Lactobacillus plantarum IS-10506 supplementation increases faecal sIgA and immune response in children younger than two years

The immature intestinal immune system in young children develops as it comes into contact with dietary and microbial antigens in the gut. Intestinal microbiota plays a significant role in host defence mechanisms as shown by inflammatory responses towards potential pathogens. We investigated the probiotic function of Lactobacillus plantarum IS-10506 of 'dadih' origin in modulating immune response in young children. We aimed to assess its effect on their immune response by assessing transforming growth factor-β1 (TGF-β1) and tumour necrosis factor-α (TNF-α) responses and faecal secretory immunoglobulin A (sIgA) titre in a randomised, double-blinded placebo-controlled trial in 12-24-month-old children (n=38). We used four treatment groups for a 90-day supplementation period: placebo (n=11), probiotic (n=9), zinc (n=8) and probiotic and zinc (n=10). Faecal sIgA, plasma TGF-β1 and TNF-α titre were evaluated using the enzyme-linked immunosorbent assay standard technique. Statistical analysis divided the results (pre/post treatment) into high (>1) and low (<1) ratios. The results showed that faecal sIgA titre increased in all treatment groups compared with the control (placebo) and significantly increased in the probiotic group (P=0.05). In addition, the TGF-β1 ratio in the zinc group was significantly higher (P=0.05) than that in the placebo group. We observed a significant positive correlation between TGF-β1/TNF-α and faecal sIgA (r=0.27, P=0.04). Post hoc test results revealed that zinc supplementation has a significant effect on body-weight gain. Taken together, probiotic L. plantarum IS-10506 supplementation stimulates TGF-β1, which in turn increases the production of sIgA, in line with the significant correlation between TGF-β1/TNF-α and faecal sIgA.

Sequence and comparative structural analysis of the murine leukaemia virus amphotropic strain 4070A RNase H domain

The sequence of a 900-nucleotide segment (encoding part of the reverse transcriptase, including the entire RNase H domain) of the pol gene of the murine leukaemia virus (MLV) amphotropic strain 4070A is presented. Alignment of the inferred 4070A RNase H amino acid sequence (157 residues) with other MLV RNase H sequences revealed only minor differences compared with the divergence between other retroviral and prokaryotic or eukaryotic RNase H sequences. Only 10 residues were invariant across the entire sample set, but secondary structure predictions for the enzymes from E. coli, yeast, human liver and diverse retroviruses (HIV, Rous sarcoma virus, foamy viruses) supported, in every case, the five beta-strands (1 to 5) and four or five alpha-helices (A, B/C, D, E) that have been identified by crystallography in the RNase H domain of HIV-1 reverse transcriptase and in E. coli RNase H. In the case of MLV, analysis of the RNase H domain sequences inferred from 10 different strains (including the amphotropic 4070A) predicted all five alpha-helices (A-E), as well as beta-strands 4 and 5. However, the N-terminal segment (residues 1-40) was predicted, without exception and with high probability, to fold uniquely into one (or two adjacent) alpha-helix(es) encompassing residues 13-37, instead of the three beta-strands known to exist in the HIV-1 and E. coli enzymes. The unerring consistency between the known and predicted structures of the HIV-1 and E. coli enzymes, and the prediction of the same structural elements (including beta-strands 1-3 within the N-terminal segment) for all other (non-MLV) RNase H proteins examined in this study, suggests that the N-terminal segment of the MLV RNase H domain assumes a conformation distinct from that of other retroviral and cellular RNase H molecules. An additional (sixth) beta-strand was also predicted uniquely within the C-terminal region of foamy virus RNase H domains.

Nucleotide sequence of the murine leukaemia virus amphotropic strain 4070A integrase (IN) coding region and comparative structural analysis of the inferred polypeptide

The complete nucleotide sequence of the integrase (IN) protein coding region of the murine leukaemia virus (MLV) amphotropic strain 4070A is presented. The sequence comprises 1,224 nucleotides, encoding a 408-residue polypeptide of M(r) 46,312. Alignment of the inferred 4070A IN amino acid sequence with the IN proteins of other MLV showed that substitutions are confined largely to segments within the N- and C-terminal domains. In the N-terminal domain the majority of substitutions occur as contiguous 2- to 6-residue blocks, whereas in the C-terminal domain they occur as isolated entities except within a short segment characterized by deletions/insertions. Selection appears to act on the C-terminal 19 residues of IN rather than on the N-terminal residues of ENV (encoded by overlapping reading frames), suggesting a functional role for this segment. Phylogenetic analyses grouped the sequences into two clusters, one comprising IN from the amphotropic strain 4070A and three ecotropic MLV (CAS-BR-E, Moloney and Friend), the other consisting of IN from three ecotropic MLV (two radiation-induced viruses and AKV) and a mink cell focus-forming (MCF) MLV virus. The same dichotomy and cluster composition was obtained from analysis of the long terminal repeat (LTR) regions from these viruses (consistent with the functional interrelationship of IN and LTR) but not from analysis of envelope protein sequences (consistent with the functional independence of ENV proteins from both IN and LTR). Secondary structure predictions supported features determined from the catalytic domain of human immunodeficiency virus and avian sarcoma virus IN, and identified probable structures within the relatively long N- and C-terminal domains of MLV IN proteins.