TASK DEFINITION: In this task, you're given a paragraph from the research paper and your task is to generate a suitable title for the research paper based on the given paper. Under 100 words is a good title length.
PROBLEM: In this paper, we analyze a delayed SEIR epidemic model in which the latent and infected states are infective. The model has a globally asymptotically stable disease-free equilibrium whenever a certain epidemiological threshold, known as the basic reproduction number R 0 , is less than or equal to unity. We investigate the effect of the time delay on the stability of endemic equilibrium when R 0 > 1. We give criteria that ensure that endemic equilibrium is asymptotically stable for all time delays and a Hopf bifurcation occurs as time delay exceeds the critical value. We give formulae for the direction of Hopf bifurcations and the stability of bifurcated periodic solutions by applying the normal form theory and the center manifold reduction for functional differential equations. Numerical simulations are presented to illustrate the analytical results.

SOLUTION: Hopf bifurcation analysis of a delayed SEIR epidemic model with infectious force in latent and infected period

PROBLEM: We determined the interferon-␥ (IFN-␥) cDNA sequence from three porcine breeds, Duroc, Landrance/Duroc hybrid, and Landrance breeds. Five single nucleotide polymorphisms (SNPs) of porcine IFN-␥ (PoIFN-␥) were identified, respectively, at positions 269 (A/G), 376 (C/T), 426 (T/C), and 465 (T/C) of the coding sequence in Landrance/Duroc hybrid, and at position 251 (A/G) in Landrance breed. Among them, A269G and A251G polymorphisms resulted in Q67R and K61R replacements in the mature protein. PoIFN-␥ cDNAs of Duroc breed (PoIFN-␥-W) and Landrance/Duroc hybrid (PoIFN-␥-M), which, respectively, encoded Q67 and R67, were introduced into a prokaryotic expression vector pET32 to express recombinant PoIFN-␥-W (rPoIFN-␥-W) and rPoIFN-␥-M protein variants in Escherichia coli. The identity of both protein variants was further confirmed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). We then compared bioactivities of these two recombinant proteins. Although both recombinant protein variants exhibited comparable activities in antiproliferation of PK-15 cells and in nitric oxide (NO) induction of porcine peripheral monocytes, antiviral activity of rPoIFN-␥-W protein was significantly higher (P < 0.001) than that of rPoIFN-␥-M protein in a plaque inhibition assay using pseudorabies virus (PRV). IC50 values of rPoIFN-␥-W and rPoIFN-␥-M protein in anti-PRV assay were determined as 5.3 ± 1.3 and 9.3 ± 4.3 nM, respectively. In conclusion, we have identified five novel SNPs in PoIFN-␥ cDNA, including two missense polymorphisms that result in Q67R and K61R replacements. Our results further demonstrate that Q67R can markedly reduce antiviral activity of the PoIFN-␥ protein. This is the first report that shows the functional SNP in the coding region of IFN-␥. In the future, it is imperative to determine whether Q67R replacement in IFN-␥ may have disease association.

SOLUTION: A missense polymorphism in porcine interferon-␥ cDNA affects antiviral activity of the protein variant

PROBLEM: Background: Bovine coronavirus (BCoV) is a widely distributed pathogen, causing disease and economic losses in the cattle industry worldwide. Prevention of virus spread is impeded by a lack of basic knowledge concerning viral shedding and transmission potential in individual animals. The aims of the study were to investigate the duration and quantity of BCoV shedding in feces and nasal secretions related to clinical signs, the presence of virus in blood and tissues and to test the hypothesis that seropositive calves are not infectious to naïve in-contact calves three weeks after BCoV infection. Methods: A live animal experiment was conducted, with direct contact between animal groups for 24 h as challenge procedure. Four naïve calves were commingled with a group of six naturally infected calves and sequentially euthanized. Two naïve sentinel calves were commingled with the experimentally exposed group three weeks after exposure. Nasal swabs, feces, blood and tissue samples were analyzed for viral RNA by RT-qPCR, and virus isolation was performed on nasal swabs. Serum was analyzed for BCoV antibodies. Results: The calves showed mild general signs, and the most prominent signs were from the respiratory system. The overall clinical score corresponded well with the shedding of viral RNA the first three weeks after challenge. General depression and cough were the signs that correlated best with shedding of BCoV RNA, while peak respiratory rate and peak rectal temperature appeared more than a week later than the peak shedding. Nasal shedding preceded fecal shedding, and the calves had detectable amounts of viral RNA intermittently in feces through day 35 and in nasal secretions through day 28, however virus isolation was unsuccessful from day six and day 18 from the two calves investigated. Viral RNA was not detected in blood, but was found in lymphatic tissue through day 42 after challenge. Although the calves were shedding BCoV RNA 21 days after infection the sentinel animals were not infected. Conclusions: Prolonged shedding of BCoV RNA can occur, but detection of viral RNA does not necessarily indicate a transmission potential. The study provides valuable information with regard to producing scientifically based biosecurity advices.

SOLUTION:
Bovine coronavirus in naturally and experimentally exposed calves; viral shedding and the potential for transmission