Impact of antigenic and genetic drift on the serologic surveillance of H5N2 avian influenza viruses

<p>Abstract</p> <p>Background</p> <p>Serologic surveillance of Avian Influenza (AI) viruses is carried out by the hemagglutination inhibition (HI) test using reference reagents. This method is recommended by animal health organizations as a standard test to detect antigenic differences (subtypes) between circulating influenza virus, vaccine- and/or reference- strains. However, significant discrepancies between reference antisera and field isolates have been observed during serosurveillance of influenza A viruses in pig and poultry farms. The objective of this study was to examine the effects of influenza virus genetic and antigenic drift on serologic testing using standard HI assays and reference reagents. Low pathogenic AI H5N2 viruses isolated in Mexico between 1994 and 2008 were used for phylogenetic analysis of AI hemagglutinin genes and for serologic testing using antisera produced with year-specific AI virus isolates.</p> <p>Results</p> <p>Phylogenetic analysis revealed significant divergence between early LPAI H5N2 viruses (1994 - 1998) and more recent virus field isolates (2002 - 2008). Results of the HI test were markedly influenced by the selection of the AI H5N2 virus (year of isolation) used as reference antigen for the assay. These analyses indicate that LPAI H5N2 viruses in Mexico are constantly undergoing genetic drift and that serosurveillance of AI viruses is significantly influenced by the antigen or antisera used for the HI test.</p> <p>Conclusions</p> <p>Reference viral antigens and/or antisera need to be replaced constantly during surveillance of AI viruses to keep pace with the AI antigenic drift. This strategy should improve the estimation of antigenic differences between circulating AI viruses and the selection of suitable vaccine strains.</p

Disease Severity in Patients Infected with Leishmania mexicana Relates to IL-1β

Leishmania mexicana can cause both localized (LCL) and diffuse (DCL) cutaneous leishmaniasis, yet little is known about factors regulating disease severity in these patients. We analyzed if the disease was associated with single nucleotide polymorphisms (SNPs) in IL-1β (−511), CXCL8 (−251) and/or the inhibitor IL-1RA (+2018) in 58 Mexican mestizo patients with LCL, 6 with DCL and 123 control cases. Additionally, we analyzed the in vitro production of IL-1β by monocytes, the expression of this cytokine in sera of these patients, as well as the tissue distribution of IL-1β and the number of parasites in lesions of LCL and DCL patients. Our results show a significant difference in the distribution of IL-1β (−511 C/T) genotypes between patients and controls (heterozygous OR), with respect to the reference group CC, which was estimated with a value of 3.23, 95% CI = (1.2, 8.7) and p-value = 0.0167), indicating that IL-1β (−511 C/T) represents a variable influencing the risk to develop the disease in patients infected with Leishmania mexicana. Additionally, an increased in vitro production of IL-1β by monocytes and an increased serum expression of the cytokine correlated with the severity of the disease, since it was significantly higher in DCL patients heavily infected with Leishmania mexicana. The distribution of IL-1β in lesions also varied according to the number of parasites harbored in the tissues: in heavily infected LCL patients and in all DCL patients, the cytokine was scattered diffusely throughout the lesion. In contrast, in LCL patients with lower numbers of parasites in the lesions, IL-1β was confined to the cells. These data suggest that IL-1β possibly is a key player determining the severity of the disease in DCL patients. The analysis of polymorphisms in CXCL8 and IL-1RA showed no differences between patients with different disease severities or between patients and controls

Transformación de la vegetación por cambio de uso del suelo en la Reserva de la Biosfera Calakmul, Campeche

The methods and techniques used to develop the vegetation and land-use map of the Calakmul Biosphere Reserve are presented. The information was processed using a Geographic Information System (GIS), generating a digital geographic database. In turn, it was used to conduct a quantitative analysis of the extent of change in forest cover due to anthropogenic activities. The current situation in the Calakmul Biosphere Reserve was assessed through the use of maps of vegetation types and land use. The data in these maps were derived from 1 500 aerial photographs from 1995 and 1996, at a 1:20 000 scale A digital photogrammetric correction was applied, fieldwork information was validated, and a variety of data layers were developed for the geographic database. The results obtained indicate that of the study area (722 121.6 ha), 96.3% corresponds to forest without any perceivable human disturbance. The areas transformed by productive human activities comprise 3.51 % of the reserve area. The major vegetation changes were found at the reserve´s eastern portion, and are directly related to colonization projects that have taken place during the last 30 years

Statistical analysis of IL-1β −511 SNP.

<p>Statistical analysis of IL-1β −511 SNP.</p

Immunohistochemistry for IL-1β and <i>Leishmania mexicana</i> staining in lesions of patients with cutaneous leishmaniasis.

<p>(A) IL-1β staining on cells of LCL patient with single small lesion; (B) small clusters of <i>Leishmania</i> parasites in LCL patient with small ulcer; (C) diffuse distribution of IL-1β in LCL patient with abundant ulcers; (D) disintegrated <i>Leishmania</i> in LCL patient with abundant ulcers; (E) diffuse distribution of IL-1β in DCL patient; (F) clusters with abundant intact <i>Leishmania</i> parasites in DCL patient. Red arrows show IL-1β⁺ staining and black arrows show <i>L. mexicana</i> staining. (G) Normal skin was used as negative control for IL-1β immunostaining. (H) Control staining with secondary antibody. All sections were counterstained with haematoxylin. (A–H) scale bar = 50 µm. Immunostaining in tissue sections was visualized at a magnification of 400×. We show a representative result of different types of lesions within each group: LCL patients with one small ulcer: (n = 8 for IL-1β staining and n = 17 for <i>L. mexicana</i> staining) (A and B); LCL patients with various ulcers (n = 3) (C and D); DCL patients (n = 6) (E and F).</p

IL-1β expression in serum of patients with cutaneous leishmaniasis.

<p>(A) Western blot of mature IL-1β (17 kDa) in 4 controls (1–4), 9 LCL patients (5–13) and 7 DCL patients (14–20). (B) Graph of percentage intensity of IL-1β bands with statistically significant differences between controls <i>vs</i> LCL patients, controls <i>vs</i> DCL patients and LCL <i>vs</i> DCL patients. (Identical symbols above different bars are statistically significant: p<0.05).</p

Analysis of IL-1β cytokine production by non-stimulated monocytes purified with anti-CD14 magnetic beads from PBMC of control subjects and patients with cutaneous leishmaniasis after 18 hours <i>in vitro</i> culture.

<p>Mean values obtained from 7 healthy control subjects and 5 patients with leishmaniasis. (Identical symbols above two different bars are statistically significant: p<0.05).</p