the coverage of the painful area, the subjective patient perception of paresthesia, and the degree of patient satisfaction were assessed.

RESULTS

The findings after analyzing the different thresholds were as follows: When varying the Pw, the differences obtained at each threshold (Tp , Tt , and Td ) were statistically significant (p < 0.05). The differences among the resulting Tp values and among the resulting Tt values were statistically significant when varying Pw from 50 up to 600 µsec (p < 0.05). For Pw levels 600 µsec and up, no differences were observed in these thresholds. In the case of Td , significant differences existed as Pw increased from 50 to 700 µsec (p ≤ 0.05). The coverage increased in a statistically significant way (p < 0.05) from Pw values of 50 µsec to 300 µsec. Good or very good subjective perception was shown at about Pw 300 µsec.

CONCLUSIONS

The patient paresthesia coverage was introduced as an extra variable in the chronaxie-rheobase curve, allowing the adjustment of Pw values for optimal programming. The coverage of the patient against the current chronaxie-rheobase formula will be represented on three axes; an extra axis (z) will appear, multiplying each combination of Pw value and amplitude by the percentage of coverage corresponding to those values. Using this new comparison of chronaxie-rheobase curve vs. coverage, maximum Pw values will be obtained different from those obtained by classic methods.

Effects of movement and postural positions in spinal cord stimulation in the new rechargeable systems

BACKGROUND

Despite recent developments in implantable neurostimulation devices, the adjustment of stimulation levels to the patient's postural changes has remained a problem so far.

OBJECTIVE

This study was conducted with the newest rechargeable devices, in order to compare its results with the ones published from conventional systems.

STUDY DESIGN

It is a prospective study.

SETTING

In 46 patients implanted with rechargeable constant current stimulation systems we measured impedance, stimulation thresholds, therapeutic range, as well patients' satisfaction and sensation in 7 different body postures.

RESULTS

Data analysis was performed in 46 patients, whose most frequent pathologies were failed back surgery syndrome (FBSS) and complex regional pain syndrome (CRPS). The lowest amplitude needed to reach the different thresholds was always scored in the supine decubitus position, with no significant changes in the therapeutic range and impedance. For all stimulation thresholds, there is always a difference between the supine position and all other postures. No statistically significant differences with regard to patients' satisfaction and sensation were found for the different postures.

LIMITATIONS

Sample sample size.

CONCLUSION

The findings of the present work are similar to those described in previous publications that showed the relationship between postural changes and several stimulation thresholds and pulse energy. The posture which requires lower energy - and whose corresponding therapeutic range (TR) is narrower--is supine decubitus.

TMPRSS4 regulates levels of integrin α5 in NSCLC through miR-205 activity to promote metastasis

Background:

TMPRSS4 is a membrane-anchored protease involved in cell migration and invasion in different cancer types including lung cancer. TMPRSS4 expression is increased in NSCLC and its inhibition through shRNA reduces lung metastasis. However, molecular mechanisms leading to the protumorigenic regulation of TMPRSS4 in lung cancer are unknown.

Methods:

miR-205 was identified as an overexpressed gene upon TMPRSS4 downregulation through microarray analysis. Cell migration and invasion assays and in vivo lung primary tumour and metastasis models were used for functional analysis of miR-205 overexpression in H2170 and H441 cell lines. Luciferase assays were used to identify a new miR-205 direct target in NSCLC.

Results:

miR-205 overexpression promoted an epithelial phenotype with increased E-cadherin and reduced fibronectin. Furthermore, miR-205 expression caused a G₀/G₁ cell cycle arrest and inhibition of cell growth, migration, attachment to fibronectin, primary tumour growth and metastasis formation in vivo. Integrin α5 (a proinvasive protein) was identified as a new miR-205 direct target in NSCLC. Integrin α5 downregulation in lung cancer cells resulted in complete abrogation of cell migration, a decreased capacity to adhere to fibronectin and reduced in vivo tumour growth, compared with control cells. TMPRSS4 silencing resulted in a concomitant reduction of integrin α5 levels.

Conclusion:

We have demonstrated for the first time a new molecular pathway that connects TMPRSS4 and integrin α5 through miR-205 to regulate cancer cell invasion and metastasis. Our results will help designing new therapeutic strategies to inhibit this novel pathway in NSCLC.

The identification of sandfly species, from an area of Argentina with endemic leishmaniasis, by the PCR-based analysis of the gene coding for 18S ribosomal RNA

The area around Río Blanco, in the Orán department in the north of the Argentinian province of Salta, is endemic for American tegumentary leishmaniasis. In an attempt to facilitate the identification of the Lutzomyia species in this area, sequences of the gene coding for the 18S ribosomal RNA (rRNA) of sandflies caught in a Shannon trap were explored, by a combination of PCR and analysis of restriction-fragment-length polymorphism (RFLP). The products from the PCR, which employed two primers developed specifically for this study (Lu.18S 1S and Lu.18S AR), were cloned into a commercial vector (pGEM-T Easy) so that their nucleotide sequences could be investigated. In the RFLP analysis, the products of single and double digestion with the AfaI and HapII restriction enzymes were separated by electrophoresis in 3% or 4% agarose. Taken together with the results of a morphological investigation of the flies, the resultant DNA fragment patterns were sufficient to identify most of the sandflies caught as Lu. neivai. Although two other species, Lu. cortelezzii and Lu. sallesi, were collected, they were relatively rare and only identified morphologically. A single digestion of the 18S-rRNA gene sequences with AfaI or HapII appeared sufficient and useful for the identification of Lu. neivai from the north of Salta province, and for several other Lutzomyia species.

Aortic Homograft for Pulmonary Artery Augmentation in Single Lung Transplantation

We present a case of unilateral lung transplantation in which a segment of the donor's descending aorta was used as a homograft for pulmonary artery augmentation in the donor lung. This technique can be used when the donor's lung artery has been cut at the base of the hilum during the harvesting procedure.

Influence of flanking sequences on presentation efficiency of a CD8+ cytotoxic T-cell epitope delivered by parvovirus-like particles

We have previously developed an antigen-delivery system based on hybrid recombinant porcine parvovirus-like particles (PPV-VLPs) formed by the self-assembly of the VP2 protein of PPV carrying a foreign epitope at its N terminus. In this study, different constructs were made containing a CD8(+) T-cell epitope of chicken ovalbumin (OVA) to analyse the influence of the sequence inserted into VP2 on the correct processing of VLPs by antigen-presenting cells. We analysed the presentation of the OVA epitope inserted without flanking sequences or with either different natural flanking sequences or with the natural flanking sequences of a CD8(+) T-cell epitope from the lymphocytic choriomeningitis virus nucleoprotein, and as a dimer with or without linker sequences. All constructs were studied in terms of level of expression, assembly of VLPs and ability to deliver the inserted epitope into the MHC I pathway. The presentation of the OVA epitope was considerably improved by insertion of short natural flanking sequences, which indicated the relevance of the flanking sequences on the processing of PPV-VLPs. Only PPV-VLPs carrying two copies of the OVA epitope linked by two glycines were able to be properly processed, suggesting that the introduction of flexible residues between the two consecutive OVA epitopes may be necessary for the correct presentation of these dimers by PPV-VLPs. These results provide information to improve the insertion of epitopes into PPV-VLPs to facilitate their processing and presentation by MHC class I molecules.

Large scale production and downstream processing of a recombinant porcine parvovirus vaccine

Porcine parvovirus (PPV) virus-like particles (VLPs) constitute a potential vaccine for prevention of parvovirus-induced reproductive failure in gilts. Here we report the development of a large scale (25 l) production process for PPV-VLPs with baculovirus-infected insect cells. A low multiplicity of infection (MOI) strategy was efficiently applied avoiding the use of an extra baculovirus expansion step. The optimal harvest time was defined at 120 h post-infection at the MOI used, with the cell concentration at infection being 1.5x10(6) cells/ml. An efficient purification scheme using centrifugation, precipitation and ultrafiltration/diafiltration as stepwise unit operations was developed. The global yield of the downstream process was 68%. Baculovirus inactivation with Triton X-100 was successfully integrated into the purification scheme without an increase in the number of process stages. Immunogenicity of the PPV-VLPs tested in guinea pigs was similar to highly purified reference material produced from cells cultured in the presence of serum-containing medium. These results indicate the feasibility of industrial scale production of PPV-VLPs in the baculovirus system, safety of the product, and the potency of the product for vaccine application.

Effect of different baculovirus inactivation procedures on the integrity and immunogenicity of porcine parvovirus-like particles

We have demonstrated earlier the usefulness of recombinant porcine parvovirus (PPV) virus-like particles (VLPs) as an efficient recombinant vaccine for PPV. Here, we have demonstrated that preparations of PPV VLPs could be contaminated by recombinant baculoviruses. Since these baculoviruses can be a problem for the registration and safety requirements of the recombinant vaccine, we have tested different baculovirus inactivation strategies, studying simultaneously the integrity and immunogenicity of the VLPs. These methods were pasteurization, treatment with detergents and alkylation with binary ethylenimine (BEI). The structural and functional integrity of the PPV VLPs after the inactivation treatments were analyzed by electron microscopy, hemagglutination, double antibody sandwich (DAS)-ELISA and immunogenicity studies. Binary ethylenimine and Triton X-100 inactivated particles maintained all the original structural and antigenic properties. In addition, PPV VLPs were subjected to size-exclusion chromatography to analyze the presence of VP2 monomers or any other contaminant. The resulting highly purified material was used as the standard of reference to quantify PPV VLPs in order to determine the dose of vaccine by DAS-ELISA. After immunization experiments in guinea pigs, the antibody titers obtained with all the inactivation procedures were very similar. Triton X-100 treatment was selected for further testing in animals because of the speed, simplicity and safety of the overall procedure.

Minor displacements in the insertion site provoke major differences in the induction of antibody responses by chimeric parvovirus-like particles

An antigen-delivery system based on hybrid virus-like particles (VLPs) formed by the self-assembly of the capsid VP2 protein of canine parvovirus (CPV) and expressing foreign peptides was investigated. In this report, we have studied the effects of inserting the poliovirus C3:B epitope in the four loops and the C terminus of the CPV VP2 on the particle structure and immunogenicity. Epitope insertions in the four loops allowed the recovery of capsids in all of the mutants. However, only insertions of the C3:B epitope in VP2 residue 225 of the loop 2 were able to elicit a significant anti-peptide antibody response, but not poliovirus-neutralizing antibodies, probably because residue 225 is located in an small depression of the surface. To fine modulate the insertion site in loop 2, a cassette-mutagenesis was carried out to insert the epitope in adjacent positions 226, 227, and 228. The epitope C3:B inserted into these positions was well recognized by the specific monoclonal antibody C3 by immunoelectron microscopy. BALB/c mice immunized with these chimeric C3:B CPV:VLPs were able to elicit an strong neutralizing antibody response (>3 log(10) units) against poliovirus type 1 (Mahoney strain). Therefore, minor displacements in the insertion place cause dramatic changes in the accessibility of the epitope and the induction of antibody responses.

Parvovirus-like particles as vaccine vectors

A wide array of systems have been developed to improve "classic" vaccines. The use of small polypeptides able to elicit potent antibody and cytotoxic responses seems to have enormous potential in the design of safer vaccines. While peptide coupling to large soluble proteins such as keyhole limpet hemocyanin is the current method of choice for eliciting antibody responses and insertion in live viruses for cytotoxic T-lymphocyte responses, alternative cheaper and/or safer methods will clearly be required in the future. Virus-like particles constitute very immunogenic molecules that allow for covalent coupling of the epitopes of interest in a simple way. In this article, we detail the methodology employed for the preparation of efficient virus vectors as delivery systems. We used parvovirus as the model for the design of new vaccine vectors. Recently parvovirus-like particles have been engineered to express foreign polypeptides in certain positions, resulting in the production of large quantities of highly immunogenic peptides, and to induce strong antibody, helper-T-cell, and cytotoxic T-lymphocyte responses. We discuss the different alternatives and the necessary steps to carry out this process, placing special emphasis on the flow of decisions that need to be made during the project.

Engineering parvovirus-like particles for the induction of B-cell, CD4(+) and CTL responses

An antigen delivery system based on hybrid recombinant parvovirus-like particles (VLPs) formed by the self-assembly of the capsid VP2 protein of porcine (PPV) or canine parvovirus (CPV) expressed in insect cells with the baculovirus system has been developed. PPV:VLPs containing a CD8(+) epitope from the LCMV nucleoprotein evoked a potent CTL response and were able to protect mice against a lethal infection with the virus. Also, PPV:VLPs containing the C3:T epitope from poliovirus elicited a CD4(+)3 log(10) units) against poliovirus. The possibility of combining different types of epitopes in different positions of a single particle to stimulate different branches of the immune system paves the way to the production of more potent vaccines in a simple and cheap way.

Intranasal delivery of recombinant parvovirus-like particles elicits cytotoxic T-cell and neutralizing antibody responses

We previously demonstrated that chimeric porcine parvovirus-like particles (PPV:VLP) carrying heterologous epitopes, when injected intraperitoneally into mice without adjuvant, activate strong CD4(+) and CD8(+) T-cell responses specific for the foreign epitopes. In the present study, we investigated the immunogenicity of PPV:VLP carrying a CD8(+) T-cell epitope from the lymphocytic choriomeningitis virus (LCMV) administered by mucosal routes. Mice immunized intranasally with recombinant PPV:VLP, in the absence of adjuvant, developed high levels of PPV-specific immunoglobulin G (IgG) and/or IgA in their serum, as well as in mucosal sites such as the bronchoalveolar and intestinal fluids. Antibodies in sera from mice immunized parenterally or intranasally with PPV:VLP were strongly neutralizing in vitro. Intranasal immunization with PPV:VLP carrying the LCMV CD8(+) T-cell epitope also elicited a strong peptide-specific cytotoxic-T-cell (CTL) response. In contrast, mice orally immunized with recombinant PPV:VLP did not develop any antibody or CTL responses. We also showed that mice primed with PPV:VLP are still able to develop strong CTL responses after subsequent immunization with chimeric PPV:VLP carrying a foreign CD8(+) T-cell epitope. These results highlight the attractive potential of PPV:VLP as a safe, nonreplicating antigen carrier to stimulate systemic and mucosal immunity after nasal administration.

A recombinant virus-like particle system derived from parvovirus as an efficient antigen carrier to elicit a polarized Th1 immune response without adjuvant

Hybrid virus-like particles (VLP) were prepared by self-assembly of the modified porcine parvovirus (PPV) VP2 capsid protein carrying a CD8+ or CD4+ T cell epitope. Immunization of mice with a single dose of these hybrid pseudo-particles, without adjuvant, induced strong cytotoxic T lymphocyte and T helper (Th) responses against the reporter epitope. The Th response was characterized by a Th1 phenotype. We also analyzed in vitro the uptake mechanism of these parvovirus-like particles and the processing requirements associated with presentation by MHC molecules. Although previously shown to be presented by MHC class I molecules, these particles also enter very efficiently the MHC class II endocytic pathway, and behave as conventional exogenous antigens. Indeed, the processing of chimeric PPV:VLP was performed in endosomal/lysosomal acidic vesicles and the presentation of the foreign epitope carried by these particles was sensitive to brefeldin A and cycloheximide, showing that the foreign peptide was loaded on nascent MHC class II molecules. These results give some indication of how PPV:VLP can be presented by MHC class I and class II molecules, and underscore the wide potency of such VLP system to deliver foreign antigens for vaccine design.

Identification of domains in canine parvovirus VP2 essential for the assembly of virus-like particles

Canine parvovirus capsids are composed of 60 copies of VP2 and 6 to 10 copies of VPl. To locate essential sites of interaction between VP2 monomers, we have analyzed the effects of a number of VP2 deletion mutants representing the amino terminus and the four major loops of the surface, using as an assay the formation of virus-like particles (VLPs) expressed by recombinant baculoviruses. For the amino terminus we constructed three mutants with progressively larger deletions, i.e., 9, 14, and 24 amino acids. Deletions of 9 and 14 amino acids did not affect the morphology and assembly capabilities of the mutants. However, the mutant with the 24-amino-acid deletion did not show hemagglutination properties or correct VLP morphology, stressing again the relevance of the RNER domain in canine parvovirus functionality. Three of the four mutants with deletions in the loops failed to make correct VLPs, indicating that these regions are essential for correct capsid assembly and morphology. Only the mutant with the deletion in loop 2 was able to assemble in regular VLPs, suggesting that this loop has little or no effect in capsid morphogenesis. Further research has demonstrated that this region can tolerate the insertion of foreign epitopes that are correctly exposed in the surface of the capsid. This result opens the door to the use of these VLPs for antigen delivery.

Immunogenicity of poliovirus B and T cell epitopes presented by hybrid porcine parvovirus particles

We have analysed the potential capacity of hybrid porcine parvovirus (PPV) capsids to present foreign epitopes to the immune system. Foreign sequences were introduced into the N and C termini of PPV VP2, which was previously shown to assemble spontaneously into parvovirus-like particles. The integrity of the C terminus was shown to be essential for preserving the structure of the capsid and therefore could not be used for epitope fusion. In contrast, insertion of sequences corresponding to T and B cell poliovirus epitopes in the N terminus did not alter the formation of particles. Moreover, the chimeric capsids containing the C3:T epitope were able to induce a T cell response in vivo. However, hybrid particles containing the C3:B epitope fused to the N terminus did not induce any peptide-specific antibody response, suggesting that the inserted B cell epitope was not exposed at the surface of the particles. These results show that the N terminus in PPV empty capsids is not an adequate site for insertion of B cell epitopes, but may be useful for T cell epitope presentation and suggest that the N terminus is located in an internal position.

The three C-terminal residues of human respiratory syncytial virus G glycoprotein (Long strain) are essential for integrity of multiple epitopes distinguishable by antiidiotypic antibodies

Recently isolated escape mutants of human respiratory syncytial virus (HRSV) are described. The mutants were selected after serial passage of the Long strain in the presence of monoclonal antibodies directed against the attachment (G) glycoprotein. The genetic changes associated to the mutant phenotype were nucleotide substitutions leading to either amino acid replacements or new stop codons that shorten the G polypeptide by one amino acid. Sequence changes within the three C-terminal residues of the G molecule abolished multiple epitopes, some of them being distinguished only by virus-binding inhibition of the corresponding antibodies with a panel of antiidiotypic antisera. These results extend previous studies that demonstrated the extreme capacity of HRSV to accommodate multiple sequence changes within the antigenically relevant G protein C-terminal third. These results are discussed in terms of both the antigenic structure of the G molecule and the generation of new antigenic variants that mimic natural variants of HRSV.

Thioether excretion, urinary mutagenicity, and metabolic phenotype in smokers

In 81 healthy individuals (51 smokers and 30 nonsmokers) biological indicators of internal exposure to electrophiles derived from tobacco smoke through metabolism were evaluated. Subgroups of smokers have been established in relation to the amount and type of tobacco smoked. Acetylator and hydroxylator phenotypes have been used as biomarkers of genetically determined susceptibility to cancer development. Urinary concentrations of thioethers (UT) and mutagenicity, with S9 mix for microsomal activation (MI-S9), were higher in smokers in relation to the level of tobacco consumption, but not to the type of tobacco. The "Slow acetylators-rapid oxidizers" category was not significant from the "rapid acetylators-rapid oxidizers" for values of UT and MI-S9. Data suggest that the biomarkers of exposure used in this study lack the necessary specificity to ascertain genetically determined susceptibility to cancer induced by tobacco smoking.

Loss of conserved cysteine residues in the attachment (G) glycoprotein of two human respiratory syncytial virus escape mutants that contain multiple A-G substitutions (hypermutations)

Two escape mutants (R10c/1 and R10c/10) of the human respiratory syncytial (RS) virus Long strain were selected after serial passage in the presence of monoclonal antibody c793 directed against the G glycoprotein. This antibody recognizes an epitope which is shared by all viruses of the two antigenic subgroups in which human RS virus isolates have been subdivided. The mutant viruses had lost most of the G protein conserved and subgroup-specific epitopes but maintained the strain-variable epitopes. The two mutants had 10 or 11 nucleotide changes in the central region of the G protein gene when compared to the Long sequence, and almost all of those changes were different between the two mutants. The majority of the nucleotide changes involved A-G transitions (U-C in the positive sense) that resulted in amino acid substitutions. Each mutant had a total of six amino acid changes, and the changes were different between the two mutants. Unexpectedly, each mutant lost one of the four conserved cysteines of the G protein, and a different cysteine (Cys 182 or 186) was lost in each mutant. They are, in fact, the first reported RS viruses with only three cysteines in the G protein ectodomain. The genetic mechanism that generated the escape mutants and its relevance for the natural history of RS virus are discussed.

Premature stop codons in the G glycoprotein of human respiratory syncytial viruses resistant to neutralization by monoclonal antibodies

Mutants of human respiratory syncytial (RS) virus which escaped neutralization by monoclonal antibodies directed against the G glycoprotein were selected from the Long strain. Most mutants showed drastic antigenic changes, reflected in the lack of reactivity with several anti-G antibodies, including the one used for selection. Sequence analysis revealed the presence of in-frame premature stop codons in the mutated G genes which shortened the G polypeptide by between 11 and 42 amino acids. In contrast, two mutants selected with monoclonal antibody 25G contained two amino acid substitutions (Phe-265----Leu and Leu-274----Pro) and had lost only the capacity to bind the antibody used in their selection. These results demonstrate that the carboxy-terminal end of the G molecule is dispensable for infectivity in tissue culture and indicate the importance of this part of the G protein in determining its antigenicity.

[Erythrocyte glutathione and urinary thioethers in smokers]

The carcinogenic mechanism of smoking is related with the production of electrophilic reactants and their possible covalent binding with DNA. On the other hand, there are detoxifying mechanisms such as glutathione-S-transferase, which results in mercaptopuric derivatives that are excreted in the urine. The integrity of the erythrocyte membrane is maintained by reduced glutathione among other factors. In the present study, the concentrations of erythrocyte reduced glutathione (GSH) and urinary thioethers (UT) were measured in a sample of 81 subjects divided in two groups. Group I: 30 nonsmokers; group II: 51 smokers, subdivided in group IIA (26 individuals smoking 10-20 cigarettes/day) and group IIB (25 individuals smoking more than 20 cigarettes/day). In the present study, the usefulness of GSH and UT as markers of collective internal contamination and of individual risk regarding tobacco exposure were evaluated. A higher concentration of GSH was found in smokers than in nonsmokers (F = 6.84, p less than 0.02). Regarding VT elimination, a significant increase in these parameters was found in association with the grade of smoking (p less than 0.05). They were higher in the subjects from the subgroup IIB than in the subgroup IIA (moderate smokers).