Foot and mouth disease virus transmission among vaccinated pigs after exposure to virus shedding pigs

The aim of this study was to design a transmission experiment that enabled quantification of the effectiveness of vaccination against foot and mouth disease (FMD) virus in groups of pigs. Previous experiments showed that intradermal injection of pigs with FMD virus 14 days after vaccination was not suitable to start an infection chain, as inoculated vaccinated pigs resisted challenge. Therefore, we carried out two experiments in which we used direct contact to a non-vaccinated pig as route of infection. In the first experiment only the vaccine effect on susceptibility was quantified by exposing pigs, either vaccinated 14 days before or not vaccinated, each to a non-vaccinated seeder pig inoculated with FMD virus O/NET/2001. Since no significant differences were observed between contact infections in vaccinated or non-vaccinated pigs, we performed a second experiment in which both susceptibility and infectivity were subject to vaccination. We quantified virus transmission in homogenous groups of vaccinated or non-vaccinated pigs in which the infection chain was started by exposure to a third group of non-vaccinated infected pigs. Transmission occurred to all contact-exposed pigs in the non-vaccinated groups and to 9 out of 10 contact-exposed pigs in the vaccinated groups. The rate of transmission (beta) was significantly reduced in the vaccine group. Yet, the estimated reproduction ratio in both groups was still above 1. In conclusion, by adjusting our transmission study design and challenge method, we were able to quantify transmission of FMDV among vaccinated pigs. According to this study a single vaccination was not sufficient to stop pig to pig virus transmission. With these results major outbreaks may still be expected, even in groups of vaccinated pigs.

pKDR/KDR ratio predicts response in a phase I/II pharmacodynamic study of erlotinib and bevacizumab for recurrent or metastatic head and neck cancer (HNC)

6021

Background: EGFR activation up-regulates VEGF, which has been correlated with resistance to anti-EGFR agents. We previously reported early results (Vokes, JCO, 2005) of a phase I-II study of the EGFR inhibitor erlotinib (E) with the VEGF antibody bevacizumab (B) in recurrent or metastatic HNC. We now present results from the pharmacodynamic analysis as well as updated outcome data. Methods: Phase I/II trial of fixed dose erlotinib (E) 150 mg orally daily with escalation of bevacizumab (B) to a maximum of 15 mg/kg q 3 weeks and continued at 15 mg/kg in the phase II portion. Pts were randomized to receive the initial bevacizumab dose on either day 1 or 15. Paired biopsies were taken at baseline and after 2 weeks of treatment (after E alone or E+B) and analyzed by immunofluorescence and laser scanning analysis for target inhibition and apoptosis markers (VEGFR2/KDR, EGFR, CD31, and respective activated forms [pKDR, pEGFR]). Results: Paired biopsies were available from 20 patients. At baseline pKDR/KDR (ratio) correlated with clinical outcome and differed significantly between responses (CR>SD: p<0.01; CR>PD: p<0.0005). Interestingly, endothelial cell EGFR levels also appeared to correlate with response (CR+SD>PD: p<0.03). Paired tissue samples showed that E or E +B treatment increased apoptosis in tumor cells (pre: 0.96%, post: 7.02%: p<0.05) and endothelial cells (pre: 0%, post: 12%: p=0.15). Further, E+B treatment reduced expression of endothelial KDR, EGFR and VEGF levels compared to E alone. We previously reported an overall response rate of 14.6% (48 evaluable patients in the phase II cohort). Updated median follow-up was 7.3 months (2.1 years for patients still alive). The updated median overall/ progression free survival was 7.3 months/ 3.9 months with 30.6%/ 8.2% of patients alive at 1/2 years. Conclusions: Compared to E alone the combination of E + B showed increased inhibition of endothelial survival factors. pKDR/KDR appears to predict response to E+B. The promising clinical efficacy of E+B and potential predictive biomarkers warrant further validation in larger cohorts. (Supported by NIH N01 CM-57018–16)

No significant financial relationships to disclose.

Updated results of a phase II trial integrating gefitinib (G) into concurrent chemoradiation (CRT) followed by G adjuvant therapy for locally advanced head and neck cancer (HNC)

6028

Background: This study was undertaken to evaluate the tolerability and efficacy of substituting G for paclitaxel into a well- described CRT regimen (Clin Cancer Res 9: 5936; JCO 21: 320) and continuing G as adjuvant therapy. Endpoints included complete response (CR) rate to CRT, progression-free (PFS), disease-specific (DSS) and overall survival (OS), and local & distant control rates. Methods: Previously untreated subjects with stage III, IVa, or IVb squamous cell, poorly differentiated carcinomas, or lymphoepithelioma were enrolled. Organ sparing surgery was allowed. Subjects received 2 cycles of carboplatin/paclitaxel induction followed by CRT with G (250 mg PO qd), 5- fluorouracil, hydroxyurea, and twice daily radiation on day 1–5 of five 14d cycles. G was continued for 2 years from the start of CRT. Results: From 2/03 to 10/04, 67 eligible subjects accrued including 51 males; median age 56; ECOG PS 0 in 47, 1 in 19, and 2 in 1; stage IV in 61 (91%). With median follow-up of 858 days, 9 have had progressive disease (PD, 3 distant, 5 local, 1 with both) and 15 have died (12 related to HNC). Estimated OS=83% at 2y, 73% at 3y; PFS=77% at 2y, 64% at 3y; and DSS=86% at 2y, 80% at 3y. In 56 evaluable subjects we observed 51 CR (91 %), 4 partial responses and 1 PD after CRT. Non-evaluable subjects underwent surgery prior to CRT (10), or died prior to evaluation (1). Grade 3/4 toxicity included mucositis (75%/10%), dermatitis (29%/3%), rash (4%/0%) and diarrhea (1%/0%). Sixty-two patients received maintenance gefitinib, with 60 reliably reporting doses (median days on gefitinib=667). Reasons for holding G included LFT abnormalities, patient refusal, diarrhea, rash, recurrence, hospitalization for acute illness, and early death. Conclusions: Adding G to concurrent CRT after induction therapy, and as adjuvant therapy is tolerable and feasible. Favorable survival and CR data suggest that this is a promising regimen for patients with locally advanced HNC.

[Table: see text]

Randomized phase II study of concomitant chemoradiotherapy with 5-fluorouracil-hydroxyurea (FHX) compared to FHX and bevazicumab (BFHX) in intermediate stage head and neck cancer (HNC)

6034

Background: Preclinical data supports inhibition of vascular endothelial growth factor (VEGF) to improve tumor radiosensitivity. Phase I data demonstates that BFHX was tolerable in HNC (Seiwert, pASCO2006). Here we present preliminary toxicity data from a randomized phase II trial in pts with PS 0–2, stage II-IV (T2–4 N0–1 M0) HNC. Methods: Pts were randomized (2:1) to receive either BFHX or FHX. Planned sample size is 72pts. Chemotherapy consists of 5- FU (600 mg/m2/day continuous infusion for 120 hrs), hydroxyurea (500 mg PO q12 hours for 11 doses) with or without bevacizumab (10 mg/kg IV on day 1), concurrently with twice daily RT on a week on-week off schedule. Results: 21pts (BFHX 14pt and FHX 7pt) have completed therapy and are evaluable for toxicity. Pt characteristics in the BFHX and FHX arms are: median age 61 vs. 55 yrs, males 78% vs. 85%, stage II-III 57% vs. 86% and IV 43% vs. 14%. All pts have PS 0–1. 20 pts are evaluable for toxicity. Two episodes of gr3 leukopenia and one episode of gr 3 neutropenia were observed in the BFHX arm; whereas no gr3 hematologic toxicities were seen in the FHX arm. Mucositis (Gr3 - BFHX 85% vs. FHX 86%) and dermatitis (Gr3 - 0% vs. 14%) were observed in every pt. Other common non- hematologic toxicities were pain (100% vs. 86%), fatigue (77% vs. 86%) and anorexia (62% vs. 51%). No hemorrhagic events were observed. In the BFHX arm, one episode of deep venous thrombosis and one non-neutropenic death from sepsis were observed. Pathologic complete response rates were 92% and 100% in the BFHX and FHX arms, respectively. Conclusions: Preliminary results support the tolerability of BFHX. Toxicity appears to be similar to FHX with an apparent increase in leukopenia consistent with prior reports. Bleeding complications were not increased with BFHX.

No significant financial relationships to disclose.

PET-CT-based auto-contouring in non-small-cell lung cancer correlates with pathology and reduces interobserver variability in the delineation of the primary tumor and involved nodal volumes

PURPOSE

To compare source-to-background ratio (SBR)-based PET-CT auto-delineation with pathology in non-small-cell lung cancer (NSCLC) and to investigate whether auto-delineation reduces the interobserver variability compared with manual PET-CT-based gross tumor volume (GTV) delineation.

METHODS AND MATERIALS

Source-to-background ratio-based auto-delineation was compared with macroscopic tumor dimensions to assess its validity in 23 tumors. Thereafter, GTVs were delineated manually on 33 PET-CT scans by five observers for the primary tumor (GTV-1) and the involved lymph nodes (GTV-2). The delineation was repeated after 6 months with the auto-contour provided. This contour was edited by the observers. For comparison, the concordance index (CI) was calculated, defined as the ratio of intersection and the union of two volumes (A intersection B)/(A union or logical sum B).

RESULTS

The maximal tumor diameter of the SBR-based auto-contour correlated strongly with the macroscopic diameter of primary tumors (correlation coefficient = 0.90) and was shown to be accurate for involved lymph nodes (sensitivity 67%, specificity 95%). The median auto-contour-based target volumes were smaller than those defined by manual delineation for GTV-1 (31.8 and 34.6 cm(3), respectively; p = 0.001) and GTV-2 (16.3 and 21.8 cm(3), respectively; p = 0.02). The auto-contour-based method showed higher CIs than the manual method for GTV-1 (0.74 and 0.70 cm(3), respectively; p < 0.001) and GTV-2 (0.60 and 0.51 cm(3), respectively; p = 0.11).

CONCLUSION

Source-to-background ratio-based auto-delineation showed a good correlation with pathology, decreased the delineated volumes of the GTVs, and reduced the interobserver variability. Auto-contouring may further improve the quality of target delineation in NSCLC patients.

Passive immunization of guinea pigs with llama single-domain antibody fragments against foot-and-mouth disease

Foot-and-mouth disease (FMD) is a highly contagious disease that occasionally causes outbreaks in Europe. There is a need for therapies that provide rapid protection against FMD in outbreak situations. We aim to provide such rapid protection by passive immunization with llama single-domain antibody fragments (VHHs). Twenty-four VHHs binding serotype O FMDV in vitro were isolated from immunized llamas by phage display and expressed in bakers yeast for further characterization. They recognized four functionally independent antigenic sites. Six strongly FMDV neutralizing VHHs bound to a peptide representing the GH-loop of viral protein 1 known to be involved in binding to the cellular receptor of FMDV. Clone M8, recognizing this antigenic site, and clone M23, recognizing another antigenic site, showed synergistic in vitro virus neutralization. Three FMDV specific VHHs were PEGylated in order to decrease their rapid blood clearance and thus enable in vivo guinea pig protection experiments. Passive immunization with individual VHHs showed no protection, but a mixture of M8 and M23 showed partial transient protection. The protection afforded by these VHHs was however low as compared to the complete protection afforded by convalescent guinea pig serum. In contrast, these VHHs showed far more efficient in vitro FMDV neutralization than convalescent guinea pig serum. This lack of correlation between in vitro neutralization and in vivo protection lends further credence to the notion that opsonophagocytosis of FMDV is important for protection in vivo.

Quantification of foot and mouth disease virus excretion and transmission within groups of lambs with and without vaccination

Sheep are well known to be susceptible for foot and mouth disease virus (FMDV), but it is unknown whether the infection can spread and persist in a sheep population. We therefore quantified virus transmission by performing experiments with FMD virus strain O/NET/2001 in groups of lambs. We used six groups of four lambs each, in which half of each group was inoculated and the other half was contact-exposed. To quantify the effectiveness of a single vaccination we also included six groups of four lambs each, vaccinated with O Manisa vaccine, 14 days prior to inoculation. Oropharyngeal fluid was obtained with a swab (OPF-swab), and blood samples were collected daily to determine virus excretion and serological response. We calculated the transmission rate beta (the number of new infections per day per infectious animal), and the reproduction ratio R (the number of secondary infections caused by one infectious individual). The mean daily virus excretion and the number of days the lambs excreted virus in the OPF differed significantly between vaccinated and non-vaccinated lambs. The transmission rate beta in the unvaccinated groups was 0.105 (95% confidence limit 0.044; 0.253) per day. The duration of the infectious period (T) was 21.11 (95% confidence limit 10.6; 42.1) days. With the final size of infection we estimated the reproduction ratio R in the non-vaccinated groups to be 1.14 (0.3; 3.3), and in vaccinated groups 0.22 (0.01; 1.78). Virus transmission as quantified by the final size did not differ statistically between the vaccinated and the non-vaccinated groups of lambs. In conclusion, FMDV seems able to persist in a sheep population, although the reproduction ratio was only slightly larger than one. As a consequence, vaccination might only have a small effect on transmission, in spite of the fact that virus excretion and duration of virus excretion is significantly reduced after vaccination.

Time trends in the maximal uptake of FDG on PET scan during thoracic radiotherapy. A prospective study in locally advanced non-small cell lung cancer (NSCLC) patients

BACKGROUND AND PURPOSE

18F-fluoro-2-deoxy-glucose (FDG) uptake on PET scan is a prognostic factor for outcome in NSCLC. We investigated changes in FDG uptake during fractionated radiotherapy in relation to metabolic response with the ultimate aim to adapt treatment according to early response.

METHODS AND MATERIALS

Twenty-three patients, medically inoperable or with advanced NSCLC, underwent four repeated PET-CT scans before, during and after radiotherapy. Changes in maximal standardized uptake value (SUVmax) were described. Patients were treated with accelerated radiotherapy with a total tumour-dose depending on normal tissue dose constraints.

RESULTS

The most striking result was the large intra-individual heterogeneity in the evolution of SUVmax. For the total group a non-significant increase in the first week (p=0.05), and a decrease in the second week (p=0.02) and after radiotherapy (p<0.01) was observed. Different time trends were shown for responders (no change during radiotherapy) and non-responders (48% increase during first week, p=0.02 and 15% decrease in the second week, p=0.04). Non-responders had a higher SUVmax on all time points investigated.

CONCLUSIONS

Time trends in SUVmax showed a large intra-individual heterogeneity and different patterns for metabolic responders and non-responders. These new findings may reflect intrinsic tumour characteristics and might finally be useful to adapt treatment.

The effect of vaccination on foot and mouth disease virus transmission among dairy cows

The aim of this study was to quantify the effect of a single vaccination of dairy cows on foot and mouth disease virus (FMDV) transmission. To estimate if vaccination could significantly reduce virus transmission, we performed two replicates of a transmission experiment with one group of vaccinated and one group of non-vaccinated dairy cows (ten animals per group). Half of both groups were intranasally inoculated, with FMDV field isolate O/NET2001, and housed with the other half of the group (contact-exposed cows) from the next day onwards. Virus transmission was quantified by estimating the reproduction ratio R, which is the average number of secondary cases caused by one infectious animal. In the non-vaccinated groups all cows became infected and Rnv was significantly above 1. In the vaccinated groups infection was demonstrated in three inoculated cows, and no transmission was observed (Rv was 0, not significantly below 1). Transmission was significantly reduced in the groups of vaccinated cows when compared to the groups of unvaccinated cows. Our findings indicate that after a single vaccination cows are protected against infection of FMD and that most likely no virus transmission will occur within a vaccinated herd.

Intra-patient variability of tumor volume and tumor motion during conventionally fractionated radiotherapy for locally advanced non-small-cell lung cancer: a prospective clinical study

PURPOSE

The aim of this study was to investigate the change in tumor volume, motion, and breathing frequency during a course of radiotherapy, for locally advanced non-small-cell lung cancer.

METHODS AND MATERIALS

A total of 23 patients underwent computed tomography-positron emission tomography (CT-PET) and respiration correlated CT scans before treatment, which was repeated in the first and second weeks after the start of radiotherapy. Patients were treated with an accelerated fractionation schedule, 1.8 Gy twice a day, with a total tumor dose depending on preset dose constraints for the lungs and spinal cord.

RESULTS

A striking heterogeneity of tumor volume changes was observed at all time points. In some patients the volume decreased >30% (3/23), whereas in others the volume increased >30% (4/24); but for the majority of patients (16/23), the tumor volume changed only slightly (<30%). No significant changes in average tumor motion or breathing frequencies were observed during treatment. Although a number of changes in individual tumor motion were seen, only in 1 patient would this have led to an increase of the internal margin >1 mm in 1 direction, 1 week after the start of treatment, and in 3 patients for 1 direction, 2 weeks after the start of the treatment.

CONCLUSION

In this patients in this study, a large variability in changes in tumor volume was observed. This underscores the need for repeated imaging during the course of radiotherapy. However, the changes in tumor motion are small, which indicates that repeated respiration correlated CT does not appear to be necessary.

Comparative evaluation of six ELISAs for the detection of antibodies to the non-structural proteins of foot-and-mouth disease virus

To validate the use of serology in substantiating freedom from infection after foot-and-mouth disease (FMD) outbreaks have been controlled by measures that include vaccination, 3551 sera were tested with six assays that detect antibodies to the non-structural proteins of FMD virus. The sera came from naïve, vaccinated, infected and vaccinated-and-infected animals; two-thirds from cattle, the remainder from sheep and pigs. The assays were covariant for sensitivity, but not necessarily for specificity. A commercial kit from Cedi-diagnostics and an in-house assay from IZS-Brescia were comparable to the NCPanaftosa-screening index method described in the Diagnostic Manual of the World Animal Health Organisation. Using these three tests the specificity and sensitivity for the detection of carriers in vaccinated cattle approaches or exceeds 99% and 90%, respectively.

Serological and mucosal immune responses after vaccination and infection with FMDV in pigs

The aim of this study was to determine a possible correlation between humoral immune responses shortly after vaccination and protection against foot-and-mouth disease virus (FMDV) infection and to study the serological and mucosal antibody responses after vaccination and infection. We used three groups of ten pigs, one non-vaccinated group, one group vaccinated with a single dose vaccine and one group vaccinated with a four-fold dose vaccine. At 7 days post vaccination, five pigs per group were challenged intra-dermally with FMDV O TAW 3/97 and the remaining pigs of each group were contact-exposed to the inoculated pigs. In each group, virus excretion and number of contact infections were quantified. The serological and mucosal antibody responses were evaluated until 116 days post infection. Vaccination resulted in a significant decrease of virus excretion. Stepwise linear regression analysis of variables from individual vaccinated pigs revealed the virus excretion after challenge to be correlated with neutralising antibody titres at the day of challenge (p<0.01). In serum and OPF samples comparable isotype-specific antibody responses (IgM, IgG and IgA), could be detected after vaccination as well as after infection. Remarkably, the pigs with the highest IgA responses after vaccination were protected against contact exposure. After infection, a long lasting (up to 116dpi) IgA response was seen in the non-vaccinated and to a lesser extent in the single dose vaccinated pigs. The induction of NSP antibodies in the vaccinated pigs after infection was lower and of shorter duration as compared to the non-vaccinated infected pigs. This experiment shows that vaccination can reduce virus excretion in pigs, which will contribute to reduced transmission of FMDV in the field, even if the pigs are not fully protected. Moreover, vaccines that induce local IgA responses may be more effective, which merits further investigation.

An “in silico” clinical trial comparing free breathing, slow and respiration correlated computed tomography in lung cancer patients

BACKGROUND AND PURPOSE

To determine which method of internal target volume (ITV) definition based on a respiration correlated CT (RCCT) allows optimal tumor coverage.

MATERIAL AND METHODS

A free breathing CT (CT(fb)) and an RCCT scan were acquired in 41 lung cancer patients. For 12 patients with a motion >7 mm in any direction, a detailed analysis was made. The RCCT scan was used to measure tumor motion and to reconstruct a CT at 10 phases (CT(10ph)), amongst which the half ventilation CT (CT(hv)). By averaging the CT(10ph), a slow CT (CT(slow)) was reconstructed. Based on those scans ITVs were delineated and treatments were planned, where for the ITV(hv) an internal margin of (motion amplitude)/4 was used. The treatment plans for the ITVs were projected on the 10 respiration phases. Doses were calculated and averaged over the 10 phases to estimate the actual CTV coverage.

RESULTS

The 3D motion was on average 8.1+/-1.0 mm (1 SD) for all patients; no statistical difference was found between lower and upper lobe tumors. The ITV(slow) was the smallest volume on average (142+/-38 cm(3)), followed by the ITV(hv) (160+/-40 cm(3)), the ITV(10ph) (161+/-41 cm(3)) and the ITV(fb) (250+/-63 cm(3)). Mean CTV doses were between 95% and 107% of the prescribed dose for nearly all patients and treatment plans. Analysis of the CTV coverage suggested that underdosage may occur when the CT(slow) is used and a geographic miss occurred using the CT(fb), due to uncorrect localization of the average tumor position.

CONCLUSIONS

The CT(hv) seems to be the optimal dataset for delineation, using an adequate anisotropic internal margin of (motion amplitude)/4.

Foot-and-mouth disease virus: a first inter-laboratory comparison trial to evaluate virus isolation and RT-PCR detection methods

Five European reference laboratories participated in an exercise to evaluate the sensitivity and specificity of their routinely employed RT-PCR tests and cell cultures for the detection and isolation of foot-and-mouth disease (FMD) virus. Five identical sets of 20 coded samples were prepared from 10 vesicular epithelia, which were derived from submissions from suspect cases of FMD or swine vesicular disease (SVD). Sixteen samples were derived from six FMD virus positive epithelia representing four different serotypes (two each of types O and A and one each of types Asia 1 and SAT 2), two from samples which had been found to be negative by antigen ELISA and virus isolation (VI) in cell culture and two from SVD virus positive epithelia. Some of the FMD virus positive samples were prepared from 10-fold serial dilutions of three of the initial suspensions. Each laboratory tested the samples by one or more of its available RT-PCR procedures and inoculated cell cultures that it routinely uses for FMD diagnosis in attempts to isolate virus, the specificity of which was confirmed by antigen ELISA. The best of the RT-PCR assays used in each laboratory gave comparable results while the sensitivity of cell cultures was variable from high in one laboratory, moderate in two and low in two others. This prototype panel of samples would appear suitable for external quality assurance of these tests but would benefit from the inclusion of more negative samples and an extension in the serial dilution range of one or more of the FMD positive sample titration series.

A phase I study of bevacizumab (B) with fluorouracil (F) and hydroxyurea (H) with concomitant radiotherapy (X) (B-FHX) for poor prognosis head and neck cancer (HNC)

5530

Background: Increased VEGF levels are found in HNC. Preclinical data suggest synergistic antitumor activity of B with radiation and chemotherapy. We conducted a Phase I dose escalation study to determine the maximum tolerated dose and dose limiting toxicity (DLT) of B, when added to infusional 5-FU, Hydroxyurea (HU), and daily radiotherapy administered every other week in patients (pts) with poor prognosis HNC. Methods: Eligible pts had recurrent, or newly diagnosed HNC with high risk of recurrence, ± metastatic disease requiring local control, ECOG PS ≤2, and life expectancy >12 weeks. Two week cycles were repeated 6–7 times (see table ). Results: 43 pts were treated (34 completed). DLT was reached at level 3 with 2 pts having gr 3 transaminase elevations and one pt gr 4 neutropenia. Treatment of 7 (6 evaluable) pts on level 4 resulted in one DLT (SMV thrombosis) and this dose level was chosen for expanded evaluation. In all level 4 pts (N = 27) gr 3 mucositis occured in 73.1% and gr 3 hand-foot syndrome in 15.4%. Additional gr 3 or worse toxicities in the expanded level 4 included: esophageal bleed (tumor bed, grade 5), stroke (grade 4), carotid rupture (3 wks post RT, grade 5), and neck ulceration with need for carotid stent (3 months post RT, grade 4). One sudden death of unclear etiology occurred. Median overall survival is 389 days. One/two year survival is 52.1/26%. Median survival for patients treated with re-irradiation for recurrent, non-metastatic HNC is 314 days; one/two year survival is 45.9/17.2%. With a median follow-up of 317 days 13 patients are still alive (12 are cancer free). Conclusions: B can be integrated with FHX chemoradiotherapy at a dose of 10 mg/m2 every 2 weeks. While B related toxicities are seen, there appears to be no major synergistic toxicity. Long term activity is observed in this very high risk patient population. A randomized phase II trial of FHX with or without B in a lower risk population is ongoing.

[Table: see text]

No significant financial relationships to disclose.

Comparison of immune responses after intra-typic heterologous and homologous vaccination against foot-and-mouth disease virus infection in pigs

This study compares the immune responses and protection induced by intra-typic heterologous vaccination with that induced by homologous vaccination against challenge with foot-and-mouth disease virus (FMDV). Humoral and cell-mediated immune responses and protection against challenge with FMDV O Taiwan were examined in a non-vaccinated group, a group vaccinated with O Taiwan FMD vaccine and a group vaccinated with O Manisa FMD vaccine. Five pigs from each group were challenged with FMDV type O Taiwan 14 days after vaccination and five other pigs were contact-exposed to the inoculated pigs. Both homologous and heterologous vaccination protected against challenge with FMDV O Taiwan at 2 weeks after vaccination. In the heterologous vaccinated group, cross-neutralizing antibody titres against O Taiwan could be detected although the ratio 'r(1)' was 0.4, which was significantly smaller than the critical r-value. Cell-mediated immune responses were detected after both homologous and heterologous vaccination. Virus-induced in vitro lymphocyte (cross-) proliferation and production of both a Th1-type (IFN-gamma) and a Th2-type (IL-10) cytokine response were demonstrated in cultures of peripheral blood mononuclear cells (PBMC). The findings show that heterologous (emergency) vaccination can prevent clinical disease and shedding of virus. The induction of the cell-mediated immune responses after (heterologous) vaccination needs more research but data on these responses might provide additional tools for both vaccine choice and vaccine development.

Herd sensitivity in relation to test sensitivity in swine vesicular disease serological tests

After the swine vesicular disease (SVD) outbreaks in 1992 in the Netherlands a national monitoring programme was initiated, testing 12 samples from every pig farm three times per year. In this monitoring a slightly higher cut-off was used than the cut-off agreed on within the European community. The author has analysed the effect of this higher cut-off on the percentage of false positive and false negative results, using information on SVD antibody titres in sera obtained from the monitoring programme and the outbreaks in 1992 and 1994. The number of false positive results was reduced by 63% when using the higher cut-off. On average the test sensitivity was reduced from 100% to 88%, resulting in a change of the average herd sensitivity from 91.7% to 91.5%, when testing 12 samples per farm. When three samples per farm were tested, the average herd sensitivity changed from 64.9% to 62.9%. The results further indicate that, in contrast to what is generally presumed, there is a relationship between test sensitivity and the prevalence of infection. The results clearly show that sample size is far more important in obtaining a high herd sensitivity than achieving a high test sensitivity.

Vaccination against foot and mouth disease reduces virus transmission in groups of calves

The aim of vaccination during an epidemic of foot and mouth disease (FMD) is not to induce clinical protection, but to reduce virus transmission. Since no quantitative data were available on the effectiveness of vaccination in cattle, we investigated whether a single vaccination against FMD could reduce virus transmission in groups of calves by estimating the reproduction ratio R, i.e. the average number of secondary cases caused by one infectious animal in a susceptible population. We performed two experiments with six groups of either four vaccinated or four non-vaccinated calves each. Vaccination was carried out with O(1) Manisa vaccine. Two weeks after vaccination, two calves per group were inoculated intra-nasally with FMDV field isolate O/NET 2001. The two other calves were contact-exposed to the inoculated calves. Contact infections were observed by clinical inspection, virus isolation and RT-PCR on heparinised blood, oro-pharyngeal fluid and probang samples and antibody response to non-structural proteins. In all six non-vaccinated groups, transmission to contact-exposed calves was recorded; in the vaccinated groups, virus transmission was observed to one contact-exposed calf. In the non-vaccinated groups R(c) was 2.52 and significantly above 1, whereas in the vaccinated groups R(v)=0.18 and significantly below 1, indicating that vaccination may successfully be applied as additional intervention tool to reduce virus transmission in a future epidemic of FMD.

Linear hoof defects in sheep infected with foot-and-mouth disease

During the epidemic of foot-and-mouth disease (FMD) in The Netherlands in 2001, a sheep farm was identified that had been subclinically infected with the disease. The FMD virus genome was detected in 12 of 16 probang samples collected from the sheep and the virus was isolated from four of these samples. Linear defects were observed, 1 to 3 cm from the coronary band, in the hooves of several of the sheep. The defects were thought to have been caused by the FMD infection. It was thought that the distance of the defects from the coronary band might be an indication of the time since the animals had been infected. To determine the growth rate of the claws of sheep, the growth of the hoof horn of uninfected lambs and ewes was measured; in the lambs the growth rate was 0.44 mm per day and in the ewes it was 0.29 mm per day.