Additional Evidence as of November 4, 1999 that The Jackson Laboratory DOES NOT have MHV
JAX® Bulletin #3, Addendum 2
November 4, 1999
A COMMUNICATION FROM THE JACKSON LABORATORY ANIMAL HEALTH STAFF: Peggy J. Danneman, VMD, MS, dip ACLAM (Acting Director of Laboratory Animal Health), James R. Fahey, PhD, DVM, dip ACVM (Head of Diagnostic Laboratory), Terrie Cunliffe-Beamer, DVM, MS, dip ACLAM (Head of Clinical Laboratory Animal Medicine), John P. Sundberg, DVM, PhD, dip ACVP (Head of Pathology, Senior Staff Scientist)
Additional negative test results have been obtained since the last update on September 29, 1999 confirming that The Jackson Laboratory does NOT have MHV. The information below describes the negative results obtained after publication of: (1) JAX Bulletin, No. 3, August 25, 1999 and (2) JAX Bulletin, No. 3, Addendum 1.
Blood samples from 671 mice from 14 rooms were tested serologically (ELISA) for antibodies to MHV. Most of the samples (665) were negative. Six samples gave nonspecific results and are being retested using the IFA test. As of this time, a minimum of 50 animals from each mouse room in the JAX® Mice Production Colonies have been tested serologically for MHV. This is in addition to the regular monthly health surveillance testing for all mouse pathogens, including MHV. The results show no evidence that any JAX® Mice have been exposed to MHV.
Testing of sentinel mice in Jackson Laboratory room AX-8 has continued as described in the JAX Bulletin, No.3, Addendum 1. Since that time, an additional 44 immunocompetent sentinels and MRL/MpJ-Faslpr (MRL-lpr/lpr) weanlings have been tested serologically (ELISA) and found to be negative for antibodies to MHV.
A total of 265 fecal samples from immunocompetent and immunodeficient sentinels and MRL-lpr/lpr weanlings from room AX-8 have also been tested by RT-PCR using 1, 2, or 3 primer sets, each of which recognizes a non-overlapping region of the MHV genome. All samples were negative using two of the primer sets - our primary set which recognizes an MHV nucleotide sequence and a second set which recognizes an MHV matrix sequence. Fourteen samples were positive using a third primer set, which recognizes another MHV nucleotide sequence. Fresh fecal samples were collected from these 14 putatively infected mice, some of which were severely immunodeficient, and tested again by RT-PCR using all three primer sets. All results were negative. Fecal samples from these mice were also examined by negative stain electron microscopy. No virus particles were found. All of the putative-infected mice that were immunocompetent were also retested serologically ELISA). All results were negative.
The overwhelming evidence continues to indicate that JAX® Mice do not have MHV. Although 14 positive results were obtained by RT-PCR using a single primer set, it must be concluded that these results were false positives. This conclusion is based on the fact that the putative-infected mice were: (1) negative for MHV RNA by RT-PCR using the 2 other primer sets; (2) negative for MHV RNA when retested using all 3 primer sets; (3) negative for MHV virus particles when studied by electron microscopy; and (4) negative for antibodies to MHV when tested and retested by ELISA.
