Tag Archives: myeloperoxidase

The type strain is the most virulent of the three

The type 1 strain is the most virulent of the three types in animal models (Marsden et al., 1980; Boulger et al., 1979; WHO, 2012) yet it causes the lowest frequency of vaccine-associated poliomyelitis and the identification of the attenuating mutations responsible has been the most difficult. If there is little selective pressure to increase its fitness further the type 1 strain should be more stable in vaccinees than the other types. If there are more mutations each with a lesser effect then selection to high virulence will also be more difficult because more mutations will be needed. Thus paradoxically a more virulent virus can be both more effective and less virulent in the vaccinee particularly if it contains many weakly attenuating mutations. The development of a live attenuated vaccine can therefore be an extremely subtle and complicated process and is difficult to approach on a purely rational basis. In myeloperoxidase the type 3 strain infects recipients given trivalent vaccine less often than the others, the mutations have a more readily detectable effect in animal models and the 5′ non-coding mutation at least is selected against more strongly in the human gut. This is consistent with strong selection against a strong attenuating effect giving a genetically unstable vaccine.
Poliomyelitis has almost been eradicated from the world thanks to the programme initiated by the World Health Organization in 1988 (WHO, 1988, 2014a). Wild type 2 virus was last isolated from a case in October 1999 apart from an incident involving of OPV batches which were probably sabotaged (Deshpande et al., 2003). At the time of writing wild type 3 virus was last isolated in 2012 (WHO, 2014a), and the last case of any type in India was in January 2011, which given the social conditions is a colossal achievement. The last case of wild type 1 poliomyelitis in Africa to date was in August 2014. An outbreak in Syria in 2014 seems to have been brought under control as there have been no cases for six months, another extraordinary achievement given the lethal conditions prevailing. Currently Pakistan has most of the world׳s cases of wild type poliomyelitis although there are some cases in Afghanistan. There is a real if fragile possibility that poliomyelitis caused by wild type virus is about to disappear. The success of the programme so far is due to the use of the live attenuated vaccines in mass campaigns so that transmission of the wild type virus is broken. However the vaccines can also revert to virulence in vaccine associated cases, and in healthy recipients the viruses change freely by mutation and recombination in response to events. Therefore in regions where vaccine coverage is poor, and the immunised and non-immunised mix in conditions of sub optimal hygiene, it is not surprising that viruses can be selected that will transmit freely from one person to another and that such viruses cause poliomyelitis. They are termed circulating vaccine derived polio viruses (cVDPV) and there are many instances of their occurrence, although given the amount of vaccine used they occur at a low frequency (Kew et al., 2002). Virus excreted by hypogammaglobulinemic individuals becomes highly virulent but does not seem to be as transmissible as cVDPVs although there is no obvious reason why they should not become so. These viruses are termed immunodeficient vaccine derived polioviruses (iVDPVs). The vaccine therefore poses a problem for the final eradication of polio and this is the final issue. cVDPVs may be eradicated by vaccinating properly; not all vaccinated individuals give rise to transmissible strains. Chronic excreters of iVDPVs usually stop eventually but some can clearly continue for decades (MacCallum, 1971; MacLennan et al., 2004) and remain a problem to be solved.

Yellow fever
Yellow fever virus is the archetypal flavivirus and is transmitted by the mosquito Aedes aegypti, as first hypothesised by Carlos Finlay in 1881 and shown by experimental transmission to army volunteers by Walter Reed in 1900 (Frierson, 2010). The virus causes yellow fever which can have fatality rates of 20–80% depending on the circumstances; while none of Walter Reed׳s 14 volunteers died a repeat of the experiment in Cuba by John Guiteras in 42 individuals resulted in severe disease in 8 and three deaths (Frierson, 2010). Many other laboratory and field workers became infected in the course of their studies (including Max Theiler who developed the vaccine in use today) and several died. Max Theiler fortunately survived. Yellow fever is now confined mostly to low and middle income countries but was initially also present in Europe and the Southern States of America including Texas and Florida; Cuba was particularly affected. While there has been much concern over the neurotropism of vaccine strains the primary cause of death from yellow fever is viscerotropic disease resulting in jaundice.

Serological tests for Johne s disease

Serological tests for Johne\’s disease have low sensitivity but reasonable specificity. Testing of individual milk specimens yielded a sensitivity of 28% (Collins et al., 2005), slightly higher than serum, and sensitivity increased with age of animal tested (Nielsen et al., 2013). PCR can also be used to test for the presence of MAP DNA in milk (Buergelt and Williams, 2004), as can the peptide-mediated magnetic separation-phage (PMS-phage) assay (Foddai et al., 2011). However, advances in PCR testing for MAP in faeces could negate the need to use antibody based tests.
Antibody based tests (ELISA) are available to measure myeloperoxidase in bulk tank milk to the abomasal parasite O. ostertagi (Forbes et al., 2008). Only an association between ELISA values and milk yield can be made using these test results, rather than confirming true positive nematode infections in the herds, so additional diagnostic testing is required to establish the parasite status of the herd.
In sheep, Q-fever (Coxiella burnetii; Klaasen et al., 2014), Brucella melintensis (Hamidi et al., 2015) and Mycoplasma agalactiae (Poumarat et al., 2012) can be tested for using milk; in goats, milk specimens can be used to test for caprine arthritis and encephalitis (Nagel-Alne et al., 2015). Q-fever outbreaks in humans are associated with C. burnetii infection in small milking ruminants in Africa (Klaasen et al., 2014). Shedding of the organism is intermittent, thus infection was not always detected by PCR and serological tests might also be required. In contrast, PCR testing of milk for B. melintensis detected was more sensitive than serology in one study (Hamidi et al., 2015). Accurate serological classification of the M. agalactiae status of sheep is difficult and PCR testing myeloperoxidase of milk specimens with two PCRs should be used to confirm the presence of the organism. The resultant PCR results also require cross checking with a dot-immunobinding technique (Poumarat et al., 1991).
Milk testing can be utilised for detection of non-infectious conditions. For example, lateral flow devices to test for progesterone concentrations in milk present opportunities to define the oestrus cycle and pregnancy status of cows (Waldmann and Raud, 2016) and technological modifications may allow for testing to occur during milking (Dobson, 2016).

Colostrum is another medium that can be used for animal disease testing instead of milk. Its availability is restricted to a shorter time period, but provides other testing and diagnostic advantages. Testing colostrum for antibodies (as an alternative or add-on to milk testing) is potentially useful because of the higher concentration of immunoglobulins in colostrum compared to milk. The concentration of IgG is estimated to be up to 100 times higher than milk in the first few days after parturition (Korhonen et al., 2000). Recent work in cattle suggests that testing colostrum increases analytical and diagnostic sensitivity compared to milk. This could be most useful for on-going surveillance of animal diseases requiring less frequent checks, as colostrum is only available during the perinatal period (Jenvey et al., 2012, 2015; Cockcroft et al., 2014).
The drawback of colostrum testing is the small window of availability and the difficulty of collection in some species. In dairy cattle, sampling of colostrum might be most usefully applied for diseases where diagnostic tests are hampered by low analytical and/or diagnostic sensitivity (such as is the case with Johne\’s disease; Reichel et al., 1999). Colostrum has also been used successfully for testing for rotavirus and mycoplasma infections (Corthier and Franz, 1981; Zimmermann et al., 1986; Rautiainen, 1998).

Hair and ear notch skin specimens
Hair and ear notch specimens have been used successfully to detect BVDV persistently infected animals (Hill et al., 2007; Lanyon et al., 2014c) and formed the basis of the recent successful Swiss BVDV eradication campaign (Presi and Heim, 2010). In this campaign, detection of BVDV antigen in skin was the specimen of choice to identify persistently infected calves, and was preferred over serum. After the ingestion of colostrum, maternal anti-BVDV antibodies can bind to BVDV antigen and prevent its successful detection in the routinely used antigen-capture ELISA (Fux and Wolf, 2012). Using ear notch skin specimens reduces this complication, as there are fewer antibodies in ear notch tissue. Heating of serum specimens under specific conditions to break up antibody-antigen complexes can overcome the interference of maternal antibody and allow successful serum testing. This adds extra steps to the procedure, but has been used effectively in BVDV testing (Lanyon and Reichel, 2016) and in heartworm serology (Little et al., 2014a, 2014b; Velasquez et al., 2014).

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Materials and Methods

Study Population

This cross-sectional study was approved by the institutional review board, and all the participants provided written informed consent. From May 2013 to February 2014, consecutive 220 individuals who visited the health screening of our hospital and met the following inclusion criteria for the study were recruited: age greater than 20 years, scheduled for conventional chest radiography, and underwent pulmonary function test. Patients with any of the following criteria were excluded: pregnant (n  =  0), potentially pregnant or lactating (n  =  0), myeloperoxidase refused to provide informed consent (n  =  22), had incomplete datasets of dynamic chest radiography (n  =  3), had incomplete datasets of pulmonary function tests (n  =  1), could not follow tidal breathing instructions (eg, holding breath or taking a deep breath) (n  =  18), or their diaphragmatic motion could not be analyzed by the software described next (n  =  4). Thus, a total of 172 participants (103 men, 69 women; mean age 56.3 ± 9.8 years; age range 36–85 years) were finally included in the analysis ( Fig 1). The data from 47 participants of this study myeloperoxidase were analyzed in a different study (under review). The heights and weights of the participants were measured, and the body mass index (BMI, weight in kilograms divided by height squared in meters) was calculated.

Figure 1. Flow diagram of the study population.Figure optionsDownload full-size imageDownload high-quality image (83 K)Download as PowerPoint slide

Imaging Protocol of Dynamic Chest Radiology (“Dynamic X-Ray Phrenicography”)

Posteroanterior dynamic chest radiography (“dynamic X-ray phrenicography”) was performed using a prototype system (Konica Minolta, Inc., Tokyo, Japan) composed of an FPD (PaxScan 4030CB, Varian Medical Systems, Inc., Salt Lake City, UT, USA) and a pulsed X-ray generator (DHF-155HII with Cineradiography option, Hitachi Medical Corporation, Tokyo, Japan). All participants were scanned in the standing position and instructed to breathe normally in a relaxed way without deep inspiration or expiration (tidal breathing). The exposure conditions were as follows: tube voltage, 100 kV; tube current, 50 mA; pulse duration of pulsed X-ray, 1.6 ms; source-to-image distance, 2 m; additional filter, 0.5 mm Al + 0.1 mm Cu. The additional filter was used to filter out soft X-rays. The exposure time was approximately 10–15 seconds. The pixel size was 388 × 388 µm, the matrix size was 1024  × 768, and the overall image area was 40 × 30 cm. The gray-level range of the images was 16,384 (14 bits), and the signal intensity was proportional to the incident exposure of the X-ray detector. The dynamic image data, captured at 15 frames/s, were synchronized with the pulsed X-ray. The pulsed X-ray prevented excessive radiation exposure to the subjects. The entrance surface dose was approximately 0.3–0.5 mGy.

Image Analysis

The diaphragmatic motions on sequential chest radiographs (dynamic image data) during tidal breathing were analyzed using prototype software (Konica Minolta, Inc.) installed in an independent workstation (Operating system: Windows 7 Pro SP1; Microsoft, Redmond WA; CPU: Intel Core i5-5200U, 2.20 GHz; memory 16 GB). The edges of the diaphragms on each dynamic chest radiograph were automatically determined by means of edge detection using a Prewitt Filter 18 ;  19. A board-certified radiologist with 14 years of experience in interpreting chest radiography selected the highest point of each diaphragm as the point of interest on the radiograph of the resting end-expiratory position (Fig 2a). These points were automatically traced by the template-matching technique throughout the respiratory phase (Fig 2b, Supplementary Video S1), and the vertical excursions of the bilateral diaphragm were calculated (Fig 2c): the null point was set at the end of the expiratory phase, that is, the lowest point (0 mm) of the excursion on the graph is the highest point of each diaphragm at the resting end-expiratory position. Then the peak motion speed of each diaphragm was calculated during inspiration and expiration by the differential method (Fig 2c). If several respiratory cycles were involved in the 10 to 15-second examination time, the averages of the measurements were calculated.