Long-Term and Seasonal Dynamics of Dengue in Iquitos,Peru

Introduction

Long-term disease surveillance data provide a basis for studying drivers of pathogen transmission dynamics. Dengue is a mosquito-borne disease caused by four distinct, but related, viruses (DENV-1-4) that potentially affect over half the world''s population. Dengue incidence varies seasonally and on longer time scales, presumably driven by the interaction of climate and host susceptibility. Precise understanding of dengue dynamics is constrained, however, by the relative paucity of laboratory-confirmed longitudinal data.

Methods

We studied 10 years (2000–2010) of laboratory-confirmed, clinic-based surveillance data collected in Iquitos, Peru. We characterized inter and intra-annual patterns of dengue dynamics on a weekly time scale using wavelet analysis. We explored the relationships of case counts to climatic variables with cross-correlation maps on annual and trimester bases.

Findings

Transmission was dominated by single serotypes, first DENV-3 (2001–2007) then DENV-4 (2008–2010). After 2003, incidence fluctuated inter-annually with outbreaks usually occurring between October and April. We detected a strong positive autocorrelation in case counts at a lag of ∼70 weeks, indicating a shift in the timing of peak incidence year-to-year. All climatic variables showed modest seasonality and correlated weakly with the number of reported dengue cases across a range of time lags. Cases were reduced after citywide insecticide fumigation if conducted early in the transmission season.

Conclusions

Dengue case counts peaked seasonally despite limited intra-annual variation in climate conditions. Contrary to expectations for this mosquito-borne disease, no climatic variable considered exhibited a strong relationship with transmission. Vector control operations did, however, appear to have a significant impact on transmission some years. Our results indicate that a complicated interplay of factors underlie DENV transmission in contexts such as Iquitos.     

Peptidoglycan from Staphylococcus aureus has an anti‐apoptotic effect in HaCaT keratinocytes mediated by the production of the cellular inhibitor of apoptosis protein‐2

Colonization of epithelium by microorganisms leads to inflammatory responses. In some cases an anti‐apoptotic response involving the cellular inhibitor of apoptosis protein‐2 (cIAP‐2) also occurs. Although strong expression of cIAP‐2 has been observed in lesional skin from psoriatic patients and in HaCaT keratinocytes treated with peptidoglycan (PGN) from Staphylococcus aureus, anti‐apoptotic responses induced in the skin by cIAP‐2 have seldom been studied. In this study, the effect of PGN on TNF‐α‐induced apoptotic HaCaT keratinocytes was assessed. Morphological analysis, quantification of cells with DNA fragmentation and active caspase‐3 detection was performed to assess apoptotic cell death. Greater LL‐37 and cIAP‐2 production was found in keratinocytes stimulated with PGN than in non‐treated cells (P < 0.05). In comparison with cells treated with TNF‐α only, a significant reduction in apoptotic cell death was observed when HaCaT were pretreated with PGN before inducing apoptosis with TNF‐α (P < 0.05). In addition, an inhibitor of cIAP‐2 activity (LCL161) stopped the PGN effect. These findings show that PGN from S. aureus has an anti‐apoptotic effect in keratinocytes mediated by cIAP‐2 production, suggesting that this anti‐apoptotic activity could favor proliferation of keratinocytes in psoriasis.     

Functional analysis of a putative holin-like peptide-coding gene in the genome of Bacillus licheniformis AnBa9

BhlA, a putative holin-like protein of Bacillus licheniformis AnBa9 expressed in Escherichia coli BL21(DE3) showed antibacterial activity against several gram-positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA) and Micrococcus luteus. Deletion analysis of bhlA suggests that a hydrophobic transmembrane domain, BhlATM is essential for antibacterial activity. Though the minimum inhibitory concentration (MIC) of BhlA was sevenfold lower than BhlATM, transmembrane domain deleted construct (BhlA∆TM) had no antibacterial activity. The expression of BhlA in E. coli was found to be toxic to cells. Therefore, the bhlA was cloned in yeast surface display vector pYD1 and expressed in Saccharomyces cerevisiae. The surface displayed yeast showed inhibition of several gram-positive bacteria. This recombinant yeast expressing BhlA may be used as biodrug for efficient control of multiple drug-resistant bacterial infections.     

Asymptomatic Middle East Respiratory Syndrome Coronavirus Infection in Rabbits

The ability of Middle East respiratory syndrome coronavirus (MERS-CoV) to infect small animal species may be restricted given the fact that mice, ferrets, and hamsters were shown to resist MERS-CoV infection. We inoculated rabbits with MERS-CoV. Although virus was detected in the lungs, neither significant histopathological changes nor clinical symptoms were observed. Infectious virus, however, was excreted from the upper respiratory tract, indicating a potential route of MERS-CoV transmission in some animal species.