Lack of association of brucellosis resistance with (GT)13 microsatellite allele at 3′UTR of NRAMP1 gene in Indian zebu (Bos indicus) and crossbred (Bos indicus×Bos taurus) cattle

Microsatellite markers reveal polymorphisms at the 3′ untranslated region of the SLC11A1 gene in Zhongdian Yellow cattle (Bos taurus)

Solute carrier family 11-member A1 (SLC11A1) gene encodes natural macrophage resistance-associated protein which regulates activity of macrophages against intracellular pathogens. The objective of this study was to study the polymorphism in the microsatellites present at 3′ untranslated region (UTR) of the SLC11A1 gene in 113 Zhongdian Yellow cattle (Bos taurus). Using DNA bi-directional sequencing, we detected seven alleles (GT10–16) for the first microsatellite (MS1), five alleles (GT12–16) for MS2, and four alleles (GT4–7) for MS3. MS3 is studied for the first time and revealed four novel variants (alleles GT4–7). Alleles GT12 (45.1%), GT13 (59.3%), and GT5 (85.4%) were the most frequent alleles at MS1, MS2, and MS3, respectively, Genotypes G12/12, G13/13, and G5/5 had the highest frequency 0.239, 0.540, and 0.743 at MS1, MS2, and MS3, respectively. Haplotypic data revealed that GT12/GT13 was the most frequent haplotype observed followed by GT12/14 haplotype. Three nucleotide variations were observed in MS1 and MS2. Comparative analysis of GT12/GT12 and GT13/GT13 genotype with other bovine genotypes showed significant difference (P > 0.05). Our results suggest that the homozygous genotypes GT12/GT12 and GT13/GT13 in Zhongdian Yellow cattle might be related to disease resistance. The findings reported in this study would be helpful in cattle breeding programs.

Mammary Transcriptome Profile during Peak and Late Lactation Reveals Differentially Expression Genes Related to Inflammation and Immunity in Chinese Holstein

Simple Summary

Milk somatic cell count, referring to the total number of somatic cells per milliliter of bovine milk, changes regularly during the lactation cycle. The somatic cell count of healthy cows is usually higher in late lactation than in peak lactation. When the inflammatory response in dairy cow mammary gland becomes more intense, the milk somatic cell count increases together with the reduction of milk quality and yield. Autoimmunity was thought to play an important role in the prevention of mastitis in late lactation of dairy cattle. However, the underlying mechanisms related to the gene expression levels during the process remain unknown. In this study, transcriptome sequencing was performed to screen the differentially expressed genes related to the inflammation and immunity in healthy Chinese Holstein mammary glands. Our findings are helpful to understand the physiological functions of mammary inflammation of Chinese Holstein during late lactation.

Abstract

Somatic cell count (SCC) in milk is widely used in the dairy industry, as an indicator of the health of mammary gland. While the SCC of dairy cattle was higher in late lactation than in peak lactation, its association with gene expressions of mammary gland were largely unknown. In this study, a transcriptomic sequencing approach and bioinformatics analysis were used to investigate the differential expressed genes (DEGs) associated with inflammation and immunity between peak and late periods of lactation in Chinese Holstein. A total of 446 DEGs (padj < 0.05 and fold change >2) were identified, 50 of which belonged to seven pathways and five terms related to inflammation and immunity. Our data suggested that the activation of nuclear transcription factor-κB (NF-κB) pathway and Toll-like receptor signaling pathway caused inflammatory response, and the activation of chemokine signaling pathway and cytokine–cytokine receptor interaction signaling pathway caused a protective immune response to ensure dairy cows health during late lactation. Our findings deepen the understanding of the molecular mechanism and physiological functions of mammary inflammation in Chinese Holstein during late lactation.

The impact of first untreated subclinical minimal acute rejection on risk for chronic lung allograft dysfunction or death after lung transplantation

Acute cellular rejection (ACR) is a significant risk factor for chronic lung allograft dysfunction (CLAD). Although clinically manifest and higher grade (≥A2) ACR is generally treated with augmented immunosuppression, management of minimal (grade A1) ACR remains controversial. In our program, patients with subclinical and spirometrically stable A1 rejection (StA1R) are routinely not treated with augmented immunosuppression. We hypothesized that an untreated first StA1R does not increase the risk of CLAD or death compared to episodes of spirometrically stable no ACR (StNAR). The cohort was drawn from all consecutive adult, first, bilateral lung transplantations performed between 1999 and 2017. Biopsies obtained in the first-year posttransplant were paired with (forced expiratory volume in 1 second FEV₁ ). The first occurrence of StA1R was compared to a time-matched StNAR. The risk of CLAD or death was assessed using univariable and multivariable Cox proportional hazards models. The analyses demonstrated no significant difference in risk of CLAD or death in patients with a first StA1R compared to StNAR. This largest study to date shows that, in clinically stable patients, an untreated first A1 ACR in the first-year posttransplant is not significantly associated with an increased risk for CLAD or death. Watchful-waiting approach may be an acceptable tactic for stable A1 episodes in lung transplant recipients.

Effects of alleles in crossbred pigs estimated for genomic prediction depend on their breed-of-origin

BACKGROUND

This study investigated if the allele effect of a given single nucleotide polymorphism (SNP) for crossbred performance in pigs estimated in a genomic prediction model differs depending on its breed-of-origin, and how these are related to estimated effects for purebred performance.

RESULTS

SNP-allele substitution effects were estimated for a commonly used SNP panel using a genomic best linear unbiased prediction model with breed-specific partial relationship matrices. Estimated breeding values for purebred and crossbred performance were converted to SNP-allele effects by breed-of-origin. Differences between purebred and crossbred, and between breeds-of-origin were evaluated by comparing percentage of variance explained by genomic regions for back fat thickness (BF), average daily gain (ADG), and residual feed intake (RFI). From ten regions explaining most additive genetic variance for crossbred performance, 1 to 5 regions also appeared in the top ten for purebred performance. The proportion of genetic variance explained by a genomic region and the estimated effect of a haplotype in such a region were different depending upon the breed-of-origin. To illustrate underlying mechanisms, we evaluated the estimated effects across breeds-of-origin for haplotypes associated to the melanocortin 4 receptor (MC4R) gene, and for the MC4Rsnp itself which is a missense mutation with a known effect on BF and ADG. Although estimated allele substitution effects of the MC4Rsnp mutation were very similar across breeds, explained genetic variance of haplotypes associated to the MC4R gene using a SNP panel that does not include the mutation, was considerably lower in one of the breeds where the allele frequency of the mutation was the lowest.

CONCLUSIONS

Similar regions explaining similar additive genetic variance were observed across purebred and crossbred performance. Moreover, there was some overlap across breeds-of-origin between regions that explained relatively large proportions of genetic variance for crossbred performance; albeit that the actual proportion of variance deviated across breeds-of-origin. Results based on a missense mutation in MC4R confirmed that even if a causal locus has similar effects across breeds-of-origin, estimated effects and explained variance in its region using a commonly used SNP panel can strongly depend on the allele frequency of the underlying causal mutation.

Systematic Profiling of Short Tandem Repeats in the Cattle Genome

Short tandem repeats (STRs), or microsatellites, are genetic variants with repetitive 2–6 base pair motifs in many mammalian genomes. Using high-throughput sequencing and experimental validations, we systematically profiled STRs in five Holsteins. We identified a total of 60,106 microsatellites and generated the first high-resolution STR map, representing a substantial pool of polymorphism in dairy cattle. We observed significant STRs overlap with functional genes and quantitative trait loci (QTL). We performed evolutionary and population genetic analyses using over 20,000 common dinucleotide STRs. Besides corroborating the well-established positive correlation between allele size and variance in allele size, these analyses also identified dozens of outlier STRs based on two anomalous relationships that counter expected characteristics of neutral evolution. And one STR locus overlaps with a significant region of a summary statistic designed to detect STR-related selection. Additionally, our results showed that only 57.1% of STRs located within SNP-based linkage disequilibrium (LD) blocks whereas the other 42.9% were out of blocks. Therefore, a substantial number of STRs are not tagged by SNPs in the cattle genome, likely due to STR's distinct mutation mechanism and elevated polymorphism. This study provides the foundation for future STR-based studies of cattle genome evolution and selection.

Molecular characterization and combined genotype association study of bovine cluster of differentiation 14 gene with clinical mastitis in crossbred dairy cattle

Aim:

The present study was undertaken with the objectives to characterize and to analyze combined genotypes of cluster of differentiation 14 (CD14) gene to explore its association with clinical mastitis in Karan Fries (KF) cows maintained in the National Dairy Research Institute herd, Karnal.

Materials and Methods:

Genomic DNA was extracted using blood of randomly selected 94 KF lactating cattle by phenol-chloroform method. After checking its quality and quantity, polymerase chain reaction (PCR) was carried out using six sets of reported gene-specific primers to amplify complete KF CD14 gene. The forward and reverse sequences for each PCR fragments were assembled to form complete sequence for the respective region of KF CD14 gene. The multiple sequence alignments of the edited sequence with the corresponding reference with reported Bos taurus sequence (EU148610.1) were performed with ClustalW software to identify single nucleotide polymorphisms (SNPs). Basic Local Alignment Search Tool analysis was performed to compare the sequence identity of KF CD14 gene with other species. The restriction fragment length polymorphism (RFLP) analysis was carried out in all KF cows using Helicobacter pylori 188I (Hpy188I) (contig 2) and Haemophilus influenzae I (HinfI) (contig 4) restriction enzyme (RE). Cows were assigned genotypes obtained by PCR-RFLP analysis, and association study was done using Chi-square (χ²) test. The genotypes of both contigs (loci) number 2 and 4 were combined with respect to each animal to construct combined genotype patterns.

Results:

Two types of sequences of KF were obtained: One with 2630 bp having one insertion at 616 nucleotide (nt) position and one deletion at 1117 nt position, and the another sequence was of 2629 bp having only one deletion at 615 nt position. ClustalW, multiple alignments of KF CD14 gene sequence with B. taurus cattle sequence (EU148610.1), revealed 24 nt changes (SNPs). Cows were also screened using PCR-RFLP with Hpy188I (contig 2) and HinfI (contig 4) RE, which revealed three genotypes each that differed significantly regarding mastitis incidence. The maximum possible combination of these two loci shown nine combined genotype patterns and it was observed only eight combined genotypes out of nine: AACC, AACD, AADD, ABCD, ABDD, BBCC, BBCD, and BBDD. The combined genotype ABCC was not observed in the studied population of KF cows. Out of 94 animals, AACD combined genotype animals (10.63%) were found to be not affected with mastitis, and ABDD combined genotyped animals was observed having the highest mastitis incidence of 15.96%.

Conclusion:

AACD typed cows were found to be least susceptible to mastitis incidence as compared to other combined genotypes.

Molecular comparison of Slc11a1 and Slc11a2 genes of swamp- and riverine-type water buffaloes

Solute-linked carrier 11a and 11a2 (Slc) have been associated with disease resistance and/or susceptibility across animal species. These genes have an important mechanism in the regulation against intracellular infection. This study analysed the genetic characteristic of Slc 11a and 11a2 in swamp-type and riverine-type water buffaloes to understand their immunological distinction. Characterization of Slc11a1 and Slc11a2 genes from swamp- and riverine-type water buffaloes was carried out by molecular cloning, sequencing and phylogenetic analysis. The cloned cDNA of Slc11a1 and Slc11a2 contained an open reading frame of 1647 and 1723 nucleotides, encoding 549 and 574 amino acids, respectively. Nucleotide sequence homology of both Slc11a1 and Slc11a2 had 99% in swamp and riverine type, which gives almost identical polypeptide. However, Slc11a1 and Slc11a2 have substitutions of 5 and 1 amino acid residues, correspondingly. These substitutions suggest as a potential gene markers for resistance and/or susceptibility to intracellular infection. Furthermore, phylogenetic analysis confirmed the degree of relationship between the bubaline species and justifies the distinctness of each breed by the bootstrap value generated.

Polymorphism of cytokine and innate immunity genes associated with bovine brucellosis in cattle

Genetic susceptibility to brucellosis is multifactorial, and it is known that impairment of the immune system could contribute to risk for getting brucellosis. The aim of the study was to find association of bovine brucellosis with 20 SNPs pertaining to bovine cytokine (IFNG, IFNGR1, IFNGR2, TNFA) and innate immunity (SLC11A1, TLR1, TLR4, and TLR9) genes using PCR-RFLP genotyping technique and it was observed that SLC11A1 (+1066 C/G), TLR1 (+1446 C/A), TLR1 (+1380 G/A), TLR4 (+10 C/T) and TLR4 (+399 C/T) loci were significantly (P≤0.05) associated with bovine brucellosis. The odds ratios (OR) of CG and CC genotypes versus GG genotype were 0.31 (0.12-0.82; 95% CI) and 0.18 (0.03-1.06; 95% CI) at SLC11A1 (+1066 C/G) locus in cases of brucellosis affected cattle. For TLR1 (+1380 G/A) locus, the OR for AG and AA genotypes versus GG genotypes were 0.15 (0.05-0.44; 95% CI) and 0.26 (0.04-1.47; 95% CI) which indicated that proportion of GG homozygote was significantly higher in brucellosis affected animals as compared to control. At TLR1 (+1446 C/A) locus the OR of AC genotype versus CC genotype was 0.24 (0.08-0.68; 95% CI) which revealed that relative proportion CC genotypes was significantly higher in case population. The TLR4 (+10 C/T) locus had three genotypes (TT, CT and CC) where OR of CT and CC genotypes versus TT genotype were near to zero. The OR of CT genotypes versus CC genotypes was 8.25 (0.94-71.92; 95% CI) at TLR4 (+399 C/T) locus and indicated that CT genotype had higher odds of bovine brucellosis than control animals.

Nitric oxide not apoptosis mediates differential killing of Mycobacterium bovis in bovine macrophages

To identify the resistance phenotype against Mycobacterium bovis in cattle, we used a bactericidal assay that has been considered a marker of this trait. Three of 24 cows (12.5%) were phenotyped as resistant and 21 as susceptible. Resistance of bovine macrophages (MΦ) to BCG challenge was evaluated for its association with SLC11A1 GT microsatellite polymorphisms within 3'UTR region. Twenty-three cows (95.8%) had a GT13 genotype, reported as resistant, consequently the SLC11A1 polymorphism was not in agreement with our bactericidal assay results. MΦ of cows with resistant or susceptible phenotype were challenged in vitro with virulent M. bovis field strain or BCG, and nitric oxide production, bacterial killing and apoptosis induction were measured in resting and LPS-primed states. M. bovis field strain induced more apoptosis than BCG, although the difference was not significant. Resistant MΦ controlled better the replication of M. bovis (P<0.01), produced more nitric oxide (P<0.05) and were slightly more prone to undergo apoptosis than susceptible cells. LPS pretreatment of MΦ enhanced all the functional parameters analyzed. Inhibition of nitric oxide production with n (G)-monomethyl-L-arginine monoacetate enhanced replication of M. bovis but did not modify apoptosis rates in both resistant and susceptible MΦ. We conclude that nitric oxide production not apoptosis is a major determinant of macrophage resistance to M. bovis infection in cattle and that the influence of SLC11A1 gene 3'UTR polymorphism is not associated with this event.

In vitro expression of the SLC11A1 gene in goat monocyte-derived macrophages challenged with Mycobacterium avium subsp paratuberculosis

Johne's disease or paratuberculosis is a chronic, progressive intestinal disease of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). One of the genes that have been targeted with regard to resistance or sensitivity to paratuberculosis is the SLC11A1 (solute carrier family 11 member A1). Here we extend our previous work to the sequence and structure analysis of the caprine SLC11A1 gene and we assess the functional impact of the most frequent polymorphisms of the 3' UTR region of the SLC11A1 gene to its expression in goat macrophages exposed in vitro to MAP. The role of these polymorphisms in primary immune response is also investigated with connection to gene expression of two interleukins (IL), one of which pro (IL-1a), and the other anti-inflammatory (IL-10). In order to assess gene response, quantitative detection of the SLC11A1, IL-10 and IL1a mRNA was performed by real time PCR before, and at 1, 3 and 24h after exposure of primary cultures of peripheral blood monocyte-derived macrophages to MAP, collected from 54 goats of the Greek native goat breed. Sequence analysis of the 3' UTR end of the caprine SLC11A1 gene determined its full length to be 522 bases. Structure analysis confirmed the presence of two microsatellites consisted of a variable number of guanine-thymine repeats (regions A and B). The homozygous B7 genotype [B(GTn)7/7] was associated at a statistically significant level with increased expression of the SLC11A1 and IL-1α genes indicating increased in vitro responsiveness and therefore resistance of mononuclear derived macrophages to MAP infection.

Microsatellite (GT)n polymorphism at 3'UTR of SLC11A1 influences the expression of brucella LPS induced MCP1 mRNA in buffalo peripheral blood mononuclear cells

A (GT)n microsatellite polymorphism at 3'UTR of SLC11A1(solute carrier family 11A1) is associated with the natural resistance to bovine brucellosis. A pleiotropic effect of SLC11A1 on other candidate genes influencing the host resistance including monocyte chemotactic/chemoattractant protein 1 (MCP1) is also hypothesized. In the present study, we report the cloning and characterization of the complete coding sequence of bubaline (bu) MCP1 and its tissue distribution at the transcript level. The buMCP1 exhibited as high as 99% and >80% of sequence identities with the bovine and other domestic animal species homologues. The buMCP1 mRNA was abundant across the different tissues: most abundant in liver and mammary gland, moderate in ovary, skeletal muscle and testis, and least in uterus. Further, quantitative real-time PCR (RTqPCR) analysis revealed that PBMCs carrying so called resistant GT13 allele produced more MCP1 mRNA endogenously as well as when induced with brucella LPS suggesting the pleiotropic roles of SLC11A1 in conferring resistance against the intracellular pathogens particularly against brucellosis. However, the underlying molecular mechanisms by which 3'UTR SLC11A1 concomitantly increases the production of chemokines like MCP1 are yet to be investigated.

Genetic analysis of the 3' untranslated region of the bovine SLC11A1 gene reveals novel polymorphisms

Polymorphisms in microsatellites at the 3' untranslated region (3'UTR) of the SLC11A1 (solute carrier family 11 member A1) gene have been associated with natural resistance to Brucella abortus and Mycobacterium bovis infection in livestock species. Here, we carried out an individual genetic analysis of the two microsatellites present at the 3'UTR SLC11A1 gene in 254 Bos taurus purebred, 125 B. indicus purebred and 54 B. taurus × B. indicus crossbred cattle. The genotyping by capillary electrophoresis showed the presence of four alleles (157, 159, 161 and 163) for the first microsatellite (MS1) and six alleles (175, 177, 179, 181, 183 and 185) for the second microsatellite (MS2). The alleles 159 and 175 were the most frequent in all breeds analyzed. B. taurus showed the most homogeneous haplotype and genotype for both microsatellites, whereas B. indicus showed the most heterogeneous haplotype and genotype. Two novel variants (alleles 161 and 163) within the MS1 are reported as well as novel variants in MS2 in Holstein breed. The knowledge of the polymorphisms distribution in both microsatellites at the 3'UTR of the SLC11A1 gene in cattle breeds is useful for future experimental design to evaluate the association between reported genotypes and natural resistance to pathogens infection.

Molecular cloning and characterization of SLC11A1 cDNA in Japanese Quail (Coturnix Coturnix Japonica)

SLC11A1 is one of the most potent candidate genes conferring host's genetic resistance/susceptibility to various antigenically different intracellular pathogens. In this manuscript, we report the cloning and characterization of the complete coding sequence of SLC11A1 cDNA in Japanese quail. The 1680bp of cloned SLC11A1 cDNA consisted of an open reading frame of 1665bp which coded for a complete protein of 555 amino acid residues. At nucleotide and amino acid sequence levels, Japanese quail SLC11A1 exhibited 95.1 and 96.9% identity with that of chicken, respectively. However, when compared with the mammalian homologues, it exhibited 64.8-66.4% and 64.5-66.9% identity, respectively. Phylogram constructed on the basis of both nucleotide and deduced amino acid sequences revealed similar pattern with the placement of Japanese quail and chicken SLC11A1 in the same clad.

Short communication: Association analysis of microsatellites and Mycobacterium avium subspecies paratuberculosis antibody response in German Holsteins

Paratuberculosis in ruminants is characterized by chronic granulomatous enteritis, resulting in persistent diarrhea and progressive wasting of cattle infected with Mycobacterium avium ssp. paratuberculosis (MAP). The disease occurs worldwide with high frequency, leading to growing economic losses in beef and dairy industries. The objective of this study was to investigate associations of microsatellites (BMC9006, BB704, BB705, BB717, BB719, BMS1617, BB702, and BOBT24) located near or within candidate genes involved in response mechanisms to paratuberculosis. Pedigree information existed for 4,686 German Holstein cows that had routinely been screened for MAP status using commercially available serum antibody ELISA test. The immunoglobulin G cutoff level was used to classify all animals as positive or negative for paratuberculosis. A total of 594 (12.7%) cows tested positive for paratuberculosis. The control group comprised 585 animals testing negative for MAP. Microsatellite BMC9006 had only 3 alleles (2 of which occurred at very low frequencies in the present data set) and was therefore not informative; the remaining microsatellites showed 3 to 12 alleles. Fisher's exact and chi2 tests revealed no significant differences in microsatellite allele frequencies between the 2 groups of German Holstein cows testing positive or negative for paratuberculosis.

A critical analysis of disease-associated DNA polymorphisms in the genes of cattle, goat, sheep, and pig

Genetic variations through their effects on gene expression and protein function underlie disease susceptibility in farm animal species. The variations are in the form of single nucleotide polymorphisms, deletions/insertions of nucleotides or whole genes, gene or whole chromosomal rearrangements, gene duplications, and copy number polymorphisms or variants. They exert varying degrees of effects on gene action, such as substitution of an amino acid for another, shift in reading frame and premature termination of translation, and complete deletion of entire exon(s) or gene(s) in diseased individuals. These factors influence gene function by affecting mRNA splicing pattern or by altering/eliminating protein function. Elucidating the genetic bases of diseases under the control of many genes is very challenging, and it is compounded by several factors, including host x pathogen x environment interactions. In this review, the genetic variations that underlie several diseases of livestock (under monogenic and polygenic control) are analyzed. Also, factors hampering research efforts toward identification of genetic influences on animal disease identification and control are highlighted. A better understanding of the factors analyzed could be better harnessed to effectively identify and control, genetically, livestock diseases. Finally, genetic control of animal diseases can reduce the costs associated with diseases, improve animal welfare, and provide healthy animal products to consumers, and should be given more attention.

NRAMP1 3' untranslated region polymorphisms are not associated with natural resistance to Brucella abortus in cattle

The NRAMP1 gene encodes a divalent cation transporter, located in the phagolysosomal membrane of macrophages, that has been associated with resistance to intracellular pathogens. In cattle, natural resistance against brucellosis has been associated with polymorphisms at the 3' untranslated region (3'UTR) of the NRAMP1 gene, which are detectable by single-strand conformational analysis (SSCA). This study aimed to evaluate the association between NRAMP1 3'UTR polymorphisms and resistance against bovine brucellosis in experimental and natural infections. In experimentally infected pregnant cows, abortion occurred in 42.1% of cows with a resistant genotype (SSCA(r); n = 19) and in 43.1% of those with a susceptible genotype (SSCA(s); n = 23). Furthermore, no association between intensity of pathological changes and genotype was detected. In a farm with a very high prevalence of bovine brucellosis, the percentages of strains of the SSCA(r) genotype were 86 and 84% in serologically positive (n = 64) and negative (n = 36) cows, respectively. Therefore, no association was found between the NRAMP1-resistant allele and the resistant phenotype in either experimental or naturally occurring brucellosis. To further support these results, bacterial intracellular survival was assessed in bovine monocyte-derived macrophages from cattle with either the resistant or susceptible genotype. In agreement with our previous results, no difference was observed in the rates of intracellular survival of B. abortus within macrophages from cattle with susceptible or resistant genotypes. Taken together, these results indicate that these polymorphisms at the NRAMP1 3'UTR do not affect resistance against B. abortus in cattle and that they are therefore not suitable markers of natural resistance against bovine brucellosis.

Protective effect of the Nramp1 BB genotype against Brucella abortus in the water buffalo (Bubalus bubalis)

We tested 413 water buffalo cows (142 cases and 271 controls) for the presence of anti-Brucella abortus antibodies (by the skin test, the agglutination test, and the complement fixation test) and the Nramp1 genotype (by capillary electrophoresis). Four alleles (Nramp1A, -B, -C, and -D) were detected in the 3' untranslated region of the Nramp1 gene. The BB genotype was represented among only controls, providing evidence that this genotype confers resistance to Brucella abortus. The monocytes from the BB (resistant) subjects displayed a higher basal level of Nramp1 mRNA and a lower number of viable intracellular bacteria than did the monocytes from AA (susceptible) subjects. The higher basal level of the antibacterial protein Nramp1 most probably provides the BB animals with the possibility of controlling bacteria immediately after their entry inside the cell.