EXHIBIT 10.20

      THIS WARRANT AND THE  UNDERLYING  SHARES OF COMMON STOCK ISSUABLE UPON ITS
EXERCISE HAVE NOT BEEN  REGISTERED  UNDER THE SECURITIES ACT OF 1933, AS AMENDED
(THE "ACT"),  OR ANY STATE  SECURITIES LAWS, AND NO SALE OR TRANSFER THEREOF MAY
BE EFFECTED WITHOUT AN EFFECTIVE REGISTRATION STATEMENT OR AN OPINION OF COUNSEL
FOR THE HOLDER,  SATISFACTORY  TO THE  COMPANY,  THAT SUCH  REGISTRATION  IS NOT
REQUIRED UNDER THE ACT AND ANY APPLICABLE STATE SECURITIES LAWS.

No. W-3

                                    FORM OF
                          COMMON STOCK PURCHASE WARRANT
                          -----------------------------

      GENETIC  VECTORS,  INC., a Florida  corporation  (the  "COMPANY"),  hereby
certifies  that,  for  value  received,   CAPITAL   RESEARCH  LTD.,  a  Delaware
corporation (the "HOLDER"),  or its registered  permitted assigns,  is entitled,
subject to the terms set forth below,  to purchase  from the Company at any time
Fifty Thousand (50,000) shares of fully paid and non-assessable shares of common
stock,  par value  $0.001 per share (the  "COMMON  STOCK"),  of the Company at a
purchase  price  per share of $0.01  (the  "PURCHASE  PRICE").  The  number  and
character of such shares of Common Stock are subject to  adjustment  as provided
herein.

      As used herein the following terms, unless the context otherwise requires,
have the following respective meanings:

      (a) The term  "COMPANY"  shall include  Genetic  Vectors,  Inc., a Florida
corporation,  and any corporation  which shall succeed or assume the obligations
of the Company hereunder.

      (b) The term "COMMON STOCK" includes the Company's Common Stock, par value
$0.001 per share,  as  authorized  on the date hereof of the  Agreement  and any
other  securities  into  which or for  which  any of such  Common  Stock  may be
converted or exchanged pursuant to a plan of  recapitalization,  reorganization,
merger, sale of assets or otherwise.

      1.  EXERCISE OF WARRANT.

          1.1.  FULL  EXERCISE.  This  Warrant may be  exercised  in full by the
Holder by  surrender of this  Warrant,  with the form of  subscription  attached
hereto as Exhibit "A" (the "SUBSCRIPTION  FORM") duly executed by the Holder, to
the Company at its  principal  office,  accompanied  by  payment,  in cash or by
certified or official  bank check or wire  transfer  payable to the order of the
Company,  in the amount  obtained by multiplying  the number of shares of Common
Stock for which this Warrant is then exercisable by the Purchase Price.

          1.2.  PARTIAL  EXERCISE.  This  Warrant  may be  exercised  in part by
surrender of this Warrant in the manner and at the place provided in Section 1.1
except that the amount  payable by the holder on such partial  exercise shall be
the amount  obtained  by  multiplying  (a) the number of shares of Common  Stock


<PAGE>

designated by the holder in the Subscription  Form by (b) the Purchase Price. On
any such  partial  exercise  the  Company  will issue and deliver to or upon the
order of the holder hereof a new Warrant or Warrants of like tenor,  in the name
of the  holder  hereof  or such  holder  (upon  payment  by such  holder  of any
applicable transfer taxes) may request,  reflecting in the aggregate on the face
or faces thereof for the number of shares of Common Stock for which such Warrant
or Warrants may still be exercised.

      2.  DELIVERY OF STOCK CERTIFICATES, ETC. ON EXERCISE. As soon as practical
after the  exercise  of this  Warrant in full or in part,  the  Company,  at its
expense (including the payment by it of any applicable issue taxes),  will cause
to be issued in the name of and delivered to the Holder  hereof,  as such Holder
(upon payment by the Holder of any  applicable  transfer taxes and, if requested
by the  Company,  demonstration  by the  Holder of  compliance  with  applicable
securities  laws) may direct,  a certificate or  certificates  for the number of
fully paid and non-assessable  shares of Common Stock to which such Holder shall
be entitled on such  exercise,  plus, in lieu of any  fractional  share to which
such Holder would otherwise be entitled,  cash equal to such fraction multiplied
by the  then-current  market  value of one full share,  together  with any other
stock or other securities and property  (including  cash,  where  applicable) to
which  such  holder is  entitled  upon such  exercise  pursuant  to Section 1 or
otherwise.

      3.  ADJUSTMENT FOR REORGANIZATION, CONSOLIDATION, MERGER, ETC.

          3.1.  REORGANIZATION.   If   the   Company   shall   (a)   effect    a
reorganization, (b)  consolidate  with or merge  into any other person or party,
or (c)  transfer all or  substantially  all of its  properties  or assets to any
other person under any plan or arrangement  contemplating the dissolution of the
Company,  then, in each such case,  the Holder of this Warrant,  on the exercise
hereof as  provided  in  Section 1 at any time  after the  consummation  of such
reorganization,   consolidation   or  merger  or  the  effective  date  of  such
dissolution  as the case may be,  shall  receive,  in lieu of the  Common  Stock
issuable on such exercise prior to such consummation or such effective date, the
stock and other  securities and property  (including  cash) to which such Holder
would have been  entitled  upon such  consummation  or in  connection  with such
dissolution,  as the case may be, if such Holder had so  exercised  this Warrant
immediately  prior  thereto,  all subject to further  adjustment  thereafter  as
provided herein.

          3.2.  CONTINUATION OF TERMS. Upon any  reorganization,  consolidation,
merger or transfer (and any dissolution  following any transfer)  referred to in
this  Section 3, this  Warrant  shall  continue in full force and effect and the
terms hereof shall be applicable to the shares of stock and other securities and
property  receivable on the exercise of this Warrant after the  consummation  of
such   reorganization,   consolidation  or  merger  or  the  effective  date  of
dissolution  following  any such  transfer,  as the case  may be,  and  shall be
binding upon the issuer of any such stock or other securities, including, in the
case of any such transfer,  the person acquiring all or substantially all of the
properties  or assets of the  Company,  whether  or not such  person  shall have
expressly assumed the terms of this Warrant as provided herein.

          3.3.  ADDITIONAL  WARRANTS.  Upon the  satisfaction  of either (a) the
Company's full payment of all of the outstanding  obligations under that certain
Promissory  Note (the  "NOTE") of even date  herewith  made by the  Company  and
payable to the Holder or (b) a closing of an  offering  of  securities,  whether


                                       2
<PAGE>

through one or more private  placements or secondary public offerings,  in which
the Company raises gross proceeds from such  transaction or  transactions  of at
least $1,500,000,  the Company shall grant to the Holder additional  warrants to
purchase  from the  Company at any time or from time to time  before  5:00 p.m.,
Eastern Time, on the fifth anniversary of the grant of such additional  warrants
to the Holder,  One-Hundred  Fifty-Thousand  (150,000)  shares of fully paid and
non-assessable  Common  Stock at a  purchase  price  per  share  of  $5.50  (the
"PURCHASE PRICE").

All warrants to be granted  pursuant to the immediately preceding sentence shall
be granted pursuant to a new  Warrant in the  same form as this  Warrant, except
that such Warrant shall contain the following provision:

            Any provision herein to the contrary  notwithstanding,  no
            adjustment in the Purchase  Price shall be made in respect
            of the  issuance of  additional  shares of Common Stock of
            the  Company  (or  upon  the  conversion  or  exchange  of
            securities  convertible  or  exchangeable  into  shares of
            Common  Stock)  unless  after  the  date  hereof  (a)  the
            aggregate  consideration to be received by the Company for
            the issuance of such  additional  shares of Common  Stock,
            whether   through  one  or  more  private   placements  or
            secondary  public  offerings  (or upon the  conversion  or
            exchange of securities  convertible or  exchangeable  into
            shares of Common Stock),  is at least $500,000 and (b) the
            consideration  per share for an additional share of Common
            Stock (or the conversion or exchange price with respect to
            securities  convertible  or  exchangeable  into  shares of
            Common  Stock) to be issued  by the  Company  is less than
            $4.00. In such event,  the Purchase Price shall be reduced
            to a price  (calculated to the nearest cent) determined by
            multiplying  such  Purchase  Price  by  a  fraction,   the
            numerator of which shall be the number of shares of Common
            Stock outstanding immediately prior to such issue plus the
            number  of  shares of  Common  Stock  which the  aggregate
            consideration received by the Company for the total number
            of  additional  shares  of Common  Stock so  issued  would
            purchase  at such  Purchase  Price in  effect  immediately
            prior to such issuance, and the denominator of which shall
            be the  number  of  shares  of  Common  Stock  outstanding
            immediately  prior to such  issue  plus the number of such
            additional shares of Common Stock so issued.

      5.  RIGHT  TO ATTEND BOARD  MEETINGS.  The Holder shall have  the right to
have a single representative present (either in person or by  telephone)  at all
meetings of the Board of  Directors of the Company for so long as any portion of
the Note  remains  unpaid.  Such  representative  shall  not be  deemed  to be a
director and shall have no voting rights.

      6.  NO DILUTION OR IMPAIRMENT.  The Company will  not, by amendment of its
Articles of  Incorporation  or through any  reorganization,  transfer of assets,
consolidation,  merger,  dissolution,  issue or sale of  securities or any other


                                       3
<PAGE>

voluntary action, avoid or seek to avoid the observance or performance of any of
the  terms of the  Warrant,  but will at all times in good  faith  assist in the
carrying  out of all such terms and in the  taking of all such  action as may be
necessary or  appropriate  in order to protect the rights of the Holder  against
dilution or other impairment.

      7.  NOTICES OF RECORD DATE, ETC. In the event of:

          (a) any taking by the  Company of a record of the holders of any class
or  securities  for the  purpose of  determining  the  holders  thereof  who are
entitled  to  receive  any  dividend  or  other  distribution,  or any  right to
subscribe for, purchase or otherwise acquire any shares of stock of any class or
any other securities or property, or to receive any other right, or

          (b) any capital reorganization of the Company, any reclassification or
recapitalization  of the capital  stock of the Company or any transfer of all or
substantially all the assets of the Company to or consolidation or merger of the
Company with or into any other person, or

          (c)  any  voluntary  or   involuntary   dissolution,   liquidation  or
winding-up of the Company, or

          (d) any proposed  issue or grant by the Company of any shares of stock
of any class or any other  securities,  or any right or option to subscribe for,
purchase  or  otherwise  acquire  any  shares of stock of any class or any other
securities  (other than this issue of Common Stock on exercise of the  Warrant),
then and in each such event the  Company  will mail or cause to be mailed to the
Holder a notice  specifying (i) the date on which any such record is to be taken
for the purpose of such dividend  distribution or right,  and stating the amount
and character of such dividend,  distribution  or right;  (ii) the date on which
any   such   reorganization,   reclassification,   recapitalization,   transfer,
consolidation, merger, dissolution, liquidation or wind-up is to take place, and
the time,  if any is to be fixed,  as of which the  holders  of record of Common
Stock shall be entitled to exchange  their shares of Common Stock for securities
or  other  property  deliverable  on  such   reorganization,   reclassification,
recapitalization,  transfer, consolidation,  merger, dissolution, liquidation or
winding-up; and (iii) the amount and character of any stock or other securities,
or rights or options with respect thereto, proposed to be issued or granted, the
date of such proposed issue or grant and the persons or class of persons to whom
such  proposed  issue or grant is to be offered or made.  Such  notice  shall be
mailed at least  twenty (20) days prior to the date  specified in such notice on
which any such action is to be taken.

      8.  CERTAIN  DELIVERIES. The Company shall deliver to the Holder copies of
all documents filed by the Company with the Securities and Exchange  Commission.
In  addition  and for so long as any  portion of the Note  remains  unpaid,  the
Company shall deliver to the Holder copies of its monthly financial  statements.
Such financial  statements  shall be delivered on or before the thirtieth day of
each month for the immediately preceding month.

      9.  RESERVATION OF STOCK ISSUABLE ON EXERCISE OF WARRANT. The Company will
at all times reserve and keep available, solely for issuance and delivery on the
exercise of the Warrant,  all shares of Common Stock from time to time  issuable
on the exercise of the Warrant.


                                        4
<PAGE>


      10. EXCHANGE OF WARRANT.  On surrender of the Warrant,  properly endorsed,
to the  Company,  the Company at its expense will issue and deliver to or on the
order of the holder thereof a new Warrant or Warrants of like tenor, in the name
of such holder or as such holder (upon payment by such holder of any  applicable
transfer taxes and, if requested by the Company, demonstration by such holder of
compliance with applicable securities laws) may direct, calling in the aggregate
on the face or faces thereof for the number of shares of Common Stock called for
on the face or faces of the Warrant or Warrants so surrendered.

      11. REPLACEMENT OF WARRANT. On receipt of evidence reasonably satisfactory
to the Company of the loss, theft, destruction or mutilation of the Warrant and,
in the case of any such loss,  theft or destruction of the Warrant,  on delivery
of an indemnity agreement or security reasonably satisfactory in form and amount
to the  Company  or,  in the  case of any  such  mutilation,  on  surrender  and
cancellation  of such  warrant,  the  Company at its  expense  will  execute and
deliver, in lieu thereof, a new Warrant of like tenor.

      12. NEGOTIABILITY. This Warrant is issued upon the following terms, to all
of which each holder or owner hereof by the taking hereof consents and agrees:

          (a) subject to compliance with all applicable  securities  laws, title
to  this  Warrant  may be  transferred  by  endorsement  (by the  holder  hereof
executing the Form of Assignment attached hereto as Exhibit "B") and delivery in
the  same  manner  as in the case of a  negotiable  instrument  transferable  by
endorsement and delivery;

          (b) any person in  possession  of this  Warrant  properly  endorsed is
authorized  to  represent  himself as absolute  owner hereof and is empowered to
transfer absolute title hereto by endorsement and delivery hereof to a BONA FIDE
purchaser  hereof for value;  each prior taker or owner waives and renounces all
of his  equities  or  rights  in this  Warrant  in favor of each  such BONA FIDE
purchaser, and each such BONA FIDE purchaser shall acquire absolute title hereto
and to all rights represented hereby; and

          (c) until this Warrant is transferred on the books of the Company, the
Company may treat the registered  holder hereof as the absolute owner hereof for
all purposes, notwithstanding any notice to the contrary.

      13. NOTICES. All notices or other communications  required or permitted to
be given pursuant to this Agreement  shall be in writing and shall be considered
as duly given on (a) the date of delivery, if delivered in person, by nationally
recognized  overnight  delivery service or (b) five days after mailing if mailed
from within the  continental  United  States by  registered  or certified  mail,
return  receipt  requested to the party  entitled to receive the same, if to the
Company,  to Genetic  Vectors,  Inc.,  5201 N.W. 77th Avenue,  Suite 100, Miami,
Florida 33166 Attention:  Mead M. McCabe, Jr., with a copy to Clayton E. Parker,
Esq., Kirkpatrick & Lockhart LLP, 201 S. Biscayne Boulevard,  20th Floor, Miami,
Florida 33131, and if to the Holder,  at the address of such Holder shown on the
books of the Company.  Any party may change his or its address by giving  notice
to the other party  stating his or its new address.  Commencing  on the 10th day
after the giving of such  notice,  such  newly  designed  address  shall be such


                                       5
<PAGE>

party's address for the purpose of all notices or other communications  required
or permitted to be given pursuant to this Agreement.

      14. GOVERNING LAW. This Agreement and the rights of the parties  hereunder
shall be governed by and construed in  accordance  with the laws of the State of
Florida,  without regard to its conflicts of law principles.  All parties hereto
(i) agree that any legal suit,  action or proceeding  arising out of or relating
to this  Agreement  shall be  instituted  only in a  federal  or state  court in
Miami-Dade  County,  Florida;  (ii)  waive any  objection  which they may now or
hereafter  have  to the  laying  of  the  venue  of any  such  suit,  action  or
proceeding;  and (iii) irrevocably submit to the jurisdiction of such federal or
state  court  in  Miami-Dade  County,  Florida  in  any  such  suit,  action  or
proceeding,  but such consent  shall not  constitute a general  appearance or be
available to any other person who is not a party to this Agreement.  All parties
hereto agree that the mailing of any processing  any suit,  action or proceeding
in accordance  with the notice  provisions of this  Agreement  shall  constitute
personal service thereof.

      15. ENTIRE  AGREEMENT;  WAIVER OF BREACH.  This Agreement  constitutes the
entire  agreement  among the  parties  and  supersedes  any prior  agreement  or
understanding  among them with respect to the subject matter hereof,  and it may
not be modified or amended in any manner other than as provided  herein,  and no
waiver of any  breach or  condition  of this  Agreement  shall be deemed to have
occurred  unless  such waiver is in writing,  signed by the party  against  whom
enforcement  is  sought,  and no waiver  shall be  claimed to be a waiver of any
subsequent breach or condition of a like or different nature.

      16. SEVERABILITY. If any provision of this Agreement shall be held invalid
or unenforceable,  such invalidity or unenforceability shall attach only to such
provision and shall not in any manner affect or render invalid or  unenforceable
any other  severable  provision of this  Agreement,  and this Agreement shall be
carried out as if any such invalid or unenforceable provision were not contained
herein.

      17. AMENDMENT.  This Warrant and any  term hereof may be changed,  waived,
discharged  or terminated  only by an instrument in writing  signed by the party
against which  enforcement of such change,  waiver,  discharge or termination is
sought.

      18. ATTORNEYS'  FEES AND COSTS.  In  the event of any  litigation  arising
under or relating to this Warrant, the prevailing party in such dispute shall be
entitled to recover its costs and expenses,  including reasonable attorney fees,
from the other.

      19. RESTRICTIONS  ON  TRANSFERABILITY;  RESTRICTIVE  LEGEND.  The   holder
acknowledges  that the shares of Common  Stock  issuable  upon  exercise of this
Warrant  are  subject  to  restrictions   under  applicable  Federal  and  state
securities  laws. Each  certificate  representing  shares of Common Stock issued
shall, upon the exercise of this Warrant, bear the following legends in addition
to such other restrictive legends as may be required by law:

      "The shares represented by this certificate have not been registered under
the  Securities  Act of 1933,  as amended (the "ACT"),  or any state  securities
laws,  and no sale or  transfer  thereof may be  effected  without an  effective
registration statement or an opinion of counsel for the holder,  satisfactory to


                                       6
<PAGE>

the  Company,  that  such  registration  is not  required  under the Act and any
applicable state securities laws."

      Dated: January 19, 1999

                                    GENETIC VECTORS, INC.


                                    By:_________________________________________

                                    Title:______________________________________




AGREED TO AND ACCEPTED:

CAPITAL RESEARCH LTD.



By:_________________________________

Its:________________________________

Date:_______________________________









                                       7
<PAGE>

                                   EXHIBIT "A"
                                   -----------


                                FORM OF EXERCISE
                                ----------------

                   (TO BE SIGNED ONLY ON EXERCISE OF WARRANT)

TO:

      The  undersigned,  the holder of the within  Warrant,  hereby  irrevocably
elects to exercise this Warrant for, and to purchase  thereunder _____ shares of
Common Stock of  ____________________,  herewith  makes  payment of  $__________
therefor,  and requests that the  certificates  for such shares be issued in the
name of, and delivered to, whose address is:

               __________________________________________________

               __________________________________________________

               __________________________________________________

               Dated:___________________.




                                    ____________________________________________
                                    Signature
                                    (Signature must conform to name of holder as
                                    specified on the face of the Warrant)
                                    

                                    ____________________________________________
                                    Print Name

                                    ____________________________________________
                                    Street Address

                                    ____________________________________________
                                    City, State and Zip Code

                                    ____________________________________________
                                    Person's Social Security Number or Tax
                                    Identification Number






                                       A-1
<PAGE>

                                   EXHIBIT "B"
                                   -----------


                               FORM OF ASSIGNMENT
                               ------------------

                   (TO BE SIGNED ONLY ON TRANSFER OF WARRANT)

      For value received,  the undersigned hereby sells,  assigns, and transfers
unto ___________________ the right represented by the within Warrant to purchase
shares of  Common  Stock of  ___________________  to which  the  within  Warrant
relates, and appoints ___________________ as its attorney to transfer such right
on the  books  of  _________________  with  full  power of  substitution  in the
premises.

      Dated:_________________.





                                    ____________________________________________
                                    Signature
                                    (Signature must conform to name of holder as
                                    specified on the face of the Warrant)
                                    

                                    ____________________________________________
                                    Print Name

                                    ____________________________________________
                                    Street Address

                                    ____________________________________________
                                    City, State and Zip Code

                                    ____________________________________________
                                    Person's Social Security Number or Tax
                                    Identification Number







Signed in the presence of:




__________________________________





                                       B-1