No abstract

Background: Human Respiratory Syncytial Virus (HRSV) is a major viral pathogen associated with acute lower respiratory tract infections (ALRTI) in children. Using monoclonal antibodies against virus proteins, it is categorized into two distinct major groups, A and B. The second hypervariable region of the G protein ectodomain gene provides a reliable surrogate for phylogenetical studies. We carried out a phylogenetic analysis of the HRSV strains isolated from children hospitalized with ALRTI in Malaysia.Methods: Nasopharyngeal aspirates (NPA) were taken from children less than five years of age hospitalized with ALRTI to Hospital Serdang, Malaysia. RT-PCR was used to detect HRSV. The second hypervariable region at the carboxyl-terminal of the G gene was amplified and sequenced using primer sets GPA/F1 and GPB/F1. Neucleotide sequences were edited and aligned with Bioedite software and Clustal X program. The phylogenetic relationships of the samples were determined separately for group A and B using neighbor joining (NJ), maximum parsimony (MP) and Bayesian methods (BI).Results: HRSV was detected in 83 of 165 (50.3%) patients studied. Sequence analysis of 32 isolates showed that multiple lineages of HRSV group A and B serotypes co-circulated. The topologies resulting from the different methods (NJ, MP and BI) congruent with each other. Phylogenetic analysis of nine retrieved sequences showed that all the HRSV-A strains were clustered into the NA1 genotype. All the 23 HRSV-B strains belonged to BA genotypes consisted of a 60-nucleotide duplication region. They were classified into three different genotypes of BA10, BA9 and BA4, respectively.Conclusion: HRSV played a prominent role for hospitalization of children in our study. The sequences of the second hypervariable region of G protein ectodomain gene from HRSV A and B demonstrated remarkable genetic diversity. The present finding seems to be consistent with other studies which found the newly emerged HRSV genotypes of NA1 and BA genotypes are replacing the previously dominant genotypes. This is the first documentation of the phylogenetic relationship and genetic diversity of HRSV isolates among hospitalized children diagnosed with ALRTI in Malaysia.

NTS bacteraemia has a high mortality (47%) and recurrence (43%) rate in HIV-infected African adults. Recurrence is caused by recrudescence rather than re-infection. As focal infections were rarely found, recrudescence may often be a consequence of intracellular tissue sequestration. There is an urgent need for improved primary treatment and secondary prophylaxis in Africa.

Colonization of the upper respiratory tract by pneumococcus is important both as a determinant of disease and for transmission into the population. The immunological mechanisms that contain pneumococcus during colonization are well studied in mice but remain unclear in humans. Loss of this control of pneumococcus following infection with influenza virus is associated with secondary bacterial pneumonia. We used a human challenge model with type 6B pneumococcus to show that acquisition of pneumococcus induced early degranulation of resident neutrophils and recruitment of monocytes to the nose. Monocyte function was associated with the clearance of pneumococcus. Prior nasal infection with live attenuated influenza virus induced inflammation, impaired innate immune function and altered genome-wide nasal gene responses to the carriage of pneumococcus. Levels of the cytokine CXCL10, promoted by viral infection, at the time pneumococcus was encountered were positively associated with bacterial load.